Supply isolator with auxiliary power for safe separation of 4...20 mA standard signal circuits

General Information
Mechanical Data
Additional Information


  • Input: 1 x analog4...20 mA
  • Output: 1 x analog4...20 mA
  • Output relay: 1 x NO contact
  • Dimensions: 22.5 x 110 x 112 mm
  • Bidirectional HART® transmission: Communication sockets HART® for sensor parameterization and evaluation of status information of a connected transmitter with HART® protocol

Fields of application

  • Galvanic isolation of 4...20 mA circuits
  • Elimination of ground loops
  • Power supply for 2-wire transmitters
  • Monitoring of SMART transmitters with early warning system
  • Intrinsically safe supply for sensor in Ex-area
  • Sensor monitoring with early warning system


The RN221N supply isolator from Endress+Hauser supplies e.g. a transmitter, if necessary also in hazardous areas, and transmits the signal galvanically isolated. With the optionally available HART® monitoring, the status of the transmitter is monitored. If an error occurs, a relay switches on the RN221N. The relay must be actively reset. This makes it easy to locate faults that only occur for a short time.

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Ohannes Markarian

A great company that provided a wide range of products from various suppliers. Support is excellent and very responsive

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Somya Gupta

The conversation was highly helpful to me. I want to know about the suitable sensors that can be used for level measurements for conical tank systems. Mr. Pedro has quickly responded and explained in very ease way. It was nice interacting with him.

Product Details