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Eddystone Court - De Lank Lane St Breward - BODMIN - PL30 4NQ Tel: +44 (0)1208 851530 - Fax: +44 (0)1208 850871 nutwooduk@nutwood.eu.com |
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Emissions Case StudyElectromagnetic Testing Services Ltd |
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This OATS emission plot was recorded from a chemical dispensing system. The source of the emissions was traced to the main data processing board which incorporated an 11.0592 MHz clock. Significant narrow band harmonics were recorded with levels far exceeding the defined limits. The highest recorded level was at 33.2 MHz, the 7th harmonic of the clock frequency. This frequency was selected for further board analysis.
An emissions analysis was carried out at the problematic 33.2 MHz on the defective board using the ETSi4334 scanner. The scan pinpointed the problem to a fast signal track running from the CPU module to a peripheral IC. The poor power decoupling of a driver IC was also revealed.
The offending signal track was suppressed by providing appropriate line termination and filtering. The power decoupling of the driver IC was also corrected. The board was then re-scanned. The effectiveness of the fixes applied at source are evident from the substantial reduction in the emission levels
Finally the board was re-tested on the OATS. The modifications resulted in a significant reduction in the emission levels, ensuring compliance with the defined limits.
This case study kindly supplied by:
Electromagnetic Testing Services Ltd (ETS)
Pratts Fields
Lubberhedges Lane
Stebbing
Dunmow
Essex CM6 3BT
Tel: 01371 856061
Fax: 01371 856144
eMail: info@etsemc.co.uk
URL: http://www.etsemc.co.uk
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© Nutwood UK Ltd 2001 |
Eddystone Court - De Lank Lane St Breward - BODMIN - PL30 4NQ Tel: +44 (0)1208 851530 - Fax: +44 (0)1208 850871 nutwooduk@nutwood.eu.com |
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