Home > New current loop isolator protects against surges and boosts voltage

New current loop isolator protects against surges and boosts voltage

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article image New current loop isolator protects against surges and boosts voltage

Omniflex has introduced three innovative new signal isolators in the Omniterm LZ series, integrated 10kA 8/20us surge arrestors to cater for applications that require both loop isolation and surge protection. Installations that are vulnerable to surges need both isolation and surge protection on field current loops to protect electronic instrumentation. Until now this has required two separate devices to be fitted to every field loop. The LZ series combines both functions in under 12mm per channel of DIN rail space.

The OMNITERM LZI and LZD are current loop interface modules designed to interface field mounted transmitters in remote applications such as interfacing for field-mounted RTUs and PLCs. These devices provide 1500Vac signal isolation and fully specified 10kA surge protection. The LZI is a single channel device with additional flexibility and support for both 2-wire and 4-wire 4–20 mA transmitters. The LZD is a dual channel device for increased packing density suitable for multiple 2-wire transmitters.

These devices also include a precision 250 ohm termination resistor, which can be linked into the circuit to provide an accurate 1-5V output when required.

In addition, the LZ series incorporates a stabilised 24Volt loop supply for the field mounted two-wire current transmitters, allowing supply voltages in the range 10-30Vdc to be used. This benefits RTU applications which often run on 12V batteries, where creating 24Volts for instrumentation can be inconvenient and costly.

The OMNITERM LZB is a dual input field contact interface module designed to protect RTU and PLC installations from external factors such as lightning surges, ground loops and wiring faults. This module includes a fully specified surge arrestor and a high side output driver allowing users to combine all these functions into a single module.

By incorporating the surge arrestor within the isolator, the need for the application engineer to match the surge arrestor to the loop, and worry about “let-through” voltage is eliminated.

These modules utilise advanced electronic techniques to achieve high accuracy and low power consumption with zero field calibration, saving on installation and commissioning time. Reliability figures in accordance with IEC61508 (SIL1) are available to allow inclusion of these devices in safety systems.

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