U.S. patent application number 09/184105 was filed with the patent office on 2001-05-24 for method and apparatus for automatically acquiring a waveform measurement.
Invention is credited to FELPS, JIMMIE D..
Application Number | 20010001849 09/184105 |
Document ID | / |
Family ID | 22675570 |
Filed Date | 2001-05-24 |
United States Patent
Application |
20010001849 |
Kind Code |
A1 |
FELPS, JIMMIE D. |
May 24, 2001 |
METHOD AND APPARATUS FOR AUTOMATICALLY ACQUIRING A WAVEFORM
MEASUREMENT
Abstract
A method and apparatus for automatically acquiring and storing a
waveform measurement using a measuring instrument having a video
display, such as an oscilloscope or spectrum analyzer, is
disclosed. According to the invention, an operator first instructs
the measuring instrument to automatically measure a probed waveform
one or more times and to automatically store at least one selected
sample set representing each probed waveform measurement.
Thereafter, the operator is not required to interact with the
measuring instrument during a measurement or series of
measurements. Once measurement acquisition and storage is
automatically completed, the measuring instrument alerts the
operator by providing at least one indication for each selected
sample set stored. The invention offers several advantages, for
example, by allowing the operator to focus on a measurement probe
in contact with a waveform source, instead of diverting his or her
attention to observe the graphic display or otherwise interact with
the measurement instrument during one or more measurement
operations.
Inventors: |
FELPS, JIMMIE D.; (COLORADO
SPRINGS, CO) |
Correspondence
Address: |
IP ADMINISTRATION
LEGAL DEPARTMENT 20BN
HEWLETT-PACKARD COMPANY
PO BOX 10301
PALO ALTO
CA
943030890
|
Family ID: |
22675570 |
Appl. No.: |
09/184105 |
Filed: |
November 2, 1998 |
Current U.S.
Class: |
702/66 ;
702/67 |
Current CPC
Class: |
G01R 13/345
20130101 |
Class at
Publication: |
702/66 ;
702/67 |
International
Class: |
G01R 013/02; G06F
019/00 |
Claims
What is claimed is:
1. A waveform measuring apparatus, comprising: an automatic
acquisition module to automatically acquire at least one sample set
of a probed waveform during a waveform acquisition period; a memory
to store each at least one sample set; a video display to display a
representation of the probed waveform based on each at least one
sample set; and a control unit to control the automatic acquisition
module, the memory, and the video display.
2. The apparatus of claim 1, wherein: the at least one sample set
is a plurality of acquired sample sets; the automatic acquisition
module determines at least one selected sample set based on the
plurality of acquired sample sets at an expiration of the waveform
acquisition period; the memory stores each at least one selected
sample set; and the representation of the probed waveform is based
on each at least one selected sample set.
3. The apparatus of claim 2, wherein the control unit includes: an
operator interface module to provide instructions to the measuring
apparatus; and a processor, coupled to the automatic acquisition
module, the memory, the video display, and the operator interface
module, to control the automatic acquisition module, the memory,
and the video display based on the instructions provided by the
operator interface module.
4. The apparatus of claim 3, wherein the operator interface module
includes a plurality of operator inputs to provide the instructions
to the measuring apparatus, the plurality of operator inputs
including a first operator input to specify the waveform
acquisition period.
5. The apparatus of claim 4, wherein the operator interface module
further includes a second operator input to specify an auto-store
delay time between determinations and storage of consecutive
selected sample sets of the at least one selected sample set.
6. The apparatus of claim 4, further comprising an indicator to
provide at least one indication that each at least one selected
sample set is determined and stored.
7. The apparatus of claim 6, wherein each at least one indication
includes at least one audible indication.
8. The apparatus of claim 6, wherein the processor is coupled to
the indicator so as to select one indication from a plurality of
indications, based on the instructions provided by the operator
interface module.
9. The apparatus of claim 3, wherein the automatic acquisition
module includes: a detection module to monitor a parameter of the
probed waveform, detect a change in the monitored parameter, and
wait a predetermined stabilization time for the monitored parameter
to be substantially constant; a sampling module to acquire, after
the predetermined stabilization time, the plurality of acquired
sample sets and to automatically stop acquisitions of the plurality
of acquired sample sets at the expiration of the waveform
acquisition period; and a signal processor to process the plurality
of acquired sample sets to determine a particular selected sample
set of the at least one selected sample set.
