Notes on Time Usage 4-83Click Run Compass Calibration Wizard to open the Compass Calibration Wizarddialog box which is shown in Figure 4-18 on page 4-14. This provides a fairlyquick and accurate method for calibrating the towfish compass. (See page 4-14 forinstructions on how to use the Compass Calibration Wizard.)The Series 3000 towfish uses a different pressure sensor than the Series 5000towfish. If your towfish is equipped with a pressure sensor for towfish depthreadings, choose Sensor from the Window menu to open the Sensor window, andthen right-click in the window to open the Sensor Configuration dialog box shownin Figure 4-61 on page 4-47. Select the correct pressure sensor scale option. Forthe Series 3000, 1500 psia is the default selection, and 300 psia is the optionalselection.4.27 Notes on Time Usage4.27.1 TPU Time in SonarProWhen using SonarPro, a date and time is displayed in the Information window.This time is also in the header in the .sdf data that comes from the TPU. The timeis set when SonarPro is started on the master computer.When the system is successfully booted, SonarPro can be started from the mastercomputer. The master computer controls the range, pulse width, etc. of the sonar,and only one master computer can be running at a time with one sonar. Any othercomputers connected to the Ethernet Hub and running SonarPro, would beconsidered slaves. The slave computers running SonarPro have no control of thesonar or the TPU.When SonarPro starts on the master computer, a message is sent to the TPU to setthe TPU clock. The TPU in turn looks at the GPS navigation input on COM2. If itsees an RMC sentence on COM2 in the GPS message, the TPU clock is set to theGPS time which is Zulu time. If an RMC message is not seen on COM2, the TPUsets its clock to the master computer’s clock.The TPU clock is set whenever SonarPro is started from the master computer.Thereafter it keeps its own time, either GPS or master computer time. Therefore ifthe navigation input is not present when SonarPro is started on the mastercomputer, and the navigation input is connected after SonarPro is started, the TPUwill not follow GPS time. SonarPro will have to be restarted, or a new state willhave to be initialized to sync the TPU to the GPS time with the RMC sentencepresent.
