# IEC 61326 — EMC for measurement, control and laboratory equipment

> IEC 61326 sets the electromagnetic compatibility (EMC) requirements — both emission and immunity — for electrical equipment used in measurement, control and laboratory applications. It defines electromagnetic environment classes and performance criteria, and its part 3-1 adds immunity requirements specific to equipment performing safety-related functions.

- Source : https://industryhub.site/en/standards/iec-61326
- Body : IEC
- Family : EMC / Instrumentation
- Status : current
- First published : 1997
- Latest revision : 61326-1:2020 (Edition 3)
- Edition : Multi-part
- Next revision : Active maintenance
- Access : Paid (IEC webstore)
- Language : English

## Document structure

- **IEC 61326-1** — General requirements : Emission and immunity requirements for measurement, control and laboratory equipment, with electromagnetic environment classes (basic, industrial, controlled) and performance criteria A/B/C.
- **IEC 61326-2-x** — Particular requirements : Configuration-specific requirements — for example sensitive test and measurement equipment, or equipment connected in an industrial control loop.
- **IEC 61326-3-1** — Immunity for safety-related systems : Additional immunity requirements for equipment intended to perform safety-related functions, where electromagnetic disturbance must not defeat the safety function.

## Key concepts

- **Immunity vs emission** : EMC has two sides: a device must not emit disturbances that affect others (emission), and must keep working when disturbed by others (immunity). IEC 61326 covers both for instrumentation.
- **Electromagnetic environment classes** : Requirements scale with the environment: a basic location, a harsher industrial location, or a controlled EMC environment. The same instrument faces different test levels depending on where it is installed.
- **Performance criteria A / B / C** : During a disturbance, equipment is judged against criteria: A — normal performance maintained; B — temporary degradation, self-recovering; C — degradation requiring operator action. The acceptable criterion depends on the function.
- **EMC for functional safety (61326-3-1)** : When an instrument is part of a safety function, a normal immunity pass is not enough: 61326-3-1 demands the safety function survive defined electromagnetic stress — the link between EMC and IEC 61508/61511.
- **Relation to NAMUR NE 21** : In process automation, NAMUR recommendation NE 21 specifies EMC for process instrumentation; it aligns with and references the IEC 61326 framework.

## Keeping instruments trustworthy in a noisy plant

A factory floor is electromagnetically hostile: variable-speed drives, switching contactors, welding, radio transmitters. An instrument that drifts or freezes under that noise is worse than useless — it lies. **IEC 61326** is the standard that makes measurement, control and laboratory equipment **electromagnetically compatible**: quiet enough not to disturb its neighbours, and robust enough to keep telling the truth when they disturb it.

## Two sides, scaled to the environment

EMC always has two faces. **Emission** limits what a device radiates and conducts onto the mains, so it does not pollute the electromagnetic environment. **Immunity** checks that the device keeps working when hit by disturbances — electrostatic discharge, fast transients, surges, conducted and radiated RF, magnetic fields. IEC 61326 sets both, and scales the immunity test levels to the **electromagnetic environment**: a basic location, a harsher **industrial** location, or a controlled environment. The same transmitter faces tougher levels on a plant floor than in a lab.

## Performance criteria — and the safety case

A device does not simply pass or fail immunity; it is judged against **performance criteria**. Criterion A means normal performance is maintained throughout; B allows temporary, self-recovering degradation; C allows degradation needing operator intervention. Which criterion is acceptable depends on the function. That distinction becomes critical for safety: **IEC 61326-3-1** raises the bar for equipment performing **safety-related functions**, requiring the safety function to survive defined electromagnetic stress — the bridge between EMC and functional safety under [IEC 61511](/en/standards/iec-61511).

## Where it sits

IEC 61326 is the instrumentation-specific application of the generic EMC framework [IEC 61000](/en/standards/iec-61000), and it travels with the safety standard for the same equipment, [IEC 61010](/en/standards/iec-61010). In process automation it is mirrored by NAMUR NE 21, the recommendation EMR engineers cite when specifying field devices.

## Applicable industries

Process instrumentation and field devices, Laboratory and test & measurement equipment, Control systems and industrial electronics, Manufacturers and EMC test laboratories

## References & further reading

- [IEC 61326-1:2020 — general requirements (standards store)](https://webstore.ansi.org/standards/iec/iec61326ed2020)