Signal Selection in Industrial Sensors: Why 4-20mA or 2mV/V?

Amazeng Technical Team
5 min read
Signal Selection4-20mAmV/VSensor DesignEngineering Guide

Introduction

One of the most important questions you encounter when designing a system is: "Which signal type should I use?" The reliability of 4-20mA or the raw precision of mV/V? This choice is an engineering decision that determines not only your wiring preference, but also the total cost and accuracy of your system. We examine why certain signals have become standard with their technical reasons.

Why 4-20mA? (For Remote Monitoring)

The biggest reason why 4-20mA is the "golden standard" in industry is its independence from electrical resistance.

  • Whether your cable length is 10 meters or 500 meters; the sent 12mA current reaches the receiver as 12mA.
  • If it were voltage (0-10V), a voltage drop would occur on the cable resistance and your data would be read incorrectly.
  • Therefore, if there is a distance between the sensor and the PLC, your choice should always be 4-20mA.

Why 2mV/V or 3mV/V? (For Raw Precision)

Almost all high-precision sensors such as loadcells give ratiometric mV/V output.

  • Reason: These sensors measure physical deformation. Passing an intermediate transmitter layer and converting it to current (4-20mA) can add extra electronic noise and error margin to the signal.
  • For the most precise measurement, the transmitter must be as close to the sensor as possible and must read the raw mV/V signal directly with a 24-bit ADC.

Decision Guide for Signal Selection

  1. Is Precision Priority?: If your answer is yes (e.g., laboratory scale or high-precision tests), use a sensor with mV/V output and a data acquisition device with a high bit value such as ZMA Data Acquisition.
  2. Are Distance and Noise Priority?: If your answer is yes (e.g., a large factory site or outdoor environment), prefer a transmitter with 4-20mA output.

Flexibility in Signal Conversion with Amazeng

As Amazeng, we know your field constraints. That's why we designed our products to work hybrid:

  • GDT Digital Transmitter, when placed in the field, reads the mV/V signal with millimeter precision and transfers it either as 4-20mA analog to the PLC or to your SCADA system via Modbus so that the error margin is zero.

Conclusion

Signal selection should be made according to the technical requirements of the application. Wrong signal selection leads to data errors that cannot be corrected with software.

To construct the most accurate signal architecture for your facility and to choose the appropriate transmitters, you can examine our technical documents or consult our engineers directly.

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