AbstractsPhysics

This thesis describes a bridge detector designed to operate between 2 kilocycles and 100 kilocycles per second. The detector is an electronic device which beats the incoming signal with a local oscillator signal. This effect is due to the heterodyne principle. The local oscillator is of the Wein Bridge type which utilizes a Wein Bridge C-R feedback circuit to produce stable harmonic-free oscillations. The beat-frequency signal is filtered by a two-section tuned amplifier tuned to 1000 cycles per second. The amplifiers are of the parallel-T feedback type which use a C-R degenerative feedback network to produce selective amplification. The output signal is detected by means of earphones. Good sensitivity is obtained by the use of high gain throughout the circuit. Several capacitors were measured at frequencies up to 20 kilocycles on a Schering bridge using the instrument. Balances of five significant figures were easily obtained.