Products > Test Equipment
Acceptance Testing
PixieDust:
Hi, as per this thread that I started a while back:
https://www.eevblog.com/forum/metrology/entry-level-metrology/msg3685063/#msg3685063
I purchased a used 2431L Tektronix and a used HP3478A multimeter. In the above thread I was asking for advice on calibration and the consensus was that I don't need it. I am happy with that assessment. However, I'm still uncertain as to whether the devices are fully functional.
I took some time to read enough of the service manuals to know what needs to be done and what equipment is needed to properly test the functionality of the devices. I obviously don't have this equipment and was wondering about ways to get around purchasing lab grade stuff to test equipment that I paid very little for.
I'm starting to learn the hidden costs of old test equipment. New stuff comes with all sorts of guarantees and expectations. With second hand stuff, all bets are off.
Anyway, just wondering if there are any tips or tricks to verify the equipment? I've used both for random things here and there and so far everything has seemed to make sense and work (except (at least so far) for one of the knobs on the Tektronix which sometimes sticks and causes unwanted behaviour. If you turn the scope off and on again, things reset and it works for a little bit and randomly stops working again), but ideally I want to learn a bit more about what I got unless you guys suggest something else/better.
tautech:
So how much did you spend on these fine old devices not to have faith in what they can do ? :-//
The first step in acceptance is Performance Verification with is also the first step in Calibration however if you have an instrument with a mechanical fault, fix it, use it regardless and watch for the fault not to catch you out or dig deeper into your pockets to get instruments that give you faith in their measurements.
So yeah point the finger at this distributor that sells bright shiny new gear that all comes with a Cal sheet for taking the piss at your predicament but do know very clearly your current position not that long ago was also mine !
There was a time I spent more time repairing my equipment than enjoying the hobby and that really sucks ! :--
Martin72:
--- Quote from: PixieDust on September 29, 2022, 12:11:15 pm --- In the above thread I was asking for advice on calibration and the consensus was that I don't need it.
--- End quote ---
For private usage not, that´s right.
For curiousity, I´ve send my new brymen 869s meter for external calibration and got it back with a 8-pages calibration report.
They checked every range and found some deviations and re-adjusted them... 8)
So now I know it really instead trusting the specs blindly.
In your case, in the case of the HP, a calibration would be useful to know if everything is alright.
I don´t know the prices in your country, but I´ve spend under 100 bucks for it and for me it was worth it.
What the tek scope concerns, hmm..
I think I would buy a newer DSO instead of spending time to fix it or to be uncertain about it´s fully functioning.
CatalinaWOW:
Only you can answer this. Because you are the only one that knows your use case. And the problem is not solved by buying new equipment. Because you need to understand your use case to know how good that equipment needs to be. Do you need a 3458 to get accurate, many digit measurements of voltage, resistance or current? Or do just need to know that the measurements are in the ball park? Do you need absolute accuracy or do you need linearity? Do you need to compare measurements made months or years apart with high precision?
If you don't know what you will be doing, the safest answer is to buy the top of the line new, and pay for regular calibration and adjustment. For most of us budgetary limits don't allow us to be that safe, and we have to trade the use of valuable brain cell operation for those unavailable dollars. Remember that most of the progress in electronics (starting from Faraday and up through Armstrong and Nyquist) was performed with instruments that provided only two or three digits of absolute accuracy assisted by bridges and other tools that allowed excellent differential accuracy.
noisyee:
Sadly no simple tricks for hobbyists to verify an instrument properly.
Most instruments have service manuals to tell how to verify, but they are not always available to public. And calibration grade instruments or standards are very, very expensive, even a second-hand one. It's almost impossible for hobbyists to do that kind of verification.
Keeping some home made "standards" is always helpful. Nowadays we have easy access to some of the most high precision factory-trimmed components that are equally precise or better than our instruments. They are simply something we could trust. I always keeps a surplus GPSDO as my timing standard. Voltage reference chips, high precision resistors and capacitors come handy too.
Behaviors verification is some what more difficult than performance verification. All you have to rely on is lots and lots of experience with that kinds of instruments and a good luck. :)
After all, warranty is what you got lose for paying much less to get a decent instrument.
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