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Loop Powered Digital Indicators – No Power Wires Needed !

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4-20 mA current loop is the standard process signal for transmitting process information such as temperature, flow, humidity, pressure, etc. over long distances.

Most of the 4-20 mA current loops require a power supply in order to operate. However, where it is not practical to supply separate power to all of the devices, the instrument on the loop can be powered by the power supply of the loop itself. These devices are referred to as loop-powered. A Loop Powered Indicator is used as the remote indicator for the purpose of measurement and control. It takes the advantage of the principle to power itself with the 4-20 mA loop without affecting the current levels in that loop.

At Alvi Technologies, we offer the loop powered digital indicators which are simply inserted into the current loop like passive analog indicators. Since power supplies and their wiring are not required, costs could decisively be reduced, allowing for displays which have been too expensive before. In addition, the reliability has considerably been improved since a power failure in the control room does not interrupt the data flow. And, in contrast to conventional digital indicators, there is no coupling between measuring loop and power supply.

These loop-powered digital indicators provide a bargraph in addition to the digital display. This gives you all information on your process variable at a single glance.

Apart from that, zero, span, and min/max outputs can be adjusted as desired, enabling direct readout of measured values such as temperature, flow, displacement, pressure, pH value etc. The indicator comes with a symbol set for standard engineering units. The symbols can easily be replaced. Thanks to microprocessor technology, you do not require a high-precision external reference current for parameter setting. Even during operation, the settings can be changed without problems.

EMC design ensures reliable measurements even under unfavourable ambient conditions.

The indicators transmit HART signals disturbance-free. Measured value display is not affected.

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