U.S. patent application number 16/165038 was filed with the patent office on 2020-04-23 for automated test equipment with relay hot-switch detection.
This patent application is currently assigned to Teradyne, Inc.. The applicant listed for this patent is Teradyne, Inc.. Invention is credited to Richard John Burns, Alan B. Hussey, Mark Alan Levin, Gregory Smith.
Application Number | 20200124661 16/165038 |
Document ID | / |
Family ID | 70279415 |
Filed Date | 2020-04-23 |
![](/patent/app/20200124661/US20200124661A1-20200423-D00000.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00001.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00002.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00003.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00004.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00005.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00006.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00007.png)
![](/patent/app/20200124661/US20200124661A1-20200423-D00008.png)
United States Patent
Application |
20200124661 |
Kind Code |
A1 |
Hussey; Alan B. ; et
al. |
April 23, 2020 |
AUTOMATED TEST EQUIPMENT WITH RELAY HOT-SWITCH DETECTION
Abstract
Apparatus and methods for detecting and identifying a cause of a
hot-switching event in an automated test system. One or more
antennae positioned near mechanical relays in the system may be
used to sense electromagnetic radiation. The antennae may be
configured to respond to electromagnetic radiation of the type
generated during a hot-switching event. Signals measured by the
antennae may be processed to determine whether the signals have
characteristics of hot-switching events. Processing may entail
generating a signal envelope and determining whether the envelope
has characteristics indicative of a hot-switching event. When a
hot-switching event is detected, information to correlate the event
to other events in the test system may also be captured. That
information may be time information, enabling program test-system
program instructions executing at the time of the event to be
identified, such that the test system may be reprogrammed to avoid
hot-switching events.
Inventors: |
Hussey; Alan B.; (Oak Park,
CA) ; Burns; Richard John; (Boston, MA) ;
Smith; Gregory; (North Reading, MA) ; Levin; Mark
Alan; (Calabasas, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Teradyne, Inc. |
North Reading |
MA |
US |
|
|
Assignee: |
Teradyne, Inc.
North Reading
MA
|
Family ID: |
70279415 |
Appl. No.: |
16/165038 |
Filed: |
October 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 17/0085 20130101;
G01R 31/2834 20130101; H04B 17/17 20150115; H04B 17/102
20150115 |
International
Class: |
G01R 31/28 20060101
G01R031/28; H04B 17/17 20060101 H04B017/17; H04B 17/00 20060101
H04B017/00; H04B 17/10 20060101 H04B017/10 |
Claims
1. A method for detecting mechanical relay hot-switching events in
a test system comprising a plurality of relays at corresponding
relay locations, the method comprising: measuring, with one or more
antennae, one or more signal waveforms representing electromagnetic
emissions from one or more relays of the plurality of relays;
analyzing the one or more signal waveforms measured with the one or
more antennae to determine whether at least one of the one or more
signal waveforms has a characteristic associated with a
hot-switching event; based on determining that at least one of the
one or more signal waveforms has a characteristic associated with a
hot-switching event, identifying a time corresponding to the
hot-switching event.
2. The method of claim 1, wherein analyzing the one or more signal
waveforms comprises selectively generating a signal envelope of a
component of each of the one or more signal waveforms based on the
component having a frequency at a ringing frequency of the
antenna.
3. The method of claim 1, further comprising: controlling switching
of the plurality of relays in accordance to a plurality of test
system instructions each having an execution time; and based on the
identified time corresponding to the hot-switching event,
identifying one or more instructions of the plurality of test
system instructions as a cause for the hot-switching event.
4. The method of claim 3, wherein: the act of identifying a time
corresponding to the hot-switching event comprises recording a time
stamp corresponding to the hot-switching event; each of the
plurality of test system instructions has an execution time stamp;
and the act of identifying one or more instructions as a cause for
the hot-switching event comprises: comparing the time stamp with
execution time stamps of the plurality of test system instructions,
and identifying one or more instructions as a cause for the
hot-switching event based on comparing the time stamp with
execution time stamps.
5. The method of claim 3, wherein: the plurality of test system
instructions are associated with relays at one or more relay
locations, and wherein the act of identifying one or more
instructions as a cause for the hot-switching event further
comprises: identifying a relay location corresponding to the
hot-switching event, selecting instructions as the one or more
identified instructions based on the instructions having associated
relay locations proximate to the relay location corresponding to
the hot-switching event.
6. The method of claim 2, wherein: analyzing the one or more signal
waveforms to determine whether at least one of the one or more
signal waveforms has a characteristic associated with a
hot-switching event comprises analyzing the generated signal
envelopes to determine whether at least one of the generated signal
envelopes has a characteristic associated with a hot-switching
event.
7. The method of claim 6, wherein the characteristic associated
with a hot-switching event is a peak amplitude or a pulse width of
the one or more generated signal envelopes.
8. The method of claim 7, wherein at least one of the signal
envelopes has a pulse width of at least 1 ns.
9. The method of claim 6, further comprising digitizing the
generated signal envelopes by sampling the signal envelopes at a
sampling period between 0.1 ns and 1 ns.
10. The method of claim 2, wherein analyzing the one or more signal
waveforms further comprises: analyzing the plurality of signal
waveforms to determine a magnitude of a hot-switching event by:
correlating a pattern of the magnitudes of the generated signal
envelopes associated with the plurality of antennae with each of a
plurality of predetermined patterns of signal envelopes detected
upon switching each a respective plurality of relays; identifying a
relay undergoing a hot-switching event based on the correlation;
determining a scale factor between a magnitude of an envelope
associated with a reference hot-switching event of the identified
relay and at least one of the magnitudes of the detected envelopes;
and computing the magnitude of the hot-switching event based on the
scale factor and a magnitude of the reference hot-switching
event.
11. A test system, comprising: a printed circuit board (PCB); a
plurality of relays on the PCB; one or more antennae each disposed
adjacent one or more relays of the plurality of relays, each of the
one or more antennae is configured to measure one or more signal
waveforms representing electromagnetic emissions from the one or
more relays; circuitry configured to analyze the one or more signal
waveforms measured by the one or more antennae to determine whether
at least one of the one or more signal waveforms has a
characteristic associated with a hot-switching event.
12. The test system of claim 11, further comprising: an envelope
detector circuit configured to generate a signal envelope based on
each of the one or more signal waveforms; wherein the one or more
processors are configured to analyze the generated signal envelopes
to determine whether at least one of the generated signal envelopes
has a characteristic associated with a hot-switching event.
13. The test system of claim 12, wherein the PCB is a first PCB,
and the test system further comprises a second PCB, wherein the one
or more antennae are disposed on the second PCB.
14. The test system of claim 13, wherein the envelope detector
circuit is disposed on the second PCB.
15. The test system of claim 13, wherein the circuitry comprises a
field programmable gate array (FPGA), and the test system further
comprises an analog to digital converter (ADC) disposed on the
second PCB and coupled between an output of the envelope detector
circuit and the FPGA.
16. The test system of claim 13, wherein the plurality of relays
are disposed on a first surface of the first PCB, the one or more
antennae are disposed on a second surface of the second PCB, and
wherein the first PCB is mechanically coupled to the second PCB
such that the first surface faces the second surface.
17. The test system of claim 13, further comprising a test system
enclosure having a plurality of slots, wherein the first PCB and
second PCB are disposed in a slot of the plurality of slots.
18. A method of operating a test system to detect hot-switching
events, the method comprising: controlling switching of relays of a
plurality of relays in the test system in accordance with a
plurality of instructions; measuring, with one or more antennae,
one or more signal waveforms representing electromagnetic emissions
from one or more relays; analyzing the one or more signal waveforms
to determine whether at least one of the one or more signal
waveforms has a characteristic associated with a hot-switching
event; based on determining that at least one of the one or more
signal waveforms has a characteristic associated with a
hot-switching event, identifying one or more instructions of the
plurality of instructions as a cause for the hot-switching
event.
