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Limit switch

Contactor with loop power supply for monitoring current or voltage signals

  • Limit switch RTA421 ©Endress+Hauser

The RTA421 contactor monitors industrial processes for safe operation. The unit analyzes current (0/4...20 mA) and voltage signals (0/2...10 V) and switches two independent output relays if the values either exceed or undercut the preset alarm set points. On the display both limit values are indicated in parallel. The bar graph informs on the connected signal at any time. Applications include pump control in the waste water industry. Level measurement in silos can be economically achieved.


  • 2 relays for set point monitoring (with SPDT contacts)

  • Loop power supply for connected sensors

  • LC display for alarm set points and bar graph

  • Compact housing

  • Front end setup using 3 push buttons

  • DIN rail mounting, 45 mm housing width

Field of application

  • Plant and machine construction

  • Panel builders

  • Process monitoring

  • Process control

Features and specifications

Documents / Manuals / Software

Accessories / Spare parts

Predecessor / Successor

Predecessor: HTA182, HTA380, HTA423, XT170


Endress+Hauser Instruments International AG
Middle East Support Centre 7WB-2100, Dubai Airport Free Zone P.O. Box 293828 Dubai United Arab Emirates
Tel.: +971 4 253 51 00
Tel.: +971 4 609 18 11

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