U.S. patent application number 10/156896 was filed with the patent office on 2003-12-04 for voltage probe systems having improved bandwidth capability.
Invention is credited to Dascher, David J..
Application Number | 20030222665 10/156896 |
Document ID | / |
Family ID | 46280671 |
Filed Date | 2003-12-04 |
United States Patent
Application |
20030222665 |
Kind Code |
A1 |
Dascher, David J. |
December 4, 2003 |
Voltage probe systems having improved bandwidth capability
Abstract
A resistive pin for use in a voltage probe includes a pin-head
that is configured to contact a test point in a device under test,
and a resistor that is attached to the pinhead. Other systems are
also provided for establishing electrical connections between
testing instruments and devices under test.
Inventors: |
Dascher, David J.;
(Monument, CO) |
Correspondence
Address: |
AGILENT TECHNOLOGIES, INC.
Legal Department, DL429
Intellectual Property Administration
P.O. Box 7599
Loveland
CO
80537-0599
US
|
Family ID: |
46280671 |
Appl. No.: |
10/156896 |
Filed: |
May 29, 2002 |
Current U.S.
Class: |
324/715 |
Current CPC
Class: |
G01R 1/06772 20130101;
G01R 1/06788 20130101; G01R 1/0675 20130101; G01R 1/06761
20130101 |
Class at
Publication: |
324/715 |
International
Class: |
G01R 027/08 |
Claims
What is claimed is:
1. A resistive pin for use in a voltage probe, said resistive pin
comprising: a pin-head that is configured to contact a test point
in a device under test; and a resistor that is attached to said
pin-head.
2. The resistive pin of claim 1, wherein the resistive pin is
configured such that a signal travel time between the test point
and the resistor is less than a time required for the signal to
travel {fraction (1/10)}th of a wavelength corresponding to a
highest frequency of interest.
3. The resistive pin of claim 1, wherein the highest frequency of
interest is equal to a bandwidth rating of a voltage probe that
includes the resistive pin.
4. The resistive pin of claim 1, wherein the resistor is located
less than 2 millimeters from a tip of the pin-head.
5. The resistive pin of claim 1, wherein the resistor is located
about 1 millimeter from a tip of the pin-head.
6. The resistive pin of claim 1, further comprising: a shaft that
is attached to said resistor, wherein at least a portion of said
shaft is configured to be inserted into a voltage probe socket.
7. A voltage probe comprising the resistive pin of claim 1.
8. A resistive pin for use in a voltage probe, said resistive pin
comprising: a dielectric pin; a first layer of high-conductivity
material that is in contact with a first portion of the dielectric
pin; a second layer of high-conductivity material that is in
contact with a second portion of the dielectric pin; and a third
layer of low-conductivity material that is in contact with a third
portion of the dielectric pin; the third portion being located
between the first portion and the second portion; the first layer
and the second layer being in contact with the third layer.
9. The resistive pin of claim 8, wherein a pin-head comprises the
first portion and the first layer.
10. The resistive pin of claim 8, wherein a resistor comprises the
third portion and the third layer.
11. The resistive pin of claim 8, wherein a shaft comprises the
second portion and the second layer, at least a portion of the
shaft being configured to fit in a voltage probe socket.
12. A voltage probe comprising the resistive pin of claim 8.
13. A resistive pin for use in a voltage probe, said resistive pin
comprising: a pin-head that is configured to contact a test point
in a device under test; a resistor that is electrically coupled to
said pin-head; and wherein a signal travel time between a tip of
the pin-head and the resistor is less than a time required for the
signal to travel {fraction (1/10)}th of a wavelength corresponding
to a highest frequency of interest.
14. The resistive pin of claim 13, wherein the highest frequency of
interest is equal to a bandwidth rating of a voltage probe that
includes the resistive pin.
15. The resistive pin of claim 13, wherein the resistor is located
less than 2 millimeters from the tip of the pin-head.
16. The resistive pin of claim 13, further comprising: a shaft that
is attached to said resistor, wherein at least a portion of said
shaft is configured to be inserted into a voltage probe socket.
