The success of this range of kits may be due to their unrivalled cost effectiveness and the focused, no nonsense approach of the company which has helped to explode the myth that EMC testing is something of a 'black art'.
The RF range of kits are now used extensively for pre-compliance and self certification tests. They can include all the items required for both radiated and mains conducted emissions: Spectrum analysers, Powerful Windows compatible PC software, RF pre-amplifier, Far field broadband antenna Radiated emissions calibrator (ERS), Near field probes, PC interface and software, LISN, RF absorption clamp, Large loop antenna, Text books, Active near field probes
The success of this range of kits may be due to their unrivalled cost effectiveness and the focused, no nonsense approach of the company which has helped to explode the myth that EMC testing is something of a 'black art'.
For many small (and not so small) companies, the costs and timescales associated with test houses are way beyond their budget. Similarly, purchasing 'conventional' instrumentation to do their own testing is out of the question. Laplace test kits offer these companies a solution to an otherwise impossible situation.
He was educated in Manchester and joined Rolls Royce (Aero Engines) in Derby as an engineering apprentice after leaving school. Although he subsequently obtained an Honours degree in Electrical Engineering at London University, he was (and still is) very much a 'hands on' practical engineer.He worked for 18 years as production manager then manufacturing director for Data Acquisition Ltd in Manchester, producing a range of instrumentation amplifiers, tape recorders and FFT (fast fourier transform analysers) based products, notably for helicopter vibration and railway research related applications. In 1988 he left Data and established Laplace, specialising in FFT frequency analysis instrumentation and their applications. One such application is a signal interface system currently in use on the Russian MIR space station. Logical extension to higher frequency analysis led to RF spectrum analysers just at the time EMC was becoming an issue (1992).
David's background of practical, pragmatic and applied engineering solutions contrasted sharply with the conventional approach of the established RF instrumentation suppliers. This together with a complete lack of historical 'baggage' or established RF instrumentation ensured that the subsequent range of Laplace EMC products were far more cost effective than any others available at the time. David ensured that Laplace adopted a low cost, no nonsense strategy and added certain unconventional features which result in a system that can produce high integrity results in spite of the demanding and error prone measurement techniques specified by the EN standards. Specifically, the use of an ERS (Emissions Reference Source) as a reference during routine EMC emission testing was unknown until the technique was introduced by Laplace. Other major contributions by David are the EMCEngineer software, shipped with every Laplace analyser. This Windows based package is recognised as one of the most user friendly and powerful systems available for EMC emissions analysis, combining the speed and utility of an analyser with the analysing power of a receiver.
David has now written several published articles and delivered seminars and presentations on EMC throughout Europe and he continues to push for a more logical and pragmatic approach towards EMC emissions measurement.
The fact is that even test house results may vary by significantly greater values simply due to variations in product configuration. (Layout of UUT connecting cables for instance) For companies establishing their own test sites on car parks/local farms/back gardens/loading bay/spare office etc.... the environment and test site conditions totally dictate the integrity of the results.
The most common problems are associated with reflections. Unfortunately, even if all reflecting metal surfaces are kept well away from the test site, some reflection will occur off the ground. This 'ground plane' reflection can lead to errors of the order of over 15dB!!
To be fair, the EN standards do describe in some detail how to avoid gross errors, but most engineers, due to lack of space or other resources, are forced to accept far less than perfect sites. In these circumstances, it is absolutely pointless to spend large sums on expensive, very accurate, spectrum analysers or tuned receivers.
A Laplace spectrum analyser at £3,645 has an accuracy of ±3dB. A typical 'big name' competitor at £18,000 will have an accuracy of 1.5dB. These must be seen in context with a typical test site variation of ±10dB or worse.
In order to overcome this large 'measurement uncertainty' Laplace have introduced an Emissions Reference Source (ERS). This unique device is capable, for the first time, of quantifying the errors associated with far field emission levels. This represents a major advance in the whole field of EMC measurement, overcoming at one stroke the most significant source of measurement error.
The fact is that a low cost analyser plus ERS £5K - £6K will provide far higher measurement integrity than a 'conventional' measurement receiver £20K - £40K without the ERS.