10. The apparatus of claim 9, wherein the signal processor includes
a selector to select a last acquired sample set of the plurality of
acquired sample sets as the particular selected sample set, the
last acquired sample set being acquired at the expiration of the
waveform acquisition period.
11. The apparatus of claim 9, wherein the signal processor includes
an arithmetic unit to calculate an average sample set from the
plurality of acquired sample sets as the particular selected sample
set.
12. The apparatus of claim 9, wherein the signal processor includes
a digital processor to filter the plurality of acquired sample sets
to determine the particular selected sample set.
13. The apparatus of claim 9, wherein: the automatic acquisition
module further includes an input and triggering module, the input
and triggering module including: a plurality of waveform channels
to receive a plurality of probed waveforms; and at least one
trigger input to receive an external trigger source; and the
operator interface module includes a plurality of operator inputs,
including: a fourth operator input to select one of the plurality
of waveform channels to provide the probed waveform; and a fifth
operator input to select a trigger source.
14. The apparatus of claim 13, wherein: the monitored parameter is
an amplitude of the probed waveform; the input and trigger module
includes an amplifier for each of the plurality of waveform
channels, each amplifier having a vertical sensitivity; and the
detection module includes an auto-scale module to optimize the
vertical sensitivity of the amplifier associated with the selected
one of the plurality of waveform channels, based on the
amplitude.
15. A waveform measuring method, comprising steps of: automatically
acquiring at least one sample set of a probed waveform during a
waveform acquisition period; and storing each at least one sample
set in memory.
16. The method of claim 15, wherein the step of automatically
acquiring includes steps of: automatically acquiring a plurality of
sample sets of the probed waveform during the waveform acquisition
period; and determining at least one selected sample set based on
the plurality of acquired sample sets at an expiration of the
waveform acquisition period; and the step of storing includes a
step of storing each at least one selected sample set in
memory.
17. The method of claim 16, further including a step of instructing
a waveform measuring apparatus to automatically acquire the
plurality of acquired sample sets and determine and store each at
least one selected set.
18. The method of claim 17, wherein the step of instructing
includes a step of specifying the waveform acquisition period.
19. The method of claim 18, wherein the step of specifying the
waveform acquisition period includes a step of specifying the
waveform acquisition period as a predetermined measurement
time.
20. The method of claim 18, wherein the step of specifying the
waveform acquisition period includes a step of specifying the
waveform acquisition period as a predetermined count of acquired
sample sets.
21. The method of claim 17, wherein the step of instructing
includes a step of specifying an auto-store delay time between
determinations and storage of consecutive selected sample sets of
the at least one selected sample set.
22. The method of claim 17, further including a step of indicating
that each at least one selected sample set is determined and
stored.
23. The method of claim 22, wherein the step of indicating includes
a step of audibly indicating that each at least one selected sample
set is determined and stored.
24. The method of claim 22, wherein the step of indicating includes
steps of: specifying an indication mode that assigns a unique one
of a plurality of patterns of indications to a respective one of
the at least one selected sample set being determined and stored;
and indicating the unique one of a plurality of patterns of
indications when the respective one of the at least one selected
sample set is determined and stored.
25. The method of claim 17, wherein the step of automatically
acquiring includes steps of: monitoring a parameter of the probed
waveform; detecting a change in the monitored parameter; waiting a
predetermined stabilization time for the monitored parameter to be
substantially constant; sampling the probed waveform, after the
predetermined stabilization time, to acquire the plurality of
acquired sample sets; and stopping acquisition of the plurality of
acquired sample sets at the expiration of the waveform acquisition
period.
26. The method of claim 25, wherein the step of determining the at
least one selected sample set includes a step of processing the
plurality of acquired sample sets to determine a particular
selected sample set of the at least one selected sample set.
27. The method of claim 26, wherein the step of processing includes
a step of selecting a last acquired sample set of the plurality of
acquired sample sets as the particular selected sample set, the
last acquired sample set being acquired at the expiration of the
waveform acquisition period.
28. The method of claim 26, wherein the step of processing includes
a step of calculating an average sample set from the plurality of
acquired sample sets as the particular selected sample set.
29. The method of claim 26, wherein the step of processing includes
a step of digitally filtering the plurality of acquired sample sets
to determine the particular selected sample set.
30. The method of claim 26, wherein the step of instructing further
includes steps of: selecting a channel of the measuring instrument
on which to measure the probed waveform; and selecting a trigger
source.
