Well, i never knew that

[golfpaul]

Electrical resistance has an inverse exponential relationship with temperature, i.e. as temperature increases, resistance will decrease and vice versa. Since the minimum acceptable IR test values are based on a fixed reference temperature (usually 20oC), the measured IR test values must be corrected to the reference temperature in order to make sense of them.



As a rule of thumb, the resistance halves for every 10oC increase in temperature (and vice versa). S if the measured IR test value was 2MΩ at 20oC, then it would be 1MΩ at 30oC or 4MΩ at 10oC.

 

[Knobhead]

What a load of codswallop

 

[stevethesparks]

Electrical resistance has an inverse exponential relationship with temperature, i.e. as temperature increases, resistance will decrease and vice versa. Since the minimum acceptable IR test values are based on a fixed reference temperature (usually 20oC), the measured IR test values must be corrected to the reference temperature in order to make sense of them.



As a rule of thumb, the resistance halves for every 10oC increase in temperature (and vice versa). S if the measured IR test value was 2MΩ at 20oC, then it would be 1MΩ at 30oC or 4MΩ at 10oC.

Resistance increases with temperature!

 

[Farmelectrics]

were or who told you this golfpaul

 

[telectrix]

paul. measure the resistance of a 100watt light bulb ( cold ). it will be about 60 ohms. when hot the resistance is R =V/I. i.e. 530ohms.

 

[Simonslimline]

Maybe have a read about Superconductors as well.

 

[Besoeker]

What a load of codswallop

Don't insult the cod!

 

[Besoeker]

Electrical resistance has an inverse exponential relationship with temperature, i.e. as temperature increases, resistance will decrease and vice versa. Since the minimum acceptable IR test values are based on a fixed reference temperature (usually 20oC), the measured IR test values must be corrected to the reference temperature in order to make sense of them.

A little personal experience that runs counter your assertion.
We do a fair bit of work in paper mills. They can be quite steamy - and I don't mean in the night club sense. Paper mills use a lot of water so humidity is high.

Typically, they have an annual two week summer shut where they maintain what needs to be maintained - then spend the next two months sorting out the new problems introduced.

I was at the start up of one in Scotland doing a few checks. The drive motors were DC and I was checking the insulation of a motor at the "wet end". The field winding was down to 50kohm to earth.
"Jimmy, I think we have a wee problem with this yin."
"Och, dinnae bother wi' it. A bit of heat is aw it needs."
"OK. You're the customer, pal."

So I energised the field and left it overnight. And, sure enough, it was up to 4Mohm by the next morning. This, I reported to Jimmy.

"Aye. Braw job. Braw job."

 

[Spoon]

What a load of codswallop

Say what you mean Tony.... Don't sit on the fence...

 

[Silly Sausage]

Electrical resistance has an inverse exponential relationship with temperature, i.e. as temperature increases, resistance will decrease and vice versa. Since the minimum acceptable IR test values are based on a fixed reference temperature (usually 20oC), the measured IR test values must be corrected to the reference temperature in order to make sense of them.



As a rule of thumb, the resistance halves for every 10oC increase in temperature (and vice versa). S if the measured IR test value was 2MΩ at 20oC, then it would be 1MΩ at 30oC or 4MΩ at 10oC.

Stick to PAT testing mate!!!

 

[Lucien Nunes]

Electrical resistance has an inverse exponential relationship with temperature

You missed out a crucial bit of information: In what material? Not metals, for example, as the above replies have pointed out.

 

[Silly Sausage]

You missed out a crucial bit of information: In what material? Not metals, for example, as the above replies have pointed out.

Interesting; Carbon, Silicon and Germanium have a negative temperature coefficient of resistance.

I never knew that!

 

[HappyHippyDad]

It looks like 'most' ceramics have a NTC as well!! Probably not that related to electrics but interesting as I thought temperature always had a positive coefficient with respect to resistance!

 

[Knobhead]

A little personal experience that runs counter your assertion.
We do a fair bit of work in paper mills. They can be quite steamy - and I don't mean in the night club sense. Paper mills use a lot of water so humidity is high.

Typically, they have an annual two week summer shut where they maintain what needs to be maintained - then spend the next two months sorting out the new problems introduced.

I was at the start up of one in Scotland doing a few checks. The drive motors were DC and I was checking the insulation of a motor at the "wet end". The field winding was down to 50kohm to earth.
"Jimmy, I think we have a wee problem with this yin."
"Och, dinnae bother wi' it. A bit of heat is aw it needs."
"OK. You're the customer, pal."

So I energised the field and left it overnight. And, sure enough, it was up to 4Mohm by the next morning. This, I reported to Jimmy.

"Aye. Braw job. Braw job."

One of the reasons some AC motors have DC applied to the stator when stopped.

 

[Knobhead]

What a load of codswallop

From the OED

[h=1]Definition of codswallop in English:[/h][h=3]noun [/h][mass noun] British informal
Nonsense: I think that’s a right load of old codswallop
More example sentences

• Is it a spiritually enriching pursuit or load of old codswallop?
• We could have been giving him a load of old codswallop.
• That's actually a load of old codswallop - the Belgians brew the best beer in the world.

[h=3]Origin[/h]1960s: perhaps named after Hiram Codd, who invented a bottle for fizzy drinks (1875); the derivation remains unconfirmed.