Telecom conformance testing – are we up to scratch?
South African Bureau of Standards (SABS) committees recently assisted the Independent Communications Authority of South Africa (ICASA) with the drafting of interim power line telecoms (PLT) regulations. The question arose as to whether our test laboratories are able to do electromagnetic compatibility (EMC) conformance testing to international standards.
EngineerIT investigated this and discussed the EMC-compliance testing question with conformance consultant Lizette de Vries-Venter.
At the request of the StanSA TC80 committee, de Vries-Venter recently conducted a survey of the four local test laboratories equipped to carry out EMC testing for telecommunications equipment. The purpose of the survey was to establish their capabilities and accreditation.
According to De Vries-Venter, it was surprising how the labs perceive themselves in terms of competency.
EMC specialists talk about full compliance and pre-compliance. Pre-compliance refers to simulated tests and requires experienced professional judgement. Full compliance means the lab can do the testing to the full extent of the standard.
Some labs will tell their clients that for a particular standard only pre-compliance testing can be done, while for other parameters full compliance testing is peformed.
It was found that some labs claim to do full compliance testing while in practice it has been shown that they don’t have EMC expertise and experience. Other labs said that all their testing is fully compliant with the requirements of the standards specification.
The challenge in testing for EMC compliance is that the lab must have the skills to interpret the results.
De Vries-Venter believes that the main problem lies with the South African National Accreditation System’s ability to accredit a laboratory. A comparative EMC study of a noise-generator carried out by various labs showed some interesting results. Some were spot-on or close, yet the lab that was way off the mark was
accredited.
“While SANAS performed extremely well to accredit calibration laboratories, it cannot be assumed that they are experienced enough toaccreditate EMC labs”, she said.
“Calibration is testing to a standard. A metre is a metre or a gram is a gram. In EMC testing a judgement component enters the equation. SANAS must have EMC-qualified personnel to be able to accredit a laboratory for EMC; just to check that the correct procedure is followed is not enough.”
De Vries-Venter believes the remedy is to invite an overseas EMC expert to be part of the accreditation process, as is presently being arranged for testing laboratories in other fields.
Many companies make use of an independent EMC consultant to interact and assist the test lab when performing conformance testing. The combined experience is more likely to ensure test results that are on a par with internationally accepted standards.
In De Vries-Venter’s survey it was found that by and large all four laboratories could perform the EMC test as laid down in CIPR 22, but she expressed concern that there is no indication that these laboratories are gearing up to testto the revised CISPR standard which becomes mandatory in 2009.
When the revised CISPR 22 standard becomes obligatory, laboratories must be able to test up to 2 GHz. In future the upper frequency will be raised to 18 GHz.
The revised protocol has several other new requirements. Currently all four laboratories can test up to 1 GHz. Upgrades of this type are very expensive. One can safely say that the upgrade cost would be many times the cost of the current installation, typically in the order of R1-million to R2-million per GHz.
One of the laboratories is a private commercial laboratory while the other three have some government connections. Investing the large sums required would hardly make business sense given the small size of the local market.
“Laboratories and industry will have put their heads together and come up with solutions that will serve them as well as the rest of the industry”, said de Vries-Venter.
Engineer IT
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