Meinberg GPS167PC, Руководство по эксплуатации

Страница: 6 / 28

6
GPS167PC Features
The hardware of GPS167PC is a plug-in board designed for computers with standard
ISA bus architecture. The rear slot cover integrates the antenna connector, two status
LEDs, and a 9 pin sub-D female connector.
The antenna/converter unit is connected to the receiver by a 50 ohm coaxial cable
with length up to 200m. Power is supplied to the unit DC insulated across the antenna
cable. Optionally, an overvoltage protection and an antenna distributor are available.
The antenna distributor can be used to operate up to 4 Meinberg GPS receivers using a
single antenna/converter unit.
The navigation message coming in from the satellites is decoded by satellite clock´s
microprocessor in order to track the GPS system time with an accuracy of better than
250nsec. Compensation of the RF signal´s propagation delay is done by automatical
determination of the receiver´s position on the globe. A correction value computed
from the satellites´ navigation messages increases the accuracy of the board´s tempe-
rature compensated master oscillator (TCXO) to ±5•10
-9
and automatically compensa-
tes the TCXO´s aging. The last recent value is restored from the non-volatile memory
at power-up. Optionally, the clock is also available with a higher precision time base.
A monitoring software shipped with the board can be used to check the clock's
status and configure some operational parameters.
Time Zone and Daylight Saving
GPS system time differs from the universal time scale (UTC) by the number of leap
seconds which have been inserted into the UTC time scale after GPS has been initiated
in 1980. The current number of leap seconds is part of the navigation message
supplied by the satellites, so the satellite clock's internal real time is based on UTC.
Conversion to local time including handling of daylight saving year by year can be
done by the receiver´s microprocessor. For Germany, the local time zone is UTC +
3600 sec for standard time and UTC + 7200 sec if daylight saving is in effect.
The clock's microprocessor determines the times for start and end of daylight saving
time by a simple algorithm e. g. for Germany:
Start of DST is on the first Sunday after March, 25th, at 2 o'clock standard time.
End of DST is on the first Sunday after October, 25th, at 3 o'clock daylight time.
The monitoring software shipped with the board can be used to configure the time
zone and daylight savings parameters easily. Switching to daylight saving time is
inhibited if for both start and end of daylight saving the parameters are exactly the
same.