Introduction

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In many industrial applications, current transducers are used to measure and convert process parameters into a 4-20 mA signal. However, there are situations where this current signal needs to be converted to a 0-10V voltage signal. This article provides a detailed guide on how to achieve this conversion using a simple circuit.

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Understanding the Basics

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A 4-20 mA current signal represents a range of process values. In industrial applications, this signal is commonly used because it is robust and suitable for long-distance transmission with minimal interference. However, a 0-10V voltage signal is often preferred for integration with existing systems, such as PLCs or analog input cards.

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The Conversion Circuit

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To convert a 4-20 mA current signal to a 0-10V voltage signal, a simple circuit can be used. The circuit consists of a few passive components: resistors, a voltage reference, and an operational amplifier (op-amp). The following steps outline the process:

r r r Power Supply and Calibrationr Resistors for Current-to-Voltage Conversionr Voltage Reference and Scalingr Op-Amp for Amplification and Bufferingr r r

Step-by-Step Process

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Power Supply and Calibration

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First, ensure a consistent power supply is available for the circuit. The circuit typically requires a DC power supply ranging from 5V to 24V. Calibration can be done using a known 4-20 mA current source and a multimeter to measure the output voltage.

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Resistors for Current-to-Voltage Conversion

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The 4-20 mA current is converted to a voltage signal using a shunt resistor. The value of the shunt resistor (Rs) is chosen based on the desired output voltage range. For a 0-10V output, a common choice is Rs 250 Ohms. The formula for calculating the output voltage (Vout) is:

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Vout (20 mA * Rs) / (20 mA 4 mA)

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For a 250 Ohm resistor, the output voltage will be:

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Vout (20 mA * 250 Ohms) / (20 mA 4 mA) 9.52 V

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To center the output around 0V to 10V, additional resistors are required.

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Voltage Reference and Scaling

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A voltage reference is used to shift the output voltage range. A simple voltage divider can be used, but a more precise method involves using a precision voltage reference such as the LM4040 or the TL431. The formula for the output voltage with a voltage reference (Vref) is:

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Vout Vref * (Rs / (Rs Rref)) Voffset

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For a 0-10V output and a 2.5V reference, the output can be recalibrated to range between 0 and 10V.

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Op-Amp for Amplification and Buffering

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An operational amplifier (op-amp) is employed to buffer and amplify the output signal. The op-amp is configured as a unity gain buffer to ensure low-output impedance and high input impedance. The op-amp helps in providing stability and ensuring the signal is clean and sharp.

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Schematic Representation

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Below is a simple schematic diagram of the circuit:

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(Insert a schematic diagram here)

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Conclusion

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Adapting a 4-20 mA current transducer to a 0-10V voltage analog input is a straightforward process that can be achieved with a few passive components and an op-amp. This conversion allows you to interface with existing systems that require 0-10V inputs, making it a versatile and practical solution.

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Keywords

r r r 4-20mA to 0-10V conversionr current transducerr voltage analog inputr r