Agilent Technologies 1141A Manual

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User and Service Guide
Publication number 01141-97002
July 2004
For Safety and Regulatory information, see the pages at the end
of this book.
© Copyright Agilent Technologies 2000-2004
All Rights Reserved
Agilent Technologies 1141A
Differential Probe and 1142A
Probe Control and Power
Module
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2
Agilent Technologies 1141A Differential Probe and
1142A Probe Control and Power Module
This manual contains information for use and service of the differential
probe system, the 1141A Differential Probe and 1142A Probe Control
and Power Module. In this document, the two models will be treated as
a system.
Each of the two instrument models that make up the differential probe
system has a serial number sticker. The sticker for the 1141A
Differential Probe is inside the probe, in the bottom cover. (See
chapter 3 for disassembly procedure.)
The 1141A/1142A probe system allows measurement of small
differential signals in the presence of much larger common-mode
signals. It has the following major features:
• 200 MHz bandwidth
• Variable offset
• dc reject
• ac coupling
• Remote operating capability
The variable offset capability can be used to measure small ac signals in
the presence of much larger dc levels. Remote operation of key
features allows the use of the probe system in automatic test situations.
The probe can be used with an oscilloscope, spectrum analyzer, or any
instrument where differential probing is required and a compatible
50 Ωinput is available.
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Contents
3
1 Operating the Probe
Accessories Supplied 6
Accessories Available 8
To inspect the probe 9
Using the probe with other instruments 9
Recommended Test Equipment 9
2 Calibration Tests and Adjustment
Equipment Required 26
The Test Board 26
Calibration Tests 27
dc Gain Accuracy 28
Bandwidth 34
CMRR Test 36
Calibration Test Record 39
Adjustments 40
Probe Adjustment 40
Adjustment Procedure 42
Attenuator Adapter Adjustment 49
3Service
Introduction 54
Performance Specifications and Characteristics 55
General Characteristics 58
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4
Contents
Theory of Operation 59
Differential Probe 60
Control and Power Module 60
Attenuator Adapters 61
Test Board 62
Service Policy 63
Troubleshooting 64
Probe Troubleshooting 64
Probe Control and Power Module Troubleshooting 64
Removing and Replacing Assemblies 66
Differential Probe 66
Probe Adapters 68
Probe Control and Power Module 70
Replaceable Parts 71
Parts List 71
Ordering Information 71
Direct Mail Order System 71
Manufacturers’ Codes 72
Exploded View 73
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5
1
Operating the Probe
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6
Operating the Probe
Accessories Supplied
Introduction
This chapter shows you how to connect and operate the 1141A
Differential Probe and 1142A Probe Control and Power Module as a
differential probe system.
Accessories Supplied
The following items are supplied as part of the 1141A/1142A probe
system. Item numbers refer to the numbers in Figure 1-1 on page -7
and Figure 1-2 on page -8. Those without item numbers are supplied
but not shown in figures. See the Replaceable Parts List for parts not
listed below.
Item Description Qty Part Number
1 Differential Probe 1
2 10x Attenuator Adapter 1 5063-2144
3 100x Attenuator 1 5063-2145
4 ac Coupling Adapter 1 5063-2146
5 Two-inch Extension Leads (package 5) 1 5959-9334
6 Mini Grabbers 2 1400-1422
7 Five-inch Ground Lead 1 5061-6162
8 Shielded Signal Lead 1 01141-68702
9 Test Board 1 01141-66504
10 Flat-blade Alignment Tool 1 8710-1961
11 Circuit Connection Posts (strip of 20) 1 1251-5943
Probe Control and Power Module 1 1142A
Power Cord 1 see parts list
Carrying case
User and Service Manual 1
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7
Operating the Probe
Accessories Supplied
Figure 1-1
1141A Differential Probe and Accessories
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8
Operating the Probe
Accessories Available
Figure 1-2
1141A Miscellaneous Accessories
Figure 1-3
1142A Probe Control and Power Module
Accessories Available
The following accessories can be ordered.
• 5959-9335 Long Extension Lead (5.5 inch/14 cm), package of 5
• 5090-4833 Mini grabber for SMT, package of 20
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9
Operating the Probe
To inspect the probe
To inspect the probe
Inspect the shipping container for damage. If the shipping container or cushioning
material is damaged, it should be kept until the contents of the shipment have been
checked for completeness and the instrument had been checked mechanically and
electrically. Accessories supplied with the instrument are listed in see “Accessories
Supplied” on page 6 of this manual.
