The immunity test world is about to change. But that shouldn’t surprise you. Every day, more products enter the market that could create and be more susceptible to EMI and RFI—an unacceptable condition especially if you need the CE Marking to sell product in Europe.
To keep pace, four new tests are being added to EN 50082, the Generic Immunity Standard for EMC. This standard is applicable to manufacturers of residential, commercial, and industrial products.
According to Tom Revesz, North American sales manager at Haefely Trench, the new tests will affect information technology equipment and other categories. More specifically, computers and telecom devices will need to pass these new immunity tests.
EN 61000-4-2 electrostatic discharge (ESD), -3 RF radiated immunity, and -4 electrical fast transient (EFT) have been required in EN 50082 for some time, said Mr. Revesz (Figure 1). But, he indicated that many people are preparing for Jan. 1, 2001, when more standards will be included.
These additional standards cover tests for surge, RF conducted immunity, power frequency magnetic fields, and power-line dips and interrupts (Table 1). Two standards now used for emissions also will be added to the immunity test requirements at that time. They are EN 61000-3-2 power-line harmonics and EN 61000-3-3 power-line flicker.
Equipment purchased for IEC 555-2 harmonics and -3 flicker testing, according to Herman van Eijkelenburg, product manager at California Instruments, may have to be upgraded or replaced when the power-line harmonics and flicker standards are adopted in 2001. Some information and audio-visual equipment which was exempt now is included and new, more stringent test limits have been added.
One-Box Testers
Two different types of one-box testers now can meet the demand for some of these immunity tests. An integrated tester being offered by some vendors builds on what formerly was a transient, surge, or lightning generator. This has resulted in a single chassis which tests to all the standards in Table 1. Optional versions may offer higher test voltages. Generally, the higher the voltages, the better the tester.
Alternatively, some harmonics and flicker testers now include capabilities to test for additional power-line anomalies, such as interharmonics, repetitive voltage variations, and frequency variations (Table 2 and Figure 2). So why have one-box immunity testers been developed along two different lines?
Tables 1 and 2 indicate what signal-coupling and signal-generating methods may allow certain tests to be combined in a single chassis. Each test requires a connection to the EUT and the generation of a signal. The harmonics and flicker tester connects to the AC mains of the EUT and delivers controlled power at common AC line voltages and frequencies. By adding more functionality, this tester can generate line interruptions and voltage and frequency variations.
On the other hand, the transient tester delivers a voltage or current of thousands of volts or amps for a brief period of time to produce ESD, EFT, or lightning simulation. To accomplish this, a waveform simulator feeds the signal to a high-power output stage. To generate a surge signal, the waveform simulator must reshape and slow down the transient signal. Also, the high-current outputs can drive large loop antennas for the magnetic-field and magnetic-pulse tests.
Pros and Cons
Integrated testers may not provide all the answers. In a busy test lab, according to Achim Gerstner, EMC system project manager at Tektronix, it might make more sense to have a tester and setup for each test. You won’t get the throughput if one EUT ties up the whole tester, making it unavailable for anything else.
An all-in-one tester may make more sense in a small lab where only occasional tests are being run. One advantage, said Dick Rogers, marketing manager at Amplifier Research, is for manufacturers who want to test for all these phenomena economically. He pointed out that different versions of integrated testers are available to meet various levels of the specifications, whether it be precompliance or full compliance testing.
Some integrated testers may meet only the minimum requirements of EN 50082. According to Mr. Revesz of Haefely Trench, it is up to you as the buyer to understand the limitations of the tester. For example, it might not have the 0° to 360° phase-angle synchronization capability called for in EN 61000-4-11 or it may not provide the high spikes and short burst durations specified in EN 61000-4-4. You also might forget to remove the ground from the tester between the EFT and surge tests and expose yourself to an electrical hazard, indicated Mr. Revesz.
RF Immunity
By contrast, RF immunity test systems usually don’t come in a box. RF radiated immunity testing requires space between the antenna and the EUT. The two kinds of RF immunity tests are radiated, per EN 61000-4-3, and conducted, according to EN 61000-4-6. There are significant differences in the test equipment and setups required (Table 3).
In RF radiated immunity testing, the EUT is subjected to an interference signal from an antenna driven by an amplifier. Sometimes, power levels can be as high as 1,000 W to develop the necessary field strength for the EUT. This test must be run in a chamber or outdoor test site.
