Effective Pre-Compliance testing can have a significant impact on product development costs and lead times.
Attaining robust Electromagnetic Compatibility (EMC) is becoming increasingly necessary across all susceptible products not only for standards compliance purposes but also to meet the stringent functional specifications for complex end products in industry, healthcare, telecommunications and the automotive industry, for example.
The cost of performing such testing in a certified test house is high and this is a necessary expense before launching the product onto the market. But what if it fails the test? Costs quickly mount when a “final” product goes back to the drawing board and submitted some time later for retesting. Such iterative approaches aren’t cost-effective and don’t meet competitive time-to-market aims.
The alternative approach is to perform in-house compliance testing, a method that’s becoming increasingly popular, especially with the availability of affordable laboratory equipment and software. These tests can never be as precise as those performed in anechoic chambers with high precision antennas in a test house but they are extremely cost effective in reducing the risk of product failure in final testing.
Types of Testing
Electromagnetic Interference (EMI) can be radiated (through the air) or conducted (along wires). EMC testing performs both tests. It also examines the product from the point of view of the emissions it gives off and its susceptibility to received interference.
For pre-compliance emissions testing, the equipment requirements are a spectrum analyser with EMC analysis software, a pre-amplier and an antenna (for radiated emissions) and a Line Impedance Stabilisation Network for conducted emissions.
Immunity testing will require a signal generator and a set of probes.
In all cases, since a high cost anechoic chamber is unlikely to be available, great care is needed in selecting the right environment in which the tests will take place so that the results aren’t influenced by stray signals such as emissions from anything other than the device under test or signal from anything other than the signal generator.
Radiated emissions tests can be performed in large parking areas or empty conference rooms for example as it’s crucial that transmissions from broadcast radio, TV or mobile phones don’t interact with the DUT or antennas.
Advanced signal analysers are a key element in the test equipment needed for pre-compliance testing and some, such as Keysight’s X-Series are available with software such as the N6141A EMI measurement application, which is a standard library of more than 25 measurement applications in the analyser. N6141A transforms the X-Series signal analysers into powerful EMI pre-compliance and diagnostic systems, providing easy-to-use data collection and analysis tools which facilitate rapid time-to-market for new designs.
Other alternatives include the TekBox EMCView Pre-compliance Testing Software, PC-compatible software for simplifying the process of EMC pre-compliance testing of radiated and conducted emissions.
EMCView complements an emissions test setup consisting of a spectrum analyser, an LISN and an EMI-quiet TEM (Transverse ElectroMagnetic) Cell. Built-in amplitude correction provides the correction and conversion coefficients for cables, amplifiers, attenuators, LISNs, TEM cells, antennas, RF current probes, striplines and capacitive coupling clamps.
Software from other suppliers is also available, including SignalVu-PC from Tektronix, for the validation of RF designs.
SignalVu-PC’s free base version has 17 signal analysis and real-time spectrum analysis channels, with paid add on options for EMI/EMC pre-compliance testing and de-bugging, vector signal analysis, pulsed signal analysis and commercial wireless signal analysis.
Interference free validation
Tools are available to assist in ensuring the test can be performed in a valid way. One example is the Microrad NHT 3DL Electromagnetic Field Analyzer for measuring electromagnetic fields in both time and frequency domains.
The hand held device has a high resolution colour touch screen display and can be remotely controlled via Wi-Fi or fibre-optic connection, with the display shown on Windows and Android devices. The Microrad NHT 3DL analyzer is particularly useful since it has been designed to operate in different modes, including as an area monitor.