Virtual Air Temperature Measurement by means of Ultrasonic Resonance
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概要
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A virtual air temperature can be obtained by measuring the velocity of ultraconic waves in the air. When compared with other thermometers, it was found that this system is affected less by heat radiation and has a very small time constant.A new quick response thermometer for measuring the change of virtual air temperature, in a small space, by means of automatic tracking of ultrasonic resonance frequency, is described. An air column one centimeter long, between the piezoelectric transmitter and receiver, is excited to establish a resonance of longitudinal sound waves. The change of sound velocity caused by a change in temperature shifts the resonance frequency. Phase differences in off-resonance, between signals of the transmitter and the receiver, are detected by a phase comparator. The output signal, proportional to the phase difference, controls the output frequency (17-18.5kHz) of a voltage-controlled oscillator and a new resonance condition is obtained. A frequency discriminator measures the oscillator frequency, and an analogue output voltage, proportional to the signal frequency, is supplied to a pen recorder. The signal frequency, a digital output, is registered by a digital frequency counter and is recorded by a printer every second.A practical test of this instrument confirmed its quick response and its low susceptibility to heat radiation. The field test made in a tobacco community, to find the distribution of air temperature, is described.
- 公益社団法人 計測自動制御学会の論文
公益社団法人 計測自動制御学会 | 論文
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