17. A voltage probe comprising the resistive pin of claim 13.
18. A voltage probe comprising: an end that is configured to
contact a test point; a resistor that is electrically coupled to
the end; and wherein a signal travel time between the end and the
resistor is less than a time required for the signal to travel
{fraction (1/10)}th of a wavelength corresponding to a highest
frequency of interest.
19. The voltage probe of claim 18, wherein the highest frequency of
interest is equal to a bandwidth rating of the voltage probe.
20. A voltage probe comprising: an end that is configured to
contact a test point; a resistor that is electrically coupled to
the end; and wherein a distance between the end and the resistor is
less than 2 millimeters.
21. The voltage probe of claim 20, wherein the distance between the
end and the resistor is about 1 millimeter.
22. A voltage probe comprising: means for forming an electrical
connection with a test point in a device under test; means for
damping resonance in the voltage probe, said means for damping
being electrically coupled to said means for forming; and wherein a
signal travel time between the test point and said means for
damping is less than a time required for the signal to travel
{fraction (1/10)}th of a wavelength corresponding to a highest
frequency of interest.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to instrumentation used in
the testing and measuring of electrical signals. More specifically,
it relates to voltage probe systems having improved fidelity at
high frequencies.
DESCRIPTION OF THE RELATED ART
[0002] A voltage probe typically uses a metal pin and/or a metal
socket to make an electrical connection between a point being
probed and an attenuator and/or amplifier circuit in the probe. The
electrical connection may be modeled as a short transmission line
having a transmission time delay that is dependent on the length of
the transmission line. The input impedance of a probe resonates low
and the response of a probe resonates high at a frequency
determined by the length of the electrical connection and by the
impedance at the far end of the connection which is usually
dominated by just a capacitance. Although this resonance exists for
all probes, lower bandwidth probes may not be adversely affected by
the resonance since the resonance may occur at a frequency well
above the bandwidth capability of the probe. However, higher
bandwidth voltage probes are often affected by this resonance. One
way to avoid the resonance problem is to make the pin and/or socket
that connect to the probing point very short so that the frequency
of the resonance is well above the bandwidth of the probe. The
problem with a very short pin and/or socket is that they can make
it difficult, if not impossible, to establish connections to
testing points that are in "tight" places. Simply put, voltage
probes having a very short pin and/or socket are difficult to use.
On the other hand, using a longer pin and/or socket makes a probe
easier to use but creates a resonance in the input structure that
degrades the input impedance and response of the probe. Therefore,
there exists a need for systems and methods that address these
and/or other problems associated with voltage probes.
SUMMARY OF THE INVENTION
[0003] Systems and methods are provided for establishing electrical
connections between testing instruments and devices under test. In
one embodiment of the invention, a voltage probe includes a
pin-head that is configured to contact a device under test, and a
resistor that is attached to the pin-head. In another embodiment, a
resistive pin for use in a voltage probe includes a pin-head that
is configured to contact a test point in a device under test and a
resistor that is attached to the pin-head. The resistive pin may be
configured such that a signal travel time between the test point
and the resistor is less than a time required for the signal to
travel {fraction (1/10)}th of a wavelength corresponding to a
highest frequency of interest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The invention can be better understood with reference to the
following drawings. The components in the drawings are not
necessarily drawn to scale, emphasis instead being placed upon
clearly illustrating the principles of the present invention. In
the drawings, like reference numerals designate corresponding parts
throughout the several views.
[0005] FIG. 1 is a schematic diagram of a voltage probe in
accordance with one embodiment of the invention.
[0006] FIG. 2 is a simplified electric circuit diagram representing
the voltage probe shown in FIG. 1.
[0007] FIG. 3A is a graph depicting a performance characteristic of
a prior art voltage probe.
[0008] FIG. 3B is a graph depicting a performance characteristic of
the voltage probe shown in FIG. 1.
[0009] FIG. 4 is a schematic diagram depicting a pin in accordance
with one embodiment of the invention.
