Agilent Technologies 1141A User manual

Agilent Technologies
Agilent
1141A Differential Probe
and 1142A Probe Control
and Power Module
User’s Guide and Service Guide

Notices
© Agilent Technologies, Inc. 2000 – 2014
No part of this manual may be reproduced in
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tronic storage and retrieval or translation
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ment and written consent from Agilent
Technologies, Inc. as governed by United
States and international copyright laws.
Manual Part Number
01141–97004
Edition
August 2014
Designed in USA
Agilent Technologies, Inc.
Oscilloscope Products Division
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Safety Symbols
This apparatus has been designed and
tested in accordance with IEC Publication
1010, Safety Requirements for Measuring
Apparatus, and has been supplied in a safe
condition. This is a Safety Class I instru-
ment (provided with terminal for protective
earthing). Before applying power, verify that
the correct safety precautions are taken
(see the following warnings). In addition,
note the external markings on the instru-
ment that are described under "Safety Sym-
bols".
CAUTION. Instruction
manual symbol. Risk of
Danger. Refer to the manual
for more information. The product is
marked with this symbol when it is
necessary for you to refer to the
instruction manual in order to protect
against damage to the product.
CAUTION. Hazardous
voltage symbol. Risk of
Electric Shock. Refer to the
manual for more information.
Earth terminal symbol: Used to indi-
cate a circuit common connected to
grounded chassis.
Safety Notices
CAUTION. A CAUTION notice
denotes a hazard. It calls attention to
an operating procedure, practice, or the
like that, if not correctly performed or
adhered to, could result in damage to
the product or loss of important data.
Do not proceed beyond a CAUTION
notice until the indicated conditions
are fully understood and met.
WARNING. A WARNING notice
denotes a hazard. It calls attention to
an operating procedure, practice, or
the like that, if not correctly per-
formed or adhered to, could result in
personal injury or death. Do not pro-
ceed beyond a WARNING notice until
the indicated conditions are fully
understood and met.
2 1141A and 1142A User’s Guide

Contents
1141A and 1142A User’s Guide 3
Contents
1Operating the Probe
Introduction 6
Safety Information 10
To Set Up the Probe 11
To Adjust Offset Null and DC Reject Gain 13
Using the Accessories 15
Grounding 20
Coupling Functions 21
Remote Operation 23
Differential Amplifiers and CMRR 25
2Calibrating the Probe
dc Gain Accuracy 29
10x Attenuator Accuracy Test 32
100x Attenuator Accuracy Test 34
Bandwidth 36
CMRR Test 38
Calibration Test Record 42
3Adjusting the Probe
Probe Adjustment 45
Attenuator Adapter Adjustment 54
4Service
Theory of Operation 60
Troubleshooting 65
Removing and Replacing Assemblies 67
Replaceable Parts 72

4 1141A and 1142A User’s Guide
Contents

5
Agilent Technologies
1
Operating the Probe
Introduction 6
Safety Information 10
To Set Up the Probe 11
To A d j u s t O f f s et N u ll and DC Reject Gain 13
Using the Accessories 15
Grounding 20
Coupling Functions 21
Remote Operation 23
Differential Amplifiers and CMRR 25
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. (Refer to
Chapter 4, “Service” for disassembly procedure.)
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.

6 1141A and 1142A User’s Guide
1Operating the Probe
Introduction
Introduction
The 1141A probe with the 1142A Probe Control and Power Module
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 50Ωinput is available.
Figure 1 1142A Probe Control and Power Module
Accessories Supplied Figure 2 on page 7 lists the items supplied with the 1141A probe
system. Unnumbered items are supplied but not shown in figures.
See the Replaceable Parts List for parts not listed below.
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.

