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| ohms issue with a Fluke 87 - solved |
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| kcbrown:
--- Quote from: istovit on September 09, 2021, 01:14:24 am ---just finished cleaning the rotary switch and were still between 2-3 ohms with leads crossed 1003 ohms at the ma. input and 2.3 at the 10a input. with the delta function I was able to read a 2 ohm resistor. I could live with this but would rather not,what protection components are involved when a voltage is applied in ohms mode? TIA --- End quote --- At this point, it's time to take the meter apart. Use one of your other meters and start measuring resistances in the ohms path inside the Fluke. Because you're able to properly measure a 2 ohm resistor in delta mode, that means you probably don't have a scaling issue, but rather an offset issue. My money's on something like a cracked solder joint, so you should certainly at least examine the joints in the measurement path, and might consider reflowing them anyway even if you don't see anything. |
| robert.rozee:
sighs... it sounds a bit like you've stretched one or both of the multimeter's leads. have you tried shorting together the multimeter's input terminals directly using a short piece of copper wire? if this reads (close to) zero ohms, then the problem is in your leads. do you have a spare set to try? if you stretch a multi-stranded length of cable (such as a multimeter lead) that has fine strands, various of the strands within the cable will snap. they will NOT all snap at the same place. the end result is that you can, after a few minor stretches of even fewer major stretches, end up with a length of cable with no single strand being connected at both ends. this will result in... well, i hope yo can imagine the result! volts will usually read fine, ohms will have a disconcerting offset, and amps will cause the damaged lead to get unexpectedly hot. cheers, rob :-) |
| LaurentR:
--- Quote from: robert.rozee on September 09, 2021, 01:38:35 pm ---sighs... it sounds a bit like you've stretched one or both of the multimeter's leads. --- End quote --- I have had a several Fluke and Pomona TL71 leads that suffered from this. They were retail-bought so probably genuine, but I was surprised to find that they were definitely conducting but had high resistance. |
| kcbrown:
--- Quote from: istovit on August 16, 2021, 12:43:42 am ---last tuesday it was 6 ohms,before I checked the leads on another meter today it was just over 4 and .3 on the other meter. if the same thing is happening here what could be doing that? thanks for the replies --- End quote --- If you've got another meter then you should also have another set of leads. Is this a problem that occurs with all of your leads or just a single set? Obviously if it's with all of your leads then the problem is almost certainly in the meter. And if it follows the leads then the problem is with the leads. The single-lead test is also a good one to do. If you find that one of your leads generates a significantly higher resistance than the other then you have a faulty lead. If both of them generate the same resistance and that resistance is the same resistance you've been reading by shorting both leads together, then you've got a problem in the meter. If the problem is with your meter then you'll need to take it apart as I suggested previously. |
| istovit:
the leads read about .5 ohms in other meters but I did notice RT1 was replaced by flux around the pads. it reads 1536 ohms. R2 is 917k,almost 8% high. I'll put something together to sub it and see what happens. |
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