Eagle Electronics FISHMARK 640C - Manual (Page 65)

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The unit's backlight level can be controlled from the Screen menu.
Calibrate Speed
The speed sensor can be calibrated to compensate for inaccuracies. Be-
fore you change the setting, first calculate the percentage that the
speed is off. You will enter this percentage in a moment.
For example, if you figure the sensor is reading 10 percent faster than
actual speed, you will enter – 10 in the calibration window. If the sen-
sor is reading 5 percent slower than true speed, you will enter + 5 in
the window.
When you make a run to compare your ground speed to speed sensor
speed, perform your test in relatively calm water, free of current, if pos-
sible. Unless, of course, you are taking the current speed into consid-
eration when making your calculation. After you have a correction fig-
ure, here's how to enter it:
1. Press MENU | MENU |
↓ to
C ALIBRATE W ATER S PEED
| ENT .
2. Enter the number you calculated earlier and press
↑ or ↓ to change
the first character (+ or –), then press
→ to move the cursor to the next
number and repeat until the percentage is correct, then press EXIT .