Thermocouple: Difference between revisions
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# with this all connected, ignite the burner or pilot of the appliance, keeping any buttons pressed in to keep the flame lit on to the thermocouple. | # with this all connected, ignite the burner or pilot of the appliance, keeping any buttons pressed in to keep the flame lit on to the thermocouple. | ||
# with the thermocouple still in the flame, check the mV displayed on your multi-meter. | # with the thermocouple still in the flame, check the mV displayed on your multi-meter. | ||
[[File:Multi-meter connected to thermocouple.jpg|alt=Multi-meter connected to thermocouple|none|thumb|200x200px|Multi-meter connected to thermocouple]] | |||
For a millivolt gas valve, such as a Robertshaw, you should expect a voltage of over 20mV for the gas valve to work. For other controls, such as gas taps a voltage of about 15mV would be expected. | For a millivolt gas valve, such as a Robertshaw, you should expect a voltage of over 20mV for the gas valve to work. For other controls, such as gas taps a voltage of about 15mV would be expected. | ||
Revision as of 17:52, 27 May 2025
Thermocouple
What is a Thermocouple?
A thermocouple, is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage. This voltage can be interpreted to measure temperature. Thermocouples are widely used as temperature or flame sensors.
How to test?
If you find that the flame, monitored by a thermocouple isn't staying lit, or is going out after a short period of time. This is possibly due to a faulty thermocouple. Depending on the type of thermocouple and gas control used, will depend on how the thermocouple is tested.
Standard Gas Millivolt Thermocouple
- Disconnect the thermocouple from the gas valve
- using a multi-meter with clamp leads
- place the red (+) clamp on the outer (Copper) of the thermocouple, anywhere along its length
- connect the black (-) clamp to the end of the thermocouple, which has been removed from the gas valve
- put your multi-meter on to mV DC (Millivolt Direct Current), this may show as the ⎓ symbol. You may need to change the range on your multi-meter for mV.
- with this all connected, ignite the burner or pilot of the appliance, keeping any buttons pressed in to keep the flame lit on to the thermocouple.
- with the thermocouple still in the flame, check the mV displayed on your multi-meter.
For a millivolt gas valve, such as a Robertshaw, you should expect a voltage of over 20mV for the gas valve to work. For other controls, such as gas taps a voltage of about 15mV would be expected.