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Oh, got extremely lucky for a change, unbelievably lucky.
A friend just sent me a FREE HP 34401A bench DMM !
I wanted one of those for 10 years now, but they cost 500 Euros here so I always had more important things to pay for, than a bench DMM.
I just received it this evening, a couple hours ago, if even that.
It was a bit rough, the exterior was covered with a dozen labels, was super dirty and sticky... 30 minutes of hard core cleaning later, it now looks much better.
Looks quite decent, other than the front bezel that's yellowed and the top of the bezel that is stained here and there due to remains of some stickers. Like the ink pigments in the stickers somehow managed to stain the plastic. eh...
However I am not too worried because both these issues will be "fixed" instantly, covered up that is... as soon as I find rubber bumpers to complement this fine instrument !
Yes, it's missing the bumpers... hopefully those can be found for a reasonable price... will start searching.
It's missing the carry handle as well, but I don't care because handles always drive me nuts anyway, as they prevent me from stacking instruments !

At the back, I have GPIB and serial, lovely ! I guess this is standard on these instruments anyway...
Still at the back, I noticed a slight damage to the plastic of the "frame" that bolts to the chassis : one of the two screws clearly was not the right one, Pozidrive instead of Torx. So, fearing that the instrument might have been messed with, I proceeded to crack it open for a quick visual inspection... which revealed nothing suspicious at all.
Everything in there looked in perfect condition and original. Date code on IC's indicate early 1993, so 36 years old.
So, I powered it up... no smoke, no explosion... all went smoothly. It powers up just fine, and there are no error codes from the CPU.
The VFD is not super bright of course, given the age, but it's still plenty usable in daylight, even with the neon tubes lit above the bench.
So I don't plan on embarking into a display replacement

So next... can it measure anything ?
I checked DC volts of course, the heart of the beast, and what is used most...
First I connected it to my lab supply so I could quickly sweep from 0V to 30V to see how the meter would react.
No issues, it reads just fine.
So then I went further and tried to test its accuracy. All I have is my cheap Chinese Vref, sorry.
If I set the Vref for a 10V output, the HP measures 10.00293V and the sticker on the Vref says the Chinese measured it at the factory at 10.00258V
So not too bad at first glance !
Did the maths anyway of course. If I got it right then the meter read 0.0035% too high.
IIRC the basic accuracy of the meter is 0.0015% right ?
So I get twice that.
However according to the sticker on the Vref, the Chinese measured their ref using a...... HP 34401A just like mine !
So could just be that my meter is just fine, within spec, and reading high, when the Chinese meter was reading low...
We will never know.
But overall what we can say I guess is that my meter most likely reads within spec, or close enough that it's perfectly usable for my humble purposes...
I certainly trust the meter unless proven otherwise.
OK so now I guess I have officially put a first finger into the rabbit hole of precision and metrology ?

I mean, I already feel the urge to find a more accurate Vref so I can check this meter again and recalibrate it to make it even better ! HELP !!!

No, no money whatsoever for metrology rabbit holes.... the most I would be able to afford for a modern and accurate TE would be 500 Euros or something.
Now that I have this meter, no need to spend 500 anymore.
If anyone knows of an affordable Vref that would be accurate enough to confidently calibrate this meter ?
I am willing to spend up to 100 Euros... would that get me anything in this day and age ? Some more Chinese things I guess ? Links, ideas/suggestions ?

Anyway, I am over the moon, my first decent bench DMM !
Need to check the rest of the features now, but Vdc is the heart of the system and every other feature comes down to measuring Vdc in the end, so I am confident....
HAPPY VINCE !!!!
