ABSTRACT
A thermal anemometer measures the velocity at a point in a owing uid-a gas or a liquid. Figure 59.1 shows a typical thermal anemometer used to monitor velocity in gas ows. It has two sensors-a velocity sensor and a temperature sensor-which automatically correct for changes in gas temperature. Both sensors are reference-grade platinum resistance temperature detectors (RTDs). e electric resistance of RTDs increases as temperature increases. For this reason, they are one of the most commonly used sensors for accurate temperature measurements. e electronics circuit passes current through the velocity sensor, thereby heating it to a constant-temperature dierential (Tv − Ta) above the gas temperature Ta, and measures the heat qc carried away by the cooler gas as it ows past the sensor. Hence, it is called a “constant-temperature thermal anemometer.”