19. The method of claim 18, wherein controlling switching of the
plurality of relays in accordance to the plurality of instructions
comprises controlling switching of the plurality of relays at a
plurality of execution times each associated with an instruction of
the plurality of instructions, and the act of identifying one or
more instructions as a cause for the hot-switching event further
comprises further comprises: identifying a time corresponding to
the hot-switching event; comparing the identified time with
execution times associated with the plurality of instructions;
identifying one or more instructions as a cause for the
hot-switching event based on comparing the time with execution
times.
20. The method of claim 18, wherein each of the plurality of
instructions is associated with relays at one or more relay
locations, and wherein the act of identifying one or more
instructions as a cause for the hot-switching event further
comprises: identifying a relay location corresponding to the
hot-switching event, comparing the relay location with relay
locations associated with the plurality of instructions, and based
on comparing the relay location with relay locations associated
with the plurality of instructions, identifying one or more test
sequences as a cause for the hot-switching event.
Description
BACKGROUND
Technical Field
[0001] The technology relates to methods and structures for
calibrating test channels and reliability improvement of automated
test equipment (ATE).
Discussion of the Related Art
[0002] Referring to FIG. 1, a conventional test configuration 100
for semiconductor devices may include automated test equipment
(sometimes referred to as a "tester" or an "ATE"). Tester 110 may
include tester resources, sometimes called instruments, that
generate or measure test signals. Within the tester, the tester
resources are connected to channel contacts forming a tester
interface 131. Each channel contact may be connected to a test
point on a device under test 150 through a device interface.
[0003] The nature of the device interface may depend on the
specifics of the device under test. In some implementations, the
device under test 150 may be a wafer while in other implementations
the device under test may be one or more packaged integrated
circuits. These differences enable the same tester 110 the ATE to
be used for testing integrated circuit devices on a wafer prior to
dicing the wafer or for testing the integrated circuits after they
have been packaged. For testing packaged devices, the device
interface may be a device interface board 135, as illustrated in
FIG. 1. But other device interfaces, including, for example, a
probe card for making connections to a wafer for testing, may be
used in other implementations.
[0004] Thus, by changing the device interface, the same tester 110
may be used to test integrated circuits at different stages in
their manufacture. Moreover, a tester 110 is programmable and can
test different types of devices that require different types of
test signals to be generated or measured to determine whether the
device under test is operating properly. Even during the test of a
device under test, different types of test signals may be generated
or measured at different times.
[0005] To support these different test requirements, a test
configuration 100 may include relays that may be opened or closed
to selectively connect specific tester resources to test points on
a device under test. Tester 110 may be programmable such that
execution of test system instructions, programmed into the tester
110 for performing specific tests on specific devices, control the
state of the relays so that appropriate tester resources are
connected to appropriate test points.
[0006] Often, the relays are mechanical relays because such relays
provide a very low on resistance as a result of metal contacts in
the relay touching each other when the relay is closed. However,
mechanical relays are susceptible to damage as a result of a
phenomenon known as "hot-switching." Hot-switching occurs when a
relay is opened or closed while a voltage exists across the
contacts within the relay. During hot-switching, the contacts
inside the relay touch as they are closing, which will generate a
high amount of current and in turn, heat that can damage the
contacts.
[0007] Hot-switching may unintentionally occur in a test system as
a result of the way a test program is written. An instruction in
the program, changing the state of a relay, may execute at a time
when a voltage exists across the relay, for example when one or
both of the relay contacts are connected to voltage source(s).
SUMMARY
[0008] The inventors have recognized and appreciated that
reliability of a test system may be increased by providing a
mechanism to detect hot-switching. A detected hot-switching event
may be correlated to a test system program instruction that
triggered the hot-switching, such that the test system can be
reprogrammed to avoid hot-switching and consequent damage.
[0009] In accordance with some aspects, a method may be provided
for detecting mechanical relay hot-switching events in a test
system comprising a plurality of relays at corresponding relay
locations. The method may comprise measuring, with one or more
antennae, one or more signal waveforms representing electromagnetic
emissions from one or more relays of the plurality of relays. The
one or more signal waveforms may be analyzed to determine whether
at least one of the one or more signal waveforms has a
characteristic associated with a hot-switching event. Based on
determining that at least one of the one or more signal waveforms
has a characteristic associated with a hot-switching event,
identifying a time corresponding to the hot-switching event.
[0010] In accordance with some aspects, a test system may be
provided. The test system may comprise a printed circuit board
(PCB) and a plurality of relays arranged on the PCB. One or more
antennae may be disposed adjacent one or more relays of the
plurality of relays, such that each of the one or more antennae is
configured to measure one or more signal waveforms representing
electromagnetic emissions from the one or more relays. Circuitry
may be provided and configured to analyze the one or more signal
waveforms to determine whether at least one of the one or more
signal waveforms has a characteristic associated with a
hot-switching event.
[0011] In accordance with yet other aspects, a method of operating
a test system to detect hot-switching events may be provided. The
method may comprise controlling switching of relays of a plurality
of relays in the test system in accordance with a plurality of
instructions. One or more signal waveforms representing
electromagnetic emissions from one or more relays may be measured
with one or more antennae. The one or more signal waveforms may be
analyzed to determine whether at least one of the one or more
signal waveforms has a characteristic associated with a
hot-switching event. Based on determining that at least one of the
one or more signal waveforms has a characteristic associated with a
hot-switching event, one or more instructions of the plurality of
instructions may be identified as a cause for the hot-switching
event.
[0012] The foregoing and other aspects, embodiments, and features
of the present teachings can be more fully understood from the
following description in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The skilled artisan will understand that the figures,
described herein, are for illustration purposes only. It is to be
understood that in some instances various aspects of the
embodiments may be shown exaggerated, simplified, and/or enlarged
to facilitate an understanding of the embodiments. In the drawings,
like reference characters generally refer to like features,
functionally similar and/or structurally similar elements
throughout the various figures. The drawings are not necessarily to
scale, emphasis instead being placed upon illustrating the
principles of the teachings. The drawings are not intended to limit
the scope of the present teachings in any way.
[0014] FIG. 1 is a block diagram depicting components associated
with an automated test equipment, according to some
embodiments;
[0015] FIG. 2A is a plan view of an assembly, including relays, and
antennae configured to receive electromagnetic signals emitted by
the relays during hot-switching, according to some embodiments;
[0016] FIG. 2B is an isometric view of the assembly in FIG. 2A,
according to some embodiments;
[0017] FIG. 2C is a schematic illustration of the assembly of FIG.
2A installed in a body of a tester;
[0018] FIG. 3 is a block diagram of analysis circuitry that
analyzes signals received from the antennae to determine whether at
least one of the one or more signal waveforms has a characteristic
associated with a hot-switching event, according to some
embodiments;
[0019] FIG. 4 is a simplified schematic diagram of an exemplary
implementation of analysis circuitry, according to some
embodiments;
[0020] FIG. 5 is a collection of signal waveforms and their
corresponding envelope signals as measured by antennae placed at
different locations of a relay module, according to some
embodiments;
[0021] FIG. 6 depicts an example of a computing environment that
may be adapted to perform portions of the analysis as described
herein, according to some implementations;
[0022] FIG. 7A is a flow chart of a method for operating a test
system for hot-switching detection, in accordance with some
embodiments;
[0023] FIG. 7C is a flow chart of a method that is an exemplary
calibration method, in accordance with some embodiments; and
[0024] FIG. 7B is a flow chart of a method for operating a test
system for hot-switching detection, in accordance with some
embodiments.
[0025] The features and advantages of the embodiments will become
more apparent from the detailed description set forth below when
taken in conjunction with the drawings.
