模入通道几个问题探讨

Some Aspects on Analog Input Channel

模入通道是把电子计算机用于自动检测和控制时,所须先解决的一个部分,但它在实用上还存在不少问题。本文对C3数据采集处理控制系统的模入通道作了简介,对研制使用中的难点,即调试中出现的通道干扰现象、采用的光电耦合器—MOS电路式变量程模拟开关、使用精密电源时的干扰现象、影响精密恒流源温度系数指标的因素、放大器调制解调晶体管对接开关的选配以及电子设备过压保护方案,进行了总结探讨,提出了解决途径。

Analog input channel is one of the crucial parts in the utiliza-tion of computer for automatic measurement and control. Currently, there are prac-tical difficulties remained to be resolved in the hook-up of the component to cer-tain system. During the development of G3 Data Aquisition/processing Control Sys-tem, we were also experiencing these difficulties, and were presented in this reportas follows. The analog switch is the fundamental part of the channel. We adopteda tube-typed, opticoelectrocoupling-MOS circuit analog switch. In theory, this is anideal type for the analog switch. Its performance has been confirmed by our prac- tice. During the test-runs of G3 system, we found that the channel interfrence phe-nomena persisted. After conducting substantial tests and careful analyses of the re-sults, we had come up with a way of suppressing the interference. Tests were per-formed and summarized for the key factor, the temperature coefficient, of the trans-ducer's constant-current source that might affect the measurement accuracy. Wefind that the temperature cofficient would depend on performances of the operationamplifier The success of choosing an appropriate amplifier enables us to resolvethe difficulty on the application of a new type semiconductor transducers. Throughexperiments, we have come up with a way to prevent voltage overloading. Bythe four pairs of transistor modulating/demodulating analog switch in the dataamplifier, we found that the selection and distribution could simply be carried outaccording to the reversed current amplification coefficient.