This SAE Aerospace Standard (AS) covers two basic types of temperature instruments as follows:

Type I: Ratiometer type, actuated by changes in electrical resistance of a temperature sensing electrical resistance element; the resistance changes being obtained by temperature changes of the temperature sensing resistance element.

Type II: Millivoltmeter type, operated and actuated by varying EMF output of a thermocouple; the varying EMF input to the instrument being obtained by temperature changes of the temperature sensing thermocouple.

Purpose:

This document establishes the essential minimum safe performance standards for electrical type temperature instruments primarily for use with turbine powered subsonic transport aircraft, the operation of which may subject the instruments to the environmental conditions specified in Section 3.4.