HIGH-FREQUENCY TYPE REMOTE SENSOR DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent an oscillation signal level from being too high even in case of a light load or no load. SOLUTION: An oscillation circuit 11 oscillates a pulse signal. A waveform generating circuit 13 generates a drive signal from the pulse signal and also outputs an integral signal of the drive signal. A resonance circuit 17 oscillates a 1st high-frequency signal with the drive signal, and transmits and outputs it to a voltage detecting circuit 19. The voltage detecting circuit 19 outputs a detection signal corresponding to the negative level of the 1st high-frequency signal. A comparing circuit 21 outputs a trigger signal to the waveform generating circuit 13 when the integral signal reaches the detection signal. The waveform generating circuit 13 drives the resonance circuit 17 with 50% duty in its maximum load state and with minimum duty in the no load state according to the input timing of the trigger signal.