Click Analyser: The Italian Job?

The definition of a click is given as "a continuous disturbance which does not exceed a limit of 200msec and that is separated from a subsequent disturbance by at least 200msec". As anyone who has to test clicks knows, it is an extremely time-consuming and laborious test. To make life easier for testers who have to perform click tests on products, Italian-based AFJ International have recently launched an innovative discontinuous disturbances analyser onto the market. It's called the CL55C, and is compliant with both CISPR 16 and CISPR 14 standards.

The CL55C is a four parallel channel (up to eight) fixed frequency (150KHz, 500KHz, 1.4MHz, 30MHz) RF receiver, with each channel provided with peak and quasi-peak detectors. The Q-P detectors fully comply with Clause 2 of CISPR 16-1. The Q-P detectors are designed to automatically perform tests in full compliance with the requirements of EN55014, where the test requests using an oscilloscope (time-domain operation). If the user needs to perform self-assessment, the analyser has a built-in impulse generator, that can produce the entire set of single and multiple disturbance pulses, in the various timing and shift configurations as required by Clause 14, Tables 14, 15 and 16 of CISPR-16-1. The PC-driven CL55C operates under the Windows 95/98 and all information gathered is displayed in real time on the computer's screen and divided into a number of Windows corresponding with the internal RF channels being used.

The main characteristic of the click analyser is it's ability to sample, in parallel, the peak and quasi-peak levels of the four channels (Fig. 1), to recognise and count all clicks (short, long, continu ous noise and switching operations), and store all numeric and graphic data, like waveforms, in the PC hard disk. This means almost limitless storage capacity.

The CL55C is not just a click counter, but a true analyser. The whole cycle history of the EUT is available (Fig. 2), complete with markers and zoom functions is available at the end of testing. The level Vs time graph of both peak and quasi-peak detectors related to each event can also be displayed. Lastly, but by no means least, the real superiority of the analyser resides in the built in power meters which enables continous monitoring of EUT current consumption. In fact, steep variations in this current are often related with disturbances (click) because of the very large bandwidth, that includes all frequencies able to generate a click.

There are three graphic modes available with the CL55C, depending on the user's needs:

1. Event history (Fig. 2): shows the whole EUT cycle

2. Zoom Analysis (Fig. 3): shows peak, quasi-peak and EUT supply current waveforms, for a selected event.

3. Level Analysis (Fig. 4): shows EUT switching operations, supply current and click events level.

As an example of this software in action, a typical test scenario might be;

1. User performs the test on the EUT according to applicable standards

2. If the EUT fails the test, open the the "analysis" window and,

3. Examine each click event together with the EUT cycle description. In the time domain graph, the level of the click is readily appreciated: if just above the limit, it's likely to be easily removed. When the disturbance level is very high, the corrective procedure should trade between reducing the total click count working on low-level clicks, or exploiting the relative influence of each click on the overall disturbance spectrum, in order to bring the EUT within limits.

4. Once all appropriate actions have been taken, the EUT will be tested again, results will be compared and a test report will be edited.

To conclude, the CL55C is not just a GO/NO GO tester, but a sophisticated analyser fully supporting a thorough investigation on the when, where and why a click occurs.

To see the CL55C Click Analyser in action and to enter the free draw to win yourself an espresso machine, please visit EMC Partner on stand number 32 at the York EMC Exhibition. EMC Partner is the sole UK representative for AFJ International. We look forward to seeing you at York!

EMC Partners U.K. Ltd Lancaster Road, Cressex Industrial Estate, High Wycombe, Bucks, HP12 3XJ. Tel: 01494 444255, Fax: 01494 444277, E-mail: laura@emcpartner.co.uk