We've been seeing a lot of failures on the 6629A's CC Load Effect test. Is anyone else seeing this issue? We had been sending them to a vendor for repair and they were reporting no issues. Turns out that their MET/CAL procedure was poorly written so they didn't have the resolution to even see the tight specification (15 uA on these units).
We've been getting results that are usually less than 20 uA, but even the ones that pass are pretty close to the limit. I wrote the MET/CAL procedure we use, and we confirm the failures manually, and when we send them in to Keysight they end up confirming and repairing them. I'm just wondering if other people are seeing the same and perhaps its a widespread issue that needs to be addressed at a wider level.
Thanks.
We've been getting results that are usually less than 20 uA, but even the ones that pass are pretty close to the limit. I wrote the MET/CAL procedure we use, and we confirm the failures manually, and when we send them in to Keysight they end up confirming and repairing them. I'm just wondering if other people are seeing the same and perhaps its a widespread issue that needs to be addressed at a wider level.
Thanks.
Based on the lack of any concrete information you've provided, it's rather difficult to respond, however:
1) How old are the 6629A's in question? One should always consider the age of any potential "failures" BEFORE searching for a systemic issue.
2) Line/Load Effects (CC or CV) are addressed by circuit "design/component selection" and not by calibration. "Soft" failures of this type are generally the result of drifting components (age) or contamination within the instrument (high resistance leakage paths) resulting from a dirty environment.
3) Electrolytic capacitors, dry out/leak with age. Additionally, many other precision components like resistors, shunts, A/D's, D/A's, etc. begin to exceed their long-term drift specification with age. Generally speaking, electrolytic caps have a projected age of somewhere <10years.
This particular instrument contains a high degree of active guarding. However, any conductive dust, or unanticipated leakage (capacitors, etc.) could result in CC Load Effect failure.
Keep in mind that as little as 10MΩ would contribute 5µA towards the product's specification of 15 µA.
Regards,
PeterW