[0010] FIG. 5 is a schematic diagram depicting a resistive pin that
includes the pin shown in FIG. 4.
[0011] FIG. 6 is a schematic diagram depicting a resistive pin that
includes the resistive pin shown in FIG. 5.
[0012] FIGS. 7A and 7B are schematic diagrams depicting a top view
and a side view, respectively, of a first slab used in
manufacturing the resistive pin shown in FIG. 5.
[0013] FIGS. 8A and 8B are schematic diagrams depicting a top view
and a side view, respectively, of a second slab used in
manufacturing the resistive pin shown in FIG. 5.
[0014] FIGS. 9A and 9B are schematic diagrams depicting a top view
and a side view, respectively, of a third slab used in
manufacturing the resistive pin shown in FIG. 5.
[0015] FIGS. 10A and 10B are schematic diagrams depicting a top
view and a side view, respectively, of a slide used in
manufacturing the resistive pin shown in FIG. 5.
[0016] FIGS. 11A and 11B are schematic diagrams depicting a top
view and a side view, respectively, of a fourth slab used in
manufacturing the resistive pin shown in FIG. 5.
[0017] FIGS. 12A and 12B are schematic diagrams depicting a top
view and a side view, respectively, of a solder washer that may be
used to bond a resistor to the pin-head or base of the pin shown in
FIG. 4.
[0018] FIG. 13 is a flow chart depicting a method for manufacturing
a resistive pin shown in FIG. 5, in accordance with one embodiment
of the invention.
[0019] FIG. 14 is a schematic diagram illustrating a perspective
view of a slab assembly that includes components shown in FIGS.
7-8.
[0020] FIG. 15 is a schematic diagram illustrating a partial
cross-sectional view of the slab assembly shown in FIG. 14.
[0021] FIGS. 16A and 16B are schematic diagrams depicting a side
view and a cross-sectional view, respectively, of a resistive pin
that may form part of the voltage probe shown in FIG. 1.
DETAILED DESCRIPTION
[0022] Systems and methods in accordance with the present invention
reduce resonance in voltage probes by placing a damping resistor
near a probing point of a voltage probe. In one embodiment of the
invention, a resistor is included in a voltage probe such that it
is within about 1 or 2 millimeters from a test point that is
contacted by the voltage probe. This and other embodiments will be
described more fully hereinafter with reference to the accompanying
drawings. These embodiments are examples, among others, of systems
and methods of the present invention. Therefore, the present
invention, which may be embodied in many different forms, should
not be construed as limited to the embodiments set forth
herein.
[0023] FIG. 1 is a schematic diagram of a voltage probe 100 in
accordance with one embodiment of the invention. The voltage probe
100 includes a pin-head 102, a damping resistor R1, a handle 108, a
cable 112, and a measurement and testing instrument (MTI) interface
114. In one embodiment, the value of the damping resistor R1 is
between 50 ohms and 500 ohms. The pin-head 102 is for contacting a
test point in a device under test (DUT). The test point is
typically contacted via a tip 120 of the pin-head 102. For optimal
electrical performance of the voltage probe 100, the length d1 of
the pin-head 102 is preferably less than 1 millimeter (mm).
However, the voltage probe 100 may be more easily used and
manufactured if the length d1 is between 1 mm and 2 mm. In one
embodiment, the length d1 may be greater than 2 mm, depending on a
desired implementation.
[0024] The damping resistor R1 is attached to the pin-head 102 and
to a pin shaft (not shown). This pin shaft fits in a socket located
within a cylindrical portion 106 and thereby connects the resistor
R1 to other voltage probe components located within the handle 108.
A ground connector 110, which is connected to the handle 108, is
for providing a connection to ground. The MTI interface 114
connects the voltage probe 100 to an MTI (not shown). The cable 112
extends between the handle 108 and the MTI interface 114. Note that
other voltage probes having fewer, greater, and/or different
components than those shown in FIG. 1 may be implemented within the
scope of the present invention. For example, in one embodiment, a
wire (not shown) may extend between the cylindrical portion 106 and
the resistor R1 in order to facilitate the use of the voltage probe
100. Furthermore, an embodiment of the invention may be implemented
in any type of voltage probe, active or passive.
