Abstract
Along with the rapid development of modern industry in the industrial field has many physical needs to be monitored to determine whether the machine work, but in the process of industrial control we often appear this kind of circumstance, or inappropriate use after the installation of sensor signal transmission cable, moreover from economic Angle, cable transmission difficult construction, installation cost is higher, Especially for the transmission distance is far, signal transmission cable in the serious distortion of industrial control signal, and then the collection and transmission is a very important topic. Meanwhile, for the continuous, stable, safe production, increase the yield, improve product quality, accordingly to process information and control a higher request.
4-20MA often used in industrial instruments, such as industrial equipment of temperature transmitter and pressure transmitter is used is 4 - the current signal transmission 20MA, anti-jamming ability nature, let alone can be guaranteed, precision instrument its resistance of these basic as infinite in external impedance within a certain range, the current signal output impedance is not because of external changes, so called constant-current source. Currently the crux of the problem is not a kind of good method can accurately in reliable, based on the collection, 4-8 20MA signal, usually through the op-amp junior AD of processing, now, if the collection of 8 to ensure accuracy of practice before the whole circuit cost will improve.
Keywords：Data acquisition、data transmission
