What is a 4-20mA to RS485 converter?
A 4-20mA to RS485 converter reads analog current signals from field instruments and sends the values over an RS485 serial bus. Many industrial transmitters output a 4-20mA current loop. RS485 is a standard serial bus that supports multiple devices on one cable. The converter links the two, so a PLC, SCADA system or PC can collect sensor data over RS485.
Key specifications
Common converter models share these characteristics:
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Analog inputs: 4-20mA, 0-20mA, 0-5V and 0-10V, with 4 or 8 channels on some models
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Resolution: 12-bit analog-to-digital conversion on some models
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Output: isolated RS485 interface using Modbus RTU
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Power supply: a wide input range, such as 10-30VDC, with power draw around 0.4W
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Isolation: outputs isolated from the RS485 line and the power supply
Some models let each output channel be set to 4-20mA, 0-20mA or 0-10V.
Use cases
Converters are used where analog transmitters must connect to digital control systems. Typical uses include process monitoring in factories, water and wastewater control, building automation and energy metering. Retaining existing 4-20mA instruments avoids replacing field equipment when a site adds RS485 Modbus communication.
Thinvent products and this technology
A 4-20mA to RS485 converter is a separate module that connects to a serial port or USB adapter. The Thinvent range does not include a built-in 4-20mA or RS485 interface. Thinvent products are computers, not signal converters. The Thinvent Aero Mini PC, with the Intel N5095A processor, 16GB DDR4 RAM and 128GB SSD, can run the software that reads data from a converter. Choose a converter module with the inputs your sensors need, then connect it to a Thinvent Aero Mini PC for data logging or monitoring.
