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Products => Test Equipment => Topic started by: Dan Moos on August 02, 2020, 10:28:15 pm

Title: Is this a valid way to change cal. battery on HP 3468A?
Post by: Dan Moos on August 02, 2020, 10:28:15 pm

Just got an old HP 3468A in great shape for 25 bucks. I want to change the cal. battery. It reads 3V, but I know that they go off a cliff when they go.

I lack an isolated soldering iron. As many know, I have to do the swap while the meter is powered so that I don't lose calibration data when I pull the old battery.

I have two ideas. One is to put a ground lift plug on the meter. If it has a linear supply with a transformer, it should be floating with the ground lifted, right?  (and thus no path to ground from 3V through my iron).

Other idea is to wire my power supply (Rigol DP832) in parallel with the battery clip, with the meter unplugged. As long as I don't ground reference the Rigol (ignore the green lug), I am safe to use my non isolated iron right?

I can't think of a problem with either method, but want to be safe This is currently my nicest meter, and I don't want to erase the calibration data!

Also, any recommendations on a good battery to replace it with?

Title: Re: Is this a valid way to change cal. battery on HP 3468A?
Post by: Miti on August 03, 2020, 12:46:21 pm

I used an UPS on battery to power the soldering iron, and the soldering iron only, while replacing the battery on my two HP3478As.

For HP3478A there's this program made by Lmester:
https://www.eevblog.com/forum/testgear/free-hp3478a-multimeter-control-program/msg3081034/#msg3081034 (https://www.eevblog.com/forum/testgear/free-hp3478a-multimeter-control-program/msg3081034/#msg3081034)

that can save, restore and manipulate the calibration constants. I don't know much about the HP-IL interface but from what I see, there are ways to interface GPIB to HP-IL, but I don't know if the command sets are the same between the two.