微安表内阻值对热敏电阻温度计设计的影响

EFFECT OF INTERNAL RESISTANCE OF MICRO AMPEROMETER ON DESIGN OF THERMISTOR THERMOMETER

由电流型非平衡电桥改装的热敏电阻温度计,微安表内阻值的大小对实验能否设计成功起到至关重要的作用。电源设计电压随微安表内阻值的增加线性增大,导致热敏电阻两端加载的最大电压线性增大。当选用量程为300微安的表头时,如果其内阻值大于1600欧姆,按照改装原理得到的参数容易直接击穿热敏电阻。为了设计出高灵敏度且安全可靠的热敏电阻温度计,电路中各阻值应保持在同一数量级且相近,并确保微安表的内阻值远低于1600欧姆。在教学中,内阻在300欧姆以下的微安表是最可靠的。

Based on the current type non-equilibrium electric bridge,the thermistor thermometer is designed with sensitivity and safety.This study indicates that the inner-resistance of micro-ampere-meter is essential in the designing process.The designed voltage of the power increases linearly with the increase of the inner-resistance of micro-ampere-meter,which results in the linear increase of the maximum voltage of the thermistor.When a 300-microampere head is selected,the inner-resistance larger than 1600 Ohms could directly destroy the thermistor.In order to design a highly sensitive and safety thermistor thermometer,all of the resistances in the circuit should be kept in the same order,and the inner-resistance of micro-ampere-meter should be much less than 1600 Ohms.In teaching,micro-ammeters with internal resistance below 300 ohms are the most reliable.