JPS5574249A - Level detection system - Google Patents

Abstract

PURPOSE: To enable to sure detection, by the discrimination whether the phase of cross point between the sinusoidal wave signal and the set threshold level is the set value or more taking the zero cross point of sinusoidal wave signal as the reference, for the level of the sinusoidal wave signal at the carrier supply unit lowered less than set level.

CONSTITUTION: The reference pulse generating circuit 12 produces pulse at the zero cross point of sinusoidal wave signal. The comparison pulse generating circuit 11 produces pulse at the cross point of the sinusoidal wave signal and the set threshold value level. The logical discrimination circuit 13 judges whether the phase difference between the reference pulse and the comparison pulse is more than the set value. The phase of the reference pulse is constant through the production of every one period of the carrier output independently of the carrier output level. Since the phase of the comparison pulse is the cross point between the carrier output level and the set threshold value level, when the carrier output is lowered, the phase is delayed. Accordingly, the lowering of the carrier output level less than the set value can be detected with the phase difference more than the set value.

COPYRIGHT: (C)1980,JPO&Japio