DESIGNER’S HANDBOOK 4189350049C EN
Page 57 of 206
The highlighted “Multi point linearization“ above is grey and cannot be changed from the menu. This is intentionally
blocked to avoid unintentional changes that may result in a critical setup error.
5.6.4
Analogue multi-point linearisation
When the analogue input is used for a data
type where the output value is type “+/-X“, for example rudder angle,
then at least 3-point calibration is normally used. This means that 3 scaling pairs are active, for example rudder
angle: -45
o
to 0
o
to +45
o
to match 4 to 12 to 20 mA.
Input
Value
Note
Input point 1
4 000
in µA equal to 4.000 mA
Output point 1
-450
- 45.0
o
Rudder angle @ x 0.1 res.
Input point 2
12 000
in µA equal to 12.000 mA
Output point 2
0
0
o
Rudder angle
Input point 2
20 000
in µA equal to 20.000 mA
Output point 2
450
+ 45.0
o
Rudder angle @ 0.1 res.
The scaling of input value for respectively 100 % portside (-) rudder angle and 100 % starboard (+) rudder angle
can now be adjusted individually during installation.
The XDi has a very strong multi-point linearisation function that allows for up to 7 calibration points.
This strong feature makes it possible to calibrate a non-linear input signal to best match a linear output.
Via the installation menu, it is possible to make a very precise calibration and linearisation of such analogue inputs
to obtain very accurate data for the indicator.
By sharing such data via CAN, all other XDi units using the same data will have direct access to those precisely
calibrated data. In this way, it is only necessary to make calibration once in the complete system.
Example:
Using a +/-45 degree rudder angle indicator system as example, it is possible to calibrate a nonlinear rudder angle
sensor to comply with the calibration accuracy requirements in the international standard: ISO 20673 Ships and
marine technology
— electric rudder angle indicator systems.
