PURPOSE: To stabilize a driving voltage and to perform highly accurate measurement, by feeding back the voltage of the secondary winding of a driving transformer to an AGC circuit of an oscillator circuit on the primary side.
CONSTITUTION: A voltage V2 at a point (b) of a secondary winding N22 of a driving transformer T is fed back to an AGC circuit 2. When the voltage V2 becomes larger than the voltage, which is determined by a diode D1 and a Zener diode ZD in the AGC circuit 2, a current flows to a resistor R5 and a negative voltage is generated at a point (c). In this way, a negative bias voltage is applied across the gate and the cource of an N channel junction type FET transistor Q1, and the channel resistance of the FET becomes large. The loop gain of the circuit becomes low and the voltage V2 is stabilized. A driving voltage Ve for a load cell LC of the transformer T is likewise stabilized. Therefore the output fluctuation of the load cell becomes very small.
MOCHIZUKI MASARU
YAMAMOTO SEIICHIROU
