The Accelerometer takes advantage of many standard measurements that derive from acceleration over time. The measurements are taken as the car is performing a particular task like braking from 60mph, or (100kph) to a complete stop for example.
The Accelerometer measures G's which represent acceleration of your vehicle. If you know how much you have been accelerating for a certain time period you'll know your speed after that time period. By the same token, if you know how fast you have been travelling for a certain time period you'll know the distance covered in that time period. These time periods are extremely fast 2.5/1000 of a second (400 Hz sample rate). Through a simple mathematical process called integration the Accelerometer derives many standard measurements which characterise the car's performance and safety. For HORSEPOWER measurement however, the user has to input the weight of the vehicle.
How do you input weight?
We call it "INTUITIVE USER INTERFACE" because it's as natural as pouring water from a glass. The more you tilt it the more water goes out. Same here, the more you tilt the Accelerometer faster the numbers change. You can very quickly dial in your weight.
The best way to look at accuracy is in two different ways. Resolution is the smallest segment of a given measurement that the Accelerometer can sense. Real Life accuracy is the worst case scenario to be expected in your measurements.
The difference between Resolution and Real Life accuracy is the result of noise, temperature dependency, vibration and other elements that influence the accelerometer and other internal electronic circuitry.

NOGGRANNHETEN?

Man kan dela in noggrannheten i två sorter. Den ena är apparatens noggrannhet, och den andra är Verkliga Livets noggrannhet. Detta är dom värsta omständigheter som kan råda. I det Verkliga Livet påverkar temperatur, skrammel, elektroniskt brus, mm accelerometern negativt.
Eftersom dina mätresultat kommer att hamna mellan mätarens egen missvisning och Verkliga Livets är det noga att du gör många mätningar och använder ett medeltal.

1. 0-100 kmh mätaren 1/100 sek Verkliga Livet +/- 1/10 sek

2. 100-0 kmh mätaren 0,3 m Verkliga Livet +/- 0,9 m

3. 1/4 mile mätaren 1/100 sek Verkliga Livet +/- 1/10 sek

4. 1/4 mile mätaren 0,16 kmh Verkliga Livet + /- 1,6 kmh

5. hkr mätaren 1 hkr Verkliga Livet +/- 3 hkr

6. G-kraft kort mätaren 1/100 G Verkliga Livet +/- 3/100 G

7. G-kraft lång mätaren 1/100 G Verkliga Livet +/- 2/100 G

How does it work?

Acceleration:

At the heart of G-TECH/Pro is a precision 3-axis accelerometer, a sensor that
measures acceleration also known as G-Force. G-Force is what's keeping you
in your seat and if it wasn't for that seat you would be accelerating to the
ground at 1 G (32 feet per second per second).

Acceleration is measured in Gs and is one of the key things the G-TECH/Pro
COMPETITION is measuring. You can see this when you position the unit
horizontally, it will show 0.00G's on the X acceleration bar. If you position it
vertically it will show 1.00G's.



Speed:

The G-Tech measures your speed and distance travelled by integrating
forward (the forward direction is chosen automatically) acceleration over time.
Basically, if you know how fast you are accelerating for a certain time period
you'll know how much your speed changed after that time period. So if you
start off from zero speed then you'll know what your speed is after every time
period. These time periods are very small (a few thousandths of a second) and
that's how G-Tech maintains its accuracy. However, if you don't start from
zero speed your measurement won't be correct because you won't have a
good reference point. Consequently, it's very important to start all of your
measurements from an absolute standstill.



Distance:

Distance is measured in the same fashion, if you know how fast you are going
for a certain time period you will know what is the distance travelled during
that time period.



Horsepower:

The G-Tech measures horsepower though the formula: speed times
acceleration times the weight of the vehicle. The more accurate the vehicle
weight you enter, the better your measurement. The G-Tech measures
delivered horsepower, sometimes also called Rear Wheel Horsepower. This
horsepower includes the loss of power through the drivetrain which is usually
10-15\%. Rear Wheel Horsepower is what most people are interested in
because that is what they experience when driving. The use of Flywheel
Horsepower measurement is often used in advertising, but not very realistic
when it comes to accelerating your vehicle.

The horsepower that G-Tech measures also includes vehicle aerodynamic
drag. This means that if you tape over your headlights and grill, remove rear
view mirrors and windshield wipers to reduce your drag, you will measure a
Horsepower increase even though you didn't make any changes to the engine.
After adding an aftermarket spoiler you will likely find a decrease in measured
horsepower, since you increased the drag losses on your vehicle.



RPM:

Engine RPMs are sensed directly from the cigarette lighter voltage. No
installation required at all with this true plug and play feature. The unique RPM
feature is used for anything from realtime torque measurements to shiftlights.



What can it do?

The new G-TECH/Pro Performance Meter COMPETITION is a very
sophisticated, cutting edge automotive tuning instrument. Weather you want
simple RPM recording or complete Data-Acquisition. As an automotive
enthusiast you will find recording acceleration runs and analyzing shift points,
delivered horsepower and reaction times extremely valuable. Just imagine,
having all that power of knowledge right there under your fingertips any time
you want it, that's the new G-TECH/Pro COMPETITION. So, no more confusion
after making modifications now simply get the results "before and after".



Measurements:

Reaction-Time
0-60ft time
0-330ft time
0-60mph time
1/8mile E.T and speed
1000ft time
1/4 mile E.T. and speed
Horsepower
Torque
RPMs
Braking distance
Handling G's
Accelerating and Braking Gs
RPM vs Time Graph
HP & Torque vs RPM Graph
Speed vs Time Graph
Speed vs Distance
Gs vs Time Graph

How accurate is it?
There are several significant improvements over the original G-TECH/Pro
Performance Meter that have been implemented in the new COMPETITION
model. First of all, there are 3 accelerometers and they are fully temperature
compensated. This in itself is a huge improvement in accuracy. Secondly there
is a very sophisticated new calibration algorithm that allows much higher
precision. Also the system now has 32 times higher resolution which speaks
for itself. New Noise-Correction algorithms have improved overall accuracy as
well. With all of these valuable features we are very proud to announce that
the accuracy is now within 5/100 second. With the consistency at 5/1000 of a
second! Absolute Horsepower and Torque measurements are within 3% and
consistency within .5%!