DETAILED DESCRIPTION
[0026] The inventors have recognized and appreciated that an
automatic test system may be imparted with longer and/or more
reliable operation by incorporating components to detect
hot-switching events. Those components may enable correlation of a
hot-switching event to one or more program instructions in a test
program that may have caused the hot-switch. Further, the magnitude
of the hot-switching event may be determined. The output of a
system with such components may be used to impact operation of the
test system, such as by modifying the order of instructions in a
program to avoid hot-switching or to avoid hot-switching above a
predetermined magnitude associated with rapid failure of
relays.
[0027] The inventors have also recognized and appreciated circuit
designs with a size and cost that make it feasible to detect very
short duration hot-switching events in an automatic test system.
The components, for example, may be sufficiently compact to fit
between boards in a conventional automatic test system without
impacting performance of the test system. Suitable circuits may
include antennae that "ring" in response to pulses of
electromagnetic radiation emitted during hot-switching.
Additionally circuitry, coupled to the output of such an antenna,
may output an envelope signal of the ringing. The envelope signal,
when present, may indicate a hot-switching event, but will be much
longer in duration, and therefore easier to detect and process with
compact circuitry, than the electromagnetic pulse emitted by a
relay during hot switching.
[0028] The components for hot-switch detection may include one or
more antennae positioned near relays that may be susceptible to
hot-switching. Components to analyze the signals picked up by the
antennae may also be included. The analysis circuitry may include a
processor, which may be implemented as a Field Programmable Gate
Array (FPGA) or other hardware circuitry, which may process a
measured signal to determine when a signal includes one or more
characteristics associated a hot-switching event. In some
embodiments, the analysis circuitry may additionally determine
which relay was hot-switched and/or the magnitude of the
hot-switching.
[0029] Further, analysis circuitry may include a component that
enables correlation of a detected hot-switching event with other
events within the test system. In some embodiments, a hot-switching
event may be correlated to execution of program instructions that
control operation of the tester. For example, a hot-switching event
may be correlated to an instruction that controls a relay. In some
embodiments, that correlation may be performed by recording in
computer memory information about the time of occurrence of the
hot-switching event. In subsequent processing, instructions
executing at the time of the event may be identified. As a specific
example, operation of the test system may be synchronized with
respect to common timing signals that track time with respect to a
start of a test or other suitable event. The time of an event,
including detection of a hot-switching event or execution of a test
system instruction, may be reflected as a time stamp derived from
the common timing signals. In this way, recording a time stamp in
connection with an indication that a hot-switching event may enable
later processing to identify a program instruction or instructions
with the same or similar time stamp as a cause of the hot-switching
event.
[0030] The relays for which hot-switching may be detected may be
any relays susceptible to hot-switching, such as mechanical relays
that operate under program control and across which a voltage
source can be connected as part of execution of a test on a device
under test. The relays may be in any portion or portions of the
test configuration. They may be, for example, in a body of the
tester, coupling inputs or outputs of instruments to specific
channel contacts in a tester interface. The relays may be
concentrated in a relay matrix or may, in some embodiments, be
distributed throughout the test system. Alternatively or
additionally, the relays may be in a device interface board or
otherwise included in a device interface, as the techniques
described herein may be applied regardless of the components of the
test system in which the relays are installed.
[0031] In some embodiments, the antennae may be positioned and
oriented with respect to the relays such that they will receive
electromagnetic radiation emitted by the hot-switching. The
antennae, for example, may be implemented as dipoles, spirals or
other patch antennae on a printed circuit board (PCB) on which the
relays are mounted. Alternatively, or additionally, the antennae
may be implemented on one or more separate PCBs or other substrates
mounted near the relays.
[0032] The inventors have recognized and appreciated that because
hot-switching events are associated with a short duration, for
example 75 ps or shorter before the voltage difference across the
relay contacts decreases, the resulting radiation energy spectrum
extends to frequency components that may be higher than 3.5 GHz and
may stimulate antennae with a resonant frequency lower than 3.5
GHz. The antennae, for example, may be tuned to a frequency in the
range of 1-5 GHz, for example, of 2-3 GHz, or 2.2 GHz in some
embodiments. According to an aspect, the antenna length can be
sized larger to increase coverage area or shorter as a high-pass
filter that may exclude other lower frequency interference. In some
embodiments, the antennae are tuned to a frequency above a minimum
frequency of the an envelope detector circuitry.
[0033] The output of the antenna may be measured and further
processed to determine whether a resonant signal associated with a
hot-switching event is present. That processing may include, in
some embodiments, amplifying the signal at the output of the
amplifier. Other processing may be performed. As an example, the
amplified signal may be gain adjusted, such as with an attenuator
or other suitable gain control circuit. The resulting signal may be
processed to detect an envelope of the signal.
[0034] In some embodiments, the envelope detector circuitry may be
configured to discriminate signals characteristic of a hot
switching event. The envelope detector, for example, may produce an
envelope of a component of a signal output by the antenna at the
ringing frequency of the antenna that would be excited by
electromagnetic radiation emitted by a relay that is hot-switching.
Alternatively or additionally, the envelope detector circuitry may
gate the output of an envelope signal based on the duration or
other characteristics of that envelope being consistent with a
signal generated by hot-switching.
[0035] Characteristics of the envelopes produced from signals
output by one or more antennae, such as peak amplitude, duration,
and/or pattern of peaks, may be compared to known characteristics
of signals known to indicate a hot-switching event to derive
additional information about the hot-switching. That additional
information may include which relay hot-switched. Alternatively or
additionally, the voltage across the relay that hot-switched may be
computed to assess the magnitude of the hot-switching.
[0036] Relevant characteristics may be determined in any suitable
way. For example, measurements may be made under conditions in
which hot-switching is intentionally introduced. Characteristics of
signals detected under these known conditions can serve to
calibrate the processing apparatus to detect hot-switching at other
times. Calibration values may be used, for example, to determine an
expected signature of signals received at each of multiple antennae
when a specific relay has hot-switched. By comparing the signals
received at multiple antennae to signatures for each of multiple
relays, a determination can be made of which relay gave rise to a
detected hot-switching and the hot-switching voltage across the
relay at the moment of the hot-switching. Such a comparison may
alternatively or additionally be used to confirm whether a
hot-switching event occurred.
[0037] Some or all of the processing may be performed digitally. In
some embodiments, the envelope may be sampled and then digitized.
Selected digitized samples may be captured as a representation of
an event. For example, a number of digital values may be captured
for subsequent processing to determine which relay gave rise to
that hot-switching event and/or determine the magnitude of the
hot-switching event.
[0038] The components for processing signals measured by the
antennae may be in any suitable form and may be located in any
suitable place within the test configuration. Some or all of the
components, for example, may be on the same PCB as the antennae or
may be on a separate printed circuit board connected to the
antennae via one or more cables or other suitable interfaces. In
other embodiments, some of the processing components may be outside
the tester, such as in a computer coupled to the tester through a
wired or wireless interface. By way of example, and not of
limitation, components for processing signals from the antennae
within the tester may generate digital representations of the
waveforms that may be transferred to a separate computer outside
the tester for further processing to identify a cause of
hot-switching event.
[0039] These techniques may be incorporated, alone or in any
suitable combination, into a test configuration, such as the test
configuration shown in FIG. 1. An exemplary implementation of such
a test system having a relay matrix assembly is shown in FIGS. 2A,
2B.
[0040] FIG. 2A depicts an assembly 200 including relays for
insertion in a tester, according to some embodiments. Assembly 200
may represent any suitable portion of a test system. It may
represent, for example, an analog or digital instrument that
generates or measures analog or digital signals under program
control while tester 110 executes a test. Accordingly, assembly 200
may have components, not expressly shown, that provide tester
resources for generating and measuring signals that pass through
the relays. However, relays in a test system need not be on the
same assembly as the tester resources, and assembly 200 may simply
be a switch matrix that is connected to other assemblies
implementing tester resources.
[0041] In the embodiment illustrated, assembly 200 comprises a
plurality of relays 212 arranged on a surface of a board 210.
Relays 212 are arranged in two-dimensional arrays on the surface of
board 210 to form part of one or more relay modules 214. While FIG.
