Agilent Technologies
Agilent 34401A
6 ½ Digit Multimeter
Service Guide
ii 34401A Service Guide
Notices
© Agilent Technologies, Inc. 1991 - 2007
No part of this manual may be reproduced in
any form or by any means (including elec-
tronic storage and retrieval or translation
into a foreign language) without prior agree-
ment and written consent from Agilent
Technologies, Inc. as governed by United
States and international copyright laws.
Manual Part Number
34401-90013
Edition
Seventh Edition. August 2007
Printed in Malaysia
Agilent Technologies, Inc.
3501 Stevens Creek Blvd.
Santa Clara, CA 95052 USA
Microsoft® and Windows® are U.S. regis-
tered trademarks of Microsoft Corporation.
Software Revision
This guide is valid for the firmware that was
installed in the instrument at the time of
manufacture. However, upgrading the firm-
ware may add or change product features.
For the latest firmware and documentation,
go to the product page at:
www.agilent.com/find/34401A
Warranty
The material contained in this docu-
ment is provided “as is,” and is sub-
ject to being changed, without notice,
in future editions. Further, to the max-
imum extent permitted by applicable
law, Agilent disclaims all warranties,
either express or implied, with regard
to this manual and any information
contained herein, including but not
limited to the implied warranties of
merchantability and fitness for a par-
ticular purpose. Agilent shall not be
liable for errors or for incidental or
consequential damages in connec-
tion with the furnishing, use, or per-
formance of this document or of any
information contained herein. Should
Agilent and the user have a separate
written agreement with warranty
terms covering the material in this
document that conflict with these
terms, the warranty terms in the sep-
arate agreement shall control.
Technology Licenses
The hardware and/or software described in
this document are furnished under a license
and may be used or copied only in accor-
dance with the terms of such license.
Restricted Rights Legend
U.S. Government Restricted Rights. Soft-
ware and technical data rights granted to
the federal government include only those
rights customarily provided to end user cus-
tomers. Agilent provides this customary
commercial license in Software and techni-
cal data pursuant to FAR 12.211 (Technical
Data) and 12.212 (Computer Software) and,
for the Department of Defense, DFARS
252.227-7015 (Technical Data - Commercial
Items) and DFARS 227.7202-3 (Rights in
Commercial Computer Software or Com-
puter Software Documentation).
Safety Notices
CAUTION
A CAUTION notice denotes a haz-
ard. It calls attention to an operat-
ing 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
proceed beyond a WARNING
notice until the indicated condi-
tions are fully understood and
met.
34401A Service Guide iii
Safety Information
General
Do not use this product in any manner not
specified by the manufacturer. The protec-
tive features of this product may be
impaired if it is used in a manner not speci-
fied in the operation instructions.
Do not install substitute parts or perform
any unauthorized modification to the prod-
uct. Return the product to an Agilent Tech-
nologies Sales and Service Office for service
and repair to ensure that safety features are
maintained.
Ground the Instrument
If your product is provided with a ground-
ing-type power plug, the instrument chassis
and cover must be connected to an electri-
cal ground to minimize shock hazard. The
ground pin must be firmly connected to an
electrical ground (safety ground) terminal at
the power outlet. Any interruption of the
protective (grounding) conductor or discon-
nection of the protective earth terminal will
cause a potential shock hazard that could
result in personal injury.
Cleaning
Clean the outside of the instrument with a
soft, lint-free, slightly dampened cloth. Do
not use detergent or chemical solvents.
Safety Symbols
WARNING
Main Power and Test Input Dis-
connect: Unplug instrument from
wall outlet, remove power cord,
and remove all probes from all
terminals before servicing. Only
qualified, service-trained person-
nel should remove the cover from
the instrument.
WARNING
Line and Current Protection
Fuses: For continued protection
against fire, replace the line fuse
and the current-protection fuse
only with fuses of the specified
type and rating.
WARNING
Front/Rear Switch: Do not
change the position of the
Front/Rear switch on the front
panel while signals are present on
either the front or rear set of ter-
minals. The switch is not intended
as an active multiplexer. Switch-
ing while high voltages or cur-
rents are present may cause
instrument damage and lead to
the risk of electric shock.
Earth Ground
Chassis Ground
Risk of electric shock
Refer to manual for addi-
tional safety information
Alternating Current
On supply
Off supply
‘In’ position of bi-stable push
switch
‘Out’ position of bi-stable
push switch
CAT II (300V)
IEC Measurement Category II.
Inputs may be connected to
mains (up to 300 VAC) under
Category II overvoltage condi-
tions.
iv 34401A Service Guide
WARNING
IEC Measurement Category II. The
HI and LO input terminals may be
connected to mains in IEC Cate-
gory II installations for line volt-
ages up to 300 VAC. To avoid the
danger of electric shock, do not
connect the inputs to mains for
line voltages above 300 VAC. See
"IEC Measurement Category II
Overvoltage Protection" on the
following page for further infor-
mation.
WARNING
Protection Limits: To avoid instru-
ment damage and the risk of elec-
tric shock, do not exceed any of
the Protection Limits defined in
the following section.