[0025] FIG. 2 is a simplified electric circuit diagram of a testing
system 200 that includes a voltage probe 100 that is coupled
between a DUT 204 and an MTI 206 in accordance with one embodiment.
The DUT 204 is modeled as a grounded voltage source Vsrc that is
connected in series with a source impedance Z1 and a point being
probed 202. The MTI 206 is modeled as a load impedance Z2 that is
grounded. In one embodiment, the impedance Z2 is a 50 ohm
resistance. The voltage probe 100 includes the following electrical
components that are connected in series: a transmission line T1
between the point being probed and the damping resistor R1, a
damping resistor R1, a transmission line T2 between the damping
resistor R1 and the input attenuator 210, an input attenuator 210,
an amplifier 220, an amplifier output resistance R2, and a
transmission line T3 between the amplifier output resistance R2 and
the MTI 206.
[0026] The electrical components of the voltage probe 100 shown in
FIG. 2 correspond to physical components of the voltage probe 100
shown in FIG. 1 as follows: the transmission line T1 represents a
connection made by the pin-head 102, the damping resistor is shown
as R1 in both figures, the transmission line T2 represents a
connection made by or within the cylindrical portion 106, and the
transmission line T3 represents a connection made by the cable 112
between the handle 108 and the MTI 206. Furthermore, the input
attenuator 210 and the amplifier 220 are components that are
located within the handle 108.
[0027] In order to provide greater improvement in high frequency
fidelity, a signal travel time between the point being probed 202
and the resistor R1 (i.e., the time delay across T1) is preferably
no more than the time it takes for the signal to travel {fraction
(1/10)}th of a wavelength corresponding to the highest frequency of
interest. In one embodiment, the highest frequency of interest
corresponds to the bandwidth rating of the voltage probe. For
example, in a voltage probe having a bandwidth rating of 4.8 GHz,
the resistor R1 is preferably within a signal travel time of about
21 pico seconds (i.e., 0.1 cycle * {fraction (1/4.8)} GHz), or
within 6.3 mm (i.e., the speed of light times 21 pico seconds) from
the point being probed 202 (i.e., from the tip 120 of the pin-head
102 (FIG. 1)).
[0028] The characteristic impedance of T1 and T2 is as high as
reasonably practical. In one embodiment, for example, each of T1
and T2 has a characteristic impedance of approximately 150 Ohms.
The time T1 required for a signal to propagate across T1 is
substantially less than the time t2 required for a signal to
propagate across T2. For example, in one embodiment where the
bandwidth rating of the probe is 4.8 GHz, t1 is about 4 pico
seconds and t2 is about 40 pico seconds.
[0029] The closer that the values of the voltages V.sub.A and
V.sub.I are to each other, the better the performance of the
voltage probe; i.e., the more accurately V.sub.O can be used to
estimate V.sub.I. This is because the output voltage V.sub.O is
linearly related to the voltage V.sub.A. The voltage V.sub.O is
equal to the output voltage V.sub.A divided by an attenuation
factor (e.g., 10). In the example shown in FIG. 2, the attenuation
factor represents the degree of signal attenuation caused by a
combination of the attenuator 210 and the amplifier 220. Placing
the resistor R1 electrically close (e.g., within a signal travel
time of 4 pico seconds) to the point being probed 202 substantially
extends the frequency range for which the values of V.sub.A and
V.sub.I are close to each other (e.g., within 3 decibels (dB) of
each other).
[0030] FIG. 3A is a graph depicting a performance characteristic
for a prior art voltage probe that does not include a damping
resistor located near its probing tip, but that is otherwise
similar to the voltage probe 100 (FIG. 1). The vertical axis 304
represents the ratio of V.sub.A (i.e., V.sub.O multiplied by a
scaling factor) over V.sub.I (FIG. 2) in decibels. In other words,
the vertical axis 304 represents 20*Log.sub.10 (V.sub.A/V.sub.I).
