Calibration Of Pressure Sensor - Furuno CN-24 Service Manual

7. CALIBRATION OF PRESSURE SENSOR

The calibration of the pressure sensor is required when either the pressure censor or the
SEN board is replaced.
Caution
1) The pressure sensor and SEN board should be replaced as a pair when either of
them is defective, because of the calibration data for each sensor is stored in the
NVRAM (U5 on the SEN board). The serial numbers marked on the transceiver case
and the PC board assembly must be identical.
2) To recalibrate the depth indication by adjusting a characteristic value of the
pressure sensor, the accurate oil pressure device (maximum pressure; 206 kgf/cm
is required, do not try to adjust without the pressurize instrument.
3) When the DIP switch S2 #4 is set to OFF, the PC board assembly is entered into
adjustment mode (depth sensor, frequency adjustment etc) automatically. DIP switch
setting should not be changed carelessly in the adjustment mode. Otherwise, the
sensor calibration data stored in NVRAM is destroyed and re-adjustment is required.
4) Since the calibration date corresponding to the given pressure are stored into the
EEROM at every 2 sec after setting the DIP switch, set the DIP switch settings after
the given pressure becomes stable.
5) The calibration data is stored into a RAM on the CONT.A board (01P5740)
temporally before the final loading into the NVRAM on the SEN board.
All calibration data stored into the RAM are cleared off if once the power is tuned off
under the adjustment mode (#4: OFF).
Do not turn off before storing the data into NVRAM.
6) Once the DIP switch is set to improper position , a wrong data is stored into RAM.
In this case, restart the adjustment from the first step.
Following shows the adjustment procedure using the oil pressurize instrument.
! Necessary instrument
1. Oil pressurize instrument
2. Adapter to link a oil pressure to the pressure sensor
3. Multimeter
4. Extension cable
5. LED indicator (2.7 k ohm resistor and LED)
! Preparation
1) Connect the PC board assembly to the transmitter by the extension cable.
2) Record the present DIP switch settings of S1 and S2 on CONT.B board.
3) Connect Multimeter to TP4 on the SEN board so as to obtain the voltage (DC).
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