31. The method of claim 30, wherein: the step of selecting a
trigger source includes a step of selecting the probed waveform as
the trigger source; and the step of specifying the waveform
acquisition period includes a step of specifying the waveform
acquisition period as a predetermined count of triggers.
32. The method of claim 30, wherein: the monitored parameter is an
amplitude of the probed waveform; and the step of waiting a
predetermined stabilization time includes a step of optimizing a
vertical sensitivity of the selected channel based on the
amplitude.
Description
FIELD OF THE INVENTION
[0001] This invention relates to electronic signal measurement
techniques, and more particularly to a method and apparatus for
automatically acquiring and storing a waveform measurement using a
measuring instrument having a video display.
BACKGROUND OF THE INVENTION
[0002] Several measuring instruments are known in the art which are
commonly used to measure or monitor an electronic signal or
waveform. The electronic signal or waveform may be present, for
example, on any one of the pins of an integrated circuit (IC)
package, or on leads or terminations of various other circuit
components.
[0003] Some measuring instruments, such as digital multimeters,
measure a single signal or electronic component value at a
particular instant of time during a typical measurement operation.
In contrast, other measuring instruments, for example an
oscilloscope or a spectrum analyzer, measure a set of signal values
over a period of time during a measurement operation, wherein the
set of values constitutes a waveform. Hence, for purposes of the
present invention, "signals" are differentiated from "waveforms" in
that the former is represented as a single value, whereas the
latter includes a set of individual signal values at different
instances of time. The present invention is directed particularly
to measuring instruments which have the capability to automatically
acquire and store measurements of waveforms.
[0004] Waveform measuring instruments typically include a video
display for illustrating a two-dimensional temporal or spectral
representation of the measured waveform. For example, an
oscilloscope typically measures and displays the amplitude of a
waveform with respect to time, while a spectrum or network analyzer
processes the amplitude-versus-time information of a waveform to
display the frequency components of the waveform. Some
oscilloscopes may also have the capability to display the amplitude
information of a first waveform on a first axis versus the
amplitude information of a second waveform on a second axis. Hence,
for purposes of the present invention, "video display" refers to a
visual display of a waveform measuring instrument on which at least
one two-dimensional representation of one or more waveforms may be
illustrated. Specifically, each representation displayed by the
video display has at least two axes or "dimensions," for example, a
vertical axis and a horizontal axis.
[0005] Waveform measuring instruments are known which have the
capability to store in memory one or more two-dimensional
representations of probed waveforms for displaying the
representations at some later time. As discussed above, such
waveform measuring instruments must measure and store a set of
signal values to represent a waveform, as opposed to merely
measuring a single value. The process of acquiring and storing a
waveform measurement using such instruments typically requires an
operator to apply, and in some cases hold, a measurement probe to a
waveform source, to watch the graphic display of the measuring
instrument to view the probed waveform, and to wait until the
display indicates that the probed waveform has stabilized. Once the
waveform has stabilized, the operator must often specifically
instruct the measuring instrument to acquire a measurement of the
probed waveform.
[0006] Typically, waveform acquisition is accomplished by
"sampling" the waveform for some period of time, or "waveform
acquisition period." During a waveform acquisition period, the
measuring instrument may collect several "sample sets" of values,
each sample set including a number of individual signal values
necessary to represent the waveform on the video display. For
example, a particular video display may be designed to have a
horizontal resolution of 500 points in a given time frame to
represent a waveform. In this case, each sample set would include
500 individual signal values dispersed in time throughout the time
frame represented on the video display. The waveform acquisition
period is often determined arbitrarily by the operator manually
stopping or "freezing" the acquisitions, perhaps after some desired
number of sample sets have been acquired.
[0007] After the operator instructs the instrument to stop
acquisitions, the operator may in some cases further instruct the
measuring instrument to store one particular or "selected" sample
set representing the probed waveform, based on the acquired sample
sets. This "acquire and store" instruction process is often
accomplished by the operator pressing one or more buttons on an
operator interface panel of the measuring instrument. Generally,
both software routines executed by a processor in the measuring
instrument, as well as hardware circuitry, initiate the acquire and
store processes by interpreting the selections made by the operator
via the buttons of the operator interface panel.