The horizontal axis 306 represents the input signal frequency in
Hertz on a logarithmic scale. The line segment 302 represents the
ratio of V.sub.A over V.sub.I in dB over a certain frequency range.
Note that the ratio of V.sub.A/V.sub.I deviates by 3 dB when the
signal frequency reaches only 2.8 GHz. Therefore, the prior art
voltage probe will allow for measurements that are at least 70%
accurate for only the frequency range of 0-2.8 GHz.
[0031] FIG. 3B is a graph depicting a performance characteristic
for a voltage probe that includes a damping resistor near its
probing tip (e.g., the voltage probe 100 (FIG. 1)). The line
segment 312 represents the ratio of V.sub.A over V.sub.I in dB over
a certain frequency range. Note that the ratio of V.sub.A/V.sub.I
deviates by 3 dB when the signal frequency reaches 4.8 GHz. In
other words, the voltage probe 100 will allow for measurements that
are at least 70% accurate for the frequency range of 0-4.8 GHz.
Therefore, the voltage probe 100 maintains an accuracy of at least
70% at higher frequencies than does an otherwise similar prior art
voltage probe that does not include a damping resistor near its
probing tip.
[0032] FIG. 4 is a schematic diagram depicting a pin 400. The pin
400 may be used to form a resistive pin that can be incorporated
into a voltage probe. The pin 400 is preferably only a few
millimeters (mm) in length. In one embodiment, for example, among
others, the pin is about 7 mm long. The exact length of a pin 400
may be determined based on a desired implementation.
[0033] The pin 400 includes a shaft 410, a base 420, a pin-head
102, and a neck 440. The shaft 410 extends between the base 420 and
the neck 440. The neck 440 extends between the pin-head 102 and the
shaft 410, and has a significantly smaller diameter than a diameter
of at least a portion of the shaft 410. As a result, the neck 440
can break when a sufficient level of torque is exerted on the pin
400.
[0034] FIG. 5 is a schematic diagram depicting a resistive pin 500.
The pin-head 102 includes a pointed tip 432 for contacting an
electrical test point, and a conical portion 434 that extends from
the pointed tip 432. The combination of the pointed tip 432 and the
conical portion 434 is durable and helps to provide good visibility
of an electrical test point during testing. The pin-head 102 and
the base 420 include substantially flat surface areas 438 and 422,
respectively, that are configured to bond to a resistor via, for
example, but not limited to, soldering material.
[0035] The base 420 may include three cylindrical portion having
different diameters: a first cylindrical portion 424 is for fitting
within a voltage probe socket, a second cylindrical portion 426 is
for contacting an area surrounding an opening of the voltage probe
socket, and a third cylindrical portion 428 is for helping to
secure a protective cast that is applied over resistor R1 during
the manufacturing of a resistive pin.
[0036] In one embodiment, the pin may comprise a Beryllium-copper
(BeCu) alloy and may be shaped using a numerically controlled
lathe. Other conductive materials may also be used. However, one
advantage of using a BeCu alloy is that it can be relatively soft
and therefore easy to shape. Furthermore, after the BeCu is shaped,
it may then be heat treated to substantially increase its
durability.
[0037] The exact dimensions of the pin 400 may be responsive to a
desired implementation. For example, the diameter of a cylindrical
portion 436 of the pin-head 102 may be selected to equal a diameter
of a resistor that is to be attached to the substantially flat
surface area 438. Furthermore the diameters of the shaft 410 and of
a first portion 424 of the base 420 may be selected such that the
parts can properly fit within a socket of a desired voltage
probe.
[0038] It is desirable to keep the length of the pin-head 102 very
short (e.g., less than or equal to 1 mm) in order to optimize the
performance of a voltage probe for ultra-high and super-high
frequency applications. However, it may be more practical to
manufacture and use a resistive pin having a pin-head 102 that is
slightly longer than 1 mm (e.g., between 1 mm and 2 mm) without
significantly departing from optimal performance. For example, in
one embodiment, the length of the pin-head 102 is about 1.25
mm.
