0-20ma or 4-20ma direct current analog quantity output device

Abstract

The invention relates to a 0-20mA or 4-20mA direct current analog quantity output device. According to the technical scheme of the invention, a voltage output end AOUT and data input ends DI0-DI7 of a D / A (Digital / Analog) converter (2) are respectively and correspondingly connected with a voltage input end VIN1 and data output ends P1.0- P1.7 of a current output type operational amplifier (4), a voltage input end VIN2 and a voltage output end VOUT of an voltage output type operational amplifier (7) are respectively and correspondingly connected with a sampling output end VSP of a sampling resistor (5) and a voltage input end AIN of an A / D (Analog / Digital) converter (8), data input ends P2.0-P2.7 of a CPU (Central Processing Unit) module (1) are connected with data output ends Do0-Do7 of the A / D converter (8), a command receiving end RX of the CPU module (1) is externally connected with the upper computer, a current output end IOUT of the current output type operational amplifier (4) and a sampling input end of the sampling resistor IIN (5) are respectively and externally connected with a current input end IL1 and current output end IL2 of a load. The device has the advantages of current output accuracy, simpleness in operation and good stability.

Description

technical field [0001] The invention belongs to the technical field of direct current output devices. Specifically relates to a 0-20mA or 4-20mA DC analog output device. Background technique [0002] In the industrial field, if the collected signal is adjusted to be a voltage signal and transmitted over a long line, the following problems will occur: First, because the transmitted signal is a voltage signal, the transmission line is easily disturbed by noise; second, the distributed resistance of the transmission line There will be a voltage drop; third, how to provide the working power of the instrumentation amplifier in the field is also a problem. [0003] In order to solve the above problems and avoid the influence of related noise, a large number of industrial sites use DC current to transmit signals. The reason for using the current signal is that it is not easily disturbed. Moreover, the internal resistance of the current source is theoretically infinitesimal, and ...

AI Technical Summary

Problems solved by technology

[0002] In the industrial field, if the collected signal is adjusted to be a voltage signal and transmitted over a long line, the following problems will occur: first, because the transmitted signal is a voltage signal, the transmission line is easily disturbed by noise; second, the distributed resistance of the transmission line There will be a voltage drop; third, how to provide the working power of the instrumentation amplifier in the field is also a problem

However, the disadvantage of this type of circuit is that the adjustment is complicated and troublesome, and the accuracy of the current output is not high. In addition, as the complexity of the circuit increases, the probability of failure also increases.

Therefore, such circuits are gradually unable to adapt to product development and application.

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