Protection Limits
The Agilent 34401A Digital Multimeter pro-
vides protection circuitry to prevent damage
to the instrument and to protect against the
danger of electric shock, provided the Pro-
tection Limits are not exceeded. To ensure
safe operation of the instrument, do not
exceed the Protection Limits shown on the
front and rear panel, and defined as follows:
Note: The front-panel terminals are shown
above. The rear-panel terminals are identi-
cal. The Front/Rear switch selects the ter-
minal set to be used. Do not operate this
switch while signals are present on the
front or rear terminals. The current-protec-
tion fuse is on the rear panel.
Input Terminal Protection
Limits
Protection Limits are defined for the input
terminals:
Main Input (HI and LO) Terminals. The HI
and LO input terminals are used for voltage,
resistance, frequency (period), and diode
test measurements. Two Protection Limits
are defined for these terminals:
HI to LO Protection Limit. The Protection
Limit from HI to LO (Input terminals) is
1000 VDC or 750 VAC, which is also the
maximum voltage measurement. This
limit can also be expressed as 1000 Vpk
maximum.
LO to Ground Protection Limit. The LO
input terminal can safely "float" a maxi-
mum of 500 Vpk relative to ground.
As is implied by the above limits, the Protec-
tion Limit for the HI input terminal is a maxi-
mum of 1500 Vpk relative to ground.
Current Input Terminal. The current input
("I") terminal has a Protection Limit of 3A
(rms) maximum current flowing from the LO
input terminal. Note that the current input
terminal will be at approximately the same
voltage as the LO terminal.
Note: The current-protection circuitry
includes a fuse on the rear panel. To main-
tain protection, replace this fuse only with a
fuse of the specified type and rating.
Sense Terminal Protection
Limits
The HI and LO sense terminals are used
only for four-wire resistance and tempera-
ture measurements ("
Ω 4W"). The Protec-
tion Limit is 200 Vpk for all of the terminal
pairings:
LO sense to LO input
HI sense to LO input
HI sense to LO sense
Note: The 200 Vpk limit on the sense termi-
nals is the Protection Limit. Operational
voltages in resistance measurements are
much lower — less than 10 V in normal
operation.
IEC Measurement Category II
Overvoltage Protection
To protect against the danger of electric
shock, the Agilent 34401A Digital Multime-
ter provides overvoltage protection for
line-voltage mains connections meeting
both of the following conditions:
The HI and LO input terminals are con-
nected to the mains under Measurement
Category II conditions, defined below,
and
The mains are limited to a maximum line
voltage of 300 VAC.
34401A Service Guide v
IEC Measurement Category II includes elec-
trical devices connected to mains at an out-
let on a branch circuit. Such devices include
most small appliances, test equipment, and
other devices that plug into a branch outlet
or socket. The 34401A may be used to make
measurements with the HI and LO inputs
connected to mains in such devices, or to
the branch outlet itself (up to 300 VAC).
However, the 34401A may not be used with
its HI and LO inputs connected to mains in
permanently installed electrical devices
such as the main circuit-breaker panel,
sub-panel disconnect boxes, or permanently
wired motors. Such devices and circuits are
subject to overvoltages that may exceed the
protection limits of the 34401A.
Note: Voltages above 300 VAC may be mea-
sured only in circuits that are isolated from
mains. However, transient overvoltages are
also present on circuits that are isolated
from mains. The Agilent 34401A are
designed to safely withstand occasional
transient overvoltages up to 2500 Vpk. Do
not use this equipment to measure circuits
where transient overvoltages could exceed
this level.
Additional Notices
Waste Electrical and
Electronic Equipment (WEEE)
Directive 2002/96/EC
This product complies with the WEEE Direc-
tive (2002/96/EC) marking requirement.
The affixed product label (see below) indi-
cates that you must not discard this electri-
cal/electronic product in domestic
household waste.
Product Category: With reference to the
equipment types in the WEEE directive
Annex 1, this product is classified as a
"Monitoring and Control instrumentation"
product.
Do not dispose in domestic household
waste.
To return unwanted products, contact your
local Agilent office, or see
www.agilent.com/environment/product
for more information.
Agilent 34138A Test Lead Set
The Agilent 34401A is compatible with the
Agilent 34138A Test Lead Set described
below.
Tes t L ead Ratin g s
Test Leads - 1000V, 15A
Fine Tip Probe Attachments - 300V, 3A
Mini Grabber Attachment - 300V, 3A
SMT Grabber Attachments - 300V, 3A
Operation
The Fine Tip, Mini Grabber, and SMT Grab-
ber attachments plug onto the probe end of
the Test Leads.
Maintenance
If any portion of the Test Lead Set is worn or
damaged, do not use. Replace with a new
Agilent 34138A Test Lead Set.
WARNING
If the Test Lead Set is used in a
manner not specified by Agilent
Technologies, the protection pro-
vided by the Test Lead Set may be
impaired. Also, do not use a dam-
aged or worn Test Lead Set.
Instrument damage or personal
injury may result.
