All of us involved in designing, evaluating, or testing instruments, data acquisition, or control equipment soon will be affected by a new EMC product standard. EN 61326-1 Electrical Equipment for Measurement, Control, and Laboratory Use—EMC Requirements covers the minimum EMC performance of electrical equipment intended for professional, industrial process, and educational use. It includes equipment and computing devices for measurement and test, control, and laboratory use and associated accessories.
EN 61326-1 was approved by CENELEC on March 11, 1997, and published as a final EN version in April 1997. It now has been forwarded to the European Commission for review and publication in the Official Journal (OJ). When published in the OJ, expected by mid 1999, it will be considered a harmonized (official) standard and can be used in support of the 89/336/EEC EMC Directive.
Amendment 1:1998 also has been adopted by CENELEC. It renumbers the standard to EN 61326 and adds three annexes covering the industrial environment, the EM environment, and portable test and measure applications. Originally, these were to appear as EN 61326-10, EN 61326-20, and EN 61326-30, respectively.
As its title suggests, EN 61326-1 addresses a broad product family. Yet in the scope section of the standard, it gives clear examples of what types of devices are covered. For instance, electrical measurement and test equipment is defined as equipment that, by electrical means, measures, indicates, or records one or more electrical or nonelectrical quantities.
Nonmeasuring equipment such as signal generators, measurement standards, power supplies, and transducers also is included in this category. Similarly detailed definitions are given for control and laboratory equipment.
Computing devices and assemblies and similar equipment falling within the scope of information technology equipment (ITE) and complying with applicable ITE EMC standards can be used without being tested in accordance with EN 61326-1. Also, where a relevant dedicated EMC standard exists, it shall take precedence over all aspects of this product-family standard.
Emissions and Immunity Requirements
EN 61326-1 specifies minimum requirements for emissions and immunity regarding EMC for devices within its scope. Allowable emissions limits differ for Class A and Class B equipment, with A and B referring to the intended location and use as identified in CISPR 11:
Class A Equipment—suitable for use in establishments other than domestic and directly connected to a low-voltage power-supply network that supplies buildings used for domestic purposes.
Class B Equipment—for use in domestic establishments and establishments directly connected to a low-voltage power-supply network that supplies buildings used for domestic purposes.
The relevant limits for Class A and Class B devices are shown in Tables 1 and 2.
When preparing immunity test plans in accordance with EN 61326-1, the intended operating environment will determine specific test applicability and limits. The standard considers four potential environments:
Minimum—equipment to be used if the others are not applicable.
Industrial—equipment used in close proximity or in direct contact with an industrial process.
Controlled EM—equipment used in laboratories or test and measurement areas with a restricted electromagnetic environment; that is, where RF transmitters such as mobile telephones may not be used in close proximity.
Portable Test and Measurement Equipment—equipment powered by battery or from a measured circuit.
If your device can operate in more than one environment, the most severe immunity test plan should be selected. Limits for the four environments are given in Table 3.
Performance Requirements vs Application
During EMC testing, the operating capabilities of the equipment under test may be impaired in many ways. Four performance criteria are defined by EN 61326-1:
Performance Criterion A—during normal performance testing within the specification limits.
Performance Criterion B—during testing, temporary degradation, or loss of function or performance that is self-recovering.
Performance Criterion C—during testing, temporary degradation, or loss of function or performance that requires operator intervention or when system reset occurs.
Performance Criterion D—during testing a loss of function or performance that is not self-recoverable due to damage to equipment, components, or software or loss of data.
The performance level that must be achieved for each test is determined by the intended application of the equipment. Table 4 shows two examples of required performance levels when conducting immunity tests.
Time to Take Action
Most measurement, control, and laboratory device manufacturers marketing in Europe today have experience with the required CE approvals. In January 1996, when the European 89/336/EEC EMC Directive became mandatory, manufacturers used harmonized EMC standards that were applicable at the time. After successful EMC testing, the standards then were documented in their Declaration of Conformity (DoC).
Today, some manufacturers are surprised when new or revised European EMC standards supersede or replace earlier versions. EN 61326-1 will supersede any earlier EMC standards. The emissions requirements (Tables 1 and 2) are identical to EN 55011 Group 1 for industrial, scientific, and medical equipment or EN 55022 ITE that most likely were used to declare conformance.
However, immunity testing is considerably different. For example, if you tested to the residential, commercial, and light industrial requirements per the generic EN 50082-1:1992, the number of immunity tests has doubled. Table 5 shows a comparison between the two.
There are some significant differences:
The newer IEC 1000-4-x series will be used instead of the 801 series.
For ESD testing, contact discharge will be required along with air discharge.
Radiated immunity will have a new frequency range of 80 to 1,000 MHz and require 80% AM @ 1 kHz.
Additional immunity tests specified are lightning surge test, RF conducted test, 50-Hz magnetic field test (industrial), and voltage-interrupt test.
Conclusion
EN 61326-1:1997 is expected to be published in the European OJ by mid 1999. The implementation date (date of withdrawal for manufacturers to convert most likely will be July 2001. This means there would be a transition period of approximately two years before it becomes mandatory.
Beginning July 2001, new or previously tested products will not be allowed into the EU until they comply with EN 61326-1. Until then, the generic standards (mandatory today) or the newer product standard (when published) can be used to show EMC conformance.
You should begin testing now to EN 61326-1 to uncover any potential problems that may arise. For some people, certain immunity tests may never have been performed, and it’s not predictable how a product will react. With this in mind, it is in your best interest to begin testing today to uncover any potential problems. Waiting until June 2001 could be too late.
