2 Wire Loop Powered Isolators

Acromag 2 wire loop powered isolators provide reliable signal isolation for 4–20 mA process and control systems. These compact devices transfer analogue signals between field instruments and control equipment while electrically separating each side of the circuit. As a result, they help prevent ground loops, reduce signal interference and protect connected equipment.

In addition, a loop-powered design draws the operating power from the process loop. Therefore, many installations do not require a separate power supply or additional power wiring. This design simplifies installation, particularly in remote instrumentation, control cabinets and industrial automation systems.

How Do 2 Wire Loop Powered Isolators Work?

A 2 wire loop powered isolator receives a 4–20 mA input signal from a field device.  Such as a pressure, level, temperature or flow transmitter. It then reproduces the signal on an isolated output circuit for connection to a PLC, DCS, data acquisition system, indicator or process controller.

Although the input and output signals represent the same process value, the electrical isolation breaks the direct conductive path between the circuits. Consequently, differences in ground potential cannot circulate unwanted current through the signal wiring.

Why Use a 4–20 mA Signal Isolator?

Long cable runs, multiple grounding points and nearby electrical equipment can introduce noise or measurement errors into an analogue signal loop. However, an isolator separates the circuits and helps preserve signal integrity.

Acromag 2 wire loop powered isolators can provide several advantages:

  • Reduce errors caused by ground loops
  • Protect control-system inputs from electrical disturbances
  • Improve 4–20 mA signal reliability
  • Simplify wiring by using loop power
  • Separate field devices from PLC, DCS and DAQ inputs
  • Support accurate process monitoring and control
  • Fit into compact industrial control cabinets
  • Assist with troubleshooting difficult analogue signal problems

Applications for Loop Powered Isolators

Engineers use 2 wire loop powered isolators across industrial automation, manufacturing, energy, water, mining and infrastructure applications. For example, they can isolate signals from process transmitters that monitor:

  • Tank and vessel levels
  • Pressure and differential pressure
  • Flow rates
  • Temperature
  • Pump and motor conditions
  • Water and wastewater processes
  • Energy and utility systems
  • Remote industrial equipment

Furthermore, loop-powered isolators suit retrofit projects because installers can often add them without introducing another local power supply.

Selecting the Correct Signal Isolator

Before selecting an isolator, consider the input and output signal ranges, available loop voltage, allowable voltage drop, isolation rating, accuracy and response time. Also review the required number of channels, mounting arrangement, operating temperature and environmental conditions.

Most importantly, confirm that the isolator provides enough loop compliance for the transmitter, isolator, receiving equipment and cable resistance. Otherwise, the circuit may not have enough voltage to drive the required 4–20 mA signal correctly.

Metromatics supplies and supports Acromag signal-conditioning products throughout Australia. Contact our team to discuss your process signal, loop voltage and isolation requirements and identify a suitable 2 wire loop powered isolator.