[0039] FIG. 5 is a schematic diagram depicting a resistive pin 500.
The resistive pin 500 is assembled after the neck 440 (FIG. 4) is
broken to separate the shaft 410 from the pin-head 102. When the
neck 440 is broken, a portion of it may remain connected to the
pin-head 102 and another portion may remain connected to the shaft
410. The resistive pin 500 includes the pin-head 102, the base 420
and the shaft 410 of the pin 400. A resistor R1 is attached to the
substantially flat surface area 438 of the pin-head 102 and to the
substantially flat surface area 422 of the base 420 (FIG. 4) via
solder. Note that the resistive pin 500 may include a pin-head 102
corresponding to a first pin 400 and a shaft 410 and base 420
corresponding to a second pin 400.
[0040] FIGS. 6A and 6B are schematic diagrams depicting a side view
and a cross-sectional view, respectively, of a resistive pin 600.
The resistive pin 600 includes the resistive pin 500 (FIG. 5) and a
cast 602 that covers a portion of the resistive pin 500. The cast
602 makes the resistive pin 600 more durable and more resistant to
breaking. The cast 602, which may be molded over the resistive pin
500, may comprise an insulating material such as, for example, but
not limited to, plastic. After the resistive pin 600 is formed, it
may be connected to a voltage probe by placing the shaft 410 into a
socket of the voltage probe.
[0041] FIGS. 7A and 7B are schematic diagrams depicting a top view
and a side view, respectively, of a first slab 700 used in
manufacturing the resistive pin 500 (FIG. 5). The first slab 700
has holes 704 formed therein for receiving pin-heads such as, for
example, the pin-head 102 (FIG. 4). The first slab 700 also has
alignment pins 706 extending therefrom. Each of the alignment pins
706 is located near a comer of the first slab 700 and is configured
to fit through alignment holes provided in other slabs that are to
be placed above the first slab 700. The first slab 700 also has an
alignment notch 710 that helps to align the first slab 700 with the
other slabs.
[0042] FIGS. 8A and 8B are schematic diagrams depicting a top view
and a side view, respectively, of a second slab 800 used in
manufacturing the resistive pin 500 (FIG. 5). The second slab 800
has holes 804 formed therein for receiving resistors, such as, for
example, the resistor R1 (FIG. 5). The second slab 800 also has
alignment holes 806. Each alignment hole 806 is located near a
comer of the second slab 800 and is configured to receive one of
the alignment pins 706 that extends from the first slab 700 (FIG.
7).
[0043] FIGS. 9A and 9B are schematic diagrams depicting a top view
and a side view, respectively, of a third slab 900 used in
manufacturing the resistive pin 500 (FIG. 5). The third slab 900
has holes 904 formed therein for receiving the body of a pin such
as for example, the shaft 410 and the base 420 of the pin 400 (FIG.
4). The third slab 900 also has alignment holes 806 and a slot 908.
Each alignment hole 806 is located near a corner of the third slab
900 and is configured to receive one of the alignment pins 706 that
extends from the first slab 700 (FIG. 7). The slot 908 is
configured to receive a slide that is configured to keep the shaft
410 and base 420 within the third slab 900 while the third slab 900
is being turned upside down.
[0044] FIGS. 10A, 10B, and 10C are schematic diagrams depicting a
top view, a side view, and an end view, respectively, of a slide
1000 used in manufacturing the resistive pin 500 (FIG. 5). A first
portion 1002 of the slide 1000 is configured to slide into the slot
908 of the third slab 900. A second portion 1004 of the slide 1000
is configured to slide on an opposing side of the third slab
900.
[0045] FIGS. 11A and 11B are schematic diagrams depicting a top
view and a side view, respectively, of a fourth slab 1100 used in
manufacturing the resistive pin 500 (FIG. 5). The fourth slab 1100
has alignment holes 806 extending therethrough. Each alignment hole
806 is located near a corner of the fourth slab 1100 and is
configured to receive one of the alignment pins 706 that extends
from the first slab 700 (FIG. 4). The fourth slab 1100 is
relatively heavy and is used to provide pressure on resistor-pin
assemblies positioned within a slab assembly that includes the four
slabs 700, 800, 900, and 1100.
