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9.2 Introduction
to the discontinuous
disturbance (click)
measurement
9-2
Click Mode Operating Instructions
Mechanical or electronic switching procedures - e.g. those due to
thermostats or program controls – may unintentionally generate broadband
discontinuous disturbances with a repetition rate lower than 1 Hz.
Indeed, CISPR 16-2-1 and CISPR 14-1 define a discontinuous disturbance,
also called "click, as a disturbance the amplitude of which exceeds the
quasi-peak limit of continuous disturbance, the duration of which is not
longer than 200 ms and which is separated from a subsequent disturbance
by at least 200 ms. The durations are determined from the signal which
exceeds the IF reference level of the measuring receiver.
A click may also contain a number of impulses; in which case the relevant
time is that from the beginning of the first to the end of the last impulse.
The test procedures and the test setup for click measurement are indicated
in CISPR 16-2-1 and in CISPR 14-1 standards.
It basically consists in the measurement of the number of clicks exceeding
a certain level determined as function of the click number and duration.
Moreover, several "exceptions" shall be dealt with by the click analyzer in
order to make the test as per the standard.
To better understand the click measurement process – automatically made
by PMM 9010 - it could be useful also to know few more definitions:
•
switching operation: one opening or closing of a switch or contact;
•
minimum observation time T: the minimum time necessary when
counting clicks (or switching operations) to provide firm evidence
for the statistical interpretation of the number of click (or switching
operations) per time unit;
•
click rate N: number of clicks or switching operations within one
minute (this figure is being used to determine the click limit);
•
Click limit Lq: the relevant limit L for continuous disturbance for the
measurement with the quasi-peak detector, increased by a certain
value (offset) determined from the click rate N. The click limit
applies to the disturbance assessed according to the upper quartile
method;
•
Upper quartile method: a quarter of the number of the clicks
registered during the observation time T is allowed to exceed the
click limit Lq. In the case of switching operations a quarter of the
number of switching operations registered during the observation
time T is allowed to produce clicks exceeding the click limit Lq.
•
short click 1: a disturbance not longer than 10 ms;
•
short click 2 (E3): a disturbance between 10 ms and 20 ms;
•
click: a disturbance longer than 10 ms and not longer than 200 ms;
•
other than click: a discontinuous disturbance longer than 200 ms.
With reference to the mentioned standards, a schematic process flow of
the measurement is the following:
●
Determination of the click rate N
●
Pass/fail decision if instantaneous switching and if N>=30
●
Check conformity to definitions
Apply Exceptions (whenever applicable)
●
Calculate Limit Quartile
●
Measurement using Upper Quartile Method
●
●
Pass/fail using Upper Quartile criterion
●
Repeat for next frequency
As PMM 9010 manages all these steps in a completely automatic way, a
detailed step by step description is here given before to describe each
command and function.
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