SA1000 EMC analysis software
 

Provides all the control, signal processing, display, results output for all EMC measurement functions. A major asset provided with the SA1000 is the PC software. This Windows compatible program, EMCEngineer, provides full control of the analyser, display of current, background, difference and limit level traces simultaneously, plus archived traces. The prime design objectives in creating this software have been simplicity of use, clarity of results presentation and the ability to cope with the factors such as background noise and test site errors which can degrade typical measurements in the ‘Real World’. Basic features such as saving and printing of results, integration with other Windows applications are included as a matter of course. Special key features available only with this EMCEngineer software are: TestDirector mode in which the user is guided through the initial test sequence, prompted as necessary to ensure the correct test configuration. The software sets up the analyser automatically thus making the system ideal for non-expert users. Auto site calibration. A technique for automatically calibrating any radiated measurements when using any broadband antenna. This technique utilises an ERS, (emissions reference source) to quantify the distortions due to the test site (and any other error source) and automatically applies the appropriate corrections to any subsequent measuements. Background signal cancelation using advanced signal processing techniques which highlight the EUT emissions even in strong background environments. Flexibility Flexibility Full software control of the analyser enables any parameters to be instantly changed as required to suit the particular circumstances of the test. Frequency start and stop points can be set to any point in the usable range of the analyser with no restriction on the frequency resolution of the display (40KHz HF range, 1KHz LF range). The EMCEngineer software is ‘open’ in that the calibration data for any third party antenna or transducer can be easily entered. This also applies to limit level data so that any custom or non-standard limit traces can be used. Any data so entered is permanently stored automatically for future use. Optimum result presentation Large easy-to-read graphical display of spectral results with clear annotation of axes, making interpretation of levels and frequencies easy. All controls and status indications are shown on the PC screen. Up to 5 traces may be shown on screen simultaneously. Current Store (background) Difference (current-store) Limit level Archive. These enable the user to see at a glance the frequency components from the EUT, background signals, compliance with the limit and comparisons with earlier results. Zoom anywhere in frequency range with cursor or keyboard entry to select start and stop frequencies. Auto interpolation of existing traces to zoomed area. Real time display of emission levels with single frequency ‘chart recorder’ mode. Easy result archiving Standard Windows facilities for data storage to disk. User entered file name and directory. All results (current, backround, limit and single frequency data all stored as one file. Immmediate file recall. Traces can be recalled in any order and compared with existing traces on screen. Hardcopy to any standard printer (including colour) via Windows drivers. Notepad for entry of comments specific to each test. All setup information retained with archived data. Results are easily transferred to third party software such as spreadsheets and word processors. Operation A basic requirement of the SA1000 was the ease of operation and the integration of software facilities to make for error free measurements, even when used by non-expert personel. All analyser operations are controlled by the PC software. The display gives a clear indication of the system status and each function is controlled by individual buttons. Thus control is simple and intuitive. Selection of system parameters such as antenna data and limit levels is by simple pull down menus with permanent on-screen indicators to show the items selected. Communication between the PC and the analyser via the standard serial port occurs continuously even when the system is apparently dormant to the user. This continuous monitoring ensures that the analyser healthy and in the correct configuration. Diagnostic analysis For effective diagnostic work, the SA1000 can be tuned to any single frequency in the working range of the analyser. The display switches to a time domain plot of signal strength against a user selected time base. This can show either peak, quasi-peak or average results in real time. Soft buttons permit manual fine tuning. Any changes in the emissions due to modifications, orientation change, added screening etc.. are immediately observed on screen without additional, time consuming scanning. A unique feature available when using this single frequency mode is an auto peak tracking capability. This is ideal for working with products such as switched mode PSUs and other non-controlled frequency sources that can drift with time or conditions. This mode is also perfect for monitoring trends and cyclic variations on products that can fluctuate in time. RFI measurement For both radiated and conducted measurements, the three detectors fitted to the SA1000 ensure the optimum combination of speed to gain an overview of the total spectrum and the accuracy of true quasi-peak and average readings. CISPR compliant IF bandwidths of 9KHz and 120KHz are automatically selected to suit the frequency range to be scannned Once the user selects the high (for radiated) or low (for conducted), the correct IF bandwidth filter is automatically invoked and the entire spectrum can be swept to identify significant peaks. In particular, the analyser uses a pseudo analogue sweep technique which ensures that NO peaks are missed, regardless of the display resolution. The PC software includes peak hold and averaging functions which are ideal for measurement and cancellation of background radiation. Once significant peaks are identified they can be zoomed to and accurately measured with the average and quasi-peak detectors. When radiated emissions are to be checked against limit levels, the software automatically corrects the limit level to take the antenna-product distance into account using the algorithms specified in the EN standards. A vital key feature is the constant monitoring of input signal level to check for compression (overload) conditions. This compression status is continuously indicated to the PC and any compression ‘events’ are marked against the spectrum as it is plotted on screen. Thus the SA1000 system uniquely ensures that results are free of compression, avoiding the one potential drawback of spectrum analysers. Practical solutions In reality, most radiated EMC testing is performed in less than ideal sites. Not only may significant levels of ambient background radiation be present, but typical sites often feature undesirable reflections and other distortions. Even conducted emissions measurements may be subject to ambient signals which make identification of the ‘real’ signals difficult. The EMCEngineer software provides simple to use facilities for measurement and cancelation of background emissions. Emissions due to the EUT are shown clearly on the colour screen even in the presence of high ambients The SA1000 and EMCEngineer software provide a unique feature to measure and correct for test site distortions and any other measurement errors that may be present between the EUT and the display screen. This all encompassing correction is obtained by using an ERS (Emissions Reference Source) together with auto-correction facilities in the PC software. These two features provide an exceptionally powerful means of acquiring high integrity measurements even in less-than-perfect sites. Note that the ERS units are traceable back to NPL and thus offer the highest levels of accuracy and confidence

 

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Revised: October 3, 1999
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