SCADALink A-485  4-20ma to Modbus RS485 Adapter

The SCADALink A-485 is designed for adding I/O to RTU/Flowcomputer/PLC  systems that are out of I/O points; or to connect industrial I/O to communication devices (cellular, satellite, or radio modem) with a RS485 communications port. The SCADALink A-485 Modbus RS485 Sensor Adapter enables Modbus RS485 connectivity to a single 4-20ma /0-36VDC Analog Input and 2 Digital Inputs.

Connect 4-20ma Transmitters via Modbus RS485

The A-485 enables Modbus RS485 connectivity with any 4-20ma process instrument. The A-485 can be configured to provide Modbus Float and Integer Register Values in 4-20ma, or Scaled Engineering Units.  The A-485 contains an internal DC-DC converter that can supply a full 24V loop power to a 4-20ma sensor across the entire 10-30VDC supply voltage range.

Convert 4-20ma Transmitters to Modbus RS485 Instrument

Use the A-485 to convert 4-20ma Transmitters to Modbus RS485. This allows your company’s standard 4-20ma instruments to be retained even where RS485 Modbus RTU communications is required.   Often commonly used process transmitter/sensor may not be available with Modbus RS485 functionality.

The A-485 has configurable scaling from 4-20ma to Modbus Float to allow scaling to be maintained in the field instrument versus at the RTU or SCADA host.

Low Power Operation

The 24VDC Loop power can be controlled to be either Always ON, ON during poll (with configurable warmup time), or ON schedule time interval.

Using controlled power operation, the A-485 can be ideal for battery or remote solar powered remote applications using 4-20ma transmitters. The A-485 allows low power operation with 4-20ma sensors for the  SCADALink SAT100 Satellite RTU.

Multidropped Modbus RS485 I/O

Multiple A-485’s with can be multi-dropped on a Modbus RS485 network.

Designed for Plug and Play Operation

The 4 Wire connection (RS485 and Power) allows one to multiple A-485 to easily connected within a enclosure panel or in the field via M12 cabling.  Using the A-485 using M12 Connectors, Cables and Tee’s allow for simple plug and play instrumentation installation.

Class I Div 2  & Class I Div 1 EXP Certified

The A-485 is hazardous area rated suitable for operation in Oil and Gas; and Pipeline applications.

Industrial Applications

The A-485 with wide temperature range operation, compact DIN Rail Mounting, and 10-30 VDC supply voltage is ideal for the rigors of industrial applications.

DIN Rail, NEMA4X, and Explosion Proof Housing Options

The A-485 is available in 3 mounting/enclosure options, providing application flexibility.


A-485 4-20ma to RS485 Modbus Adapter






 Mounting 30.5mm DIN Rail
 Dimensions3” L x 1.34” W x 1.77” H (77mm L, 34mm W, 45mm H)
 Modbus Interface
 Supply Voltage 10 to 30VDC
 Communication RS485 2 Wire  – Modbus RTU Protocol
 Sensor Inputs
 Loop Power 24 VDC – 20 ma
 Analog Input 4-20ma or 0-36VDC Referenced to Ground
 Digital Input 2 Digital Inputs – Pull to GND
 Power Consumption
 24 VDC Loop Off 0.73mA @24V
 24 VDC Loop On 37 mA @24V
 Operating Temperature -40 to +70°C
 Hazardous Location Class 1 Div 2, Group C, D T3C – Pending
 Suitable for use in: Class 1 Zone 2, IIB, T3


RTU / EFM Systems

The SCADALink A-485 can be used to add I/O to Legacy Systems with Limited I/O.  With small size and low power operation the A-485 can easily be added to existing enclosures.

Environmental Monitoring 

The SCADAlink A-485 is ideal for environmental monitoring applications where simple and rapid deployment is required.  Sensors can be connected using M12 Cable and M12 Tees.


Manuals & Datasheets — A-485 4-20ma to Modbus Converter

  • SCADALink A-485 Manual
  • SCADALink A-485 Datasheet

Application Notes

  • SCADALink A-485





The A-485 GUI is a windows-based application used to configure, save and restore all A-485 family settings. It is connected to the A-485 device via RS485 converter to a COM port.




A485-DIN                        DIN Rail Mount – Class I Div 2 – Panel Mounted

A485-4X                           NEMA 4X Enclosure – Class I Div 2 – Interface to Field Sensor

A485-EXP                        EXP Case  – Class I Div 1 XP –  Interface to EXP Field Instrument

A-485 4-20ma to RS485 Modbus Adapter