[0046] FIGS. 12A and 12B are schematic diagrams depicting a top
view and a side view, respectively, of a solder washer 1200 that
may be used to bond a resistor R1 to a pin-head 102 or to a base
420. The solder washer 1200, which includes solder, is very thin.
In one implementation, for example, the solder washer is about
{fraction (1/10)} of a millimeter thick, and has an exterior
diameter 1202 that is equal to the diameter of the cylindrical
portion 436 of the pin-head 102 (FIG. 4). Furthermore, the solder
washer 1200 is preferably coated with a solid layer of flux to
facilitate the flowing of solder and to help prevent formation of
oxides during the soldering process.
[0047] FIG. 13 is a flow chart depicting a method for manufacturing
a resistive pin 500 (FIG. 5). As indicated in block 1301, a
pin-head 102 that is part of a pin 400 (FIG. 4) is placed in a pin
hole in a first slab 700 (FIG. 7A). The pin-head 102 is then broken
off from the remainder of the pin and is left in the first slab 700
(block 1302). The remainder of the pin (e.g., the shaft 410 and the
base 420) is placed in a third slab 900 (FIG. 9A) with the base 420
facing up (block 1303). The steps indicated in blocks 1301-1303 are
repeated until all the pin holes for receiving pin portions are
occupied (block 1304). After all such pin holes are occupied, the
first slab 700 may be tapped (block 1305) to insure that the
pin-heads 102 are settled into the pin holes in the first slab
700.
[0048] A first portion 1002 of a slide 1000 (FIG. 10A) is placed
into the slot 908 in the third slab 900 (block 1306) to help ensure
that the pin portions inside the third slab 900 do not fall out
when the third slab 900 is turned upside down. Furthermore, a
solder washer 1200 (FIG. 12) is placed on top of each pin-head 102
in the first slab 700 (block 1307). The solder washers 1200 are for
bonding the pin-heads 102 with respective resistors that are to be
positioned over the pin-heads 102.
[0049] After the solder washers 1200 are placed on top of
respective pin-heads 102, the second slab 800 (FIG. 8A) is placed
over the first slab 700 (block 1308). The alignment pins 706 are
placed through the alignment holes 806 of the second slab 800 in
order to align the two slabs. Furthermore, the first slab 700 and
the second slab 800 are positioned relative to each other such that
alignment notches 710 in the two slabs are aligned.
[0050] After the second slab 800 is placed over the first slab 700,
a resistor is placed in each of the pin holes of the second slab
800 (block 1309) and a solder washer is placed over each of the
resistors (block 1310). The third slab 900 is then turned upside
down and is placed over the second slab 800 (block 1311). The
alignment pins 706 are placed through the alignment holes 806 of
the third slab 900 in order to align the third slab 900 with the
second slab 800. Furthermore, the second slab 800 and the third
slab 900 are positioned relative to each other such that alignment
notches 710 in the two slabs are aligned.
[0051] The slide 1000 that was inserted into the slot 908 of the
third slab 900 is then removed (block 1312) so that the bases of
the pins contained in the third slab 900 come into contact with
respective solder washers 1200 located on top of the resistors in
the second slab 800. The third slab 900 may also be tapped (block
1313) to insure that the bases settle onto the solder washers
1200.
[0052] A compliant barrier is placed over the necks 440 extending
from pin shafts 410 positioned through pin holes in the third slab
900 (block 1314). The compliant barrier may comprise, for example,
but not limited to, rubber. Then, as indicated in block 1315, the
fourth slab 1100 (FIG. 11A) is placed over the third slab 900 in
order to apply pressure on resistor-pin assemblies located within
the slab assembly. The alignment pins 706 are placed through the
alignment holes 806 of the fourth slab 1100 in order to align the
fourth slab 1100 with the third slab 900. Furthermore, the fourth
slab 1100 and the third slab 900 are positioned relative to each
other such that alignment notches 710 in the two slabs are
aligned.
