Electronics > Metrology
Data Precision 8200 calibrator - repair and other fun stuff
Rax:
Hi all,
I was very lucky to score one of these calibrators during the slow days of holidays - I'm more convinced every year that's a very good time to be combing through listings and get good deals - and, as they seem to typically need, the only real issue was a complete restoration of the switches. All of these seem to look like they've been immersed for years in households of heavy smokers or something, as the grime on those switches is just incredible.
Enclosed pics depict some of this work, though not the perfect cleanliness of the finished product after I switched to using an eraser. I simply forgot that I used to do this (I even have an electric eraser and a full set of tips...) - I guess sometimes one forgets their own figured out methods. In any case, with the eraser, the circular concentric lines are gone too and the tin surface is perfectly clean and shiny. I used IPA and ammonia alternatively to clean this, before the eraser, with a good wash of IPA wrapping it up every time, so if there's anything left from the eraser, it'd be removed.
I'd be interested in hearing some overall thoughts on this calibrator. My units are up to 6.5 digits, so this seems to be perfectly adequate. This far, everything I measured generated by this unit has been absolutely perfect to all digits (by instruments' agreement). I may bite the bullet, and, when everything is confirmed working, have this calibrated (meaning, verification) and tagged as such for high confidence provisions.
One thing I'm not really sure of is its 100mV output. I don't seem to measure it at the front terminals - but some sources seem to indicate that should only come out at the back. If that's the case, does anyone have some info how to achieve this? Is there some proprietary cable? I am not sure what needs to be connected to the "J301" and/or "J302" ports at the back of the unit.
Thank you for your input in advance.
jwet:
Don't know what you paid but that's a great score- first class calibrator. Basic spec is 10 ppm and 1 ppm/C drift which is 5 digits worst case. You generally want a standard to be 10x of your DUT so you're probably shy of 6-1/2 digits technically. I wouldn't hesitate to send it to a cal lab once you've got basic operation- see if they can give you actual readings rather than just running the standard cal.
The 100 mV output is indeed only available on the back. Its kind of an unbuffered output vs the front panel kelvin 4 wire stuff- two wire only and 100 ohm output Z. Don't know why its done this way.
You might add some anticorrosion lubricant to the switches on reassembly- Boeshield T-9 or Deoxit D5. Most common alcohols are 91 or 99% with the rest being water.
Have fun.
Rax:
--- Quote from: jwet on January 03, 2023, 05:17:27 pm ---Don't know what you paid but that's a great score- first class calibrator. Basic spec is 10 ppm and 1 ppm/C drift which is 5 digits worst case. You generally want a standard to be 10x of your DUT so you're probably shy of 6-1/2 digits technically. I wouldn't hesitate to send it to a cal lab once you've got basic operation- see if they can give you actual readings rather than just running the standard cal.
The 100 mV output is indeed only available on the back. Its kind of an unbuffered output vs the front panel kelvin 4 wire stuff- two wire only and 100 ohm output Z. Don't know why its done this way.
You might add some anticorrosion lubricant to the switches on reassembly- Boeshield T-9 or Deoxit D5. Most common alcohols are 91 or 99% with the rest being water.
Have fun.
--- End quote ---
Thank you, jwet.
I actually forgot to mention that I did indeed recondition the contacts with Deoxit. To do that, I used cotton swabs just to keep the Deoxit on the metal surface only. The switches work great now (I still have to do the +/0/- and the range... which are working fairly OK but I can't resist!).
Conrad Hoffman:
It's a great unit. Those switches are the weak point and I didn't know you could get them apart for cleaning. Mine are terrible and no amount of soaking or Deoxit has gotten them back to reliable. Still, whatever the display says, is correct, even if you have to fiddle the switches a bit to get there. The reference is a LM399. I suspect a cal house would charge an arm and leg to properly calibrate it, as all the (clever) octal? ranges need to be adjusted. You'd be way better off to find a good KVD and reference, and do it yourself. Does yours have the HV or GPIB options?
Rax:
--- Quote from: Conrad Hoffman on January 03, 2023, 05:52:32 pm ---It's a great unit. Those switches are the weak point and I didn't know you could get them apart for cleaning. Mine are terrible and no amount of soaking or Deoxit has gotten them back to reliable. Still, whatever the display says, is correct, even if you have to fiddle the switches a bit to get there. The reference is a LM399. I suspect a cal house would charge an arm and leg to properly calibrate it, as all the (clever) octal? ranges need to be adjusted. You'd be way better off to find a good KVD and reference, and do it yourself. Does yours have the HV or GPIB options?
--- End quote ---
I highly recommend doing the switches - not a difficult job and shouldn't take long (there are some youtube videos on this). Getting to them is pretty straight forward and even the switches are pretty clearly intended to offer the possibility of servicing (which, really, applies to the entire unit). Once done, all switches will operate flawlessly and done with care - for instance, I've obstructed the adjustment holes through the shielding inside to protect the reference circuitry during the work - nothing else should be disturbed.
I'd probably just have a cal house check their performance, not adjust them - I am in Southern California and, with all the wealth of them around, I am not aware of any here willing to adjust something like this. But checking and possibly providing long form data paperwork for not much $ is possible. As the unit seems to close or dead on, I think I'd be willing to risk it.
That said, if anyone in this community is near me and would have what it takes to adjust this to calibrated state, please do let me know.
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