24-01-2013, 12:02 PM
SIMPLE ACCELEROMETER MEASURES POSITIVE OR NEGATIVE G FORCE
1SIMPLE ACCELEROMETER.pdf (Size: 661.72 KB / Downloads: 23)
INTRODUCTION
EVER WISH THAT YOU had some overall road performance and may even
way to check your car’s acceleration help in correcting poor driving habits.
performance under actual road conditions?
Or, would you like to check the
effect that a tune up, carburetor adjustment,
change of fuel grade, timing correction,
valve setting, or change in tire
pressure has had on your car’s performance?
Or, if you have stick shift, would
you like to determine the optimum shift
speeds for each gear to get best performance
and fuel economy?
In coming years, accelerometers like
this one may become standard equipment
on all new high-performance cars,
so here is your chance to get ahead of
the times.
You can do all of this with the “GWhiz,”
an indicating accelerometer similar
to instruments used widely in aerospace
applications, military aircraft, and
missile systems. The G-Whiz is specially
designed for automotive use and measures
both acceleration and deceleration.
Except for a 12-volt power supply, it requires
no electrical connection to the
vehicle. It provides the driver with an
accurate means of checking the car’s
Construction. The circuit of Fig. 1 is
assembled in the U-shaped portion of a
5” x 3” x 2%” metal case, drilled as
shown in Fig. 2. A cover fabricated by
following the layout of Fig. 3 can be
covered with a contact-adhesive leatherette
finish. Construct the mounting
brackets for R5 and R4 as shown in Fig.
4. Build, or purchase (see Parts List)
the pendulum following the information
given in Fig. 5.
HOW IT WORKS
The circuit, shown in Fig. 1, is basically a
bridge that can be balanced at zero G by means
of potentiometer R5. The pendulum is physically
attached to the shaft of potentiometer R4; and
if the pendulum tries to rotate about its pivot
axis, the bridge becomes unbalanced and meter
Ml indicates the amount of unbalance (meter)
scale is calibrated in G values). The position of
S2 determines the direction of current flow
through R4 so that an increasing positive-going
voltage may be obtained from the movement of
the R4 wiper arm in response to either a backward
swing (acceleration) or forward swing (deceleration)
of the pendulum. Resistor R6 is selected
to set the full-scale current through Ml to
correspond to +45°, or -45° of potentiometer
shaft rotation from its normal (zero G) position.
Diode D3, in series with the meter, permits
current to flow in only one direction,, preventing
the needle of Ml from slamming against its limit
stop during a sudden stop when S2 is set for acceleration.
or vice versa. Capacitor Cl provides
electrical ‘damping of the meter to smooth out
peak transients due to the inertial effects of the
eccentric weight.