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Fluke meters measuring 110 on 220 outlet (US) with no neutral
tmorris9:
I am in the U.S. and was having an issue with a 220 outlet, my Fluke meters (77 & 101) both said I had 110 from neutral to either hot which is what there is suppose to be but the equipment would not work properly. I had an electrician come out and his meter (a plug in one with just lights for each voltage) showed no voltage across the neutral to hots, he found in another box that was daisy chained to this one the neutral had come loose.
My question (and one that concerns me very much) is why did my Fluke meters show 110v when they should not have? BTW I plugged mine in with electrician there and showed him it said it basically had the neutral and was OK, he just said I don't know but there was definitely no neutral hooked up to that outlet. He hooked up the loose neutral and everything worked.
Now I have used Fluke's for 30+ years and I just lost confidence in them.
Can anyone explain why it showed proper voltage with no neutral?
Thanks!
bdunham7:
--- Quote from: tmorris9 on October 24, 2022, 07:35:06 pm ---Now I have used Fluke's for 30+ years and I just lost confidence in them.
Can anyone explain why it showed proper voltage with no neutral?
--- End quote ---
Your meters are fine, but they are high impedance (~10M) and put no load on the circuit. Depending on how loose the neutral was and what else might be on the circuit, you'll get results like yours that are known as 'ghost voltages'. The voltage is actually there, but goes away as soon as you put any load on it. Meters and testers with a Lo-Z function have a lower input impedance in that range and thus put at least a very small load on the circuit. Your old 77 and entry-level 101 don't have this Lo-Z feature.
https://www.fluke.com/en-us/learn/blog/digital-multimeters/dual-impedance-digital-multimeters
electr_peter:
DMM has high input impedance (around 10 MOhm) and pick ups stray voltage (also called ghost voltage) on the line (from capacitive or inductive coupling). It is "real" voltage, but it has very high impedance (i.e. cannot provide real power). Small load (in the order of few kOhm) on the line is needed to eliminate ghost voltage. This is typically done with LoZ mode on DMM.
Some material from Fluke on ghost voltages and mitigation dual-impedance-digital-multimeters
How To Determine If Voltage Is Real Or a Ghost Voltage Using your Fluke Digital Multimeter
electr_peter:
There are special adapters for regular DMMs to eliminate ghost voltage. DIY is also an option if you know what you're doing.
Fluke SV225 stray voltage eliminator
diy-fluke-sv225-stray(ghost)-voltage-adapter
BeBuLamar:
In another word your Fluke meter is correct that is if you touch between the hot and the neutral you would get a shock because there is 110V potential between them. Only when you connect a load does the voltage went away.
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