Interface circuit for RS232 interface and current loop circuit

Abstract

The invention discloses an interface circuit for an RS232 interface and a current loop circuit. The interface circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a first triode, a second triode, a third triode, a photoelectric coupling tube, a first diode, a second diode, a third diode and a fourth diode, wherein a first positive electrode voltage input end is connected with a first end of the eighth resistor and a first end of a first electric wire, an RS232 input end is connected with a first end of the eleventh resistor, a second end of the eleventh resistor is respectively connected with a negative electrode of the fourth diode and a base electrode of the third triode, and a positive electrode of the fourth diode is connected with a first end of the tenth resistor and then is grounded. The interface circuit for the RS232 interface and the current loop circuit have the advantages that the transmitted voltage signal can be converted into a 20mA current signal, and a digital signal is effectively transmitted by a current loop; the structure is simple, and the requirement of maximum transmitting rate is met.

Description

technical field [0001] The invention relates to an interface circuit, in particular to an interface circuit used between an RS23 interface and a current loop circuit. Background technique [0002] RS232 is the earliest and most widely used asynchronous serial communication bus standard. It was published by the American Electronics Industry Association in 1962 and finally revised in 1969. Because the current is not sensitive to noise, the current loop circuit is used to solve the following problems. In the industrial field, an instrumentation amplifier is used to complete the signal conditioning and long-term transmission, resulting in the following problems: First, because the transmitted signal is a voltage The signal and the transmission line will be disturbed by noise; second, the distributed resistance of the transmission line will cause a voltage drop; third, how to provide the working voltage of the instrumentation amplifier on site is also a problem. Because RS232 tr...

AI Technical Summary

Problems solved by technology

Because the current is not sensitive to noise, the current loop circuit is used to solve the following problems. In the industrial field, an instrumentation amplifier is used to complete the signal conditioning and long-term transmission, resulting in the following problems: First, because the transmitted signal is a voltage signal, the transmission line will be disturbed by noise; second, the distributed resistance of the transmission line will produce a voltage drop; third, how to provide the working voltage of the instrumentation amplifier on site is also a problem

The current circuit structure of the interface circuit used between the RS232 serial interface and the current loop circuit is complicated, and the current loop cannot be used to transmit digital signals effectively, and the maximum transmission rate cannot meet the needs

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