| 摘要 |
PURPOSE:To reduce the influence of a creep phenomenon and that of drift under various conditions by applying a voltage developed at a pyroelectric body to the electrode of a surface acoustic wave delay medium while varying it at a constant frequency, and then detecting variation in oscillation frequency. CONSTITUTION:An feedback oscillator consists of a surface acoustic wave propagation medium 1, electrodes 2 and 3, and an amplifier 4, and its output frequency varies with an electric field between electrodes 7 and 8. When a pyroelectric body 10 is oscillated at a frequency f1 by a driving circuit 26, electrostatic capacity between a charge plate 16 and the pyroelectric body 10 varies to vary a potential V1, and the oscillation output is led out as a signal which is frequency-modulated at the oscillation frequency f1. This FM signal output is applied to an arithmetic circuit 28 through a mixing circuit 21, an FM detecting circuit 23, and an amplifier 25 and multiplied by the phase shift output of the driving circuit 26 to detect a potential to be measured from spectral components of the frequency f1. Consequently, stability against noises is obtained and the S/N ratio of the output signal is improved. |