Radiated immunity testing gets a lot of attention, even more so now that upper-frequency limits are increasing to accommodate the Bellcore GR-1089 specification which calls for testing to 10 GHz. Some radiated immunity test systems, according to Mr. Gerstner of Tektronix, perform well to 1 or 2 GHz. To address the higher frequencies, he said that Tektronix has one system that tests to 1 GHz and another from 1 to 10 GHz.
The equipment and setups for RF radiated immunity tests are undergoing a metamorphosis to keep up with higher frequency requirements. According to Mr. Rogers of Amplifier Research, the amplifier/antenna combination must meet the frequency coverage and power necessary to generate the required field and harmonic content, like the one required in the Bellcore spec. In addition to antennas, he added that directional couplers and field-monitoring equipment also should match the amplifier requirements.
The broader frequency range raises several other concerns. At higher frequencies, the antenna’s beam width may be reduced, which creates a nonuniform field at the EUT. It also is a challenge for equipment and test sites to maintain their calibration and low uncertainty measurement values over an increasing frequency spectrum.
In RF conducted immunity testing, on the other hand, an amplifier drives the interference signal through a coupling device to the power lines of the EUT. No antenna is needed. The RF amplifier’s power can be as little as 10 W, with a frequency response typically below 1 GHz.
Automotive Immunity
It’s beginning to look as though no product is immune to immunity testing—as evidenced by the automotive industry’s growing use of this type of testing. According to Mr. Rogers, conducted immunity generators are constantly evolving to meet SAE as well as international ISO standards. In addition, he said, each automaker is likely to have its own specification. For example, presently there are nine versions of a load-dump simulator.
Be aware of one thing, warned Mr. Revesz of Haefely Trench: Automakers generally impose over-test specifications on vendor-supplied parts and subassemblies. In particular, he said, companies in the automotive field follow the procedures outlined in EN 61000-4-2 and ISO TR 10605, but they test at higher voltage levels.
Conclusion
Jan. 1, 2001, is 20 months away. On that day, more immunity tests will be required for most products. Test equipment manufacturers are keeping pace by building greater capabilities into their products.
|
Standard |
Subject |
Signal Coupling Method |
Signal Generating Method |
|
EN 61000-4-2 |
ESD |
Coupling Plane |
ESD Generator |
|
EN 61000-4-4 |
EFT |
Coupling Device |
EFT Generator |
|
EN 61000-4-5 |
Surge |
Coupling Device |
Surge Generator |
|
EN 61000-4-8 |
Magnetic Field |
Loop Antenna |
50/60 Hz Current Source |
|
EN 61000-4-9 (draft standard) |
Magnetic Pulse |
Loop Antenna |
Pulsed Current Source |
|
EN 61000-4-11 |
Dips and Interrupts |
Coupling Device |
Inrush Current Source |
Table 1
|
Standard |
Subject |
Signal Coupling Method |
Signal Generating Method |
|
EN 61000-3-2 |
Harmonics |
AC Mains |
Controllable 50/60Hz Source |
|
EN 61000-3-3 |
Flicker |
AC Mains |
Controllable 50/60Hz Source |
|
EN 61000-4-11 |
Dips and Interrupts |
Coupling Device |
Inrush Current Source |
|
EN 61000-4-13 (draft standard) |
Interharmonics |
AC Mains |
Harmonic Generator and Controllable 50/60Hz Source |
|
EN 61000-4-14 (draft standard) |
Repetitive Voltage Variations |
AC Mains |
Waveform Generator and Controllable 50/60Hz Source |
|
EN 61000-4-28 (draft standard) |
Frequency Variations |
AC Mains |
Variable Frequency AC Source 45/65 Hz |
Table 2
|
Standard |
Subject |
Signal Coupling Method |
Signal Generating Method |
|
EN 61000-4-3 |
RF Radiated Immunity |
RF Antenna |
RF Generator and RF Amplifier |
|
EN 61000-4-6 |
RF Conducted Immunity |
Coupling Device |
RF Generator and RF Amplifier |
Table 3
EMC IMMUNITY TEST PRODUCTS
Waveform Simulator
The UCS500M/6 Ultra Compact Simulator tests to EMC standards EN 61000-4-2 ESD to 9-kV contact, -4 ETF to 4.4-kV, -5 surge to 6.6-kV, -8 magnetic field to 1,000-A/m, and -9 pulsed magnetic field. These tests anticipate the new IEC and EN standards for household, industrial, and medical electronics and telecom devices. In addition to surge, simulated waveforms include burst, power and pulsed magnetic field, power fail, and voltage dips and interrupts. ESD testing and contact or air discharge are optional. $25,700. Amplifier Research, (215) 723-8181.
