Raymarine i70, Operation Instructions Manual

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Manually calculate a calibration factor
New calibration factors can be calculated manually following the steps below.
Prerequisites:
• You will need to be underway, with sufficient space to maneuver unhindered.
• To ensure accuracy, water conditions should be calm with zero tide and zero current.
• You will need to calibrate each calibration speed point, starting with the lowest
1. Run your vessel at a steady speed, approximately that of the selected calibration speed, over a
measured distance making a note of:.
• The measured distance in nautical miles
• The current speed value in knots
• The time in minutes it takes to cover the measured distance
2. Calculate the actual speed over the measured distance using the calculation: (Speed = (60 x
Distance) / Time) ‘60’ is used to ensure the calculation is in minutes rather than hours or tenths
of an hour.
e.g. Distance (D) = 14 nautical miles, Time (T) = 105 minutes (1 hour 45 minutes) so:
• S = (60 x D) / T
• S = (60 x 14) / 105
• S = 840 / 105
• S = 8 kts
If the calculated speed is:
• the same as the current speed, (noted during the Speed Run Calibration) then the calibration is
correct at this speed so no action is required.
• not the same as the current speed. Calculate a new, corrected calibration factor, as follows: e.g. if
actual speed equals 8 kts, indicated speed was 7.5 kts and the old calibration factor was 1.4 then:
– new cal factor = actual speed x old factor / indicated speed
– new cal factor = 8 x 1.4 / 7.5
– new cal factor = 11.2 / 7.5
– new cal factor = 1.49
Adding a Calibration point
Calibration points can be manually added to the Calibration table. The amount of Calibration points
that can be stored is determined by the type of speed transducer and method of connection.
From the Transducer set up menu:
Menu > Set-up > Transducer set-up > Continue :
1. Select the device that the transducer you are calibrating is connected to.
A list of available transducer data is displayed.
2. (1) Select Speed .
Important:
(1)Step only applicable to iTC-5.
3. Select Speed Calibration .
4. Select Advanced .
5. Select Adjust Calibration .
6. Select Start .
The current Calibration table is displayed.
7. Select the relevant Calibration point from the table.
8. Select
Options .
9. Select Add cal point .
10. Use the Up and Down buttons to adjust the displayed Log speed to match current SOG if
available or to match your estimated actual speed.
11. Select Add .
12. Select OK .
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