Use of a Direct Current Amplifier and Recorder to Balance a Mueller Resistance Bridge

By taking corrective action for electrical noise resulting from alternating current pickup and induced electrostatic charges, it has been possible to use a commercially available high gain dc amplifier and a recorder to balance a G-3 Mueller resistance bridge. Noise levels below 0.01 μv peak to peak were observed with a response time of approximately five seconds. Using a 25-ohm platinum resistance thermometer and 1-ma thermometer current, a precision of 0.0001°C was obtained in temperature measurement. The permanent and continuous record provided offers advantages over the ordinary optical galvanometer for the observation of time-dependent phenomena and the study of sources of error.