| 摘要 |
<p>PURPOSE:To make it possible to adjust the polarization voltage of a capacitor microphone accurately without destroying an amplifying circuit by providing a polarization voltage supervisory resistor and polarization voltage supervisory terminal. CONSTITUTION:A calibration signal, supplied from the calibration system of a sound-pressure calibrator to calibration input terminal 8, is supplied to output terminal 7 by way of calibration output terminal 2, capacitor microphone 12, input terminal 1, coupling capacitor 5 and amplifying circuit 6. In comparison with the output voltage of DC polarization electric power source 3, the polarization voltage of capacitor microphone 12 falls slightly because of the relation between the insulating resistance of capacitor microphone 12 and coupling capacitor 5, and polarization resistor 4 and consequently, it is measured through polarization-voltage supervisory resistor 10 to adjust the output voltage of DC polarization power source 3 to a normal polarization voltage.</p> |
