4-20mA to Voltage Two-Wire Passive Isolated Converter IC

SunYuan ISO 4-20mA-O is a two-wire passive 4-20mA to voltage signal isolation converter IC.，It can isolate the input active 4-20mA current signal into voltage signal output. The IC adopts two-wire input circuit power supply mode, unique high-efficiency signal circuit stealing technology, without external working power supply. It greatly simplifies the user's design and reduces the user's wiring cost. The module contains internal current signal modulation and demodulation circuits, signal coupling and isolation conversion circuits, power inversion circuits, subtraction circuits, and buffer processing output circuits. The very small input equivalent resistance enables the IC to collect current signals from the sensor signal output loop and achieve a voltage drop of ≤10V when inputting a 20mA signal to meet the user's need for long-distance, distortion-free signal transmission without an external auxiliary power supply.

         ISO 4-20mA-O is often used for isolation of 4-20mA current to voltage signals, eliminating the need for an external power supply to make wiring more simple, and low power consumption, low self-heat (basically no temperature rise), high reliability. The most important feature of the product is that it does not require an external auxiliary power supply and contains internal subtraction circuits and amplifier buffer output circuits, which bring the advantages of simplicity and reliability as well as limitations in use. Products for sensors, PLC output 4-20mA signal isolation and transmission, from another definition is the transmission of electrical power, so there must be internal power loss. This loss is expressed in the input current value and its own input voltage drop product. In this case the 4-20mA signal source must have the ability to drive a 500Ω load in order to make the two-wire passive 4-20mA to voltage signal isolation converter ISO 4-20mA-O work properly. At present, from the industrial field practical application experience, most of the field instruments and sensors, PLCDCS, etc. can meet the 4-20mA signal output has the ability to drive 500Ω load. If customers need to drive low load products on site, please contact Shunyuan Technology Company to solve the problem.

          In the industrial field practical applications, some although only use a I / V conversion sampling resistor, can be converted to the input current signal into a voltage signal. This circuit is simple but impractical. First of all, its practical significance is that when the zero signal is zeroed, there will be a zero current flowing through the sampling resistor, and if it is analyzed according to the conversion of the 4~20mA input current to the maximum 5V voltage, the zero is exactly 1V, and this 1V can be subtracted from it by the microcontroller software when the microcontroller has enough resources. But then, its useful voltage will be left with 5-1=4VDC instead of 5VDC. As the maximum input voltage of the microcontroller's A/D is the microcontroller's power supply voltage, which is usually 5 VDC, it is more troublesome to deal with this simple input conversion circuit, in order to achieve the number of bits of A/D conversion, which will lead to an increase in the cost of the chip. A simple way to solve the above problem is to configure the input of the microcontroller before an operational amplifier composed of subtraction and buffer processing circuitry to increase this level of circuitry can play on the processing of the zero point becomes more convenient, without the need to use up the internal resources of the microcontroller, especially the microcontroller is to use the A/D interface to accept this zero-point signals and the actual value of the zero-voltage inputs, you can ensure that the number of bits of the resources of the A/D converter can be fully applied to the useful signal.

Product Selection Example    

Example 1: Input signal: 4-20 mA; Output signal: 0-5V; Model No.: ISO 4-20mA-O4  

Example 2: Input signal: 4-20 mA; Output signal: 1-5V; Model No.: ISO 4-20mA-O6  

Example 3: Input signal: 4-20 mA; Output signal: 0-2.5V; Product Model: ISO 4-20mA-O2.5  

Example 4: Input signal: 4-20 mA; Output signal: 0-3.3V; Model No.: ISO 4-20mA-O3.3