User manual

PQM-702, PQM-703 Operating Manual
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2.10.3 Data flagging concept
The analyzer saves measurement records along with the flag indicating the lack of time syn-
chronization. If for the whole averaging period the analyzer was synchronized to UTC, then the flag
is not turned on and during data analysis the icon indicating the lack of synchronization is not
displayed. The absence of this icon indicates full compliance of gathered data with Class A in terms
of time marking. Synchronization with UTC is also indicated on the screen of the analyzer by green
date and time on the top bar.
When the analyzer was initially synchronized to UTC (GPS status on the analyzer screen dis-
played as YES) and later the signal was lost (No signal status), this does not mean that the analyzer
immediately lost the synchronization of its clock. In fact, for some time (even a few minutes or more)
internal timing accuracy is sufficient to meet the requirements of IEC 61000-4-30 in part relating to
the accuracy of determining time data. This is because the internal clock of the analyzer is very
slow in de-synchronizing from UTC time (due to no GPS signal), and the error does not exceed a
few milliseconds for an extended period of time. Thus, despite the "No signal" status, data will con-
tinue to be saved without the flag signalling the lack of synchronization to UTC. Only when the error
exceeds the limit value the flag will be turned on.
2.10.4 Time resynchronization
As the availability of the GPS signal cannot be guaranteed on a permanent basis, it is necessary
to ensure proper management of internal time when the GPS signal becomes available and when
it differs from the internal time of the analyzer.
When no recording is on - the situation is simple - after receiving the satellite time, the analyzer
clock automatically synchronizes with it without any additional conditions.
When the recording process is on, a sudden change of the internal time may lead to a loss of
measurement data when time is reset, or it may create a time gap in gathered data, when UTC time
is ahead of the analyzer time. To prevent this, a slow synchronizing mechanism was introduced to
synchronize the internal analyzer time with UTC time. The implementation of this concept is based
on the deceleration or acceleration of the internal analyzer clock in such a manner that after a time
the two clocks - internal and GPS - are equalled and achieve synchronization. The advantage of
this solution is the fact that there is no data loss or discontinuity.
The user has the option to set two configuration parameters that affect the resynchronization
during the recording process. One of them (resynchronization factor) defines the speed of the syn-
chronization. The lower is the factor value, the longer is resynchronization, but the length of the
measurement intervals will be close to the averaging time.
Despite the aforementioned disadvantages of an abrupt time change, there is an option to carry it
out even when recording process is active. A threshold is defined in seconds (Time resynchroni-
zation threshold parameter), to set the minimum difference between internal and UTC time at
which the abrupt (one-step) time change will be performed.
To avoid the problems with time measurement during recording, please remember the following
issues:
 The analyzer must have properly set its time zone and the time displayed on its screen must be
precisely compatible with local time (if there is no GPS signal before starting the recording).
 Turn slow resynchronization of time, by setting Time resynchronization threshold parameter
to zero value and set resynchronization factor at a low value (e.g. below 25%).
Note
Abrupt change of time during the recording process may lead to irreversi-
ble loss of recorded data, therefore it is advised to use the slow resyn-
chronization mode.