The common theme to this section is conducted noise. Noise is not just a consideration when complying with EMC legal requirements, its is also potentially damaging and/or cause of failure of product performance or communications, even if the noise level is below EMC standards limits.

The two basic themes in this section are

  • the detection and measurement of ‘noise’ and
  • the use of filters to reduce it to acceptable levels.

Noise is commonly found on high voltage circuits such as mains supplies. The EMI adaptors featured in the detection and measurement page are specifically designed to provide a low cost, safe and effective interface between these lines and your ‘scope or spectrum analyser. They offer bandwidth to over 200MHz and are therefore ideal for PLC (Power Line Communications) applications, and any investigations into suspected noise related incidents.

Conventional filters tend to be focussed on EMC compliance requirements. These are not necessarily adequate for ‘real world’ conditions. A classic situation occurs when transient noise injection occurs some distance from the ‘victim’. Transient noise is broadband, so frequency components cover a very wide band, from KHz up to 100’s MHz. Over distance, the higher frequencies tend to ‘dissipate’ (radiation and coupling effects). On the other hand, lower frequency components are not dissipated, so it is these components that can become dominant and need to be blocked (filtered). EMC filter requirements tend to match the requirements for EMC compliance, which for most products is 150KHz up to 30 or more MHz.  but, as just explained, ‘real’ noise is often dominated by lower frequencies below 150KHz, where these filters have reduced effectiveness.

The ‘Cleansweep’ range of filters avoids this situation by extending the effective filter bandwidth down to block these lower frequency components.

A wide range of mains filters, plus ground filters, filters for servo & VFD motors, data lines and DC line filters are available to match your specific requirements.

Detection and measurement.


Mains filters

Ground filters

Servo and VFD motor filters

DC filters