The scaling type of a thermocouple measurement is defined as either Polynomial
. The scaling type used in a thermocouple acquisition will determine the range of temperatures that can be accurately calculated from the measured raw voltage values.
, the measured voltage values are scaled using an Nth order polynomial equation. For most thermocouples, the equation for converting voltage to temperature is the following:
is the temperature in degrees Celsius, E
is the voltage in millivolts, and Di
is a coefficient determined by the thermocouple type and temperature range. The accuracy of a polynomial fit greatly reduces after a certain range, so the DAQmx Polynomial
scaling type will only let you set a min and max temperature that is known to be accurate for a given thermocouple.
By setting the scaling type to Table
, a wider temperature range can be measured for K, N, T, B, and E type thermocouples.