Conducted RF Immunity System
The PMM 6000S/10 Conducted RF Immunity Test System includes an RF generator; a 10-W amplifier; a 10-W, 6-dB attenuator; and control software. With the software, you can calibrate the system, perform tests, and prepare reports. The frequency ranges for the generator and amplifier are 100 kHz to 1 GHz and 9 kHz to 230 MHz, respectively. Under $10,000. Antenna Research, (301) 937-8888.
AC Immunity System
The Compliance Test System Series performs AC immunity tests needed to receive a CE Marking. It combines a programmable AC power source with a high-speed data acquisition system that works in conjunction with the PC for complete automation. Standard tests run are EN 61000-3-2 harmonics, EN61000-3-3 flicker, EN 61000-4-11 voltage dips and interruptions, EN61000-4-13 interharmonics, EN 61000-4-14 voltage variations, and EN 61000-4-28 frequency fluctuations. The Series is available in single- and three-phase versions from 1,250 VA to 15,000 VA. From $10,000. California Instruments, (619) 677-9040.
Field Monitor
EMAlert® EMI Protection Modules mount on a PCB or chassis and monitor equipment for excessive local EM field or ESD. The module signals an out-of-bounds condition which may jeopardize operation of critical equipment such as medical or aviation. It then tests the equipment like a watchdog timer. If the host does not respond, another signal is given to reset the host or to warn the operator. A DC voltage output also is provided as a constant field monitor. Up to 10 devices may be networked. From $125. Credence Technologies, (831) 459-7488.
Integrated System
The European Standards Tester (EST) is a an integrated system that tests electrical equipment for compliance to EN 61000-4-13, -14, and -28 AC power immunity standards; and EN 61000-3-2 and -3 AC power emissions standards. The system consists of a low-output impedance power source (SWAE), an interharmonic generator for immunity testing, a harmonic and flicker analyzer (PA-1000), and software for Windows 95, 98, and NT. The EST complies with EN 61000-4-15 and IEC 868. As a stand alone, the SWAE power source meets EN 61000-4-13. From $16,585. Elgar, (800) 733-5427.
E-Field Probe
The Model 7201 E-Field Probe makes radiated immunity measurements per EN 61000-4-3 requirements. The probe has a bandwidth of 26 MHz to 4 GHz and a dynamic range of 1 to 500 V/m. It has a cantilevered, nonmetallic probe head with three orthogonally placed dipoles and measures both CW and 1-kHz AM fields. An internal converter can perform up to 4,000 conversions per sample. Applications for field mapping can daisy-chain up to 16 probes. $5,995. EMC Test Systems, (512) 835-4684.
Clamp-On Injection Probe
The F-120-9A Clamp-On Current Injection Probe is a transformer used to test to EN61000-4-6 when the direct capacitive coupling technique is not possible or appropriate. EN 61000-4-6 defines the methods for testing the immunity of electronic equipment to conducted common-mode currents between 150 kHz and 230 MHz. The probe typically is used to test unshielded cables less than 0.5 meters long. The devices can test to the EN standard with 20 W or less RF power. $3,000 with calibration and accessories. Fischer Custom Communications, (310) 891-0635.
High-Voltage Discharge Tester
The PESD 3000 High-Voltage Discharge Tester performs to the EN 61000-4-2 electrostatic discharge immunity requirement. The tester has a microprocessor-controlled base unit with a built-in power supply. A lightweight, ergonomic pistol comes with two interchangeable impedance units which also allow the system to test to ISO TR 10605. It supplies a voltage discharge of 30 kV in air and 25 kV by direct contact with both single and repetitive modes. $11,750. Haefely Trench, (703) 494-1900.