2A illustrates three relay modules 214, each having a matrix of 14
relays 222, it should be appreciated that such arrangement is by
way of example only, and any suitable arrangement of relays on the
board 210 may be provided.
[0042] Electric inputs (not shown) to relays 212 in the relay
modules 214 of assembly 200 can be switchably connected to test
points on a device under test 150 (FIG. 1). In some embodiments,
assembly 200 may be mounted within tester 110 (FIG. 1) so that
inputs on the relay matrix assembly electrically connect to tester
channel contacts exposed at tester interface 131. By switching the
relays within the relay matrix assembly, a selected tester channel
contact may be quickly connected to a tester resource to generate
or analyze test signals. In some embodiments, board 210 may be a
multi-level PCB. Relays 212 may be arranged on either or both
surfaces of the board 210.
[0043] Assembly 200 may be physically integrated into test
configuration 100 in any of multiple ways. In some embodiments,
board 210 may have a number of contacts arranged in a pattern that
physically matches to a distribution of tester channel contacts at
the tester interface 131. In such an embodiment, the assembly 200
may be attached to a tester interface 131, and electrical
connection may be made to each of the tester channel contacts on
the tester head through the input contacts of the assembly 200.
[0044] In other embodiments, and as depicted in FIG. 2C, assembly
200 may be a channel card or other instrument installed in one of a
plurality of slots 292 of a test system enclosure 290. In such an
embodiment, contacts on board 210 of the relay matrix assembly may
be arranged to be electrically and mechanically coupled to
corresponding contacts within the slot 292. These contacts may, in
turn, be connected to other assemblies mounted in other slots 292
and/or other components inside or outside tester 110, such that
power, ground reference voltage, analog and digital test signals,
as well as control signals may be communicated between assembly 200
and other components of the tester configuration 100. In some
embodiments, slot 292 of test system enclosure 290 may provide
connection to one or more buses in accordance with any suitable
communication techniques. The buses may configured to carry power,
ground reference voltage, analog and digital test signals between
assembly 200 and other components so as to enable the functions
described herein to be performed.
[0045] One such other component is a timing component that
synchronizes operation of the other components. In accordance with
some embodiments, timing components may distribute timing signals
to all of the assemblies in slots 292 and/or other components such
that the components may operate in a coordinated manner during a
test of a device under test. As a specific example, some components
may execute test systems instructions as part of a test program
loaded into tester 110. The instructions may be executed at times
defined by tester cycles. For example, one instruction may be
executed per tester cycle. The tester cycles may be numbered
consecutively from a start event, such as the start of a test, and
this numbering may create a time stamp for each instruction. As
other components similarly have access to these timing signals, the
timing of other events triggered or detected by other components
can similarly be indicated relative to these timing signals,
including the time stamps. As described below, the timing of
detected hot-switching events may be indicated in this way
[0046] Referring again to FIG. 2A. Relays 212 may be mechanical
relays with opposing contacts that close or open in response to
control signals received at contacts on the relay matrix assembly.
Hot-switching in a relay may occur when opposing contacts within
the relay are closed and/or opened while a voltage difference
exists across the opposing contacts. Components may be integrated
into test environment 100 to detect such hot-switching and output
information on the cause of a hot-switching event. Those components
may include antennae to receive and respond to electromagnetic
radiation emitted by a relay that is hot-switched.
[0047] As shown in the exemplary assembly 200 in FIG. 2A, a
plurality of antennae 222 are positioned adjacent the relays 212
within relay module 214, and oriented to receive electromagnetic
radiation emitted by hot-switching within the relay module 214. Any
suitable form of antennae may be used. For example, the antennae
may be implemented as dipoles, spirals or other patch antennae on a
printed circuit board (PCB) on which the relays are mounted. It
should be appreciated that while six antennae are shown in FIG. 2A,
six is not a requirement. Any number of antennae, including a
single antenna, may be placed adjacent one or more relays to detect
hot-switching events. Antennae may be placed adjacent a portion, or
all of the relays on board 210. For example, while FIG. 2A
illustrates antennae only adjacent one of the relay modules 214, it
should be appreciated such illustration is by way of example of
only and that additional antennae may be provided.
[0048] The antennae may be arranged in any suitable distance and
orientation for picking up hot-switching electromagnetic radiation
emissions within the relays. For example, the antenna may be
oriented such that a long axis of the antenna is parallel to a long
dimension of a relay under test, which may correspond to an
elongated dimension of the contacts where they contact inside the
relay. In some embodiments, the antenna may be a dipole antenna
having a long axis with an angle of up to 45.degree. from, and
preferably aligned with the current signal direction across a
relay. The antennae may be mounted on any suitable substrate that
is near the relays, including on PCB 210, itself. However, in the
embodiment illustrated, the antennae are mounted on a separate
PCB.
[0049] FIG. 2B is an isometric view of the assembly in FIG. 2A,
according to some embodiments. FIGS. 2A and 2B illustrate an
exemplary embodiment where antennae 222 are arranged on a surface
of PCB 220 that is parallel and facing the surface of board 210
where relay modules 214 are located. Arranging the antennae
generally in a plane parallel to the surface of board 210 may allow
an antenna to be sensitive to electromagnetic emissions from more
than one relays on the surface of the board 210. Arranging PCB 220
to be parallel to board 210 may also reduce the overall package
thickness of the relay matrix assembly in a direction normal to the
surface of board 210. For example, board 210 may be kept close to
PCB 220 such that the assembly 200 may still fit within a slot 292
of the test system enclosure 290, without interfering with
components located in adjacent slots, either electrically or
mechanically. Any suitable method may be used to couple PCB 220 to
board 210. For example, the assembly 200 may include couplers 226
as shown in FIGS. 2A, 2B. Couplers 226 may be mechanical fasteners,
while any suitable techniques may be used to couple 220 to 210,
such as but not limited to coupling by adhesive, soldering, or
wafer bonding.
[0050] In some embodiments, PCB 220 may also include a circuitry
224 that is coupled to antennae 222, as shown in FIG. 2A, 2B.
Circuitry 224 comprises components that receive and process signals
from antennae 222. The components may be configured to perform
analog processing, such as noise reduction, signal attenuation,
amplification, filtering, and envelope detection; and digital
processing such as digitization or pattern matching. Other
processing may also be performed.
[0051] While not shown, PCB 220 may include traces and contact
points such as pads for circuitry 224 to be connected electrically
with components on board 210 or external to the assembly 200. The
communication may include power and ground reference voltage,
analog and digital signals, as well as control signals. The
specific mechanism for that electrical communication is not
critical to the invention. Electrical connectors, for example, may
connect PCB 220 to PCB 210, such that electrical signals may be
coupled through the interfaces between PCB 210 and other components
within the test system. Alternatively or additionally, interfaces
may be provided from PCB 220 to other components, such as through
cables or other suitable connection technologies.
[0052] Electrical communication between antennae 222 and other
components of tester 110 enables processing of signals from
antennae 222 to be performed in any suitable location. In some
embodiments, at least some analysis is performed within circuitry
224 similarly mounted to PCB 220.
[0053] FIG. 3 depicts an analysis circuitry 300, some or all of
which may be within circuitry 224 or in any other suitable
location, that analyzes signals received from the antennae to
determine whether at least one of the one or more of the antennae
is outputting a signal waveform that has a characteristic
associated with a hot-switching event, according to some
embodiments. As shown in FIG. 3, signal waveforms 321 generated at
one or more antennae 222 may be amplified at the output of an
amplifier unit 332. Other processing may be performed by amplifier
unit 332. For example, the amplified signal waveforms may be gain
adjusted, such as with an attenuator or other suitable gain control
circuit.
