Thermocouple_contact

Small thermocouple, coupled with the heater, used to measure true rms value of an alternating current. The current flows in the heater, causing its temperature to rise proportionally to the rms value. The thermocouple generates an EMF proportional to the temperature reached by the heater.

The bulb is evacuated to prevent convection cooling of the heater by surrounding atmosphere.

Samples in the photos were made by American Thermo Electric, LA, Ca.

• Heater 8 mA, 33 ohms, 264 mV
• Couple resistance 10 ohms
• EMF 6 mV at 8 mA heater
• Thermocouple is not insulated from heater

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