Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Process instrumentation and analytical measurement

Loop-powered transmitter

Also known as: Loop-powered device, Loop-powered instrument

German: Schleifengespeister Messumformer

In process instrumentation, a loop-powered transmitter is a transmitter that draws its operating power from the 4–20 mA signal loop it controls, so no separate power supply is needed at the device.

  • Process instrumentation
  • Process industry

In one sentence

A loop-powered transmitter draws its operating power from the 4–20 mA loop it controls and needs no separate power supply.

Example

A loop-powered pressure transmitter operates from the 24 V supplied by the analog input card of the control system through its two signal wires.

How it applies

  • Engineering: The device must operate on less than the minimum loop current, and the loop supply must cover the device's minimum terminal voltage plus the voltage drops across input resistors, barriers and cables. A load calculation confirms this.
  • Installation: Loop-powered devices simplify field wiring and suit intrinsically safe circuits because of the low energy.
  • Troubleshooting: A too-low supply voltage causes the signal to saturate below 20 mA at high values, which looks like a process limit rather than a fault.
  • Documentation: Include the load calculation or maximum loop resistance in loop documentation, especially when devices such as indicators or barriers are added later.

Loop-powered vs. two-wire transmitter

In practice, the terms describe the same device class. Loop-powered emphasizes the power source; Two-wire transmitter emphasizes the wiring. Some loop-powered displays are not transmitters, so loop-powered is the broader description.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: AI TechDoc Knowledge editorial definition, based on process instrumentation practice

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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