Changing the temperature of the measurement junction causes a difference in voltage between the two junctions, which appears on the connector pins. Temperature response of common thermocouple probes. A thermistor located within the DMM is used to establish the ambient temperature, which is assumed to be similar to that of the reference junction in the connector. This provides a measurement point for the DMM's microprocessor to periodically compute the temperature of the external measurement junction. Tips for Measuring Temperature with Maximum Accuracy Selecting The Appropriate Thermocouple Form Factor.
Thermocouples are available from several suppliers in many materials and styles.
It's important to use only thermocouples of the type for which the measurement instrument is specified. In the case of the DMM916, the common type K is specified. It consists merely of a welded bead junction formed at the end of two wires. The bead is applied to the surface being measured with tape, adhesive, or a thermally conductive compound, or suspended in air for ambient measurements. Other thermocouple styles include air probes, immersion probes, surface probes, and piercing probes.