MEASUREMENT OF SURFACE TEMPERATURE

Improvements in and relating to electrical resistance measurements

... 886,548. Measuring-bridges; resistance measurement. PARSONS & CO. Ltd., C. A. May 26, 1959 [May 12, 1958], No. 15163/58. Class 37. In a Kelvin double bridge network (Fig. 2a) for measuring the resistance value R x of a large inductance (e.g. a transformer winding) the bridge supply voltage is raised to n times that normally used in such a bridge to give adequate sensitivity, where n is an integer, e.g. 10, and applied thereto through a resistance R z in series with a non-inductive current limiting resistance T of the bridge ; the value of R z being such that the steady state supply current to the bridge is unaltered, e.g. such that R Z =(n-1)Rb, where Rb is the input resistance of the bridge, including T. When the bridge is switched into operation, normally closed relay contacts C short-circuit R z until the voltage across T reaches a value ET/Rb corresponding to the steady state drop when R z is in circuit. A damped voltmeter V across T operates an alarm contact at this value to trigger ...