When planning your in-house EMI testing kit, it is important that you understand the differences between debugging or general troubleshooting EMI problems and pre-compliance. A set of near field probes or RF Current probes is used for general troubleshooting. This can also be combined with a spectrum analyzer and an RF-capable oscilloscope. The goal of this is to locate sources of harmonic energies and find fixes that decrease harmonic amplitudes. Relative changes are what we are looking for. Full compliance testing procedures are meant to produce exact, calibrated measures. However, relative measurements can be used for troubleshooting.
To get the best results, the radiated-and-conducted emissions test is typically performed in a semianechoic room or GTEM cells. This allows for outside signals to be eliminated (ambient signal), such as television, broadcast radio, and two-way radio. This is a costly procedure that may not be necessary emc testing lab with modern test equipment or software. Therefore, it is possible to conduct in-house emissions compliance tests outside a protected chamber. These tests can also be used to differentiate ambient signals from those from the product under testing.
EMC pre-compliance software can be used to make an ambient measurement of the surrounding environment, even when the product has been turned off. This provides a baseline for RF noise. This can then be subtracted using a math trace to allow the user to differentiate between failures from the device under testing and the environment.
How do you create a pre-compliance testing lab and troubleshooting EMI? It isn’t as expensive as you might imagine. It’s not as expensive as full compliance testing equipment. Pre-compliance EMC Testing and Troubleshooting is possible without the need for a semi-anechoic chamber.
Figure 3 illustrates the equipment required to conduct radiation emissions precompliance testing. It includes a calibrated antenna, preamp and spectrum analyzer using EMC software. Conducted emissions testing requires a spectrum analyser, line impedance stabilization networks (LISN), optional power filters or preamps. Radiated emissions is the most common EMC failure in a full EMC compliance testing.
This application calls for a USB-based realtime spectrum analyzer. It is affordable and can capture intermittent and infrequent signals with high precision. The real-time signal/spectrum analyzer can measure signals using narrow resolution bandwidths (RBW), which is orders of magnitude faster than traditional swept tuned analyzers. This allows users to save time searching for low-level RF spikes and scans more efficiently. The signal analyzer can verify the performance and quality of any wireless radio or module. It can also do signal analysis like EVM measurements and constellation diagrams.
However, for those with limited budgets and who prefer to test EMI problems, it may be more sensible to invest in a multipurpose RF-capable oscilloscope. This device has an independent RF input that is coupled with an internal spectrum analyser. Multi-domain capabilities are also available in the latest mixed-signal oscilloscopes. This is in addition to traditional oscilloscope frequency domain controls over multiple channels. This allows for troubleshooting to be significantly simplified by being able to correlate signals across both domains.
A measurement probe is used to measure E field waves and H-field waves near the circuit. This is the cheapest method designers use to identify problems in EMI testing of their products.