The ERS provides a unique solution to all these problems.
The ERS is a small, battery powered unit complete with aerial which emits a calibrated signal over the complete range 30MHz to 1GHz. It is supplied complete with plots of field strength as measured on an accredited open area test site (OATS), both for vertical and horizontal polarisations. The exact test conditions are quoted, so enabling the user to replicate these conditions regarding antenna position and height.
By substituting the ERS for thesource a measure of how the user's site differs from a true OATS is immediately obtained. This 'correction factor' can then be applied to measurements from the UUT thus largely eliminating errors due to test site reflections, ground plane condition, proximity of other objects, antenna and instrumentation errors, in fact any and all potential variables.
In essence, the ERS enables radiated emissions measurements to be made with a far greater degree of confidence even if the test site is 'corrupt'.
For instance, manufacturers of large equipment such as machine tools, production machinery, control cabinets or complete installations, who cannot move the equipment into an OATS, can now measure in situ using the ERS to characterise the errors. Even those who can approximate to a proper test site will now be able to measure emissions with far greater confidence than before.
The ERS is a true 'end-to-end' calibrator. It takes into account not only the site conditions, but errors due to antenna, pre-amplifiers, cables and analyser. It can be used with any EMC measurement system and can even be used to correct readings taken in screened rooms which otherwise would be subject to potentially massive errors due to reflections and standing waves.
Key features: 10KHz to 1GHz frequency span; 9KHz and 120KHz bandwidths with 200Hz option; PC controlled with powerful display/analysis software; TestWizard feature for automated compliance testing; Tuned frequency modes for average and quasi-peak detection; Chart display of average and quasi-peak levels plotted against time; Audio demodulator; Overload detector
The SA1000 analyser has been developed from the very successful SA450B but incorporates many totally new ideas. The SA1000 is a 'black box' analyser, having no controls of its own but completely controlled from a PC via the serial port. The PC software is included with each analyser and runs on any PC that supports Windows.
Experience has shown that many users wish to self-certify their products but lack the expertise to conduct tests correctly. The SA1000 software includes a TestWizard feature that takes the user through the test procedure step by step and includes 'intelligent' selection screens to help choose the correct EN standard and to 'set up' the test configuration correctly.
Each analyser can be supplied as part of a complete kit which includes broadband antenna, pre-amplifier, near field probes, LISN or RF absorption clamp, all connecting cables and text book . This provides the user with a completely integrated solution. Options include a reference source for radiated emissions. This enables all the measurements to be correlated against known levels, thus removing the uncertainty due to test site.
The SA1000 has a unique tuned frequency mode which emulates a tuned receiver and shows the average or quasi-peak level plotted against time. This is a specific requirement of CISPR16 which is not normally found on any spectrum analyser. A built-in input monitor checks for overload conditions and displays a warning message on screen if the possibility of signal compression (always a problem with spectrum analysers) is present. The wide frequency range of 10KHz to 1GHz covers all the common EN standards and the software automatically selects the appropriate 9 or 120KHz I.F. bandwidth to suit the test type.
The 'test site problem' can be overcome if the test site is calibrated and the errors quantified. Laplace kits now include an ERS (Emissions Reference Source) which produces an accurately known field strength. By measuring the output of the ERS on the users site and correlating the results with the calibration data, the test site errors become immediately obvious and can be quantified. This simple technique has now been 'automated' in the software for our analysers so that the correction factors are automatically calculated and applied to measurements of the equipment under test (EUT). Now, for the first time ever, there is a system that will produce good results on typical test sites. This powerful and important (if not critical) feature is unique to Laplace and the SA1000 1.1GHz analyser.
The latest versions of the EMCEngineer software package included with the SA1000 analyser have a 'TestDirector' mode. TestDirector is essentially an expert system integrated into the EMC analyser system such that a non-expert user can conduct tests on their products with confidence in the knowledge that the TestDirector will ensure that the test technique and test procedure is correct for the EUT in question.
The functions provided by the TestDirector are:
As with the ERS auto calibration facility, this feature is included with all SA1000 analysers at no charge.
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