[0008] In contrast to conventional acquisition and storage of a
waveform measurement as outlined above, a measuring instrument such
as a digital multimeter typically measures and displays, in
alpha-numeric form, only a single value associated with a signal or
circuit component at a particular instant of time, as opposed to a
set of values. Some digital multimeters may additionally have a
limited ability to store a single signal measurement to be recalled
and displayed numerically at a later time, or may sound a "beep" to
indicate that a particular measurement is ready for observation on
the alpha-numeric display. Digital multimeters, however, do not
acquire and store sets of values corresponding to two-dimensional
representations of waveforms, and do not display stored waveform
representations on a video display, as do measuring instruments
such as oscilloscopes and spectrum analyzers.
[0009] With respect to the electrical connection of a waveform
measuring instrument to a waveform source, various terminations or
measurement probes are known for placing a wire or cable attached
to a measuring instrument in contact with a waveform source. Some
terminations, for example, a probe with a fine "tip," require an
operator to hold the termination to the waveform source during a
measurement. This requirement may pose particular challenges to the
operator during conventional manual waveform measurement
acquisition and storage operations, as discussed further below.
[0010] One problem encountered during manual waveform measurement
operations relates to measurement probe "slippage." This problem
may be particularly exacerbated by ongoing improvements in
semiconductor and printed circuit board technology. For example,
with continued advances in semiconductor fabrication technology,
the size of integrated circuits (ICs) becomes progressively
smaller. One consequence of reduced IC package size is that the
connection terminals or "pins" of the IC are smaller and are closer
together, or more densely packed. The packing density and size of
IC pins is referred to as "lead pitch." Reduced IC package size
also results in printed circuit boards that are more densely
occupied by IC chips and other circuit components.
[0011] In view of the foregoing, it is to be appreciated that in
many instances, acquisition and storage of waveform measurements
requires careful application of a measurement probe to a waveform
source in order to avoid probe slippage. In such cases, the
operator may choose to summon an assistant to perform the manual
"stop acquisition and store" functions so that the operator's
attention is not diverted from the probe in contact with the
waveform source. Examples of potentially challenging waveform
measurements include using a fine tip probe on densely packed
printed circuit boards having ICs with a small lead pitch, as
discussed above, or applying a measurement probe to an IC or a
component in a difficult to reach position.
[0012] Alternatively, to facilitate the stop acquisition and
storage functions and alleviate the need for an assistant, some
known measurement probes are equipped with a button to allow the
operator to "remotely" perform these functions, in lieu of a button
on an operator interface panel of the measuring instrument. Other
more elaborate schemes are known for facilitating remote operator
instruction of a measuring instrument, some of which employ, for
example, a foot pedal or a sound sensitive trigger, such as a voice
recognition device, so that the operator may indicate to the
measuring instrument to stop acquisitions and/or store an acquired
waveform measurement without having to touch the measuring
instrument itself.
[0013] The above alternative solutions for remotely acquiring and
storing a waveform measurement often suffer several disadvantages,
however, in that 1) they nonetheless require the operator to look
at the video display of the measuring instrument to determine if a
probed waveform has stabilized, and 2) the acquisition and storage
operations are still performed manually, thereby requiring manual
action by the operator or an assistant. This need for the operator
to monitor the display and to perform manual operations, either
remotely or proximately with the measuring instrument, limits the
operator's ability to concentrate on the measurement probe, or to
perform some other task during a measurement. In particular, while
the operator's attention is diverted from the measurement probe to
the video display or the manual operation, especially in the case
of a fine tip probe, the probe may slip off of the pin, lead, or
termination carrying the waveform of interest.
[0014] The risk of accidental probe movement may be especially
aggravated in the case of an operator pushing a stop acquisition
and/or storage button on a probe equipped with such a button. As
discussed above, as the lead pitch on integrated circuits becomes
smaller and the component density of printed circuit boards
increases, any disturbance of measurement probe placement poses a
greater risk of causing damage to a circuit, by contacting or
"shorting" multiple pins or component leads with the probe while
the operator looks away from the probe to observe a visual display,
or pushes a button to stop sample acquisition and store a waveform
measurement.
SUMMARY OF THE INVENTION
[0015] Accordingly, in view of the foregoing, the present invention
is directed to methods and apparatus for automatically acquiring
and storing a waveform measurement using a measuring instrument
having a video display. Waveform measuring instruments suitable for
purposes of the present invention include, but are not limited to,
oscilloscopes, spectrum analyzers, and network analyzers. The
invention provides several advantages in that it allows an operator
to be free to perform other tasks during a waveform measurement
operation. In particular, according to the invention, an operator's
attention need not be diverted from the vicinity of the waveform
source during a measurement.
