250 Ohm HART Loop Resistor

The R-LOOP is a 250 ohm, 1 watt resistor for HART communication and 4-20mA signal measurement.

A HART communicator or modem needs at least 250 ohms of resistance in the current loop to read and send the digital HART signal. Many loops, especially on the bench or with low impedance power supplies, do not have enough. Placing the R-LOOP in series with the loop adds the resistance needed so your HART communicator, modem or documenting calibrator can talk to the transmitter.

The same resistor also converts a 4-20mA current signal into a 1-5V voltage signal (Ohm's law: 4mA x 250 ohm = 1V, 20mA x 250 ohm = 5V), for PLC and DCS analogue inputs or for reading the loop with a voltmeter.

Typical uses

• Bench configuration of HART transmitters with a HART communicator or USB/Bluetooth HART modem
• Field loops where the power supply or barrier does not provide enough loop resistance for HART
• Converting 4-20mA to 1-5V for PLC, DCS and data logger inputs

Specifications

• Resistance: 250 ohm
• Power rating: 1W
• Tolerance: ±5%
• Temperature coefficient: ±300 PPM/°C

Need a quicker connection? The same resistor is available fitted in a 4mm banana plug as R-LOOP-BP.