[0054] The resulting signal waveforms may be processed at an
envelope detector 334 to detect an envelope 331 of a ringing
signal, as would be induced in an antenna exposed to
electromagnetic radiation from a hot-switching relay, in the time
domain. In some embodiment, the envelope detector may be configured
to discriminate a hot-switching induced ringing signal from noise
based on characteristics of the envelope, such as its duration,
peak amplitude, and/or pattern of peaks as compared to known
characteristics of signals known to indicate a hot-switching event.
Relevant characteristics may be determined in any suitable way. In
some embodiments, the envelope 331 may be sampled and then
digitized at a digitizer 336. Selected digitized samples may be
captured as a representation of a hot-switching event and these
digitized samples may be analyzed at one or more processor 338 to
determine whether the captured event is a hot-switching event. For
example, when an output of an envelope detector indicates a
hot-switching event occurred, a number of digital values,
representing a time window around the event, may be captured for
subsequent processing. The subsequent processing may determine
which relay hot-switched, compute the magnitude of the
hot-switching or serve other purposes, such as to confirm that the
event was a hot-switching event.
[0055] In some embodiments, one or more components of the analysis
circuitry 300 shown in FIG. 3 may be arranged on the PCB 220 and
coupled to antennae 222 as shown in FIG. 2. For example, amplifier
unit 332 and envelope detector 334 may be disposed on the same PCB
and close to antennae 222, to reduce noise and attenuation in the
measured signal waveform. Processor 338 may be external to the PCB
220 and coupled to an output of circuitry on PCB 220 by conductors
such as wiring or cables, although such arrangement is not a
requirement. Digitizer 336 may be located on a separate assembly
with process 338 or may be located on PCB 220, depending on whether
the signals area communicated in analog or digital form from PCB
220. It is not a requirement that the components of analysis
circuitry 300 be located on any specific assembly. In some
embodiments, all the components of analysis circuitry 300 including
digitizer 336 and processor 338 may be disposed on the PCB 220 to
reduce component foot print and increase signal to noise ratio.
[0056] FIG. 4 depicts an exemplary implementation of analysis
circuitry 300, according to some embodiments. In FIG. 4, signal
waveforms 421 picked up at one or more antennae 222 may be
amplified at an amplifier unit 432 configured to process and
amplify electromagnetic signal waveforms that are characteristic of
a hot-switching event.
[0057] The inventors have appreciated and recognized that during
hot-switching in a relay having opposing metal contacts with a
voltage across, the metal contacts may approach each other at a
rate of for example approximately 8 atom diameters per nanosecond.
While the contacts are closing in, asperities on opposing surfaces
of the contacts become vaporized until sufficient asperities are
molten or through other processes that may happen during such
events such that an electrical connection can be completed and held
in the two contacts to reduce the voltage across. Such a "hot"
connection process tends to generate a short, .ltoreq.75 ps
duration connection that may cause an electromagnetic voltage
gradient and magnetic field having high frequency components which
is captured by one or more of the antennae adjacent the relay. The
antennae, in response, initiate a voltage oscillation at a tuned
resonance frequency with an amplitude that decays over time. Such
oscillation is referred to as "ringing," and the tuned frequency of
the antenna is referred to as a ringing frequency.
[0058] According to an aspect of the present application, the
antennae 222 may be tuned to be more sensitive to electromagnetic
radiations from relay hot-switching events, compared to
electromagnetic signals that are not related to hot-switching. The
antennae may have a ringing frequency in a range that overlaps the
frequencies of electromagnetic radiation from hot-switching events,
while the range is outside of frequencies of signals propagation in
components of the test system. The ringing frequency may be between
1-5 GHz. In the example shown in FIG. 4, the antennae are
configured such that the ringing frequency is 2.2 GHz, which is
above the frequency of propagating signals in the test system
components. In such a configuration, the antennae may selectively
generate signal waveforms representing the short duration
electromagnetic radiations from hot-switching events, while being
relatively insensitive to other signals, thereby reducing false
positives.
[0059] Other techniques may alternatively or additionally be used
to increase the ability of the antenna and/or other circuitry to
discriminate electromagnetic radiation associated with a relay
hot-switching. For example amplifier unit 432 or additional
circuitry (not shown) to may be used to provide selective screening
on the received electromagnetic radiation, for example by rejecting
noise signals or signals having relatively amplitude lower than a
noise threshold, such that signal waveforms 421 are selectively
generated to represent hot-switching events that occur in the
relays. Based on the measured signal waveforms, aspects of the
present application may provide a determination of the timing
and/or relay location responsible for one or more hot-switching
events, and in turn identify the one or more instructions in the
test program as a cause for the hot-switching events.
[0060] The inventors have recognized and appreciated that the
signal waveforms with ringing frequency on the order of multiple
GHz would require large, complex and/or expensive high-bandwidth
electronic components for further processing, and that a signal
down conversion may be provided to generate a lower bandwidth
representation of the signal waveforms. In one aspect, a signal
envelope may be generated with an envelope detector, such as
envelope detector 334 as shown in FIG. 3 for each single waveform.
The envelope detector may generate an envelope of the component of
the output of the antenna representative of the antenna "ringing"
excited by a relay hot-switching. FIG. 4 illustrates another
exemplary embodiment with an envelope detector 434.
[0061] In the embodiment shown in FIG. 4, relay hot-switching
related emission induces a signal waveform 421 of antenna 222,
amplified with an amplifier 444, gain adjusted with an attenuator
446, further amplified with another amplifier 448 and sent to an
envelope detector 434, which generates a representation of the
envelope of the ringing signal. In the illustrated embodiment, that
representation may be a pulse 431 representing a signal envelope of
the ringing signal waveform 421. Pulse 431 may have an amplitude
that varies in proportion to the amplitude of the signal envelope.
Pulse 431 may have a pulse width sufficient to enable detection of
the ringing signal with relatively compact and low cost circuitry
in comparison to circuitry required to detect a much shorter pulse
of electromagnetic radiation emitted by a relay hot-switching. The
pulse width of the envelope of the ringing signal, for example, may
be between 1 and 20 ns. For example, the pulse width may be 2 ns or
more.
[0062] Thus the envelope detector 434 provides a greater than 2 ns
wide pulse in the signal envelope based on the fast ringing signal
waveforms 421 from antennae 222. This represents a pulse widening
of more than 20 times compared to the short, .ltoreq.75 ps
radiation pulse radiation in the hot-switching event. Such pulse
widening may present several advantages. For example, the wide
pulse of the signal envelope may be relatively easily digitized
without requiring expensive and complex circuitry. In some
embodiments when the analysis circuitry 300 shown FIG. 4 is
implemented as part of assembly 200 in the form of a channel card
as shown in FIG. 2C, the wide, 2 ns or more pulse width of the
signal envelopes generated by the envelope detectors may be
transmitted easily out of the confined space between slots 292
using a suitable lower bandwidth technique. For example, flexible
cables may be used without the need for relatively complex and
bulky transmission lines.
[0063] In the embodiment illustrated, the envelope signal is
further processed in digital form. In this embodiment, each pulses
431 is sent to an Analog to Digital Convertor (ADC) 436 to be
digitized at a sampling rate that provides a sufficient number of
samples for further analysis of the pulse in digital form. In some
embodiments, the signal envelopes are sampled at the ADC at a
sampling period between 0.1 ns and 1 ns. As a specific example,
sampling may generate 1.8 GS/s.
[0064] The digitized pulse waveform is received by a processor, in
this example implemented within an FPGA, which analyzes the signal
envelope within the digitized pulse waveform to determine
characteristics associated with hot-switching events. As shown in
FIG. 4, multiple antennae may be present in a test system, each
having a different position relative to relays being monitored for
hot-switching. The outputs of each antenna may be processed as
described above to generate an envelope of a ringing signal when a
hot-switching relay is close enough to that antenna to induce such
ringing. As a result, there may be one or more envelope signals for
each hot-switching event. Characteristics of the detected envelope
signals may be used for further processing, such as to determine
which relay hot-switched, confirm that hot-switching occurred or
compute the magnitude of the hot-switching event. For such
processing, characteristics of the signal envelopes, such as peak
amplitude, pulse duration, pulse width, and/or pattern of peaks may
be compared to known characteristics of signals known to indicate a
hot-switching event.
