| 摘要 |
PURPOSE:To enable zero adjustment in a short time and attain a prescribed accuracy of zero adjustment, by adding a state detector to change the frequency of a clock signal depending on the state of the zero adjustment. CONSTITUTION:One input terminal e- of a servo unit 2 is connected to a zero point and the other terminal e+ is connected to the output Eo of an amplification circuit 1. The inputs to a comparator 21 have a relationship with each other as e+>e- when the output Eo deviates toward the positive side during zero adjustment in which clock pulses C are applied to a counter 23 by an oscillation control input A. At that time, the output Ea of a D/A converter 24 increases but the output Eo decreases toward zero and finally repeats small oscillation near zero. An input detector 25 detects that the input e+ approaches zero or passes it. The detector controls a pulse generator 22' to reduce the frequency of the clock pulses C to a degree to attain enough accuracy. Thus, the output Eo approaches zero in a short time when the frequency of the pulses C is high. After that, the frequency of the pulses C becomes low. As a result, zero adjustment of enough accuracy can be effected. |
