温度测量经常需要远地读数,传感器所发送的实际上是一个4～20mA的电流。商品电流发送器价格昂贵;而此电路简单,成本很低。 集成块LM3911内含一个10mV/℃的电压源,一个6.8V的参考电压和一个可外用的运放。附加少量无源元件和一个晶体管,就构成了一个温度控制的电流源电路。 电阻R1与Ra、Rb为星形连接,它们与R2、R3确定了运放的电流增益,使该电路在温度为-20℃ Temperature measurements often require far readings, and the sensor actually sends a 4-20 mA current. Current transmitters are expensive; this circuit is simple and low cost. The LM3911 contains a 10mV / ° C voltage source, a 6.8V reference voltage and an external op amp. With a small number of passive components and a transistor, a temperature-controlled current source circuit is formed. Resistor R1 and Ra, Rb for the star connection, and they R2, R3 determine the current gain of the op amp, so that the circuit at a temperature of -20 ℃