Trial Manufacture of Thermistor Anemometers

Abstract

A thermistor has a large temperature coefficient of resistance and fit hot resistance, and yet is small in size. If such thermistor is used in place of the hot wire of hot wire anemometer, therefore, it is possible to obtain a simple but high-sensitivity instrument. However, it has been difficult to compensate its ambient temperature. The writer manufactured for trial a thermistor anemometer employing the idea of temperature compensation. In the constant resistance method, it has become possible to make the temperature compensation using the resistance compensation shown in Eq. 13 or 14 by means of the fundamental circuit of Fig. 3. As a direct reading type anemometer using the constant current method, the relation between wind speed and Ig. was obtained by Eq. 20 and then it was confirmed that this relation coincided with that between the results of actual measurement and experiment(Fig. 10). It was alstudied to what extent the discrepancy among the resistance values of detecting thermistor and compensating thermistor, constant B and various characteristics of dissipation constant is permissible when using the circuit shown in Fig. 12(a) as a method for temperature compensation(Eqs. 26, 31, 34 and Fig. 14). As shown in Fig. 16, the meter circuit needs the resistance compeation of Eq. 36. If such adaptor as shown in Fig. 20 is attached to the thermistor, it becomes possible to measure high speed wind. Concerning the direction of detecting part, the data shown in Figs. 23 and 24 were obtained.