Our Fluke 8508A has started to behave strangely. When the unit has been ON around one week (Fluke's own shorting plate on all the time on input), resistance starting to drift heavily when doing zero like in 2ohm range, then select 20kohm range. Zero drifting a lot. When doing selftest, it gives an error FAIL: OHM 2661. Such happening randomly and dissapear when turn off/on the the unit. The zeroing goes well and selftest pass after unit cold boot. Our lab another 8508A has the same behaving but disappeared when Fluke repair it "PCA Ohms Repaired" in 2019. Currently 8508A is end of support from Fluke official service. What might cause such behaving and can it fix somehow?
Hello, what you mean by zero drifting? Do you have data captured from instrument , perhaps a plot?
Do the reading also drift with full-scale input (e.g. measuring fixed resistance standard?). Check electrolytic capacitors on resistance PCB module, if meter is old I'd suggest preventively replacing them.
Does your meter use older generation ohms board with TDP1603 networks or newer Fluke resistors? I'd also check operation in TrueOhm and normal 4w modes.
@bbs_tin, Big thanks your detailed information. I meant zero drifting, when all inputs are shorted by Flukes shorting plate. Are those TDP1603 or newer resistors easy fo find somewhere? I will check the ohm board model
TDP1603 still can be found, but first you'd need to do more definitive testing. I don't quite get what you mean by "zero drifting", you'd need to show some data captured with duration and environment conditions monitoring data.
Could be normal. It's been years since I last touched 8508A, as I prefer better 1281 in my lab. :) Also useful to repeat same tests in multiple ranges or at least monitor output current stability of 8508A current source with another DMM.
Here's how older ohms board look like, you can clearly see some capacitors that I've been replacing and bunch of current sources around TDP1603 resistors:
Our Fluke 8508A has started to behave strangely. When the unit has been ON around one week (Fluke's own shorting plate on all the time on input), resistance starting to drift heavily when doing zero like in 2ohm range, then select 20kohm range. Zero drifting a lot. When doing selftest, it gives an error FAIL: OHM 2661. Such happening randomly and dissapear when turn off/on the the unit. The zeroing goes well and selftest pass after unit cold boot. Our lab another 8508A has the same behaving but disappeared when Fluke repair it "PCA Ohms Repaired" in 2019. Currently 8508A is end of support from Fluke official service. What might cause such behaving and can it fix somehow?
Hello, what you mean by zero drifting? Do you have data captured from instrument , perhaps a plot?
Do the reading also drift with full-scale input (e.g. measuring fixed resistance standard?). Check electrolytic capacitors on resistance PCB module, if meter is old I'd suggest preventively replacing them.
Does your meter use older generation ohms board with TDP1603 networks or newer Fluke resistors? I'd also check operation in TrueOhm and normal 4w modes.
@bbs_tin, Big thanks your detailed information. I meant zero drifting, when all inputs are shorted by Flukes shorting plate. Are those TDP1603 or newer resistors easy fo find somewhere? I will check the ohm board model
TDP1603 still can be found, but first you'd need to do more definitive testing. I don't quite get what you mean by "zero drifting", you'd need to show some data captured with duration and environment conditions monitoring data.
Could be normal. It's been years since I last touched 8508A, as I prefer better 1281 in my lab. :) Also useful to repeat same tests in multiple ranges or at least monitor output current stability of 8508A current source with another DMM.
Here's how older ohms board look like, you can clearly see some capacitors that I've been replacing and bunch of current sources around TDP1603 resistors: