Accuracy

VBOX

Under open sky conditions, the VBOX can provide one of the most accurate ways of measuring Velocity and Distance travelled. The first VBOX was shipped in 2001, and since then the majority of vehicle manufacturers and tyre companies have tested the VBOX back to back with their existing equipment, and gone on to purchase VBOX for their own testing. Have a look at our customer list to see just how many people now use the VBOX for brake, acceleration and chassis development.

The best way to see if the VBOX is accurate enough for your tests is to try one out. We offer a full money back guarantee if you are not satisfied and wish to return your VBOX within 30 days of purchase.

Example of Brake Stop accuracy

The following is a video of a test we carried out to check the Accuracy of the Braking distance of the VBOXIII

Brake Test Video

Units	Resolution	Accuracy	Accuracy with DGPS
Velocity	0.01 kmh	0.1 kmh full scale	0.1 kmh full scale
Distance	1 cm	0.05%	0.05%
Absolute position	1 cm	3 m 95% CEP**	1.8m 95% CEP*
Height	1 cm	6 m 95% CEP**	3m 95% CEP*
Lateral accel	0.01 g	0.5%	0.5%
Longitudinal accel	0.01 g	0.5%	0.5%
Heading	0.01 °	0.1 °	0.1 °
Time	0.01 s	0.001 s	0.001 s

*95% CEP (Circle Error Probable) means 95% of the time the position readings will fall within a circle of the stated radius.

Note: to obtain these accuracies, good visibility to the sky must be maintained. If you test close to trees, bridges or tall buildings, then these accuracies will be degraded.

Calibration

We provide fully traceable calibration certificates for each VBOX, by using a sophisticated GPS Doppler shift simulator from Spirent Communications. This unit allows us to test the VBOX under a number of different conditions, and provide a calibration certificate for all of the outputs from the VBOX. This is regarded as the definitive method of checking calibration on GPS devices, and we are the only company involved in vehicle test equipment who have invested in this equipment. Other companies who use this level of equipment include the National Physics Laboratory, NASA, The European Space Agency, and the US Military.

On request from customers, we have carried out detailed checks on the distance calculations using a survey grade GPS RTK system. (see Brake Distance Evaluation.pdf)

We have also done back to back testing with optical sensors (see Comparison of non contact speed sensors.pdf). (comp-graph.gif)