[0016] According to one aspect of the invention, an operator is
relieved from such tasks as verifying waveform stabilization on a
video display, terminating waveform acquisition, and initiating
storage of a waveform measurement. For waveform measurements in
which a measurement probe is used to contact a waveform source, the
invention particularly reduces the risk of the probe slipping and
making an unreliable measurement and/or possibly "shorting out" and
damaging circuitry. In general, the method and apparatus of the
invention affords the operator a greater degree of freedom in
making waveform measurements and provides an efficient, lost cost,
and easy to implement solution for waveform measuring instruments
to automatically acquire and store waveforms and indicate
successful storage thereof to an operator. Specifically, the
present invention is especially useful for monitoring waveforms
from ICs with very small lead pitch.
[0017] According to a feature of the invention, an operator
performs one or more setup steps on the measuring instrument to
instruct the measuring instrument to begin an automatic
acquisition, storage, and indication procedure. Once the measuring
instrument is instructed, the operator is not required to interact
further with the instrument during the course of a waveform
measurement.
[0018] In one embodiment, the invention provides for the automatic
acquisition and storage of a number of waveform measurements in
succession, as well as the indication of successful acquisition and
storage of each measurement. Each measurement in a succession of
measurements is independent and may be taken from the same pin of
an IC, a different pin of the same IC, an entirely different IC,
various other circuit components or terminations, or combinations
of the above. Once automatic waveform acquisition and storage are
completed for a single waveform measurement, the measuring
instrument alerts the operator of a successful measurement by
providing at least one indication, for example, by sounding one or
more audible indications or patterns of indications. The operator
may then keep the probe on the source, or remove the probe from the
waveform source and apply it elsewhere to a new source, to
automatically proceed with a subsequent measurement. In this
manner, the invention affords the operator the freedom to perform
other tasks, and in particular, to keep his or her attention on a
measurement probe in contact with a waveform source throughout a
series of waveform measurements, if desired.
[0019] Other advantages, novel features, and objects of the
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated herein by
reference, are schematic and are not intended to be drawn to scale.
In the drawings, each identical or nearly identical component that
is illustrated in various figures is represented by a like numeral.
For purposes of clarity, not every component may be labeled in
every drawing.
[0021] In the drawings:
[0022] FIG. 1 is a block diagram of a waveform measuring instrument
including an example of one apparatus according to the
invention;
[0023] FIG. 2 is a detailed block diagram of a control unit of the
apparatus of FIG. 1;
[0024] FIG. 3 is a detailed block diagram of an automatic
acquisition module of the apparatus of FIG. 1;
[0025] FIG. 4 is a detailed block diagram of a signal processor of
the apparatus of FIG. 3; and
[0026] FIG. 5 is a flow chart diagram illustrating an example of a
method, according to the invention, of automatically acquiring and
storing a waveform measurement and indicating the success
thereof.
DETAILED DESCRIPTION
[0027] FIG. 1 is a simplified schematic block diagram of a waveform
measuring instrument 1 including an example of an apparatus
according to the invention. The waveform measuring instrument of
FIG. 1 may be, for example, an oscilloscope, a spectrum analyzer,
or a network analyzer. FIG. 1 shows that the waveform measuring
instrument 1 includes a control unit 30, coupled to an automatic
acquisition module 5 via line 70, a memory 36 via line 82, a video
display 80 via line 84, and an indicator 39 via line 86. Each of
lines 70, 72, 82, 84 and 86 may include one or more conductors.
[0028] In FIG. 1, the automatic acquisition module 5 automatically
acquires one or more acquired sample sets of a probed waveform 11
present on cable 74, as measured by a measurement probe 10 during a
waveform acquisition period. Automatic acquisition module 5 also
determines a selected sample set, based on the acquired sample
sets, at an expiration of the waveform acquisition period. The
control unit 30 controls the automatic acquisition module 5 via
control line 70 and the memory 36 via line 82 to store in memory
36, via line 72, each selected sample set determined by module 5.
The control unit 30 also controls the memory 36 and the video
display 80 such that each stored sample set may be retrieved from
memory 36, and the waveform represented by the selected sample set
may be viewed on video display 80.