Operating the Probe 1
Introduction
1141A and 1142A User’s Guide 7
Figure 2 1141A Differential Probe and Accessories
Item Description Qty
Part
Number Item Description Qty
Part
Number
1 Differential Probe 1 9 Test Board 1 01141-6650
4
2 10x Attenuator Adapter 1 5063-2144 10 Flat-blade Alignment Tool 1 8710-1961
3 100x Attenuator 1 5063-2145 11 Circuit Connection Posts
(strip of 20)
1 1251-5943
4 ac Coupling Adapter 1 5063-2146 Probe Control and Power
Module
1 1142A
5 Two-inch Extension Leads
(package 5)
1 5959-9334 Power Cord 1 see parts
list
6 Mini Grabbers 2 1400-1422 Carrying case
7 Five-inch Ground Lead 1 5061-6162 User and Service Manual 1
8 Shielded Signal Lead 1 01141-6870
2

8 1141A and 1142A User’s Guide
1Operating the Probe
Introduction
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 “Accessories
Supplied” on page 6.
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 50Ω.
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 Table 1 on page 9 lists 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.
Cleaning Requirements If the instrument requires cleaning: (1) Remove power from the
instrument. (2) Clean the external surfaces of the instrument with
a soft cloth dampened with a mixture of mild detergent and water.
(3) Make sure that the instrument is completely dry before
reconnecting it to a power source.

Operating the Probe 1
Introduction
1141A and 1142A User’s Guide 9
Table 1 Recommended Test Equipment
Equipment Required Critical Specifications
Recommended
Agilent
Model/Part Usea
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
Test Board No substitute (supplied accessory) 01141-66504 A
Load BNC feed-through, 50ΩPasternack Enterprises
PE6008-50 or
Huber+Suhner 22543742
P
Cables (2) BNC, 50 W 36-inch 10503A P,A
Cable BNC, 50 W 9-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
a P = calibration tests. A = adjustments

10 1141A and 1142A User’s Guide
1Operating the Probe
Safety Information
Safety Information
This apparatus has been designed and tested in accordance with
IEC Publication 1010, Safety Requirements for Measuring
Apparatus, and has been supplied in a safe condition. This is a
Safety Class I instrument (provided with terminal for protective
earthing). Before applying power, verify that the correct safety
precautions are taken (see the following warnings). In addition,
note the external markings on the instrument that are described
under "Safety Symbols" on page 2 of this book.
WARNING Before turning on the instrument, you must connect the protective earth terminal
of the instrument to the protective conductor of the (mains) power cord. The
mains plug shall only be inserted in a socket outlet provided with a protective
earth contact. You must not negate the protective action by using an extension
cord (power cable) without a protective conductor (grounding). Grounding one
conductor of a two-conductor outlet is not sufficient protection.
WARNING Only fuses with the required rated current, voltage, and specified type (normal
blow, time delay, etc.) should be used. Do not use repaired fuses or
short-circuited fuse holders. To do so could cause a shock or fire hazard.
WARNING If you energize this instrument by an auto transformer (for voltage reduction or
mains isolation), the common terminal must be connected to the earth terminal
of the power source.
WARNING Whenever it is likely that the ground protection is impaired, you must make the
instrument inoperative and secure it against any unintended operation.
WARNING Service instructions are for trained service personnel. To avoid dangerous
electric shock, do not perform any service unless qualified to do so. Do not
attempt internal service or adjustment unless another person, capable of
rendering first aid and resuscitation, is present.
WARNING Do not install substitute parts or perform any unauthorized modification to the
instrument.
WARNING Capacitors inside the instrument may retain a charge even if the instrument is
disconnected from its source of supply.

Operating the Probe 1
To Set Up the Probe
1141A and 1142A User’s Guide 11
WARNING Do not operate the instrument in the presence of flammable gases or fumes.
Operation of any electrical instrument in such an environment constitutes a
definite safety hazard.
WARNING Do not use the instrument in a manner not specified by the manufacturer.
To Set Up the Probe
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.
NOTE The 1141A/1142A probe system (specifically the 1142A) requires a power source
of either 115/230 Vac, 47 to 440 Hz, 25 VA maximum.
CAUTION Before connecting power to this instrument, be sure the line voltage switch on the
instrument’s rear panel is properly set as described in this section.
1Verify the setting of the LINE SELECT switch on the 1142A’s rear
panel. The slide switch can be set to either 115 or 230V. See
Figure 3 on page 12 for the location of the switch.
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.

