EMI and RFI overview

RFI testerElectrical and electronic circuits or devices emit electromagnetic and radio signals. These signals are quite harmful to other circuits or embedded systems. These radio and electromagnet signals are constant. Instead they vary continuously both in intensity and speed. These varying speed signals interfere with other signals and can cause harm to other instruments. These unwanted signals can also interfere with the manufacturing process. You can experience EMI and RFI in low quality receivers. You can also observe EMI and RFI in microprocessors, switching power supplies, and AC motors. On the whole any electrical or electronic component offers an electro magnetic or radio frequency interference to some extent. But an authenticated and well-known industry always keeps in mind the protection from RFI and EMI. Therefore the embedded systems and other industrial and commercial equipment is pre tested for RFI and EMI. For this purpose EMI and RFI testers are most important instruments.

EMI and RFI testers

EMI and RFI testers locate the electro magnetic and radio frequency waves emitted by electronic circuits. They indicate various parameters such as speed, direction, or intensity of signals. Most sophisticated testers display the continuously varying waveforms. EMI and RFI testers vary among the schemes they use to detect interference. The most common is LISN (line impedance stabilization network).

LISN

Line impedance network is a technique to determine EMI and RFI in a manufacturing process. In the network EMI and RFI testers continuously measure the power lines to the equipment. LISN offers a port for RF connection that can measure the conducted emissions. On the other hand radiated emissions detected by an antenna or current probe.

Frequency Options for EMI and RFI testers

EMI and RFI testers operate on four bands. These include vertical high and low frequency bands, and horizontal high and low frequency bands.

EMI tester's Range

Mostly you'll find EMI testers ranging 30 Mega Hz to 200 Mega Hz with low band and 200 Mega Hz to 1 Giga Hz for its high band.

RFI tester's Range

In RFI testers range conducted RFI lies in low frequency band (Kilo Hz to 30 Mega Hz). Whereas the radiated RFI is measured in high frequency band (30 Mega Hz to 3000 Mega Hz or more). All in all you can always find sophisticated EMI and RFI testers with adjustable frequency band options. But such testers cost way much than the standard ones.

EMI and RFI regulatory authorities

FCC (Federal Communication Commission), IEC (International Electro-technical Commission), SAE (Society of automotive engineers) are the major authorities for restrictions over RFI and EMI equipment. All the equipment including EMI and RFI testers must comply with the rules and regulations defined by these authorities. Rules and regulation include restriction over operating temperature rise, maximum leakage current, mechanical designs, and other such elements that cause electro magnetic and radio frequency interference.