EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: 001 on July 08, 2018, 12:59:01 pm
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Hi folks!
I`m owner of two almost identical Flukes 115 and 117
But see my photos!
While 115 is always say zero at AC mode, but 117 says "22" or "21" or "23" at two right digits at all ranges
How can I fix it?
Thanx
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The one that says 0.22 is actually the best one out of the two. :popcorn:
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The one that says 0.22 is actually the best one out of the two. :popcorn:
The readings are must be SAME :-//
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It's pretty normal for meters to jump around a bit when in AC mode. Try switching the leads between the two meters and see if the meters stay the same.
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The one that says 0.22 is actually the best one out of the two. :popcorn:
The readings are must be SAME :-//
What happens when you short the leads together?
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What happens when you short the leads together?
Absolutely NO. The "22" digits is ALWAYS presents. At ALL ranges (see photos)
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Test some AC with both meters and so long as the results are the same you have nothing really to worry about. All my meters jump about a bit when in AC mode.
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maybe thIs gives an answer
http://en-us.fluke.com/products/digital-multimeters/digital-multimeter-frequently-asked-questions.html (http://en-us.fluke.com/products/digital-multimeters/digital-multimeter-frequently-asked-questions.html)
or
https://www.eevblog.com/forum/testgear/3478a-ac-offset/
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The one that says 0.22 is actually the best one out of the two. :popcorn:
The readings are must be SAME :-//
No, 117 infact is better, read the "FINE" print of yours 117 datasheet, as usual, the devil is in the details. >:D
True RMS reading always have the weakness on it's accuracy at both lowest and highest ends. Personally, I always try to switch to the range manually that my measurement result is between 25% up to 75% of the measurement limits.
If a meter claimed to be true RMS, if both probes shorted it shows a perfect zero in AC RMS mode, you should doubt it's accuracy.
Here, your 117 spec ...
(https://www.eevblog.com/forum/testgear/fluke-ac-zero-fault/?action=dlattach;attach=473579;image)
Or here the top end Fluke 287/9 DMM spec ...
(https://www.eevblog.com/forum/testgear/fluke-ac-zero-fault/?action=dlattach;attach=473585;image)
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If a meter claimed to be true RMS, if both probes shorted it shows a perfect zero in AC RMS mode, you should doubt it's accuracy.
What about multi-point calibration/adjustment? Why is it not possible to correct this error in software?
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If a meter claimed to be true RMS, if both probes shorted it shows a perfect zero in AC RMS mode, you should doubt it's accuracy.
What about multi-point calibration/adjustment? Why is it not possible to correct this error in software?
I dunno :-// and its beyond my pay grade. :P
All I said was derived from various DMM's datasheets fine print, and also I said "doubt", not an absolute certainty.
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I have a number of Flukes here including a 117 but can't pull them out for comparison until tomorrow morning as it's a bit late here now and too cold anyway, the 115 and 117 are virtually identical except for a couple of features so providing they are a similar age I would have expected a closer comparable reading, perhaps the OP could swap them around and place the 115 to the left of the 117 in case something is being affected by the meters proximity or orientation.
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If a meter claimed to be true RMS, if both probes shorted it shows a perfect zero in AC RMS mode, you should doubt it's accuracy.
What about multi-point calibration/adjustment? Why is it not possible to correct this error in software?
Well...
a) We don't know how much program memory or calibration storage is available.
b) A lot of people will want the software to be as simple/reliable as possible
c) A lot of people will want the calibration procedure to be as simple/reliable as possible
d) This is only a feel-good issue, not a problem in practice (the meter performs according to spec).
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Two sundry answers from Swedish and USA Fluke supports:
"While the Fluke 117 consistently shows a value on AC volts with zero volts, there's not necessarily a problem. These meters aren't specified at zero volts AC. A recalibration might cause the meter to read closer to zero, but it may not."
vs
"The magnitude of the error would suggest the 117 is faulty, the product has a three year warranty, please return it to the distributor you purchased from or if you indicate your location we can direct to a local service center."
LOL :-//
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Well, I checked my four meters, none of them shows anything above ~30mV after a while and with leads short (or without leads). My DMMs are: two cheap aneg meters, ut61e and 121gw.
In my opinion, even if something is not specified it doesn't mean it is good. So, technically, they can say "it's normal" and get away with this. But this is not what I'd like to hear if i were a customer. I use common sense and performance of similar products from other brands to judge what is normal and what is not. If all DMMs were like this I wouldn't say anything.
So, I'm glad USA support acknowledged the problem. I think that's what Fluke users pay premium.
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While I'd agree that a slight jumping around is normal with open leads, it seems that the O.P. doesn't have that problem. He has a consistent offset of almost exactly 0.4% - and that does seem odd. If it were my meter, I'd test whether that offset remained at actual measured voltages and go from there. In the back of my mind that would always bother me though regardless.