中央空调控制系统的二线制湿度传感变送器设计

Design of Two-Wire Humidity Sensing Transducer of Central Air Conditioning System

介绍了所研制的二线制湿度传感变送器的电路原理及设计计算。该变送器将湿度信号经C／V和V／I转换电路变成电流信号，送入中央空调控制系统，完成对生产车间的湿度控制。变送器触发源电路保证产生的脉冲串具有改善的波形，单稳态电路实现输出波形的稳定。设计的无源积分器有较好线性度，放大电路的高输入阻抗和高共模抑制比保证了可靠测量远距离小信号。给出了4～20mA二线制湿度传感变送器的电路原理图，实例说明，中央空调控制系统使用的湿度传感变送器具有测量范围宽，精度高，抗干扰能力强等特点。

Circuit principle and design calculation of two-wire humidity sensing transducer for central air conditioning system are introduced. The humidity signal is converted into current signal with C/V and V/I conversion circuit of the humidity sensing transducer. And, the current signal is transmitted to central air conditioning system to controlling humidity of the workshop. Pulse train produced by clock circuit of the transducer has improved waveform and output waveform is stable implemented by mono-stability circuit. The linearity of designed passive integrator is fineness. Small signal at a far distance is measured reliably implemented by high input impedance and high ratio of common-mode rejection of amplifier circuit. Circuit principle diagram of 4-20 mA two-wire humidity sensing transducer is given. By practice, the two-wire humidity sensing transducer used by central air conditioning system has many characteristics such as wide measure range, high measure accuracy and good anti-jamming.