2-13
3.1 BTU-PCB
The BTU-PCB unit consists of two boards T2F and T2R (one additional T2R in T3+), placed
in a rack on the T2-M motherboard which also includes a power supply and an amplifier
section for the transmit pulse.
T2F has the function to condition and amplify the signals received from the five piezo-electric
elements in the transducer, T2R is the main processor board in the BT unit. The amplifier
integrated on the T-M motherboard is used to amplify the transmit pulse which is generated by
T2R.
3.2 WTU-Assy
The WTU – Assy. PCB consists of a double board assembly docked to the T-M motherboard in
the same rack as the BTU-PCBs. The WTU PCB is powered from a separate power supply also
included on the T2-M motherboard.
3.3 Data transmission / reception
Data is sent and received from the log as serial NMEA messages on standard IEC 61162-1 /
NMEA (RS 422/485) output / input.
Serial NMEA messages used by the speed log are described in detail in document 700164.
The following NMEA sentences are transmitted in a standard setup:
Serial port Function NMEA sentences transmitted
NMEA0(TxBT)
Terminal 102/103
This output carries basic information. Can
be used by external users.
VDVBW, VDDPT
NMEA1(RxMain)
Terminal 105/106
Main input. -
NMEA2(TxMain)
Terminal 108/109
Main output, also containing internal
information.
VDVBW, VDDPT,
VDVLW, PSALS, PSALX
NMEA4(Tx)
Terminal 114/115
Not Used.
NMEA5(Rx)
Terminal 117/118
Not Used. -
NMEA6(TxWT)
Terminal 120/121
Messages are generated in the WTU. Used
as a redundancy output that will continue
to operate also if the BT unit is
malfunctioning.
VDVBW, VDDPT,
VDVLW, PSALS
Note that also other NMEA sentences than those mentioned above might be transmitted on any
channel depending on setup and working mode.
NMEA-messages are also available through RS232 on two 9-pole D-sub-connector, one on
T2R and one on WTU. It is used for data logging and software updates. Thus it is possible to
read out information directly on an ordinary PC using for instance a terminal emulator program.
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