
When I purchased my HP 34750A Display module, it came with a somewhat beat-up 34702A Multimeter module. I was mainly interested in the display module to pair up with my existing HP 34703A module, but this is also an interesting module worthy of further exploration.
The Hewlett Packard 34702A Multimeter module is part of the HP 3470 Measurement System. The modular system consists of the HP 34701A DC Voltmeter, this 34702A Multimeter, 34703A DCV/DCA/Ohm Meter, 34740A 4–1/2 digit Display, 34750A 5–1/2 digit Display, 34721B BCD module, 34722A preamplifier module, and the 34720A Battery module.

The 34702A Multimeter module provides four ranges of DC and AC (1 V to 1,000 V ) plus 6 ranges of resistance measurement (from 100 Ω to 10 M Ω). The AC mode frequency range is 45 Hz to 100 kHz. It doesn’t have a current mode or automatic ranging like the HP 34703A though.

Even though it is a much simpler module compared to the HP 34703A, it uses some very high quality / precision components. C10 is a massive 10,350 pF 1% mica capacitor and is used in the AC attenuator circuit. R1 and R2 are a matched set of precision high voltage resistors with a 0.1 % tolerance. There is a matched set of five, 0.05% tolerance resistors in the Ohms Converter circuit.


I was able to clean up the front panel considerably from its original condition, but there are some deep scratches in the paint where calibration stickers had been removed in the past, and some permanent staining on the switch buttons and terminals.

All the capacitors on this board tested good, and the only issue was some circuit board cracks passing thru traces at the mounting cutouts. This seems to be a typical problem with these module boards.
After a thorough cleaning I used some thin cyanoacrylate glue for the cracks and then followed up with some thin wire bent to conform to the existing trace then flow soldered and cleaned with isopropyl alcohol.

All in all the 34702A seems like a very capable module, even though I spent less than 20 minutes making sure that it was operational.
If I can find a HP 34740A 4–1/2 digit display module for a reasonable price I might pair it up for a complete system. — ( Update, I found a 34740A and will post an update) —

The operation and service manual for most of the 3470 measurement system except the 34703A, can be found at hparchive.com.
Higher resolution photos are available in my HP 3470 Album on Flickr.