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                                    Your new 3478A is a fully programmable HP-IB* digital multimeter.
In an automatic test or on the bench, the 3478A offers 3 1/2 to 5 1/2
digit resolution for measuring dc volts, true RMS ac volts, 2- and 4-
wire ohms, and dc and RMS ac current. The 3478A offers dc voltage
performance from 100 nanovolt sensitivity up to 300 volts (full scale),
true RMS capability up to 300 kHz, and resistance measurements from
100µΩ sensitivity to 30MΩ (full scale). Its dc and true RMS
ac current measuring capability is from 1µA sensitivity up
to 3A. The fast autorange capability of the 3478A allows you
to make measurements over a wide dynamic range without
sacrificing throughput rates.

By selecting the number of digits displayed and using the
autozero feature, the 3478A allows you flexibility in
measurement speed and accuracy. Up to 71 readings per
second can be made with the 3478A in the 3 1/2 digit mode.
The 3478A has a fast trigger mode which lets you bypass the
built-in settling time delay to make fast true RMS ac
measurements in systems applications.

Serials 2619A37795 and above

1-2. The information in this manual is for the Installation,
 Operation, Performance, Calibration, and Service of the
 3478A Digital Multimeter. The manual is designed for the
 use of Service Trained Personnel. Other users should refer
 to the Operators Manual. This manual is separated into the
 following sections.

1-3. Section I, General Information

1-4. A short description of the manual and introduction to
 the 3478A is in Section I. The section also lists instrument
 options, specifications, and accessories.

1-5. Section II, Installation Procedures

1-6. This section explains how the 3478A is prepared for use
 and includes power requirements, line voltage selection, etc.
 The section also explains how to connect the multimeter for
 remote operation.

1-7. Section III, Operation

1-8. The condensed operating instructions of the 3478A, for the
 use of Service Trained Personnel, is in this section. For more
 complete instructions, refer to the Operators Manual.

1-9. Section IV, Performance Test and Calibration

1-10. The 3478A’s Performance Test and Calibration Procedures
 are in Section IV. The Required Equipment Table and an
 abbreviated specification table are also included.

1-11. Section V, Replaceable Parts

1-12. Section V lists the replaceable parts of the 3478A.
 It also includes pictures and illustrations of chassis
 and mechanical parts.

1-13. Section VI, Backdating

1-14. This section has information which adapts this manual
 to 3478A’s with serial numbers below the ones shown on the
 title page.

1-15. Section VII, Service

1-16. The 3478A’s Troubleshooting Procedures, Theory Of Operation,
 and Schematics are in Section VII. The troubleshooting
 information is in the form of Service Groups which are symptoms
 oriented (i.e., what is the failure). The complete theory of
 operation is in Service Group F and the Schematics are
 in Service Group G (last group).

1-17. Appendix A

1-18. The appendix has a condensed description of the HP-IB (Hewlett-Packard Interface Bus).