Calibrating the sensors – Raymarine L470 User Manual
Page 30
Installation
24
Note –
Press firmly when inserting the power cable and transducer cable to
ensure a tight seal.
8.
When you press the
PWR
button, the display unit should turn on. If
the
unit
will
not turn on and you suspect that you may have reversed the
power connections, check the DC power lines all the way back to the
battery. If the polarity is not correct, reconnect the leads properly and
try again.
Calibrating the Sensors
The transducer most often used with this unit includes sensors for boat
speed and water temperature. These sensors are normally very accurate,
but you may want to calibrate them. The procedure appears on page 64.
See the section on “System Setup Menu.”
The speed indication on your FishFinder is usually very accurate. How-
ever, there are some special cases where the speed reading may be high
or low. This means that the speed of the water past the transducer may
not
be
the same speed that your boat moves through the water. The hull of
the boat may have a shape which channels water past the transducer at a
speed which is faster or slower than normal.
1.
To calibrate the speed sensor, set up a course between two known
points. As markers you can use buoys, range markers, or landmarks.
Measure the length of time the boat takes to cover a known distance.
2.
You may also use locations indicated by a G.P.S. or Loran unit. (If you
choose this method, remember that these devices measure “speed
over ground” or “speed over the bottom.” Tides, currents, or winds
can create a difference between the FishFinder’s “speed through
water” measurement and the boat’s “speed over ground.” Before
calibrating using a G.P.S. or Loran unit, wait for still water or slack tide
conditions.
3.
If the display unit is reading high or low, you can correct for this using
the entry for “Speed Cal.” (To reach Speed Cal, go to the System
Setup Menu. This is described in Section 4.) The entry for Speed Cal
is a percentage. An entry of “100” equals 100%, meaning that there
is no correction. If the display unit is producing a
low reading, use a