| 摘要 |
1,163,169. Measuring bridge circuits. NEDERLANDS APPLIED SCIENTIFIC RESEARCH FOR INDUSTRY TRADE & COMMERCE. Dec.6, 1967 [Dec. 7, 1966], No.55474/67. Heading G1U. [Also in Division H3] A circuit comprises a relaxation oscillator 1 whose frequency is controlled by the out of balance voltage of a bridge circuit 2, the oscillator including two transistors 4, 5 connected in a crosscoupled push-pull arrangement and having their emitters connected to a reference potential and each having its collector coupled through a capacitor 26, 46 to the base of the other, the collectors also being coupled to the bridge input and the output of the bridge being fed to feed resistors 40, 41 for the bases of the transistors. The oscillator has a fixed central frequency e.g. Kc/S and any out of balance voltage of the bridge is fed through an amplifier 14 and transformer T2 and alters the frequency of the oscillator linearly upwards or downwards of the central frequency, the frequency being read off at point B. The oscillator includes protective diodes 24, 25 in the base circuits of the transistors, temperature compensation in the circuit is provided by a negative temperature coefficient resistor 31 and resistors 32, 33 provide sensitivity control. Resistors 29, 30 and diodes 27, 28 prevent local oscillation in the loop comprising the capacitors 26, 46 and the self and leakage inductance of the primary winding of transformer T1. |