[0053] The compliant barrier transfers pressure applied by the
fourth slab 1100 (FIG. 11A) to a corresponding resistive pin. This
pressure helps to ensure that components of the resistive pin are
firmly pressed against each other during a soldering process. In
the absence of the compliant barrier, pin assemblies that are
slightly shorter than others may receive little or no pressure from
the fourth slab 1100.
[0054] The slab assembly that includes the four slabs is then
placed on a hot plate (block 1316) in order to melt the solder
washers 1200. The slab assembly is then removed from the hot plate
and is allowed to cool (block 1317). Cooling the slab causes the
resistors to bond with respective pin-heads 102 and pin bases that
are positioned within the slab assembly. After the slab assembly
has cooled enough to be handled, it is disassembled and the
resistor-pin assemblies 500 are removed therefrom (block 1318).
[0055] FIG. 14 is a schematic diagram illustrating a perspective
view of a slab assembly 1400. The slab assembly 1400 includes a
first slab 700, a second slab 800, a third slab 900, and a fourth
slab 1100. The slabs 700, 800, 900, and 1100 preferably comprise
titanium which resists bonding to solder. Alignment pins 706 and
alignment notches 710 help to ensure that the slabs are properly
aligned.
[0056] FIG. 15 is a schematic diagram illustrating a partial
cross-sectional view of the slab assembly 1400. The slab assembly
1400 includes a resistive pin 500 and a compliant barrier 1502 that
is positioned between the resistive pin 500 and the fourth slab
1100. The fourth slab 1100 applies pressure on the resistive pin
500 via the compliant barrier 1502. This pressure helps to ensure
that components of the resistive pin 500 are firmly pressed against
each other during a soldering process. The soldering process
includes heating the slab assembly 1400 in order to melt solder
that is located between components of the resistive pin 500.
[0057] FIGS. 16A and 16B are schematic diagrams depicting a side
view and a cross-sectional view, respectively, of a resistive pin
1600 that may form part of a voltage probe 100 (FIG. 1). The
resistive pin 1600 is an alternative embodiment to the resistive
pin 500 shown in FIG. 5. The resistive pin 1600 includes a pin-head
102, a resistor R1, and a shaft 1602 that each comprise a
respective portion of a dielectric pin 1610. The dielectric pin
1610 may comprise a non-conductive material such as, for example,
ceramic, glass, or porcelain, among others.
[0058] The pin-head 102, which may be used to contact an electrical
test point, includes a highly conductive layer 1604 that is applied
to an exterior portion of the dielectric pin 1610. The highly
conductive layer 1604 may comprise a conductive material such as,
for example, copper or an alloy thereof. However, the conductive
layer 1604 preferably includes highly conductive diamond which can
make the pin-head 102 very durable.
[0059] The resistor R1 includes a low-conductivity layer 1606 that
is applied to an exterior portion of the dielectric pin 1610. The
low-conductivity layer 1606 is less conductive than the highly
conductive layer 1604, but is still capable of conducting an
electric signal between the pin-head 102 and the shaft 1602. The
low-conductivity layer 1606 may comprise, for example, among
others, low-conductivity diamond which can make the resistor R1
durable and scratch resistant.
[0060] The shaft 1602, which may be partially or fully inserted
into a voltage probe socket, includes a highly conductive layer
1608 that is applied to an exterior portion of the dielectric pin
1610. The highly conductive layer 1604 may comprise a conductive
material such as, for example, copper or an alloy thereof. However,
the conductive layer 1604 preferably has the same composition as
the highly conductive layer 1604 in order to help reduce the
manufacturing cost of the resistive pin 1600.
[0061] It should be emphasized that the above-described embodiments
of the present invention are merely possible examples, among
others, of the implementations, setting forth a clear understanding
of the principles of the invention. Many variations and
modifications may be made to the above-described embodiments of the
invention without departing substantially from the principles of
the invention. All such modifications and variations are intended
to be included herein within the scope of the disclosure and
present invention and protected by the following claims.
* * * * *