thermocouple test

[gk]

how do i test a thermocouple with a multimeter

 

[kevplumb]

warm it it and check the voltage at the other end usually in the region of 30 mv ish

 

[gk]

warm it it and check the voltage at the other end usually in the region of 30 mv ish

if i took off the thermocouple and heated it up , on my multimeter what setting should it be, been told to use uf but mv is this the right scale are they the same i have a fluke 16 cheers kev

 

[kevplumb]

dunno mate ive got a fluke 179 and its marked mv on mine

if my memory serves uf is capacitance (no doubt im wrong) but im not a spark


names a giveaway

 

[gk]

dunno mate ive got a fluke 179 and its marked mv on mine

if my memory serves uf is capacitance (no doubt im wrong) but im not a spark


names a giveaway

just checked it kev its mv but says 7.5 to 13mv in a worcester manual

 

[kevplumb]

30 ///13
i was close
least i got 1 no right

sounds about right

 

[gk]

30 ///13
i was close
least i got 1 no right

sounds about right

no woorrys

 

[htgeng]

HRPC sell a gadget that you connect to the TC. You push a button and it gives you a pass/fail result.

 

[DP]

13mv will be voltage when the thermocouple is loaded. Open circuit voltage, as Kevin suggests, will be around 30 mv

It is like measuring voltage on a car battery. It reads 12 volts on most meters but will not carry a load if it is done.

 

[ChrisR]

According to the fisiks I done, a tc output can be calculated from the properties of the dissimilar metals. If anyone can tell me why the open circuit voltage of a tc goes down with age I'd love to know!

 

[gk]

According to the fisiks I done, a tc output can be calculated from the properties of the dissimilar metals. If anyone can tell me why the open circuit voltage of a tc goes down with age I'd love to know!

what range do i put my multimeter on and where do i put the probes what reading will i have if fc is nackerd and what reading should i have if it is ok

 

[COG]

You need a good contact with the earth, crocodile clip on a tag is good and meter set at DC mv and as said above a max of around 30 but if below 20 check flame and tip position if ok then replace if fluctuateing wildly then you prob have a bad connection ,most honywell gas valves will hold above 8 mv but more is good if you can fit an interupter lead at the gas valve then you can test it under load. The pos conection goes to the earth and neg to the tc

 

[PEDANTICVINDICTIVEMAN]

Rob the little gizmo the t/couple connects to on an old (a working one) gasvalve, screw it onto the end of said t/couple,light the pilot on the boiler, push the plunger on the gizmo and if it stays up t/couple is ok if not t/couple nacked, costs nowt.

 

[crofty]

You need a good contact with the earth, crocodile clip on a tag is good and meter set at DC mv and as said above a max of around 30 but if below 20 check flame and tip position if ok then replace if fluctuateing wildly then you prob have a bad connection ,most honywell gas valves will hold above 8 mv but more is good if you can fit an interupter lead at the gas valve then you can test it under load. The pos conection goes to the earth and neg to the tc

so when you say the positive connection goes to earth and negative to the tc where does the earth go and where would the negative lead go on the thermocouple

 

[crofty]

Rob the little gizmo the t/couple connects to on an old (a working one) gasvalve, screw it onto the end of said t/couple,light the pilot on the boiler, push the plunger on the gizmo and if it stays up t/couple is ok if not t/couple nacked, costs nowt.

do you mean unscrew the tc from gas valve screew it into a spare gas valve heat tc up with a lighter and what next............