Communications

Current Loop Interface provides Isolation and Surge Protection

12th April 2010
ES Admin
The OMNITERM LZI and LZD are current loop interface modules that can be inserted into any 4-20mA current loop to isolate the instruments in the loop and provide surge protection. They are designed to interface field mounted transmitters in remote applications where signal isolation and surge protection is required. Applications include interfacing for RTU’s, PLC’s etc. The LZI is a single channel device with additional flexibility and support for both 2-wire and 4-wire 4-20mA transmitters whilst the LZD is a dual channel device for increased packing density, suitable for multiple 2-wire transmitters.
In many applications there is a need to convert the 4-20mA into 1-5Volts for an RTU, PLC or DCS etc. This is normally inconvenient because the precision resistor needs to be sourced, mounted and wired independently without causing loop errors. To overcome this obstacle, the LZI version also includes a precision 250ohm resistor that can be connected into the circuit to convert the output into 1-5V within the module.


Combining the surge arrestor, isolator and 250 ohm termination into a single module, saves significant cost, engineering time and panel space in monitoring applications.

The Omniterm LZI and LZD both include

A fully specified 10kA surge arrestor to prevent electrical surges induced on the field wiring from damaging sensitive equipment in the panel
1500Vac isolation from input to output so that ground loops cannot occur, that might otherwise affect instrument accuracy.
A stable 24Vdc field power supply to power two-wire transmitters from lower voltage sources such as 12V battery systems without compromising available loop voltage or loop resistance.
Reliability figures in accordance with IEC61508 (SIL1) are available to allow inclusion of these devices in safety systems.

These modules utilise advanced electronic techniques to achieve high accuracy and low power consumption with zero field calibration, saving you installation and commissioning time.
Forming part of OMNIFLEX’s extensive OMNITERM range of industrial instrumentation, the OMNITERM LZI and LZD are designed to be DIN rail or surface mounted and are a space-saving 22.5mm wide.

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