One-Box Test Solution
The HP 6843A Regulatory Test Solution (RTS) tests to EN 61000-3-2 harmonics, EN 61000-3-3 flicker, and EN 61000-4-11, -13,-14, and -28 voltage, frequency, and interharmonic disturbances. Three modules incorporate a selection of tests. The RTS includes an AC power source, a power analyzer, a harmonic analyzer, a flicker meter, and a digitizing oscilloscope. Single-phase AC power is supplied to 230 Vrms and 16 Arms. Measurements comply with EN 61000-4-7, IEC 868, and IEC 725. Windows-compatible software embeds 17 virtual programmable instruments, and lifetime software enhancements are free. From $21,830. Hewlett-Packard, (800) 452-4844.
EMF Meter
The HI-4460 Graphical Hand-Held EMF Readout accommodates the company’s line of System 4000 Broadband EMF probes. This combination readout/datalogger shows individual-axis and resultant readings, bar graphs, and running time plots simultaneously. A menu system eases setups for measurements and data-gathering. An RS-232 interface downloads software or uploads data to the PC. Alarm, threshold, and percent features are included. $3,395. Holaday, (612) 934-4920.
Immunity Test System
The ECAT® Immunity System tests the EU requirements for the CE Marking. It performs EN 61000-4-2 ESD tests to 15 kV, EN 61000-4-4 EFT tests to 8 kV, and EN 61000-4-5 surge at 1.2/50-µs and 8/20-µs waveforms to 22 kV or 10/700-µs to 7 kV for telecom. Testing also is included for EN 61000-4-9 pulsed magnetic fields at >1,000A/m, and EN 61000-4-11 dips and interrupts. The system provides surge levels that meet ANSI, CCITT, and UL requirements and Bellcore lightning specifications. It also meets FCC Part 68 for both telecom and power lines and GR-1089-CORE. From $29,500. KeyTek, (978) 275-0800.
Lightning Simulator
The Models LSS-6010 and LSS-6030 Lightning Surge Simulators test to EN 61000-4-5 and ANSI C62.41 up to 6 kV and 3 kA. LSS-6010 generates the combination waveform (1.2/50 µs, 8/20 µs) and couples the pulses to single-phase AC. LSS-6030 adds a 0.5-µs 100-kHz ring and CCITT 10/700-µs telecom waves. Voltage, current, and the pulse repetition rate can be adjusted via a control panel. These units have an RS-232 interface and are powered by 120/240 VAC at 50/60 Hz at 200 VA. $20,250. Noise Laboratory, (011) 81 44 959 1951.
Harmonics and Flicker System
The TMX Series Harmonics and Flicker Test System provides compliance testing to EN 61000-3-2 harmonics, EN 61000-3-3 flicker, EN 61000-4-13, -14, and -28 voltage, frequency, and interharmonic disturbances. It also tests to EN 61000-4-11, voltage dips and interrupts. The TMX includes an AC power source, a power analyzer, dual simultaneous harmonic analyzers per EN 61000-4-7, dual flicker meters per IEC 868, impedance per IEC 725, and a digitizing oscilloscope. Windows-compatible software controls tests from a virtual instrument screen. From $12,000. Pacific Power Source, (714) 898-2691.
Modular Test System
The System 2050 Modular Test System combines an open-architecture mainframe unit with a series of plug-ins to create a user-configured setup to meet standard or custom test specifications. This system supports a range of immunity testing to EN 50082-1 and -2 and related product standards as well as EN 61000-4-x and ANSI C62.41. Telecom options test to CCITT, FCC, ETSI, and Bellcore specifications. This range of testing covers industrial electronics, office automation, telecom equipment, domestic appliances, medical equipment, and components. From $17,000. Schaffner EMC, (800) 367-5566.
Compact Test Chamber
The S-Line Series of shielded TEM cells offers a compact alternative to anechoic chambers for precompliance emissions or immunity testing. For emissions testing, filtered feedthroughs are provided for connecting the EMI receiver or spectrum analyzer. The VSWR of the empty cell is 2.5 maximum. The cell has a frequency range of 150 kHz to 1 GHz, and the shielding effectiveness is ³ 75 dB at <500 MHz. The S-700 accommodates an EUT of 13.7 in.3, and the S-1000 increases the volume to 18.9 in.3. S-700: $29,500; S-1000: $54,500. Tektronix, (800) 426-2200.Copyright 1999 Nelson Publishing Inc.
April 1999