Physical parameter measurement and digital display - using negative temp. coefficient transducer resistance in high stability bridge circuit

摘要

A device for measuring a physical parameter and displaying it digitally is suitable for measurement of voltage, current, force, pH value etc. and esp. for temp. It contains a non-linear transducer, esp. a resistor with negative temp. coefficient, and is practical and economical whilst being accurate and reliable enough for medical use, i.e. as a medical thermometer. The transducer resistor R(V) is connected in series with one (R2) of four high stability resistors (R1 to R4) in a bridge circuit. The input voltage (UE) to an analogue-to-digital converter is derived from a bridge potential. The converter reference voltage (UR) is that across the transducer resistance R(v) and its series resistor (R2). The bridge resistor values are chosen according to the ratio of the converter input and reference voltages and the value of the transducer resistance R(V).