Products > Test Equipment
Keithley 197A owners' corner
electrold:
I just received the AN/USM-486A military model of the Keithley 197 multimeter which I purchased on eBay. It came with its carrying case, IEC line cord, test leads, and RF probe. It has the battery and looks new. It powered up fine and some preliminary checks give me confidence that it will perform as it should. This model has the battery option and the rear panel CALIBRATION switch.
One thing I observed from reading the military manual and the Keitlley manual is that the military model has relaxed accuracy specs. For example, the Keithley 197 spec for the 2VDC range is 0.011% +2 counts for 1 year, whereas the military spec is 0.05% +10counts for 1 year. Other specs are similar with the Kiethley having the better specs. I don't know if the Keithley model is actually better or if the military has just loosened their required specs. If anyone has any knowledge about this I would appreciate a reply.
rastro:
I haven't dug into it, but did you take in account for the environmental range expectation on the "M" version?
electrold:
Environmental specs are identical on commercial and military versions according to the manuals. I do find a difference in warm-up times though. The commercial 197 has 1 hour warm-up to rated accuracy but the military 197M has a warm-up time of 5 minutes. Perhaps this is the reason for the relaxed accuracy spec on the 197M. If it is operated on battery, you can't wait around for an hour for it to settle down to the better accuracy.
rastro:
You're probably right about the 5-minute warm up needing 'relaxed' specifications. Most likely the 'M' version is probably on par with the standard K197 if you allow a full hour warm up.
As mentioned before I still prefer the 'M' version because it has an added fuse on the 10 Amp input and removable power cord. It also looks like it has better noise shielding.
rastro
electrold:
The battery in my meter was, of course, discharged and could not be charged as 5 of the 10 cells in the pack were unchargeable. Who needs battery operation for this anyhow? Certainly I don't - so I removed the pack and the battery board.
My meter has a CAL sticker on it - it was last calibrated Dec 2, 2016 and has a cal void date of Mar 22, 2019. Using my A584-M Voltage Reference Module with the meter warmed up for more than an hour, it is well within the 197 commercial specs, at least at 2.5, 5, 7.5, and 10VDC.
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