An analog signal input circuit

Abstract

The invention discloses a simulation signal input circuit. The simulation signal input circuit comprises a signal input end, a signal processing unit, a plurality of diverter switches, a current source, a current sampling resistor, a signal isolation diode and an overcurrent protective circuit. The power source is connected with the signal processing unit through the diverter switches; the current sampling resistor, the signal isolation diode and the overcurrent protective circuit are connected with the signal processing unit through the diverter switches; and the overcurrent protective circuit is respectively connected with the signal isolation diode and the current sampling resistor. According to invention, the switching-on and the switching-off of the different diverter switches are controlled through the signal processing unit, such that isolation among channels is realized during a signal input process, signal interference among the channels during signal sampling is avoided, and the problems are solved that a conventional signal input circuit with a signal isolation function cannot protect a sampling resistor and a three-wire system resistor samples lead wire resistance to carry out a sample compensation function.

Description

Technical field [0001] The invention relates to the field of analog signal measurement, in particular to an analog signal input circuit. Background technique [0002] The most basic measurement parameters in the industrial field are temperature, pressure, flow and level. The main equipment to measure these parameters are transmitters and sensors. Various transmitters and sensors convert these physical quantities into voltage, current, resistance or digital quantities. signal. For current and voltage signals, signal acquisition devices or instruments are equipped with current sampling resistors and sampling circuits with high input impedance. The lead resistance can be neglected. However, for resistance sensors, the measured signal is inherently resistance, due to the connection between the field sensor and the sampling instrument Often far away, the lead resistance will be superimposed on the real signal, and it cannot be ignored in the occasions with high accuracy requirements....

AI Technical Summary

Problems solved by technology

However, this sampling circuit has two defects. One is that when measuring resistance, the current sampling resistor and the lead resistance are connected in parallel, which requires software to perform nonlinear compensation during measurement, which cannot completely eliminate the error of the lead resistance; the other is that the current sampling resistor When R1 is connected to 24V externally (for example, the transmitter is short-circuited), the 24V voltage is directly connected to the sampling resistor, resulting in excessive power on the sampling resistor and burning

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