Thermocouple, grounded or ungrounded check

[slepax]

Hello,

I am wondering if there's a way to know whether the thermocouple I have is grounded or ungrounded? Would it be fair to assume the ungrounded type would have zero resistance from the negative connector to the shield?

Thanks!

 

[MaxHeadRoom78]

I would expect a shielded device may be have a the shield separate to conductors, this leaves the option open whether to earth ground a device conductor or not, the shield is usually connected to GND at the source end.
Max.

 

[KeepItSimpleStupid]

"grounded" thermocouples are a "special case" of the rule your citing. Yes, there will be a connection to the "sheath" as it's normally called from both wires. "zero resistance" is hard to achieve.

Grounded thermocouples have a much better response time. Ungrounded ones play better with instrumentation.

 

[MaxHeadRoom78]

Zero resistance (0 ohms) on my meter is a dead short, open circuit is OL or Infinity.
Max.

 

[KeepItSimpleStupid]

Depends on your definition of zero - 0.000000000 (infinite number of zeros)

The point, I was trying to make is that wire has finite resistance, likely in mlilliohms. I had to worry at both extremes with currents from about 2 pA to 3000 A and I had to worry about mV drops near say 400 mV.

 

[Tony Stewart]

grounding can create another bimetallic thermal voltage. so generally not done.