Futaba 8SGAP - Manual (Page 14)

Make all speed measurements outdoors under
natural lighting. Accurate speed measurements
cannot be made indoors under artificial lighting
because of the affect of the 50 or 60 Hz power.
OPERATING INSTRUCTIONS
Tachometer
Set the tachometer/times POWER switch to ON.
appears on the display. Next, press the
MODE SEL key switch at the upper-right corner
three times. The display changes to and
the tachometer mode is selected. Hold the sensor
about 20 to 30 cm from the rotating propeller
(two blade). The propeller speed is displayed on
the LCD.
indicates that the propeller is rotating at
12,300 rpm. For propeller speeds up to 30,000
rpm, set the REVOLUTION RANGE switch at the
upper left-hand corner to LOW and for propeller
speeds above 30,000 rpm, set the REVOLUTION
RANGE switch to HIGH.
The speed of a three blade propeller is displayed
value- 3 x 2 .
The speed of a four blade propeller is 1/2 the dis-
played value.
Connect the accessory tachometer
sensor to the sensor connector
as shown above.
Sensor
Sensor
connector
Fig. 14
The speed of model boat
and car engines can also be
measured in this fashion.
Warning: Use extreme cau-
tion. There is danger of
serious injury or death.
Measure the speed of the
rotating propeller at this
point.
Sensor
Make all
measurements
under natural
lighting.
Holding the sensor too close
to a spinning propeller is
dangerous.
Draw two lines
on the flywheel
with magic ink.
Fig. 15
To measure the speed of the main rotor of a
model helicopter, measure the speed of the tail
rotor as shown in Fig.16. and calculate the exact
speed from the equation.
Tail rotor speed
Main rotor speed = ——————--—--—————————
Main rotor and tail rotor gear ratio
Sensor
Helicopter tail rotor
Fig. 16