A digital multimeter K thermocouple interface can be made using this circuit diagram. Type K thermocouples has a wide range of temperature, is used in many temperature applications from cryogenic applications to analyze the exhaust gases of jet engines. Described circuit converts the output signal of the thermocouple into a DC voltage of 10 mV slope / ° C, signal that can be applied to a multimeter or a computer.
Interface is achieved using Cl AD595A manufactured by Analog Devices, integrates into a monolithic chip an instrumentation amplifier and a cold junction compensation of a thermocouple
Type K thermocouple is connected to a special connector, K1.
AD595A provides an alarm output, ALM + (pin 12), which here is used to control a low power LED. Output + ALM move in "L" when one or both of the thermocouple wires are broken. Readings taken when the alarm is activated is not valid because the thermocouple output voltage is linearly related to temperature.