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Products => Test Equipment => Topic started by: Rax on September 16, 2015, 05:50:28 pm

Title: Fluke 8000a calibration issue - period adjustment
Post by: Rax on September 16, 2015, 05:50:28 pm

Hi all,
I've built a rig around the calibration procedure specified in the manual for the 8000a, and proceeded to calibrate it yesterday.

The rig is comprised by a MAX6225ACPA+, a couple of resistive dividers based on PTF56 precision resistors (0.02% or 0.01%, as I could find them, ppm also 5 or 10) that output very close to, again, the specified points of adjustment: 185.2mV vs. 190mV and 1.865V vs. 1.900V.  You can see I love this old DMM, judging by my investment in this rig.

To cut a long story short, the adjustments went flawlessly (this is probably now better calibrated than my Fluke 189, though it doesn't win at consistency in time...), but there's one roadblock I'd appreciate help with, very much.

I was unable to successfully execute the period adjustment step (4-25). I hooked up my Leader LDC822 set for time interval mode, but upon going full range left to right on R20, I cannot get it anywhere close to 100ns. My counter shows somewhere in between 143ns and 145ns by running that pot all the way end to end.

I am not sure why that is. I also assume this would also only impact my ACV measurements - right? I'd love this to be fully calibrated, but if it's just that, I can live with it. I use my 189 for any ACV measurements, being true RMS.

I also have an Instek GFG-8216A I could use as a counter, but I don't think it has time interval mode. And yet, I could just adjust for 10Hz in frequency counter mode as opposed to 100ns in time interval mode to the same effect, isn't it?

Thanks a lot for your thoughts!

Title: Re: Fluke 8000a calibration issue - period adjustment
Post by: Analysator on September 20, 2015, 09:53:28 pm

Hello Rax,

what revision of the 8000A Instruction Manual do you refer to?

Regards
Martin