Hewlett Packard 34401a

Since March 2015 I am an owner of HP 34401a, one of the top range multimeters, which is also bench multimeter. I can measure voltage, current, 2 wire and 4 wire resistance measurement, frequency and so on. Since it is used peace of equipment, but said it was calibrated not too long ago, I wanted to compare it to something, something that would be even better.

Luckely, Faculty of Electrical Engineering was kind enough, so that I could compare my meter to theirs, agilent 34420a, 7 and 1/2 digit nano volt/micro ohm meter.

Here are some results. Using Fluke 731B as DC reference standard:

Here is 1Vdc output:

10Vdc output:

To use higher voltage, we used HP 6205B dual supply, wired in series, to get around 100v

Next was to read around 100mV and this is the result:

And some random voltages:

Since 34420a is not multimeter, we used 1R etalon, 0.01% for 0.1 nominal current, 0.03% for full current, max current being 3A. So my 34401a will read in amp, while 34420a will read voltage on that 1R:



310mA, note that my hand meter is reading 2mA high all the time



Also tested 4 wire resistance, on 100m and 10mR, both readings were ~3mR high, so still usable down to 10mR, very nice

I think this was 360€ well spend, don't you think so?


Hidden 10mA AC range


To enable : "DIAG:POKE 25,0,1"

To disable : "DIAG:POKE 25,0,0"



34401a visits:

Application Note on bridging audio amplifiers

A discussion on bridging audio amplifier circuits like LM3886. Includes a schematic to drive a matched pair of amplifiers in a bridged configuration, power supply considerations for LM3886 and TDA1514 power amplifier circuits-especially in bridged pairs.

Application Note on parallel-bridging LM3886 audio amplifiers

How to make it loud - real loud. (230 watts rms into 8 ohms without clipping from 4 ICs. How to match LM3886s for parallel operation, then bridge the matched parallel banks. If you are not familiar with bridging amplifiers (BTL configuration), read the Application Note on bridging listed left in article Application Note on bridging audio amplifiers.

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