[0029] As shown in FIG. 1, measurement probe 10 is used to monitor
a waveform of interest carried by a waveform source, such as an IC
pin, a component lead, or a circuit termination. While measurement
probe 10 is illustrated in FIG. 1 as a "tipped" implement, for
purposes of the invention, the probed waveform 11 may be derived
from any one of several terminations known in the art serving as a
measurement probe. Examples of terminations suitable for use as a
measurement probe according to the invention include, but are not
limited to, a cable equipped with a tipped probe as shown, a BNC
termination, a "banana-type" termination, a "clip-lead"
termination, and the like. Similarly, cable 74 carrying the probed
waveform 11 may be connected to the measuring instrument using any
number of appropriate connections known in the art.
[0030] Furthermore, for purposes of the present invention, the
probed waveform 11 refers to the waveform being acquired by
automatic acquisition module 5 at any given time; for example, at
two different instances of time, the probed waveform 11 may be
derived from the same waveform source, or two different waveform
sources, respectively, as the operator is free to move the
measurement probe 10 among several possible sources.
[0031] In particular, it is to be appreciated that the automatic
acquisition module 5 may acquire a number of waveform measurements
in succession. For each waveform measurement, the automatic
acquisition module 5 acquires one or more sample sets and
determines a selected sample set based on the acquired sample sets,
and the control unit 30 causes each selected sample set to be
stored in memory 36. For a series of waveform measurements, an
operator has the option to specify a delay time between consecutive
acquisition and storage operations for each measurement, as
discussed further below.
[0032] FIG. 2 is a more detailed block diagram of the control unit
30. FIG. 2 shows that the control unit 30 includes an operator
interface module 32 for providing instructions to the measuring
instrument, and a processor 38, coupled to the operator interface
module 32, as well as the automatic acquisition module 5 via line
70, to the memory 36 via line 82, to the video display 80 via line
84, and to the indicator 39 via line 86. The processor 38 controls
the module 5, the memory 36, the video display 80 and the indicator
39 based on the instructions provided via the inputs 34 of the
operator interface module 32.
[0033] The operator interface module 32 includes a number of
operator inputs 34 for providing specific instructions to the
measuring instrument. For example, the operator inputs 34 can be
used to specify the waveform acquisition period, as well as an
auto-store delay time between selections and storage of consecutive
selected sample sets for a succession of waveform measurements.
With respect to the waveform acquisition period, the operator may
utilize one of the operator inputs 34 to specify the waveform
acquisition period as, for example, a predetermined measurement
time or as a predetermined count of acquired sample sets.
[0034] Returning to FIG. 1, the example of an apparatus according
to the invention includes an indicator 39 to provide at least one
indication that each selected sample set has been successfully
determined by the automatic acquisition module 5 and stored in
memory 36. Examples of possible indications provided by the
indicator 39 include, but are not limited to, audible tones, visual
indications using a lamp or LED, messages or pictorial
representations superimposed on the video display, one or more
patterns of audible tones of various durations and/or pitches,
audible voice messages, or combinations of the above.
[0035] A unique mode of indication may be specified by the operator
using an input 34 of the operator interface module 32, such that
the operator is informed of various aspects of successful
measurement acquisition and storage. For example, in a series of
automatic waveform measurements, a unique predetermined pattern of
duration, number, or pitch of audible tones indicating a particular
acquisition or storage event can be assigned by the operator to
each of a sequence of selected sample sets, so that the operator
may be informed of how many measurements have been acquired and
stored. Additionally, as discussed above, the various audible
indications of a particular indication mode may also include voice
messages, for example, identifying the number of acquired
measurements, and may be accompanied by one or more visual
indications as well, for example, a message or pictorial
representation superimposed on the video display of the measuring
instrument, an LED or other lamp illuminated on the operator
interface panel, and the like.
[0036] FIG. 3 is a more detailed block diagram of the automatic
acquisition module 5. The automatic acquisition module 5 includes a
detection module 12 to monitor a parameter of the probed waveform
11, to detect a change in the monitored parameter, and to wait a
predetermined stabilization time for the monitored parameter to be
substantially constant. Automatic acquisition module 5 also
includes a sampling module 14 to acquire, after the predetermined
stabilization time, the acquired sample sets. The sampling module
14 also automatically stops acquisitions of the acquired sample
sets at the expiration of the waveform acquisition period. The
automatic acquisition module 5 further includes a signal processor
16, connected to sampling module 14 via line 76, to process the
acquired sample sets and to determine a particular selected sample
set from the acquired sample sets for each waveform measurement
operation. The signal processor 16 outputs each selected sample set
to the memory 36 via line 72. Processor 38 of the control unit 30
controls the detection module 12, the sampling module 14, and the
signal processor 16 via line 70.
