Tektronix Encore

The Importance of Pre-Compliance Testing

October 01, 2018

EMC pre-compliance testing can be a company-saver—a way to make sure a new product will pass electromagnetic-compatibility (EMC) compliance testing. EMC pre-compliance testing is basically an earlier version of EMC compliance testing, a way to determine the EM emissions from a new design as well as its immunity to nearby EM energy. Not only can it save time to market, it can save the costs of re-designing a product that fails EMC compliance testing.

Almost any new electronic product can be at risk of failing EMC compliance testing. EMC pre-compliance testing is a way to minimize that risk by performing some simple measurements before shipping the new product to an EMC compliance test lab for evaluation. Failing EMC compliance testing at an accredited EMC compliance test lab can lead to expensive search time to find the problem. It may also mean expensive re-design time, depending upon how close the product is to final production (and customers’ expectations).

EMC pre-compliance testing can improve the chances of a successful new-product introduction. Testing seeks to learn if an electronic design conducts EM energy from the environment around it or radiates EM energy at sufficient levels to cause interference with other electronic devices. Different areas of the world follow different standards as guidelines for acceptable maximum EM levels.


What Type of Gear

The measurements are straightforward and can be performed with versatile instruments, such as a real-time spectrum analyzer or an EMI test receiver with enough bandwidth to cover the operating frequency range of the device under test (DUT). Additional instruments include a signal generator for a source of controlled EM energy, antennas and/or probes, and a place to make the measurements relatively free of other sources of EM radiation. While an anechoic chamber comes to mind as an EM-free environment, it can be costly to construct and is not mandatory for effective EMC pre-compliance measurements. Depending on the intended market for a new product, EMC pre-compliance testing can be performed according to the same requirements as EMC compliance testing, such as per CISPR and military standard (MIL-STD) requirements.

Bandwidth and dynamic range are key specifications for any spectrum analyzer or test receiver, with wider ranges providing greater measurement versatility and the capability to perform EMC pre-compliance testing on a wider range of DUTs. For example, the Rohde & Schwarz ESR7 EMI test receiver offers generous test bandwidth through its two input ports, for AC- and DC-coupled measurements with antennas and probes. Input 1 covers an AC-coupled range of 10 MHz to 7 GHz and a DC-coupled range of 9 kHz to 7 GHz. Input 2 features a DC-coupled range of 9 kHz to 1 GHz. It features a wide display dynamic range (110 dB) and spurious-free dynamic range (SFDR) of -70 dBc that allow detection and display of the EM levels that cause problems for an electronic design in need of EMC compliance.

The Rohde & Schwarz ESR7 EMI test receiver doubles as a spectrum analyzer, providing a user with enough instrument control to change the width of a frequency sweep, the sweep time, the frequency resolution and internal resolution bandwidth (RBW) filters, and many more of the analyzer measurement functions that support practical EMC pre-compliance measurements. For those in need of additional EMC pre-compliance measurement bandwidth, Rohde also offers its ESW line of EMI test receivers, with models extending from 2 Hz to 8, 26.5, and 44 GHz and functionality much like the R&S ESR7 EMI test receiver. The company also offers many options for the test receivers to support EMC pre-compliance testing, including a line of signal generators covering the appropriate frequency ranges for each receiver and remote controls to operate the equipment from a distance, such as while outside an EMI-shielded test chamber.


Ready to Test

The Rohde & Schwarz test receivers/analyzers provide a great deal of measurement power but must be programmed in advanced of EMC pre-compliance measurements. In contrast, Haefely Technology tries to make testing as simple as possible with its axos5 Compact Immunity Test System, which combines many of the measurements required for EM immunity testing (including a single-phase coupling/decoupling network) with an extremely simple control interface. The result is an instrument that almost anyone can operate to perform effective measurements. In addition to its capabilities to perform automated measurements according to the most common IEC, EN, ANSI, IEEE and UL standards, it also allows a user to control voltage and current measurement ranges and monitor results on a large color display screen or remotely via a PC. It is also equipped with many safety features to protect the occasional user from harm.

The Haefely ECOMPACT 4 is another highly integrated EM immunity tester that features the compact functionality the company is known for but with more front-panel command and control. It can meet or exceed the measurement power of the axos5 system and with similar one-button control. But when programming control is needed from the instrument, it is readily available and straightforward, allowing a user to change measurement parameters quickly and easily. The instrument is fully capable of making EMC pre-compliance tests as well as EMC full compliance measurements.

Such compact testers are like having a full measurement lab in a box. For those using a separate EMI receiver, the associated test gear, such as a test signal source, will still be needed for EMC pre-compliance testing. The EM TEST NX5 signal generator is an example of just how much test capability can be integrated into a compact housing. It provides transient and surge signals at voltages to 5 kV for both EMC pre-compliance and full compliance testing according to most standards. It includes a simple color touch-screen interface for local control and includes a variety of computer interfaces (Ethernet, USB, and optical) for remote control via a PC and its dedicated software. The test signal source is available with many accessories to extend its capabilities to other applications, such as magnetic field testing.

EMC pre-compliance testing applies to so many different markets for electronic products that some test instrument suppliers even tailor measurement solutions for those markets, such as the Teseq NSG 438 ESD Simulator. The tester is designed mechanical and electrically for automotive ESD testing. It fits easily in a tester’s hand but meets all the electrostatic discharge (ESD) measurement requirements of current automotive standards, showing results on a bright color touch-screen display. It is simple to use and performs accurate discharge measurements per worldwide standards.

Of course, these instruments are just a few examples of some of the measurement tools available for EMC pre-compliance testing; more information on these and more instruments can be found on the Axiom Test Equipment website. To learn more, please visit Axiom’s website at, contacting Axiom Test Equipment’s sales department at, or by calling an Axiom sales representative at 760-806-6600.

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