| 摘要 |
PURPOSE:To reduce spike noises by modulating a carrier by an analog signal like a strain gauge output and by specifying the relation between the switching frequency of the switching power source of electronic equipment, which performs synchronous detection at the carrier frequency, and a synchronizing frequency. CONSTITUTION:A carrier supplied from a modulating circuit 2 is modulated by the analog output of a strain gauge, etc., which operates by being supplied with a direct current from electronic equipment using a switching power source. This modulation output is synchronized and detected to obtain a detection output. A commercial power source AC is rectified 6 and supplied to a switching circuit 7'. Firstly, the moving contact of a relay 12 is connected to a side (a) to obtain the operation of an asynchronous switching power source. With its power, the modulating circuit 2 and a frequency converter 10 operate to connect the moving contact to a side (b). Then, the switching power source operates at the same driving frequency as the output frequency of the converter 10. For the purpose, a switching frequency and modulation frequency are set at an even-numbered ratio and this constitution reduces spike noises. |
