NE 21 has been revised

from 2011-09-01

Abstract NE 021 – 15.08.2011

This recommendation describes uniform practical procedures for determining whether the devices used in laboratory and process control are immune to interference. The objective is to increase the functional safety of equipment.

Based on past experience, most of the interference effects are covered by this recommendation. These requirements have been taken into account during the preparation of IEC/EN 61326-3-2. For specific applications, it may be necessary for the manufacturer and the user to make special arrangements regarding the requirements with respect to type, scope and degree of immunity to interference.

General technical discussion of NE 21 has taken place and the recommendation has, in part, been revised. It has thus been adapted to take current marginal conditions and constraints in members' companies into consideration.

The following changes were realised:

  1. The Evaluation criterion C in Chapter 3 has been dropped.
  2. The frequency range during testing has been adapted to suit operational frequencies.
  3. An indication relating to informative measurements (100 kHz) was added.
  4. The interference emission was introduced in Chapter 5.
  5. The former appendix with the test report has been dispensed, as there was no practical necessity for it.
  6. All tests are conducted in compliance with the standards cited, with the exception of the deviations mentioned in Appendix A (informative). Appendix A illustrates the actual level of technical discussion at the time of publication of the recommendation.

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