Reference
EN 61326-1 Electrical Equipment for Measurement, Control, and Laboratory Use—EMC Requirements, Part 1: General Requirements (IEC 61326-1:1997), CENELEC, April 1997.
Additional Information
To order EN 61326-1 in its entirety, contact Qualified Specialist at (281) 448-5622.
About the Author
Stephen W. Grimes is an EMC sales and applications engineer at D.L.S. Electronic Systems. He has eight years of experience in the field as an EMC test engineer and three years in sales and applications. He also is a member of the IEEE EMC Society. Mr. Grimes received a B.S.E.E.T. in electronic engineering technology from DeVry Institute of Technology. D.L.S. Electronic Systems, 1250 Peterson Dr. Wheeling, IL 60090, (847)537-6400.
Table 1
|
Limits in dBµ V |
|||||
|
Class A Devices |
Class B Devices |
||||
|
Frequency Range (MHz) |
Quasipeak Detector |
Average Detector |
Quasipeak Detector |
Average Detector |
|
|
0 to 0.002 |
— |
— |
* |
* |
|
|
0.15 to 0.5 |
79 |
66 |
66 to 56 |
56 to 46 |
|
|
0.5 to 5 |
— |
— |
56 |
46 |
|
|
0.5 to 30 |
73 |
60 |
— |
— |
|
|
5 to 30 |
— |
— |
60 |
50 |
|
|
* As specified in IEC 1000-3-2 and IEC 1000-3-3. The limit decreases linearly with the logarithm of the frequency in the 0.15- to 0.5-MHz range. For alternative test site areas, see annex A of CISPR 22. For discontinuous disturbances, see CISPR 14. |
|||||
Table 2
|
Limits in dBµ V/m @ 10m |
||
|
Class A Devices |
Class B Devices |
|
|
Frequency Range (MHz) |
Quasipeak Detector |
Quasipeak Detector |
|
30 to 230 230 to 1,000 |
40 47 |
30 37 |
|
For alternative test site areas, see annex A of CISPR 22. |
||
Table 3
Environment
Test
Basic Standard
Minimum
Immunity
Industrial
Controlled EM
Portable Test and Measurement Equipment
(battery operated)
Electrostatic
Discharge
IEC 1000-4-2:1995
(5-ns rise, 30-ns pulse)
+8-kV Air
+4-kV Contact
+8-kV Air
+4-kV Contact
+8-kV Air
+4-kV Contact
+8-kV Air
+4-kV Contact
Radiated
Field
IEC 1000-4-3:1996
(80 to 1,000 MHz
80% AM @1 kHz)
3 V/m
10 V/m
1 V/m
3 V/m
Electrical
Fast Transients
IEC 1000-4-4:1995
(5-ns rise, 30-ns pulse
@ 5 kHz)
AC and DC
+1 kV
+2 kV
+1 kV
N/A
I/O Signal/Control
+0.5 kV
+1 kV
+0.5 kV
N/A
I/O Signal/Control
connected to mains
+1 kV
+2 kV
N/A
N/A
Surge
IEC 1000-4-5:1995
(1.2 m s/50 m s open, 8-m s/20-m s short)
AC and DC
line-to-line
line to earth
+0.5 kV
+1 kV
+1 kV
+2 kV
+0.5 kV
+1 kV
N/A
I/O Signal/Control
(lines > 30 m)
+1 kV
+1 kV
N/A
N/A
I/O Signal/Control
connected to mains
+0.5 kV
+1 kV
+1 kV
+2 kV
N/A
N/A
RF
Conducted
IEC 1000-4-6:1996
(0.15 to 80 MHz
80% AM @ 1 kHz)
AC and DC
3 Vrms
3 Vrms
1 Vrms
N/A
I/O Signal/Control
3 Vrms
3 Vrms
1 Vrms
N/A
I/O Signal/Control
connected to mains
3 Vrms
3 Vrms
N/A
N/A
Power- Frequency
Magnetic Field
IEC 1000-4-8:1993
N/A
30 A/m
50 Hz
N/A
N/A
Voltage Interrupt
IEC 1000-4-11:1995
1 cycle
@ 100%
0.5 cycle
each polarity
@100%
0.5 cycle
each polarity
@ 100%
N/A
Table 4
|
Essential Operation (functional safety) |
Continuous Unmonitored Operation |
Continuous Monitored Operation |
Noncontinuous Operation |
|
|
ESD IEC 1000-4-2 |
A |
B |
B |
C |
|
Voltage Interrupts IEC 1000-4-11 |
A |
B |
C |
C |
Table 5
Test
EN 50082-1:1992
EN 61326-1:1997
(Minimum)
Electrostatic
Discharge
IEC 801-2
+8-kV Air
N/A
IEC 1000-4-2
+ 8-kV Air
+4-kV Contact
Radiated RF Field
IEC 801-3
26 to 500 MHz
3 V/m
No modulation
IEC 1000-4-3
80 to 1,000 MHz
3 V/m
w/80% AM @ 1 kHz
Electrical
Fast Transients
IEC 801-4
AC, +1 kV
I/O lines, +0.5 kV
IEC 1000-4-4
AC, +1 kV
I/O lines, +0.5 kV
Surge
N/A
IEC 1000-4-5
See Table 3 for details
RF Conducted
N/A
IEC 1000-4-6
See Table 3 for details
Voltage Interrupt
N/A
IEC 1000-4-11
See Table 3 for details
Copyright 1998 Nelson Publishing Inc.
December 1998