New Hart Loop Converter Increases the Performance of 4…20 mA Field Devices

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

TURCK GmbH

Anton Paar GmbH

Pepperl+Fuchs SE

Increase process safety

For the set-up of efficient Hart infrastructures, Pepperl+Fuchs supplies a variety of components that form the so-called Hart Interface Solution (HIS). This includes devices for single circuits and multiplexers for up to 7,936 field devices.

A recent innovation from Pepperl+Fuchs for individual field circuits is the Hart Loop Converter (HLC). It converts the digital Hart signals into analog 4…20 mA current signals. Here, up to three digital Hart variables are captured and made available to the host system, or DCS, in the form of analog signals. These three Hart variables enable not only the actual measured result but also process-related parameters such as reaction-time and temperature to be determined and used selectively to control the process.

This functionality for the control and monitoring of the process provided by the installed Hart field device is possible without any additional cabling or modification of the infrastructure. If required, the Hart Loop Converter can also be programmed to enable a single digital value to be split via a signal splitting feature that makes the signals an output on three analog channels available to a variety of systems. In addition, it is possible to perform limit switching via an optional relay. The HLC can be used as a transmitter power supply. It can also be used on a pre-existing field circuit in passive mode. The HLC only evaluates the Hart signal. Analog measured value information cannot be processed. The HLC converts the digital Hart data into analog 4…20 mA outputs. The 4…20 mA signal from the transmitter is not directly repeated; rather, the primary variable can be selected and converted into an equivalent 4…20 mA output signal. As soon as the HLC detects a connected Hart field device, it sets the field device via a Hart command into burst mode where an updated measured value packet is automatically transferred three to four times a second. These signals are then converted into analog or relay contact limit outputs. Additional isolated barriers for explosion protection are not required due to the intrinsic safety circuitry on the input.

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