A CLASS OF DOUBLE-BALANCE QUADRATURE BRIDGES FOR INTERCOMPARISON OF 3-TERMINAL RESISTANCE INDUCTANCE AND CAPACITANCE STANDARDS

Double-balance a.c. bridge circuits are described, in which two or three sources generating voltages with 90°phase differences are used. Null balancing of both indicators may be rapidly and precisely accomplished if a certain succession of operations is observed and the four variable parameters are properly chosen. Particular types of such bridges allow familiar balance relations (such as those met with in classical Wien, resonance, Maxwell etc. bridges) to be reproduced, without series connection of the three-terminal bridge elements. Reciprocal comparisons of resistance, inductance and capacitance standards by using these bridges were carried out; typical values of errors observed were 1...2 ppm.