FLUKE AC zero fault - Page 1
Forum section: electronics / testgear

author: 001
author_rank: Super Contributor
timestamp: July 08, 2018, 12:59:01 pm
content: Hi folks!I`m owner of two almost identical Flukes 115 and 117But 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 rangesHow can I fix it?Thanx

author: Fungus
author_rank: Super Contributor
timestamp: July 08, 2018, 01:11:35 pm
content: The one that says 0.22 is actually the best one out of the two.

author: 001
author_rank: Super Contributor
timestamp: July 08, 2018, 02:27:46 pm
content: Quote from: Fungus on July 08, 2018, 01:11:35 pmThe readings are must be SAME

author: Terry01
author_rank: Frequent Contributor
timestamp: July 08, 2018, 03:01:38 pm
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: July 08, 2018, 03:18:22 pm
content: Quote from: 001 on July 08, 2018, 02:27:46 pmWhat happens when you short the leads together?

author: 001
author_rank: Super Contributor
timestamp: July 08, 2018, 09:06:46 pm
content: Quote from: Fungus on July 08, 2018, 03:18:22 pmAbsolutely NO. The "22" digits is ALWAYS presents. At ALL ranges (see photos)

author: Terry01
author_rank: Frequent Contributor
timestamp: July 09, 2018, 06:18:46 pm
content: 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.

author: DuPe
author_rank: Regular Contributor
timestamp: July 11, 2018, 05:39:42 am
content: maybe thIs gives an answerhttp://en-us.fluke.com/products/digital-multimeters/digital-multimeter-frequently-asked-questions.htmlorhttps://www.eevblog.com/forum/testgear/3478a-ac-offset/

author: BravoV
author_rank: Super Contributor
timestamp: July 11, 2018, 05:56:51 am
content: Quote from: 001 on July 08, 2018, 02:27:46 pmNo, 117 infact is better, read the "FINE" print of yours 117 datasheet, as usual, the devil is in the details.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 ...Or here the top end Fluke 287/9 DMM spec ...

author: exe
author_rank: Unknown
timestamp: July 11, 2018, 10:54:16 am
content: Quote from: BravoV on July 11, 2018, 05:56:51 amWhat about multi-point calibration/adjustment? Why is it not possible to correct this error in software?

author: BravoV
author_rank: Super Contributor
timestamp: July 11, 2018, 11:08:39 am
content: Quote from: exe on July 11, 2018, 10:54:16 amI dunnoand its beyond my pay grade.All I said was derived from various DMM's datasheets fine print, and also I said "doubt", not an absolute certainty.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 11, 2018, 11:28:34 am
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: July 11, 2018, 12:50:13 pm
content: Quote from: exe on July 11, 2018, 10:54:16 amWell...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 possiblec) A lot of people will want the calibration procedure to be as simple/reliable as possibled) This is only a feel-good issue, not a problem in practice (the meter performs according to spec).

author: 001
author_rank: Super Contributor
timestamp: July 11, 2018, 05:09:56 pm
content: Twosundryanswers 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

author: exe
author_rank: Unknown
timestamp: July 11, 2018, 06:19:17 pm
content: 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 supportacknowledged the problem. I think that's what Fluke users pay premium.

author: eKretz
author_rank: Frequent Contributor
timestamp: July 11, 2018, 09:37:19 pm
content: 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.