If the contents are incomplete, if there is mechanical damage or defect, or if the
instrument does not pass calibration tests, notify the nearest Agilent Technologies office.
If the shipping container is damaged, or the cushioning materials show sign of stress,
notify the carrier as well as the nearest Agilent Technologies office. Keep the shipping
materials for the carrier’s inspection. The office will arrange for repair or replacement
at Agilent Technologies’ option without waiting for a claim settlement.
Using the probe with other instruments
The 1141A/1142A probe system can be used with other instruments as well as
oscilloscopes. You can use it with a spectrum analyzer or frequency counter, or any
instrument with an input that can be terminated with 50 Ω.
If you are going to use the probe system with an instrument other than an oscilloscope,
you may need to set up the probe with an oscilloscope first. This will allow you to select
coupling and reject modes, and set offset, so the output of the probe is compatible with
signal requirements of the other instrument.
Recommended Test Equipment
The following table is a list of the test equipment required to test calibration, make
adjustments, and troubleshoot this instrument. The table indicates the critical
specifications of the test equipment and for which procedure the equipment is necessary.
Equipment other than the recommended model may be used if it satisfies the critical
specifications listed in the table.
Recommended Test Equipment
Equipment Required Critical Specifications
Recommended
Agilent
Model/Part Use
Signal Generator 1 to 200 MHz, 400 m Vrms 8648A P
Function Generator 2.5 to 500 kHz, 600 m Vp-p to 16 Vp-p 33120A A
Oscilloscope >400 MHz bandwidth, 1 mV/div sensitivity 54830B P,A
dc source ± 100 mV to 7 Vdc E3632A P
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10
Operating the Probe
Recommended Test Equipment
Setting up the probe
The following paragraphs cover system preparation and initial adjustments.
Power Requirements
The 1141A/1142A probe system (specifically the 1142A) requires a power source of
either 90 to 132/198 to 264 Vac, 47 to 440 Hz, 25 VA maximum.
CAUTION Before connecting power to this instrument, be sure the line voltage switch on the rear
panel of the instrument is set properly.
Line Voltage Selection
Before applying power, verify the setting of the LINE SELECT switch on the rear panel
of the 1142A. The slide switch can be set to either 115 or 230 V.
Test Board No substitute (supplied accessory) 01141-66504 A
Load BNC Feedthrough, 50 ΩPasternack
Enterprises PE6008-
50 or Huber+Suhner
22543742
P
Cables (2) BNC, 50 Ω36-inch 10503A P,A
Cable BNC, 50 Ω9-inch 10502A A
Cable Type N (m) 24-inch 11500B P
Adapter Type N (m) to BNC (f) 1250-0780 A
Adapter Type N (f) to BNC (m) 1250-0077 P
Adapters (2) BNC (f) to dual banana (m) 1251-2277 P
Alignment tool Small flat blade (supplied accessory) 8710-1961/
Sprague-Goodman
part number GTT-5G
A
P=Calibration Tests, A=Adjustments
Equipment Required Critical Specifications
Recommended
Agilent
Model/Part Use
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11
Operating the Probe
Recommended Test Equipment
WARNING Before connecting this instrument, the protective earth terminal of the instrument must
be connected to the protective conductor of the (Mains) power cord. The Mains plug
must be inserted in a socket outlet provided with a protective each contact. The
protective action must be negated by the use on an extension cord (power cable)
without a protective conductor (grounding). Grounding one conductor of a two-
conductor outlet does not provide an instrument ground.
This instrument is provided with a three-wire power cable. When connected to an
appropriate ac power outlet, this cable grounds the instrument cabinet. The type of
power cable plug shipped with the instrument depends on the country of destination.
The 1142A Power Control and Power Module does not have a power switch. A power
switch is not required because of the low mains power requirement.
Figure 1-4
1142A Rear Panel
Procedure
1Use the power cord to connect the 1142A to the ac mains.
2Connect the 1141A probe cable power connector to the PROBE connector on
the rear panel of the 1142A power module.
3Connect the output of the probe to the input of the oscilloscope.
4Set the input impedance of the oscilloscope to 50 Ω.
If the oscilloscope does not have a selectable 50 Ωinput impedance, connect a 50 ΩBNC
feedthrough termination between the probe output and the input of the oscilloscope.
5If making an initial equipment setup, continue with the initial adjustment in
the following section.
Initial Adjustment
For a given combination of 1141A Differential Probe and 1142A Probe Control and Power
Module, you may want to adjust the Offset Null and DC Reject Gain. Typically, you need
to make these adjustments only once, before the probe is first used. You can make them
any time to optimize the system. These adjustments do not affect the specifications of
the probe system.
