R2Sonic 2022, Руководство по эксплуатации

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Page 44 of 133
Version 3.0 Rev r000
Date 25-08-2010
Part No. 96000001
6.3 Sensor Setup (Serial Interfacing)
The Sonar system receives various data on the SIM serial ports as noted in Section 5. Select Settings
| Sensor setting to setup the serial communications parameters.
Figure 36: Sensor communication settings
6.3.1 GPS
The GPS input is for the ZDA time message ($GPZDA) or Trimble UTC message, other NMEA
messages may be in the same string; it is not necessary to isolate the ZDA or UTC. In the GPS
receiver’s operation manual, there will be an entry that will detail which edge of the PPS pulse is
used for synchronisation; this will be either synch on rising edge, or synch on falling edge. Selecting
the correct polarity is vital for correct timing.
The firmware supports the ZDA integer part (HHMMSS) and accepts PPS pulses if they pass a basic
stability test: the last two pulses must be within 200ppm. If the PPS is unstable or absent, the SIM's
internal clock free-runs with a high degree of accuracy.
The decoded time, from the bathymetry packet, is visible in the main display on the lower left along
with the cursor position information. If the displayed time is 01/01/1970 it indicates that timing is
not set up correctly.