# Reading high ohms through coil



## Jlarson (Jun 28, 2009)

nitro71 said:


> Today I was troubleshooting a small relay. Self contained one. Cube style. Was reading 2.2 M ohms through the coil. Thought the coil was bad but it functioned fine. Anyone know why I was getting a reading that high?


what voltage?


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## nitro71 (Sep 17, 2009)

120 volt. I was really baffled.


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## Jlarson (Jun 28, 2009)

nitro71 said:


> 120 volt. I was really baffled.


Was it hooked up, and do you know what brand it was?


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## nitro71 (Sep 17, 2009)

Not sure, pulled it out. Tested it across the coil. 2.2 M Ohms. Same on some replacement ones we got. Wasn't really my rodeo. Was just there to help. Coil reading seems super high or wrong.


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## Jlarson (Jun 28, 2009)

You sure it wasn't 2.2k cause at 2.2m that's the most energy efficient coil ever. I know a lot of relays have snubers and stuff in parallel but that wouldn't cause a higher resistance.


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## nitro71 (Sep 17, 2009)

I might have been K, i'm not keen on the Ideal meter I've got. We were going pretty fast to. Seems like Meg. That's almost a open.


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## micromind (Aug 11, 2007)

Some digital meters don't do well when measuring resistance across an inductive device when they're set to autorange. 

Try it with the range manually set to 2K, 4K, or something like that.

Rob


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## Jlarson (Jun 28, 2009)

nitro71 said:


> I might have been K, i'm not keen on the Ideal meter I've got. We were going pretty fast to. Seems like Meg. That's almost a open.


I don't like the ideals I have seen stuff like this happen to them in the past.



micromind said:


> Some digital meters don't do well when measuring resistance across an inductive device when they're set to autorange.
> 
> Try it with the range manually set to 2K, 4K, or something like that.
> 
> Rob


Good tip for everyone to remember, I see auto range trip people up when they use logging multimeters a lot too cause some of them don't range fast enough to catch some quick events.


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## nitro71 (Sep 17, 2009)

This other coil I tested read 146 ohms I think. That sounded correct to me. Not the same model of cube though. Same pin out though.


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## Jlarson (Jun 28, 2009)

nitro71 said:


> This other coil I tested read 146 ohms I think. That sounded correct to me. Not the same model of cube though. Same pin out though.


The different 120 volt ice cubes I stock all fall somewhere in the 3 to 5 K range depending on model. At 146 that thing would be drawing like almost an amp.


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## nitro71 (Sep 17, 2009)

Wouldn't the lower ohms one have lower amp reading.. V=IR?


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## Jlarson (Jun 28, 2009)

nitro71 said:


> Wouldn't the lower ohms one have lower amp reading.. V=IR?


I couldn't find my scientific calculator what do you want from me here:jester:
V=IR
V=120
I = IDK
R= 146

120
---- = I
146

I = .82

V=IR
V=120
I= IDK
R= 2200000

120
----- = I
2200000

I= .000055

Right because to solve for I its I=V/R I could be wrong it happens a lot


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## nitro71 (Sep 17, 2009)

I think I was really tired yesterday. I woke up thinking how could I have that equation wrong. Higher resistance = less amperage like you are saying. Basicaly what I had was a very low amperage coil. I probably had 2.2K Ohms. I'm glad I got that sorted out. Was kinda bugging me. Thanks for the help!


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## Introyble (Jul 10, 2010)

nitro71 said:


> Today I was troubleshooting a small relay. Self contained one. Cube style. Was reading 2.2 M ohms through the coil. Thought the coil was bad but it functioned fine. Anyone know why I was getting a reading that high?


2.2K is pretty normal, 2.2 M is like OUTHEREMAN


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## kielarsp (Apr 9, 2009)

guy's
don't forget about cold resistance to hot resistance. Example when you ring a 60 watt light bulb the resistance is 7 ohms. That would be 17.142 amps per bulb. the hot resistance is about .05 amps.


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## RIVETER (Sep 26, 2009)

kielarsp said:


> guy's
> don't forget about cold resistance to hot resistance. Example when you ring a 60 watt light bulb the resistance is 7 ohms. That would be 17.142 amps per bulb. the hot resistance is about .05 amps.


Tell us what is going on...why the difference?


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## micromind (Aug 11, 2007)

RIVETER said:


> Tell us what is going on...why the difference?


All conductors have lower resistance at lower temperatures. As temperature increases, resistance also increases. 

Rob


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## Jlarson (Jun 28, 2009)

micromind said:


> All conductors have lower resistance at lower temperatures. As temperature increases, resistance also increases.
> 
> Rob


But still a 146 ohm 120volt ice cube relay coil ain't right.


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## RIVETER (Sep 26, 2009)

micromind said:


> All conductors have lower resistance at lower temperatures. As temperature increases, resistance also increases.
> 
> Rob


Okay, you are are talking about a positive co-efficient of temperature.


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