|
25th January 2010- TDEMI: Reliable measurements of
complex disturbing signals
Today many electronic appliances, such as automatic coffee dispensers or as-sisting systems in an automobile, perform a sequence of multiple steps by pushing a button. With the more complex electronics the complexity of disturbing signals in EMC rises as well. The standard CISPR-16-2-x defines the requirements and measuring procedures for emissions including complex interfering signals. Time-domain measuring systems (TDEMI) allow to measure these complex signals reliably, under realistic operating conditions and with a reasonable effort.
In the commercial field measuring instruments according to CISPR 16-1-1 are used for emission measurements. The standards CISPR 16-2-1, CISPR 16-2-2 and CISPR 16-2- describe the measurement methods for the radio interference voltage, radio interference power and radio interference field strength and are referenced by the product standards.
As the emission characteristic of a device under test (DUT) is not known in advance, the standard CISPR 16-2-x describes how measurements should be performed and how results should be interpreted. The standards require that the DUT is operated under realistic operating conditions, while the maximum emission is documented. The dwell time shall always be higher than the pulse repetition time. In extreme cases s a measurement time of 15 s is recommended. If such a measurement is performed by using a RF test receiver, which can measure one frequency at a time only, a well-experienced test engineer is required, to obtain reproducible results within a reasonable testing time. Time-domain measuring instruments allow to perform the measurement at several thousand frequency points at the same time. This way, dwell times up to 100times higher may be used. This facilitates the correct detection of pulsed interfering signal.
Spectrogram of an fully automatic coffee dispenser:
till 2,5 s: grounding of beans,
- 4 s - 6 s: water pump for coffee brewing,
13 s and 18 s: switching on and off of serveral components
The standards require a timing analysis, to analyze the pulse repetition rate. With the traditional RF receiver this timing analysis can be performed at only one frequency at a time. By the parallel evaluation at several thousand frequency points, the TDEMI system facilitates even measurements of DUTs with varying pulse repetition rates at different frequency points. The spectrogram mode helps to perform the timing analysis not only at one frequency but for a complete frequency range of 160 MHz at the same time.
Complex interferences appear more and more often these days. The emission measurement system TDEMI makes it possible to apply the in the standards described methods also for complex interferences efficiently.
The TDEMI product line consists recently of four models for different frequency ranges:
- TDEMI 30M (9 kHz - 30 MHz)
- TDEMI 1G (9 kHz - 1 GHz)
- TDEMI 3G (9 kHz - 3 GHz)
- TDEMI 6G (9 kHz - 6 GHz)
The TDEMI Products will be presented at the EMV 2010 in Düsseldorf from
9th - 11th March at booth CCD-203.
 further information on the TDEMI Series
|
|
|
