Specifications
OWNER’S GUIDE INTERFACE CARDS | 18437
This button denes the current input and output settings as power on default settings. This way the DEWE-
CLOCK will always start up with the predened settings.
What Happens If the Timinig Source is Lost?
For synchronizing the internal oscillator with the PPS signal at least 4 satellites are required. If the GPS or
IRIG signal is lost during acquisition the DEWE-CLOCK continues sourcing the data acquisition system with
a precision clock source. Without synchronising to the GPS or IRIG signal, the oscillator may drift. Therefore
the absolute time synchronisation cannot be guaranteed anymore. However, as soon the GPS or IRIG signal
is available again, the DEWE-CLOCK recognizes a possible drift and tries to correct this inaccuracy. If the
drift during the free-run time is higher than 200 ms, a new data le is automatically generated with exact time
stamping.
The graph below gives an idea how the DEWE-CLOCK behaves when the GPS or IRIG signal is lost during
data acquisition. In this example the drift of the oscillator is smaller than the allowed 2 ms (xed).
A) This state shows the normal operation. The internal clock is synchronized to the GPS/IRIG
once per second.
B) At this point the time source signal is lost.
C) In the free-run operation the oscillator drift is obvious.
D) After the time source signal is received again, the error during the free run cycle is calculated.
E1) Because the oscillator drift is smaller than 200 ms, the DEWE-CLOCK automatically corrects
the drift for getting again time synchronized data. So the data acquisition is not interrupted
although the time source signal was lost. The correction is done with the maximum rate of 5
μs/sec.
However if the time source signal is lost for too long, the oscillator drift may be higher than 200 ms. In this
case automatically the existing data le is closed and a new le is generated with adding “Lost” of the cur-
rent lename: “DataFilennameLostX” where X is a running number for each time source signal loss.