[0037] FIG. 4 shows a more detailed block diagram of the signal
processor 16 of the automatic acquisition module 5. The signal
processor 16 may include a selector 17 to select one of the
acquired sample sets to be stored in memory. For example, the
selector may select the last acquired sample set, acquired at the
expiration of the waveform acquisition period, to be stored to
memory. Signal processor 16 may also include an arithmetic unit 18
to calculate an average sample set from the acquired sample sets to
be stored to memory.
[0038] Additionally, FIG. 4 shows that signal processor 16 may
include a digital processor 19 to filter the acquired sample sets
to determine the selected sample set for each measurement. Digital
processor 19 may be constructed and arranged so as to implement any
number of digital signal processing techniques known in the art.
For purposes of the present invention, any analog and/or digital
signal processing technique may be utilized to determine each
selected sample set from the acquired sample sets. For example,
selector 17, arithmetic unit 18, and digital processor 19 of FIG. 4
may be used alone or in combination with each other to determine a
selected sample set from the acquired sample sets.
[0039] Returning to FIG. 3, the automatic acquisition module 5
further includes an input and triggering module 6. FIG. 3 shows
that the input and triggering module 6 includes a plurality of
waveform channels 7. For example, many waveform measuring
instruments known in the art typically include two or more input
waveform channels, wherein each waveform channel may include some
form of impedance matching and waveform conditioning circuitry. In
this manner, a number of waveforms of interest may be measured by
one or more probes similar to measurement probe 10, to provide
measured waveforms to the measuring instrument.
[0040] In the input and triggering module 6 shown in FIG. 3, an
amplifier 8 is associated with each waveform channel 7. Each
amplifier 8 provides signal amplification or attenuation to a
respective waveform channel for conditioning a particular probed
waveform. The amplification or attenuation provided by each
amplifier is referred to as the gain or "vertical sensitivity" of
the amplifier. The term "vertical sensitivity" is used in the art
in conjunction with waveform amplification as it relates to the
video display generally associated with waveform measuring
instruments, in which a vertical display axis typically represents
waveform amplitude.
[0041] As shown in FIG. 3, the input and triggering module 6 may
include a number of waveform channels 7 and associated amplifiers
8, to which a number of probes and cables similar to measurement
probe 10 and cable 74 may be respectively connected. Processor 38
of the control unit 30, shown in FIG. 2, controls the input and
triggering module via control line 70 so as to select one of the
waveform channels 7 at any given time to provide the probed
waveform 11 to the detection module 12. Hence, the probed waveform
11 shown in FIG. 3 may be a conditioned (amplified or attenuated)
version of one of several waveforms input to the input and
triggering module 6. The operator interface module 32 of FIG. 2
includes an input 34 to allow the operator to select a particular
waveform channel of interest.
[0042] FIG. 3 additionally shows that the detection module 12
includes an auto-scale module 13 to optimize the vertical
sensitivity of the amplifier 8 corresponding to the selected
waveform channel 7, based on the amplitude of the probed waveform
11. The auto-scale module 13 determines if further amplification of
a waveform as measured by probe 10 is possible without saturating
the amplifier 8, and if possible, the auto scale module 13
automatically increases the vertical sensitivity of the amplifier
accordingly. Similarly, if the auto-scale module 13 senses that the
amplifier is saturated, it decreases the vertical sensitivity of
the amplifier 8. In this manner, the auto-scale module 13 insures
that the dynamic range of amplifier 8 is utilized as effectively as
possible to provide the probed waveform 11 to the detection module
12.
[0043] The input and triggering module 6 shown in FIG. 3 also
includes at least one external trigger input 9 to receive an
external trigger source. A trigger source refers to a periodic
signal that activates a timing reference or "time base" of the
measuring instrument used for waveform measurements. Various
methods and apparatus for providing time bases are well known in
the art. Possible trigger sources for a measuring instrument such
as an oscilloscope or spectrum analyzer may include, but are not
limited to, the power supply line used to power the measuring
instrument, or a dedicated timing circuit internal to the measuring
instrument. A probed waveform itself, as measured by probe 10, may
also provide the trigger source, or an arbitrary waveform may be
applied to the external trigger input 9 and may serve as the
trigger source.
