Scientific, Test, Measurement:  EN 61326-1

• Overview
• Sample Test Matrix for EN 61326-1: 2006 (Basic)
• Sample Test Matrix for EN 61326-1: 2006 (Industrial)
• Sample Test Matrix for EN 61326-1: 2006 (Controlled EM)
• Sample Test Matrix for EN 61326-1: 2006 (Portable Test & Measurement)
• Technical Notes Concerning I/O Cables
• Scheduling

Overview

Compliance with the EMC Directive for the European Union (EU) entails meeting both emissions and immunity requirements.  EMC requirements for scientific, test and measurement hardware are defined in EN 61326-1. The 2006 version of this standard became mandatory on February 1, 2009 and the updated version of this standard contains some significant changes over the 1997 version. The most significant of these may be summarized as follows:

1. Stop frequency for radiated RF immunity testing increased from 1 GHz to 2.7 GHz (all environments)
2. Drastic increase in scope of testing for voltage dips and interrupts testing
3. Defined performance criteria for immunity testing

The last of these changes closed a (commonly used) loophole in the 1997 version which gave only “recommended” performance criteria for immunity tests. The old standard stated that “It is highly recommended that performance criteria A be chosen for all phenomena and all tests. However, performance criteria B and/or C may be accepted provide that both the specification and the test report highlight such deviation(s)…” (Ref. EN 61326: 1997, Table 2 Note)

For example, if a product locked up and required a power cycle to reset when electrostatic discharges were applied, under the old standard, this would have been acceptable, provided that it was appropriately documented in the product specification and the immunity test report. The 2006 version defines Performance Criterion B for ESD testing, which means that while the product may be upset during testing, it must self-recover after the environment has been withdrawn without user intervention.

Typical equipment covered by this product family standard includes test and measurement equipment, as well as equipment which could be used in a laboratory.

*required only for products which require Class B for emissions

EN 61326-1 defines the immunity environments for different locations. These are defined as basic, industrial, controlled electromagnetic (EM) and portable test and measurement (in Annex A). The environments, along with a sample test matrix for each, are given in the following sections.

Rather than repeat emission requirements, EN 61326-1 simply references emission standards. For radiated and conducted emissions, it calls out CISPR 11 (i.e., the emissions standard on which EN 55011 is based) and for AC power line harmonics and flicker, it calls out IEC 6100-3-2 and IEC 61000-3-3, respectively. It is important to note that AC power line harmonics and flicker testing are only required for products needing to comply with the Class B emission limits.

In the United States, compliance of this type of equipment with federal requirements is governed by the Federal Communications Commission (FCC).  Limits are defined by the Code of Federal Regulations (CFR) Title 47, Part 18, which regulates the emissions (unintentional and intentional) from industrial, scientific and medical (ISM) products.

Sample Test Matrix for EN 61326-1:  Basic [top of page]

The “basic” immunity environment defined by this standard is roughly equivalent to that defined by the light industrial standard. Environments which would fall under this category include 1) standard laboratory, 2) test and measurement area or 3) an area that is specifically used for analysis, testing and servicing.  Equipment within the scope has to be operated by trained personnel.

Products falling into this category will most likely not be used in a residential environment.  It is important to note that under EN 61326-1, AC power line harmonics and flicker are specifically excluded from Class A (non-residential) hardware.

Emission Requirements

Immunity Requirements - Basic

Sample Test Matrix for EN 61326-1:  Industrial Locations [top of page]

Industrial locations are characterized as having a separate power network and one or more of the following:

• frequent switching of inductive or capacitive loads,
• high currents and associated magnetic fields (e.g., nuclear magnetic resonance (NMR) machines or magnetic resonance imaging (MRI) machines
• presence of industrial manufacturing hardware (e.g., welding machines)

Products falling into this category will most likely not be used in a residential environment.  It is important to note that under EN 61326-1, AC power line harmonics and flicker are specifically excluded from Class A (non-residential) hardware.

Emission Requirements

Immunity Requirements

Immunity Requirements - Industrial

Sample Test Matrix for EN 61326-1:  Controlled EM Environments [top of page]

A controlled EM environment within the scope of this standard is usually characterized by recognition and control of EMC threats by the users of the equipment or the design of the installation.  Examples of this include the following:

• use in an ESD-controlled area (ESD smocks, wrist straps, ESD floor, etc. required)
• prohibited use of cellular telephones, hand-held transmitters

Products falling into this category will most likely not be used in a residential environment.  It is important to note that under EN 61326, AC power line harmonics and flicker are specifically excluded from Class A (non-residential) hardware.

Emission Requirements

Immunity Requirements – Controlled EM.

Sample Test Matrix for EN 61326:  Portable Test/Measurement Equipment [top of page]

This environment is defined for equipment which is powered by an internal battery, or from the circuit being measured.  That is, when the unit is operating, it has no AC mains connection.  If equipment can be operated while charging, its environment would be defined by one of the other three environments of this standard.

Since the operating environment for portable products is uncontrolled (that is, they can be used just about anywhere), it is advisable to comply with the Class B emission limits for residential environments.

It should be emphasized that this environment assumes that the product is battery powered. Thus, emissions testing typically entails radiated emissions testing only. In the event that the product is equipped with rechargeable batteries, it would connect to the AC mains when charging. In that case, conducted emissions testing could apply. However, this standard specifically excludes immunity requirements for mains chargers for these types of devices.

It is interesting to note that no performance criteria have been defined for products tested under this category. Presumably, this is due to the fact that the standard assumes products in the category will be used by “…personnel capable of interpreting the results obtained.” (Ref. EN 61326-1: 2006, Annex A, Note 1) While EMCI recommends taking a conservative approach: namely, that the traditional performance criteria be used (Level B for ESD and Level A for RF immunity). However, this view is not supported by the standard. As such, the performance criteria (A, B or C) that the product achieved would simply be documented in the test report.

Emission Requirements

Immunity Requirements

Technical Notes Concerning I/O Cables [top of page]

Approximately 80% of EMC compliance issues are related to cables.  Power and I/O cables create the “antenna structure” for a product.  These unintentional antennas can both radiate electromagnetic energy generated by electronics inside the product and receive electromagnetic energy impinged upon the product.  The former could result in non-compliance with regard to emissions and the latter could create an immunity problem.

Since cables are an integral part of a product’s function and configuration, clients should realize some significant factors about cables prior to testing for EMC compliance.

• For emissions testing, all I/O ports (excluding service or maintenance) should be loaded with a cable of at least 2 meter in length, per CISPR 16
• For immunity testing, if a cable can be greater than 3 meters in length, electrical fast transient testing via capacitive clamp applies to this cable
• Non conductive cables (e.g., fiber optic or plastic tubes) are exempt from cable testing requirements

Scheduling [top of page]

EMC Integrity generates a detailed quotation for all formal compliance testing that we perform.  Our quotations state the name of the product to be tested, the standards to which the product will be tested, the individual tests that will be performed and any additional testing that may be requested by the client.  Tests are listed on a line-item basis, thus clearly delineating both the scope of work and the cost of each test.  An outline of our process is given below.

Overview of EMCI’s RFQ Process.

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