Author Topic: Thermistor wiring - school lessons forgotten  (Read 227 times)

Offline JerryNotts

  • Jr. Member
  • **
  • Posts: 27
  • Country: gb
Thermistor wiring - school lessons forgotten
« on: August 13, 2018, 10:49:06 AM »
Good afternoon all, I need some advice and perhaps a refresher on the wiring and connection of thermistors.

I have a small thermistor, operating range 0 deg C to 300 deg C. My recollection is that the wires from the junction need to be exactly the same, but is my memory faulty?

What can I do if one of the wires becomes cut between the thermistor and the temperature controller? Can I simply solder the 2 cut ends together?

Don't ask how it happened, one moment it was in one piece, the next in two pieces!!

Jerry
 :scratch:

Offline John Rudd

  • Hero Member
  • *****
  • Posts: 2237
  • Country: gb
Re: Thermistor wiring - school lessons forgotten
« Reply #1 on: August 13, 2018, 11:06:00 AM »
Jerry,
I think you are confused between thermistor and thermo couple.....

The thermistor is a resistive device with either a neg or pos coefficient....( ohms come down on increasing temp or vice versa..), thermo couple is made from two different materials, e.g iron and constantan or platinum rhodium.....these give a millivolt output dependant on temperature (Seebeck effect...) and ideally, should be connected to the measuring device with an extension lead with similar properties to avoid cold junction compensation....

Hope this helps...John ( retired instrument engineer..) temperature measurement department.. :D
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

Skype: chippiejnr

Offline JerryNotts

  • Jr. Member
  • **
  • Posts: 27
  • Country: gb
Re: Thermistor wiring - school lessons forgotten
« Reply #2 on: August 13, 2018, 11:22:28 AM »
Hi John,

I may be confused in my terminology. The sensor is definitely a thermistor, even if it was a thermo couple my memory would not help although I have cobbled a dozens of these together with the help of our chemical engieers department in the past.

I am a mere chemist so my head is full of useless information of no relevance to this problem.

The question still applies to the cut wiring.

Thanks for th eclarification.

Jerry


Offline John Rudd

  • Hero Member
  • *****
  • Posts: 2237
  • Country: gb
Re: Thermistor wiring - school lessons forgotten
« Reply #3 on: August 13, 2018, 11:28:53 AM »
Either way, just rejoin the two ends of the wire..they are the same metallic element so no consequence..
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

Skype: chippiejnr

Offline JerryNotts

  • Jr. Member
  • **
  • Posts: 27
  • Country: gb
Re: Thermistor wiring - school lessons forgotten
« Reply #4 on: August 13, 2018, 11:35:45 AM »
Thanks John,

I'll do trhat. As you would understand that was the answer that I was hoping for.

Thanks once again.

Jerry :wave: