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How it Works
How an Accelerometer works
Plate B is a mass suspended by springs
between plate A and plate C. At
zero G’s plate B is equidistant from plate A & plate C. When
you apply the brakes the vehicle pulls negative G’s and B moves closer to C and farther away from
plate A. As B moves
closer to C the voltage from B to C increases at the rate of one
volt per G. .01 volt will equal .01 G. 1 volt will equal 1 G. When
you increase your speed plate B moves closer to plate A and farther
away from plate C. When this occurs we are measuring the positive
acceleration of the vehicle.
ABS & Standard Brakes
Most braking test devices take only one G
reading and assume constant deceleration, therefore they can not
measure the difference between ABS and standard brakes. However the VC3000 measures the instantaneous G-force 100
times per second, effectively measuring the difference between ABS
and standard brakes. Other
devices without a critically damped accelerator have a slower
response time and can not pick up the sudden change in friction,
which occurs as the ABS controls the angular velocity of the tire.
How the VC3000 works
The VC3000 has 3 major components: an
accelerometer, a crystal clock and a Microcontroller. Knowing the acceleration and the time the Microcontroller
calculates velocity every 1/100 second (V=a´t). Knowing the
velocity and the time the Microcontroller calculates distance every
1/100 second (D=V´t).
This concept is called inertial navigation, which has been used for
more than 50 years in guided missiles, airplanes and submarines.
There is nothing new about this technology: what is new is that
modern technology makes it possible for us to manufacture this
device inexpensively so that it is cost effective for the
application of vehicle brake testing.
Mounting
Attach the VC3000 to the windshield of
the vehicle with suction cups. The
unit comes with suction cups, mounting brackets and NiMH batteries. Vacuum cups provide a more powerful mounting grip and
are included with some models. No electrical or mechanical
connections are needed. It can be installed in less than one minute.
Tested accurate
The VC3000 is so accurate that it is
considered the most modern and reliable braking test device used by
the leading experts in traffic accident investigation worldwide. It is used by automobile, truck and bus manufacturers,
thousands of law enforcement officers, universities, transit
companies and training academies. The
G-force is measured within .001 G, this is an accuracy of 1/10 of
1%. The VC3000 can measure a 1/4 mile within 14 feet, this is an
accuracy of 1% over 1,320 ft. From
0 to 100 mph the VC3000 is accurate within 1 mph, this is an
accuracy of 1% at 100 mph. Most
road vehicles have a pitch greater than .02 and less than .04. The VC3000 defaults to a pitch adjustment value of .03.
Greater than 1% accuracy can be achieved by adjusting the pitch
factor.
Confirming Accuracy
There are several ways to confirm the accuracy of the
VC3000. The two easiest
ways are: 1) Utilizing the continuous G mode, rotate the VC3000 90
degrees. The VC3000
will display 1.000 which is the gravitational pull of the Earth and
the sine of 90 degrees. 2)
a radar gun or accurate speedometer may be used to confirm the speed
displayed by the VC3000. If the speed is correct then the G-force is correct.
Vehicle types
The VC3000 will work on all types of
vehicles including trucks, automobiles, buses, school buses, trains,
light rail, motorcycles, pick- ups, vans, ATVs and snowmobiles.
Activation
The VC3000 is activated at a .2 G threshold, which
can be changed to any G value. Activation can also be initiated with
the 12V-36V brake light switch, reaction time switch or brake pedal
load cell, or any sensor.
Calibration
A calibration test is simple and easy to do because the VC3000 has a continuous G
mode. Rotate the VC3000
90º and it will display the gravitational pull of the earth which
is 1.00 G. Easy to follow calibration check instructions are in the
operators manual.
