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Fluke 185 Review

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shakalnokturn:
How much of a full performance check have you made? Enough to see that ACV measurements are no good, anything else?
In your situation I'd start by swapping the suspicious EEPROM for a copy of one of the dumps provided here, at least with that you should be able to find out if the ACV being wrong is due to a lost calibration or hardware fault.

ErnestB:
Hi. Thanks for replying. The DCV is within the +/-0.05% compared to HP3478A. Frequency measurement is correct. I will check the resistance mode. I do not think it just "lost" the calibration data from the EEPROM, but I don't rule out anything yet. The meter was several years in the annual calibration program and one year they couldn't calibrated it anymore (they don't gave the specifics about the fail). That's why the meter ended up as a hobby project. I have ordered the meter and was only used by me all the time. Regarding the AC voltage being out of the specifications I see a clear strong frequency dependant behavior so first I suspect one of the capacitors, or a RC combination. Resistors being more stable over the time and could easily being measured, and even have clear value marking on it. As the capacitors doesn't makes it more difficult without the parts list. Now I will try different C values to try to understand better what it does. As I can see on the block diagram it should be some kind of high pass filter or better compensation network. But I suspect they did some part of the compensation with hardware and some in the firmware. That would be a bummer as I can not do the calibration. If I put a random cal data in it I do not expect much accuracy, and still can not calibrate the damn thing.

ErnestB:
Did some testing but still don't know what is causing this systematic AC Voltage reading error. There are a lot compensating capacitors, for every range a few, but I think that chance that all of them are wrong is very low. There must be one main source of error. The main AC couple capacitor C72 is common for all ranges, but if I short circuit that one not much change. Then we have the serial combination of C99 and C100, that are maybe also used for all ranges. These could be the source of common error for all (tested) ranges.

maxniz:
hi,
i friend gave me an'185 .. it is a bit inaccurate but above all when I measure a voltage it takes 20 seconds for a correct indication. it rises very slowly and stops at the end showing the more or less correct value and this for any measure and on any scale. it makes me think that there is an altered resistance but I have no diagram and no values..can someone help me thanks

shakalnokturn:
That sounds typical of PCB contamination. Any signs of battery leakage such as deposit or corrosion on the battery terminals?

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