[0065] If hot-switching is detected, the FPGA may output an
indication that the hot-switching event was detected. This
information may be provided in a format that enables further
processing in response to an indication of the hot-switching event,
such as correlation to a test system instruction that caused the
hot-switching event.
[0066] In the illustrated embodiment, the FPGA may store
information about hot-switching events detected during a test and
provide an indication of these events after the test is concluded
at other convenient time. This indication may include information
indicating the timing of the event. Accordingly, the FPGA may be
configured to assign a time-stamp and/or save a record of the
signal envelop representing the hot-switching event. When the
measurement period is complete the saved signal envelops may be
transferred to an external processor, such as a computer 452 via an
interface 454.
[0067] Other information may alternatively or additionally be
provided for processing. Signal waveforms having high frequency
resonances may also be saved and transferred to computer 452 via an
interface 450. The computer 452 may reconcile the time-stamp
aligned events, as well as location of antennae to identify a relay
location corresponding to the hot-switching event. Further
processing may also be provided to identify a program instruction
or instructions with the same or similar time stamp as a cause of
the hot-switching event.
[0068] Aspects of the present application are directed to analyzing
a signal waveform output by the antennae to determine whether at
least one of the one or more signal waveforms has a characteristic
associated with a hot-switching event. Examples of such analysis
are described below with reference to FIGS. 5 and 6.
[0069] FIG. 5 depicts a collection of signal waveforms and their
corresponding envelope signals as a result of signals received by
antennae (not shown) placed at different locations of a relay
module 514, according to an embodiment of the present application.
Relay module 514 comprises a plurality of relays 512. A test
program, or test job comprising a plurality of instructions,
including instructions to close or open relays in the relay module
514, is executed by a computer. Signal waveforms 521, 522 . . . 528
are time domain voltage waveforms produced at the output of the
antenna when the antenna was placed above locations 1, 2 . . . 8 of
relay module 514, respectively. Signal envelops 531, 532 . . . 538
are the detected envelopes of signal waveforms 521, 522 . . . 528,
respectively, using for example an envelope detector as discussed
above in FIGS. 3 and 4.
[0070] Using signal waveform 524 and signal envelop 534 as an
example, at time T1, a ringing oscillation is "kicked off" as shown
in waveform 524. At time T2, a pulse 534 begins in the
corresponding signal envelop 534. The ringing oscillation in signal
waveform 524 indicates that a hot-switching event has occurred in
the vicinity of location 4, where waveform 524 is measured. It
should be appreciated that although FIG. 5 shows T2 as having a
delay from T1, the delay may be for illustration purpose only, and
has no bearing on using the time value of T2 as a time stamp for
signal envelope 534. More generally, envelopes from signals output
by each of multiple antennae detected close tougher in time may be
regarded as associated with the same hot-switching event. Those
envelopes may therefore be assigned the same time stamp, which may
be assigned based on the time of occurrence of just one or multiple
of such envelope signals.
[0071] Antennae near locations 2, 3, 6 and 7 as shown in FIG. 5 are
located close to location 4, and signals from a relay near location
4 may be picked up by those antennae. Other processing may be
performed when signals picked up from multiple antennae indicate
hot-switching to determine which relay experienced a hot-switching
event. In a simple example, the signal envelope picked up with an
antenna at location 4 has the largest peak amplitude in about the
same time frame around any of the signal envelopes picked up with
locations 2, 3, 6 and 7, which may be an indication that a relay
located closer to location 4 than locations 2, 3, 6 and 7 is
responsible for the signal envelope at time stamp T2. Signal
envelope 534 may then be selected for further processing as
representing hot-switching in such a relay. However, an
antenna--though close to a relay may be on the opposite side of the
PCB from the relay or otherwise separated from the relay by
components that attenuates to the effect of the radiation from hot
switching on an antenna. The inventors have recognized that there
can be wide variability of peak amplitude by the closest antenna to
a relay that hot-switched. Accordingly, other information may be
used in combination with envelope information to determined which
relay hot-switched. As another example, other information, such as
program instructions executed at the time may be used to determine
which relay had a hot-switching event.
[0072] In other embodiments, the location of a relay having a
hot-switching event may be identified in other ways. For example,
the magnitude of multiple peak amplitudes in signal envelopes at
various locations may act as a signature characterizing a
particular relay. Such patterns may be identified by measuring
signals as part of a calibration process when hot-switching is
intentionally induced. Once the pattern of peak amplitudes of the
envelopes of ringing signals from multiple antennae is determined,
it may be compared to pre-stored patterns similarly measured when
each of multiple relays was intentionally hot switched during a
calibration phase. As a specific example of such a comparison, a
pre-stored pattern with the highest correlation to the measured
pattern of envelopes of ringing signals during a hot switching
event may be selected. The relay associated with the selected
pre-stored pattern may be indicated as the relay undergoing
hot-switching.
[0073] It should be appreciated that any reasonable measurable
indication of a hot-switching event may be selected as a
characteristic associated with a hot-switching event. More than one
type of characteristics may also be used in combination. For
example, some relays will generate more than one pulse in the
signal envelope during hot-switching events, due to asperities in
opposing relay contacts first becoming vaporized, and later
followed by a more complete connection for a second time, while a
voltage exists across the contacts. Such behavior may manifest in
two or more pulses in the signal envelopes, each pulse separated by
a relatively long period of pulse interval, such as 3-50 ns.
Patterns as such in signal envelopes may be used as a
characteristic sign of hot-switching events and may be used alone
or in addition to other characteristics associated with
hot-switching.
[0074] In some embodiments, peak amplitude in one or more detected
signal envelopes may indicate a magnitude of the relay
hot-switching event. For example, once a relay is identified as the
source of hot-switching has been detected, the magnitude of a
signal envelope at an antenna may be compared to a pre-stored
magnitude of a signal envelope similarly measured when
hot-switching was intentionally induced in that relay during a
calibration phase. The ratio between the measured magnitude and the
pre-stored magnitude may serve as a scale factor. During the
calibration phase, the relay may have a known voltage across it
during hot-switching. To determine the magnitude the detected
hot-switching event, the known calibration voltage may be
multiplied by that scale factor. Such an approach may work for any
suitable measure of envelope magnitude, such as peak amplitude,
average amplitude, or RMS amplitude. Moreover, as described above,
a hot-switching event may induce a pattern of signal envelopes at
more than one antennae, both during operation of a test system to
detect hot-switching and during calibration. In some embodiments, a
scale factor may be computed by comparison of patterns of multiple
signal envelopes.
[0075] According to an aspect, magnitude of a relay hot-switching
event may be useful in a number of ways. For example, a higher
voltage difference across the relay contacts may generate a higher
peak amplitude in signal envelopes picked up by an antenna during
hot-switching in the relay. Therefore the magnitude may be used as
an indication of the voltage difference during hot-switching. As
risk for permanent hardware damage increases with the voltage
difference across the relay contacts, a higher hot-switching
magnitude may warrant higher degree of concern, and may, in some
embodiments, be highlighted so that the cause of the hot-switching
is identified and mitigated. In some embodiments, relay
hot-switching with a low magnitude may be ignored when the
associated voltage difference is not likely to cause significant
reliability concerns. A calibration may be performed to correlate
the measured peak amplitudes in the signal envelope to voltage
difference across a relay during hot-switching, for example, by
measuring under conditions in which hot-switching is intentionally
introduced with a known voltage difference across the relay.
