论文部分内容阅读
工业气相色谱仪中的调零电路是一个高精度的自稳零系统.使用运算放大器组成的这种电路,能对热导检测器(由钨丝组成的电桥电路)输出AB间经常出现的偏离零位的正负几微伏至正负几百微伏、乃至几毫伏间变化的电压信号及时准确地测量和调整,保证热导检测器输给记录仪不测量时的起始电压永远是零(其电路原理图见图1).调零电路工作原理当程序发出调零控制信号后,干簧继电器J_1,吸合,其常开触点合上.来自热导检测器的“0”偏离信号经A_1放大R_4/R_1=1MΩ/20K=50倍,送与A_2放大R_9/R_7=2MΩ/100K=20倍,总放大倍数K=K_1·K_2=50×20=1000倍.同时,由于J_1的常闭触点断开,用作开关元件的场效应管3DJ6E导通,A_2输出至运算放大器A_3组成的积分器.在设定的时间周期10～15秒之后,电
The zeroing circuit in industrial gas chromatographs is a high precision auto-zeroing system that uses an op-amp circuit of this type that outputs frequently-occurring signals to the thermal conductivity detector (a bridge circuit made up of tungsten wires) Deviation from zero plus or minus a few microvolts to plus or minus a few hundred microvolts, and even a few millivolts of voltage signal changes in a timely and accurate measurement and adjustment, to ensure that the thermal conductivity detector to the recorder does not measure when the starting voltage is always Is zero (the circuit diagram shown in Figure 1) Zero-adjustment circuit works When the program sends a zero control signal, the reed relay J_1, pull the normally open contact closed from the thermal conductivity detector 0 "deviation signal amplified by A_1 R_4 / R_1 = 1MΩ / 20K = 50 times, sent and A_2 amplification R_9 / R_7 = 2MΩ / 100K = 20 times the total magnification K = K_1 K_2 = 50 × 20 = 1000 times. At the same time, due to the normally closed contact J_1 is open, the FET used as a switching element, the 3DJ6E turns on, and A_2 is output to the integrator of the operational amplifier A_3. After the set time period of 10 to 15 seconds,