Thermocouple Alarm Sensor
A type-K thermocouple produces a voltage that is proportional to temperature. The characteristic of a type-K thermocouple is shown in Figure (a).
In an application, this transducer is used to detect when the temperature reaches 1250°C and then to cause a safety shutoff to trip and stop an operation.
The safety shutoff can be modeled by a 5-kΩ input resistance, while the transducer can be modeled by a variable voltage source, v(T), in series with a resistance of 33 Ω to account for the transducer's wires and internal resistance as shown in Figure (b). The safety shutoff will trip when exactly 10 mV is applied. Select an appropriate resistance R that will cause the safety shutoff to trip at exactly 1250°C.
