A convenient linearity calibration method for precision ratio bridges

The ratio bridge is a common facility in measurement especially in temperature measurement. Four resistances are combined into a resistance network to obtain the ratios that cover almost the range of the ratio bridge. This paper proposes a convenient method to calibrate the linearity of the bridge. It also proposes a new simple way to evaluate the accuracy of the bridge. Finally, a precision thermometry bridge F900, a standard resistance in a thermostatic oil bath and four high stable resistances in a thermostat which made the value of resistances network steady were used to evaluate the new method in National Institute of Metrology.