[0076] Peak amplitude measured under these known hot-switching
conditions can serve to calibrate the processing apparatus to
generate a calibration value that can proportionally convert a
measured peak amplitude to voltage across the relay during
hot-switching. A calibration value may be generated for a relay and
an antenna used for the measurement during calibration. In the
example shown in FIG. 5, a calibration value may convert the peak
amplitude of 60 mV in signal envelope 534 to a magnitude of 5 V
across a relay within relay module 514. As a result, geometric
factors such as distance and relative alignment of an antenna
relative to a relay may be corrected by the calibration value when
interpreting peak amplitude of signal envelopes measured in an
antenna. For example, different calibration values may account for
differences in scenarios when an antenna measuring hot-switching
events from a relay located on the side of a PCB facing away the
antenna generates a weaker signal compared to a relay on the
antenna-facing side of the PCB, given the same magnitude of the
hot-switching event.
[0077] According to an aspect, one goal of identifying
hot-switching events is to identify instructions in the test job
that cause the hot-switching, such that the culprit instructions
may be corrected to prevent future hot-switching. An instruction in
the test program, changing the state of a relay, may execute at a
particular time when a voltage exists across a relay at a
particular location. Therefore two analysis of the identified
hot-switching event, based on time and location, may help identify
the culprit instructions.
[0078] To identify culprit instructions by time, the measured time
stamp of signal envelopes may be correlated with a time value
related to the test instructions. For example, T2 of the onset of
signal envelope pulse 534 in FIG. 5 would be correlated to
instructions executing at a time corresponding to the same time T2.
The correlation may take into account delays between execution of
an instruction and actuation of a relay as well as delays between
actuation of a relay and detection of electromagnetic radiation
indicating a hot-switching event at one or more antennae.
[0079] Such a correlation may be performed in any suitable way. In
embodiments in which instructions are identifiable with an
execution time stamp, correlation may be performed by recording a
time stamp for detection of a hot-switching event. The time stamps
recorded for test instructions execution and those recorded for
hot-switching event detection may be synchronized in any suitable
way. As an example, synchronization pulses may be sent with known
intervals to start the ADC time-stamps and then mark initial and
completion time markers in the measured signal envelopes. The
synchronization pulses may be sent when certain test program
instructions are being executed. These time stamps enable alignment
between the ADC captured values as well as the computer time stamps
for program instructions.
[0080] Because locations of relays being controlled by a test
instruction is generally known, such information may be used in
combination with spatial measurements to facilitate identification
of culprit instructions that cause hot-switching. In general,
hot-switching from a particular relay will generate higher
amplitude signal in an antenna that is closer to the relay.
Therefore when a hot-switching event detected in multiple antennae
will generally show a decaying envelope peak amplitude when
measured away from the "epi-center" of the culprit relay. Culprit
relays may, for example, be identified as most probably the relays
nearest to the location measuring the highest envelope amplitudes.
A further comparison using the time stamp of the hot-switching
event, in relation to the test instruction time values, may provide
a more accurate indication of which relay and which instruction
causes hot-switching events. An example of spatial measurement is
shown in FIG. 5, where the peak amplitudes in signal envelopes 534,
538, 533, 536, 531 and 535 generally decrease in that order when
the antenna location moves farther away from location 4 at the
bottom of the figure. In this example, the culprit relay may be
identified as most probably one of the relays nearest location
4.
[0081] The inventors have recognized and appreciated that each
relay within a relay module may be different, and may generate
substantially different amplitude of electromagnetic waves during
hot-switching. For example, there may be a 10:1 variation between
relays on the under-side of a board 210 facing away from the PCB
220 having antennae, compared with relays facing nearby antennae.
Therefore a weak peak in the signal envelope does not necessary
result from a remote relay from a measuring antenna. To enable
recognition of hot-switching events despite such variation, the
test system according to an aspect of the present application may
apply calibration values determined for each relay in the relay
module, such that signal amplitudes picked up by an antenna
adjacent particular relays may be scaled by the calibration values.
A calibration value may be a gain and/or offset factor applied to
measured signal waveforms more accurately report the relay
hot-switch level despite differences in strength of the signal
picked up by an antenna. These calibration values may be applied to
subsequent measurements, such as by the circuitry in FIG. 4. These
values may be applied to the analog signals, such as by adjusting
the gain of amplifiers 444 or 448 and/or attenuation of attenuator
446. Offsets my similarly be applied in the analog components, but
offsets, and other calibration values, may alternatively or
additionally be applied in digital processing circuitry.
[0082] The calibration values may be determined for relay-antenna
pairs using the closest antenna to that relay or for each of
multiple close antennae, such as the closest, two, three, four,
etc. antennae. Alternatively or additionally, the relay-antenna
pairs may be selected for each relay based on the antennae expected
to pick up the largest from the relay. Calibration values may be
computed from measurements taken under which hot-switching is
intentionally induced. The calibration values may be determined as
parameters, such as gain and offset, that normalize a signal
received from a relay at a particular antenna to a specific peak
amplitude and offset. With these calibration values applied to
signals picked up during a test, the signals picked up by each
antenna may be compared to the same threshold to determine whether
the signal picked up at a particular antenna represents a hot
switching event at a particular relay.
[0083] Calibration values may be determined after taking multiple
measurements and averaging, with or without other statistical
processing, such as discarding outliers. In some embodiments, the
calibration values may be determined by calculation, such as by
computing the gain and offset or values of other calibration
parameters that normalize a signal. Alternatively or additionally,
the calibration values may be determined by adjusting the
calibration parameters until the normalized signal results.
[0084] In some embodiments, the test job having the same test
instructions may be run multiple times to collect a statistical
significant sample for relay activities. In a production
environment, a test job may be repeated on multiple devices under
test successively as those devices are manufactured. Data may be
collected over a portion of a production run to indicate that
hot-switching occurred. Alternatively or additionally,
hot-switching might be detected during qualification of a test
program or at any other suitable time in which the test job is run
on the same device.
[0085] Additionally, the test job may be repeated with the
processing circuitry calibrated to detect signals representative of
hot-switching events at different relays during different
repetitions of the test job.
[0086] Alternatively or additionally, processing of signals
received from each of multiple antennae may increase confidence in
detection of a hot-switching event and/or identify a relay giving
rise to a hot-switching event. In some embodiments, the signals
measured at each of multiple antennae may indicate which of
multiple relays in a test system experienced a hot switching event.
Such a determination may be made by using information about the
configuration of the test system. The configuration, including
locations of relays and antennae and components between the relays
and antennae, impacts characteristics of the signal received at an
antenna. The impacted characteristics may be, for example,
amplitude and timing of the received signal. In some embodiments,
the impacted characteristics are the same characteristics for which
calibration values are determined. For example, gain and offset
calibration values should be inversely related to amplitude and
timing of the received signals. This variation is illustrated, for
example, in FIG. 5. Hot-switching of a relay near location 4
produced a signal envelope 534 with a relatively large peak
amplitude, starting at time T2. Different antennae picked up
different signal envelopes 532, 533, 536, 537 and 538 with
different peak amplitudes and times of arrival. The pattern of peak
amplitude and times of arrival may be correlated to a specific
relay near location 4 such that a specific relay may be located by
correlating the received signals to known patterns produced for
specific relays.
[0087] In some embodiments, the known patterns may be determined by
a calibration process as described above. Applying the inverse of
the calibration values for a specific antenna-relay pair to a
measurement at that antenna yields an estimate of the hot-switching
signal at the specific relay, if that relay had been responsible
for the hot-switching event. By repeating this computation for each
of multiple relay-antenna pairs, an estimate of the hot-switching
signal at each relay can be made for each of multiple antennae. If
a relay is responsible for a hot-switching event, the estimates for
each of the multiple antennae should be consistent. A low variance
of the estimated hot-switching signal at each relay made for each
of multiple antennae indicates the relay likely emitted the
hot-switching signal. In some embodiments, the relay for which the
lowest such variance is computed may be deemed the relay that
caused a hot-switching event. Alternatively or additionally, a low
variance, below a threshold, increases a confidence that a
hot-switching event occurred, and indication of a hot-switching
event, in some embodiments, may be conditioned on a variance below
a threshold.
