#ACS #Gas Understanding Controls / ACS Gas Training ACS Gas Training Controls. Gas controls / FSD’s / Thermostats Thermocouple A thermocouple is a device made of two metals, that when heated, will create a small current. This current is sufficient enough to energize the magnet withing a thermos electric valve so that the valve remains open so long as the thermocouple is being heated. When the flame is extinguished, the thermocouple stops creating the current and, as a result, the thermoelectric