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12
Operating the Probe
Recommended Test Equipment
• Offset null zeroes the dc level at the output of the probe. The range of adjustment is
about ±4 mV.
• DC Reject Gain adjusts the gain of the dc reject circuit to accurately null the dc
component of an input signal. The range of adjustment is about ±0.5%.
Figure 1-5
1142A Front Panel
Equipment Needed
The following equipment is necessary for initial adjustment.
• 5 V power supply
• DVM that can measure 25 µV
•50ΩBNC feedthrough terminator
• 01141-66504 test board
Equipment Setup
Use the following procedure to setup the differential probe system for initial adjustment.
CAUTION Do not exceed ±7 V when using the test board for this procedure. If the voltage is too
high, it will cause excessive power dissipation in the 50 Ωtermination on the test board.
1Use the probe setup procedure to set up the probe system.
2Connect a 50 ΩBNC feedthrough terminator to the output of the probe.
3Disconnect all accessories from the input of the probe.
4Connect the DVM to measure the dc output of the probe at the 50 Ωload.
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13
Operating the Probe
Recommended Test Equipment
5Set up the 1142A:
aSet the Local/Remote push button to Local.
bUnder DC Couple, press Zero offset.
6Set the power supply output to 5 V.
7Arrange a connection between the power supply and the test board. The
negative terminal of the supply should connect to the shield of the test board
BNC.
If your power supply has standard binding posts, you can connect a banana-to-BNC
adapter to the supply and connect a BNC cable between the supply and the test board.
Adjustment
Warm up the 1141A for 30 minutes before making adjustments.
1With the 1141A probe inputs unconnected, adjust Offset Null on the 1142A for
a minimum reading on the DVM.
The voltage swing of the adjustment is approximately ±4 mV.
2On the 1142A, under DC Reject, press 5.0 Hz.
3Read and record the reading on the DVM, _________ mV.
4Connect the probe to the test board in the position shown below
(signal to + input).
Figure 1-6
Signal to + input
5After the DVM reading stabilizes, adjust DC Reject Gain to the reading recorded
in step 3.
With a 5 V supply, the voltage swing is approximately ±12.5 mV. With a lower supply, the
voltage swings proportionally less.
Using the Accessories
The 1141A Differential Probe and accessories are designed to provide a variety of ways
to connect to circuitry and make measurements. In the descriptions, any method used
to connect to the probe signal inputs also applied to the adapters. The figure below
shows, in a general way, the use of accessories.
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14
Operating the Probe
Recommended Test Equipment
Figure 1-7
Basic Accessory Connections
Probe Tips
Probe tips fit into the receptacles in the probe and are held in place with probe tip caps.
If necessary, you can solder the probe tips into a circuit or wires can be soldered to the
tips. If you solder to the probe tips, be careful not to melt the plastic probe tip caps.
Note Because of the close tolerances between the probe tip caps and probe tips, it will be
difficult to separate the probe tips and caps once the probe tips have been soldered.
Ground Leads
The circular end of the ground lead fits over the screw on the top side of the probe.
Extension Leads
The extension leads provide a flexible connection between circuitry and the probe.
• To provide a male connection to other circuitry, connect the extension lead over the
probe tips.
• To provide a female connection, remove the probe tip caps and probe tips and connect
the extension leads to the probe.
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15
Operating the Probe
Recommended Test Equipment
Note Use extension leads and similar connection accessories carefully. Extension leads
compromise the high-frequency specifications of the probe. CMRR is particularly
sensitive to unbalanced input parameters.
To prevent pickup of stray fields when you use extension lead, either the ones supplied
with the 1141A or others, dress them carefully as follows:
• Connect the leads at right angles to the circuitry under test.
• Keep the leads as parallel as possible before they connect to the probe.
Mini-Grabbers
Mini-grabbers can be attached to the probe or adapter through the extension leads.
1Remove the probe tip caps and tips.
2Attach the extension leads to the probe or adapter.
3Attach the mini-grabbers to the extension leads.
Circuit Connector Posts
These 0.025-inch square posts can be used to connect either directly to the probe or to
the extension leads.
Solder the posts directly into your circuitry or use them to make extension leads that
plug into the inputs of the probe or adapters.
Shielded Signal Leads
The shielded signal leads allow connection to points in a circuit that are up to 10 inches
apart. The leads are shielded to within approximately 1/2 inch of the end of the lead so
they minimize pick-up due to stray fields from adjacent circuitry.