[0088] In some embodiments, processing to identify hot-switching
may be repeated multiple times to determine whether any of the
relays in a test system is hot-switching. In each repetition, the
analysis circuitry may be configured based on calibration values
for a different specific relay. In this way, hot-switching at each
of multiple relays may be simply detected.
[0089] Some of the processing and analyzing signal waveforms to
identify instructions that cause hot-switching events may be
performed on the same PCB as the antennae or may be on a separate
printed circuit board connected to the antennae via one or more
cables. In other embodiments, some of the processing components may
be outside the tester, such as in a computer coupled to the tester
through a wired or wireless interface, such as, for example,
computer 452 shown in FIG. 4. An example of a computer 600 is
depicted in FIG. 6, according to some embodiments. According to
some embodiments, a computer may include machine-readable
instructions stored in memory that are executed on at least one
processor to manage operation of one or more components of the test
system.
[0090] As an example, a computer 600 may include at least one
processor 610 a, 610 b and related hardware. The at least one
processor may be configured to control and provide user interaction
for operating the device. The at least one processor may be used in
combination with memory devices 620 a, 620 b. The memory may
include any type and form of RAM-type memory device and ROM-type
memory device. A memory device may store machine-readable
instructions that can be loaded onto and executed by the at least
one processor to specially adapt the at least one processor to
perform functionality defined by the machine-readable instructions.
When in operation, an operating system may execute on at least one
processor and provide for user interaction and operation of an
instrument, which may include running multiple software
applications and/or programs on the processing system.
[0091] According to some embodiments, a processor 610 a, 610 b may
comprise any type and form of data processing device, e.g., any one
or combination of a microprocessor, microcontroller, a digital
signal processor, an application specific integrated circuit
(ASIC), and at least one field-programmable gate array (FPGA).
There may be more than one processor in the system in some
embodiments, e.g., dual core or multi-core processors, or plural
processors communicating with at least one controlling processor.
In some implementations, there may be a single processor in the
processing system.
[0092] An instrument that includes the computer 600 may further
include a display 640 (e.g., comprising any one or combination of a
video monitor, an LCD display, a plasma display, an alpha-numeric
display, LED indicators, etc.). The instrument may further include
one or more input/output devices 660 in some embodiments (e.g.,
keyboard, touchpad, buttons, switches, touch screen, microphone,
speaker, printer), and communication apparatus 630 (e.g.,
networking software, networking cards or boards, wireless
transceivers, and/or physical sockets). The instrument may include
device drivers, e.g., software modules specifically designed to
execute on the one or more processor(s) and adapt the processor(s)
to communicate with and control system components. In some
embodiments, the processing system may include
encryption/decryption hardware and/or software 670 that may be used
to encrypt selected outgoing data transmissions and decrypt
incoming encrypted data transmissions. Components of an instrument
in which the processing system is located may communicate over a
bus 605 that carries data and control signals between the
components. The bus may provide for expansion of the system to
include other components not shown in FIG. 6.
[0093] The technology described herein may be embodied as a method.
FIG. 7A is a flow chart of a method 700 for operating a test system
for hot-switching detection, in accordance with some embodiments.
As shown in FIG. 7A, method 700 begins at act 702 by executing a
test job having instructions to control a plurality of relays in
the test system to open or close. At act 704, signals from one or
more antennae placed adjacent the plurality of relays are
collected. The signals may represent ringing induced by
electromagnetic emissions during hot-switching events from the
relays. The collected signals are analyzed at act 706 to determine
a characteristic of the collected signals. The analyzing may be
performed using any of the techniques as described in embodiments
above, including but not limited to with an analysis circuitry 300
as shown in FIG. 3. If it is determined at act 708 that a
characteristic associated with hot-switching is present, captured
data such as the time stamp of the hot-switching event and a
corresponding relay location may be captured and saved, such as in
a computer. The method at act 712 may go back to the test job
execution at 702 and repeat hot-switching detection as described in
acts 702-708, to test a full range of instructions written in the
test program for the test job. In some embodiments, the same test
job may be repeated more than once, to create a statistical picture
of hot-switching events. In some embodiments, components in an
analysis circuitry 300 may have their setting parameters readjusted
during a repeat, such that a gain/offset setting for a new
antenna/relay pair will be selected during acts 704 and 706. At act
714, upon collection of data for all relays, data representing
hot-switching events detected are analyzed at act 714 for each of
multiple relays to determine which of relay or relays was the
source of the hot switching. At act 716, the method identifies the
particular instructions in the executed test job as a cause for the
hot-switching event, by for example comparing time stamps of the
hot-switching event, locations of the hot-switching relays, with
execution times of the instructions. Once cause for hot-switching
is identified, the instructions may be adjusted at act 718, by for
example rewriting the instructions to maintain both contacts of
each relay are of the same voltage potential prior to the relay
switching.
[0094] FIG. 7B is a flow chart of a method 806 that is an exemplary
implementation of act 706 as shown in FIG. 7A, according to some
embodiments. In act 810, each collected signal waveforms may be
analyzed, for example using analysis circuitry 300 of FIG. 3, to
generate a signal envelope based on the signal waveform. The signal
envelope is further processed to determine a peak amplitude as the
characteristic that is associated with a hot-switching event.
[0095] Additional calibrations may be performed by an operator
prior to operating the test system for hot-switching detection.
FIG. 7C is a flow chart of a method 900 that is an exemplary
calibration method, according to some embodiments. At act 910,
relay-antenna pairs are measured to derive calibration values for
one or more calibration parameters, such as by measuring signal
envelopes corresponding to emissions from relays closest to an
antenna, when the relays are intentionally instructed to exhibit
hot-switching. Calibration values, such as gain and offset, that
normalize a signal received from a relay at a particular antenna to
a specific peak amplitude may be determined at this act.
Subsequently, at act 920, an analysis circuitry may be configured
with the determined calibration values, prior to beginning of the
hot-switching detection operation in the method 700.
[0096] The acts performed as part of the method may be ordered in
any suitable way. Accordingly, embodiments may be constructed in
which acts are performed in an order different than illustrated,
which may include performing some acts simultaneously, even though
shown as sequential acts in illustrative embodiments. Additionally,
a method may include more acts than those illustrated, in some
embodiments, and fewer acts than those illustrated in other
embodiments.
[0097] Having thus described at least one illustrative embodiment
of the invention, various alterations, modifications, and
improvements will readily occur to those skilled in the art.
[0098] For example, processing is described in connection with a
single antenna. Similar processing may be performed for each of
multiple antennae. The processing, for example, may enable
detection of hot-switching events in relays installed over a wider
area than could be detected with a single antenna. Alternatively or
additionally, signals output from multiple antennae may be used to
more reliably detect a hot-switching event by correlating signals
such that a hot-switching event is indicated when multiple antennae
detect the same signal characteristic of a hot-switching event.
[0099] As another example, it was described that hot-switching of
relays on a single assembly 200 was identified. A test system may
include multiple assemblies with relays and the processing as
described herein may be performed for each such assembly. Such
processing may be performed in parallel or may be performed
sequentially.
[0100] As yet another example, hot switching was described as being
detected to identify instructions in a test system program that
caused unintended hot-switching. Such processing was described as
enabling changes of the test program. Such information may be used
for other purposes, such as to track the number of hot-switching
cycles that a relay is exposed to and to plan maintenance of a test
system accordingly.
[0101] Further, processing was described to identify a specific
relay of a plurality of relays that is hot-switching at a specific
time. In some embodiments, an indication that a relay hot-switched
during a test job or at a particular time during a test job,
without an identification of a specific relay that hot-switched may
be useful. In such an embodiment, analysis to identify a specific
relay may be omitted.
[0102] Such alterations, modifications, and improvements are
intended to be within the spirit and scope of the invention.
Accordingly, the foregoing description is by way of example only
and is not intended as limiting. The invention is limited only as
defined in the following claims and the equivalents thereto.
* * * * *