12 1141A and 1142A User’s Guide
1Operating the Probe
To Set Up the Probe
Figure 3 1142A Rear Panel
2Use the power cord to connect the 1142A to the ac mains.
The rear- panel fuse (F1) is a 0.25A, 250V time- delay fuse.
The fuse used is the same regardless of line voltage
selection. To replace the fuse:
aLocate the fuse holder shown in Figure 3. Gently push the
fuse holder in using your finger or a flat-bladed
screwdriver.
bWhile the fuse holder is pushed in, gently turn the fuse
holder counterclockwise.
3Connect the 1141A probe cable power connector to the 1142A’s
rear- panel PROBE connector.
4Connect the output of the probe to the input of the oscilloscope.
5Set the input impedance of the oscilloscope to 50Ω..
NOTE If the oscilloscope does not have a selectable 50Ωinput impedance, connect a
50ΩBNC feed-through termination between the probe output and the input of the
oscilloscope.
6If making an initial equipment setup, continue with the initial
adjustment in the following section.

Operating the Probe 1
To Adjust Offset Null and DC Reject Gain
1141A and 1142A User’s Guide 13
To Adjust Offset Null and DC Reject Gain
For a given combination of 1141A Differential Probe and 1142A
Probe Control and Power Module, you can 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.
■Offset null zeros 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 4 1142A Front Panel
Equipment Needed The following equipment is necessary for initial adjustment.
■5V power supply
■DVM that can measure 25 µV
■50ΩBNC feed- through terminator
■01141- 66504 test board
CAUTION Do not exceed ±7V when using the test board for this procedure. If the voltage is
too high, it will cause excessive power dissipation in the 50Ωtermination on the
test board.
1Perform the steps in “To Set Up the Probe” on page 11.
2Connect a 50ΩBNC feed- through terminator to the output of the
probe.
3Disconnect all accessories from the input of the probe.

14 1141A and 1142A User’s Guide
1Operating the Probe
To Adjust Offset Null and DC Reject Gain
4Connect the DVM to measure the dc output of the probe at the 50Ω
load.
5On the 1142A, set the Local/Remote push button to Local. Under
DC Couple, press Zero offset.
6Set the power supply output to 5V.
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.
8Warm up the 1141A for 30 minutes before making adjustments.
9With 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.
10 On the 1142A, under DC Reject, press 5.0 Hz.
11 Read and record the reading on the DVM, _________ mV.
12 Connect the probe to the test board in the position shown below
(signal to + input).
Figure 5 Signal to + input
13 After the DVM reading stabilizes, adjust DC Reject Gain to the
reading recorded above. With a 5V supply, the voltage swing is
approximately ±12.5 mV. With a lower supply, the voltage swings
proportionally less.

Operating the Probe 1
Using the Accessories
1141A and 1142A User’s Guide 15
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. Figure 6
shows, in a general way, the use of accessories.
Figure 6 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.

16 1141A and 1142A User’s Guide
1Operating the Probe
Using the Accessories
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.
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.

Operating the Probe 1
Using the Accessories
1141A and 1142A User’s Guide 17
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.
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.
2As shown in Figure 7 on page 17, fit 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 7 Attaching the Adapters

18 1141A and 1142A User’s Guide
1Operating the Probe
Using the Accessories
Adapter Combinations Figure 8 on page 19 shows the allowed adapter and probe
connections. There are two specific combinations that should not be
used.
CAUTION 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.
CAUTION 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.
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 B oard 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.

Operating the Probe 1
Using the Accessories
1141A and 1142A User’s Guide 19
Figure 8 Allowed Adapter Connections

20 1141A and 1142A User’s Guide
1Operating the Probe
Grounding
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 fastens to this ground.
See Figure 9. 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 9 Probe Grounds