Compensated air velocity meter using thermistors - has differential heating corrected in bridge using feedback amplifiers

摘要

The compensated air-velocity meter consists of a pair of thermistor probes in line in a detector tube. Each thermistor is connected into a bridge circuit containing a standard resistor and a differential amplifier. The output of each amplifier is fed back to the bridge so that the temp. of each thermistor is equal to that of the other. This compensates for differential heating of the thermistors which would otherwise occur. The feed-back voltage component of the amplifiers is tapped off and fed to a comparator whose output signal is proportional to the air-flow velocity in the tube. The device can be used as a rate-of-climp indicator in aircraft.