A balance-detector for alternating-current bridges

A balanced valve arrangement with a portable d.-c. galvanometer of pointer type is described for use as balance-detector in a.-c. bridge work. Over an extensive range of frequencies its sensitivity is comparable to that of a vibration galvanometer or telephone. The direction of deflection shows which way the bridge must be adjusted to secure a balance as in the case of a d.-c. bridge or electrodynamometer, but the false-zero effect found with the latter is absent. The arrangement could be adapted for use at radio frequencies.