[0044] While a time base or timing reference module for the
waveform measuring instrument is not explicitly shown in FIG. 3,
the timing information provided by a trigger source, in some cases
by way of external trigger input 9, may be utilized by the sampling
module 14 in a known manner to acquire sample sets of the probed
waveform 11. A point along a trigger source waveform that is
specifically used to activate a timing reference is commonly
referred to as a "trigger." The operator interface module 32 shown
in FIG. 2 may include an operator input 34 to select a trigger
source. As discussed above, a suitable trigger source may be
provided by an internal dedicated timing circuit, by the waveform
of interest itself, or by an arbitrary external trigger source.
When a desired trigger source is selected, the operator has the
option to additionally specify the waveform acquisition period as a
predetermined count of triggers.
[0045] FIG. 5 is a flow chart illustrating an example of a method
of automatically measuring a probed waveform according to the
invention. Beginning with step 40, the operator selects an
"auto-store" mode to automatically acquire and store waveform
measurements according to the invention. The operator may then
instruct or "arm" the measuring instrument to automatically acquire
a number of sample sets, and determine and store a selected sample
set representing the waveform of interest. The step of arming may
include, for example, selecting a channel of the measuring
instrument on which to acquire samples of the waveform, selecting a
trigger source, specifying a waveform acquisition period and an
auto-store delay time for continuous acquisition and storage of a
series of measurements, and selecting an indication mode. It should
be appreciated that the step of arming the measuring instrument may
include various other steps that pertain to a specific measuring
instrument, and that some steps may differ for different
instruments.
[0046] As discussed above, during the step of arming, the operator
may specify the waveform acquisition period as a predetermined
measurement time, a predetermined count of acquired sample sets, or
as a predetermined count of triggers. Additionally, a signal
processing mode may be specified by the operator, such as averaging
or digital processing of the acquired sample sets.
[0047] The waveform of interest is acquired by first monitoring a
parameter of the waveform and detecting a change in the monitored
parameter, as shown in step 42. Examples of waveform parameters
monitored according to methods of the invention may include the
waveform amplitude or frequency. In step 44, the example method of
FIG. 5 allows for the monitored parameter of the waveform of
interest to stabilize for a predetermined stabilization time. In
step 46, the amplification or attenuation applied to the waveform
of interest by the amplifier associated with the selected channel
is optimized by adjusting the vertical sensitivity of the amplifier
while the waveform amplitude is stabilizing. Should the waveform
amplitude fluctuate during stabilization, the vertical sensitivity
of the amplifier associated with the selected channel is optimized
to accommodate the fluctuations in waveform amplitude, as discussed
above in connection with the input and triggering module 6 of FIG.
3.
[0048] Following parameter stabilization, sample sets of the
monitored waveform are acquired in step 48 during the specified
waveform acquisition period following the predetermined
stabilization time. At the expiration of the waveform acquisition
period, the acquired sample sets of the monitored waveform are
signal processed in step 50 to determine a selected sample set, and
in step 52 the selected sample set is stored to memory. Once the
selected sample set is stored to memory, at least one indication is
provided to the operator in step 54. Step 56 determines if the
operator has selected a continuous automatic acquire and store
procedure by selecting an auto-store delay time in step 40. If the
answer is yes, the method waits for the auto-store delay time,
indicated in step 60, and then returns to step 42, wherein a
parameter of a new waveform of interest is monitored. The new
waveform of interest may be the same waveform at some later time,
or a waveform from a different source. If a continuous automatic
acquire and store procedure has not been selected by the operator,
the method is completed with the indication of step 54, and the
process ends at step 58.
[0049] According to the method and apparatus of the invention as
described herein, an operator can perform an initial setup by
selecting functions and parameters of a measuring instrument, probe
a waveform of interest, and have the measuring instrument indicate
that a waveform measurement has been automatically acquired and
stored, while the operator is free to perform other tasks. In
particular, the operator can perform a waveform measurement without
ever having to take his or her eyes off of a measurement probe
during the acquisition and storage. As a result, the risk of
accidentally moving the probe to a position that might cause
unreliable measurements or damage circuitry is reduced. The method
and apparatus of the invention may be conveniently applied to a
single waveform measurement or to a number of consecutive
measurements, the operator being alerted of the successful
acquisition and storage of each measurement by an indication
provided by the measuring instrument.
[0050] 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. 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.
* * * * *