Resistance measurement Mueller bridge

Platinum Resistance Thermometer. Platinum resistance thermometers are based on the electrical resistance of Pt. This resistance for Pt wires wound on a mica support and enclosed in a glass or silica vessel can be manufactured to be either 25.5 Q at 0°C or 2.5 Q at 0°C. The electrical resistance, typically measured in a Wheatstone or Mueller bridge, increases by about 0.1 Q or 0.01 Q, respectively, per degree centigrade (0.4%/°C). Empirical equations convert Pt resistance and its small nonlinearities to temperature ... 

FIGURE 16.12 Mueller bridge circuit for precision resistance measurement. 

The resistance of the platinum thermometer was measured by means of a Mueller bridge. The electrical input energy was determined from the measurements of the current and potential across a 100 Q Constantan wire heater and the time interval of heating. The heater current and potential were measured by means of a Wenner potentiometer in conjunction with a resistor and a volt box. The time interval of heating was measured by means of a precise interval timer. 

Accessories. Some forms of Wheatstone-bridge circuits are used for the measurement of temperature with base-metal or industrial platinum resistance thermometers, while the Mueller bridge is used with precision platinum resistance thermometers. 

---