Operation Manual

33
Diesel fuel flow sensor kit Installation and Operation Manual
NAVMAN
This section describes how to install the
tachometer pickup. The tachometer is optional
and need not be installed, however the
tachometer gives a precise measurement of
engine RPM, essential for measuring engine
fuel consumption at different speeds.
The pickup operates by sending a beam of
pulses of infrared light towards the crankshaft
pulley. A piece of reflective tape applied to the
crankshaft pulley reflects the beam back to the
pickup, where an infra-red receiver detects the
light pulses. A light on the sensor will light up
when its detector is receiving enough reflected
light to operate properly.
Locating the tachometer pickup
It is important that the reflective tape is attached
to part of the crankshaft, such as the flywheel or
a pulley. Do not attach the tape to any part that is
not rotating at the same RPM as the crankshaft,
such as a pulley driven accessory.
The optimum distance from the pickup to the
reflective tape is about 50 mm (2 in) away from
the reflective tape. If it is positioned closer than
25 mm (1 in) to most flywheels or pulleys then
enough infra red will be reflected back from
the surface of the wheel to trigger the pickup.
Further away than about 75 mm (3 in) and not
enough infrared is reflected from the reflective
tape, so the pickup is never triggered.
The pickup does not have to be at right angles
to the face of the tape - up to 45° each way is
permitted.
The pickup should be mounted on the boat,
not the engine. Some angle is beneficial. The
tachometer pickup has a built in 4 metre (12
ft) cable to connect it to the return sensor.
Locate the tachometer so that the cable run is
accessible, neat and tidy. An extension cable
can be fitted if required.
7-6 Installing the tachometer pickup
Rotating
flywheel
or pulley
Infra-red light
from tachometer
When tape is
under tachometer,
light is reflected
back to tachometer
Piece of
reflective
tape
Reflective tape
Tachometer about 50 mm
(2 in) from reflective tape
Tachometer
pickup up to
45° from a
right angle
Tachometer
pickup up to
45° from a
right angle
Tip: Mount the sensor, power it on, then
place the reflective tape where the light
strikes the pulley.