1Connect the end with the ground connector to the probe pins and ground of
the differential probe or adapter.
2Connect the free ends of the leads to 0.025-inch square or 0.030-inch round pins
in your circuitry or to the mini-grabbers.
Note Each lead has an input capacitance of approximately 15 pF. This capacitance may limit
the bandwidth of your measurement (depending on the impedance of the circuit). Also,
CMRR may be affected because of slight differences between the input capacitance of
the two leads. CMRR is also affected by differences in impedance between the two
measurements points.
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16
Operating the Probe
Recommended Test Equipment
Adapters
There are three adapters for use with the differential probe. Two adapters are
attenuators, a 10x and a100x. The other is an ac adapter for blocking dc from the probe
input.
The adapters are installed on the probe after the probe tip caps and probe tips have been
removed. The adapter fastens to the probe using a thumb wheel located on the underside
of the adapter. the figure below shows a good way to hold the probe while attaching the
adapter.
1Remove the probe tip caps and probe tips, from the probe.
2Fit the adapter over the end of the probe and rotate the thumb wheel with your
finger until the adapter fits snugly.
A snug fit is important because the ground is maintained through the thumb wheel screw.
A loosely attached adapter compromises the mechanical and electrical integrity of the
combination.
Figure 1-8
Attaching the Adapters
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17
Operating the Probe
Recommended Test Equipment
Adapter Combinations
The figure below shows the allowed adapter and probe connections. There are two
specific combinations that should not be used.
• Do not attach the ac adapter between an attenuator adapter and the probe.
An attenuator adapter must be terminated by the input resistance of the probe. The
ac adapter isolates the probe input resistance.
• Do not cascade two attenuator adapters.
The attenuator adapters are designed to be terminated by the 1 MΩresistance of the
probe. The input resistance of the attenuator adapter is 9 MΩfor the 10x adapter and
10 MΩfor the 100x adapter.
Figure 1-9
Allowed Adapter Connections
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18
Operating the Probe
Recommended Test Equipment
Connector Compatibility
The following are general connector characteristics for the probe, adapters, and
accessories.
• The female connectors on the probe, adapters, and other accessories are designed to
mate with 0.030-inch round or 0.0250-inch square pins.
• The probe, adapter, and extension lead pins are 0.030-inch round.
• The strip of circuit connection posts provided as an accessory has 0.025-inch square
pins.
• The mini-grabber has a 0.25-inch square pin.
• The ground connection at the end of the probe and adapters (where the adapters
fasten) accepts an M3 metric screw.
Test Board
The primary use of the test board is to apply test and calibration signals to the input of
the probe or adapters. Specific use of the test board is covered wherever it applies.
Grounding
Grounding is very important when probing circuitry. Improper grounding can increase
the common mode signal level. This reduces the effectiveness of the differential probe.
The mechanical connections at the input of the probe are ground for probe signals. The
screw where the ground lead attaches (see figure 1-7) fastens to this ground. Also, the
attenuator and ac adapter fasten to this ground through the screw connection and the
ground is carried through each adapter to its front.
Figure 1-10
Probe Grounds
Coupling Functions
There are three methods for blocking or compensating for the dc component of a signal.
Each has specific advantages.
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19
Operating the Probe
Recommended Test Equipment
Probe System Coupling Functions
dc Reject
dc Reject is the best method of eliminating the dc component of a signal when dc is not
a factor in the measurement.
The key characteristics are:
• The low-frequency component (from dc to the selected corner frequency) is
automatically nulled by the dc reject circuitry.
• Probe CMRR specifications are not compromised as happens when the ac coupling
adapter is uses.
• There is a selectable low frequency corner with -3dB points at 0.05 Hz, 0.5 Hz,
or 5.0 Hz.
• The voltage reject range is ±20 V with the probe alone, ±200 V with the 10x attenuator,
and ±500 V with the 100x attenuator.
dc offset dc Reject ac Coupling
Adapter
dc Blocked
Probe alone
Probe with 10x
Probe with 100x
± 20 V
± 200 V
± 500 V
± 20 V
± 200 V
± 500 V
± 20 V
± 500 V
± 500 V
Set-up needed Adjust offset to put
signal on screen
Select DC Reject
low-frequency
corner
Attach ac Coupling
adapter to
differential probe
Remote Control? Yes1Yes1No
CMRR
degradation?
No No Yes
Low-frequency
degradation?
No Yes Yes
1Isolated external dc reference and control signals are needed
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