Application notes

Various speed measurement systems compared

The RXS-SOG-10 requires a 10 degree tilt downwards for accurate speed measurements. The radar is installed on the car as follows:

A comparison test has been performed with a test car equipped with GPS, tachometer (pulses from the ABS system) and the RXS-SOG-10. The car was driving a constant speed of 90 km/h set and controlled by the cruise control system. In below graph the measured speed is logged from the RXS-SOG-10 and the tachometer.

The red curve from the radar follows the measured speed from the abs tachometer very closely. (The used tachometer’s accuracy depends on the quality of the calibration and on the tyre pressure etc. The measured speed by the radar is proportional to the measured Doppler and doesn’t require a calibration.)

Measurement with the RXS-SOG-15 module installed on a metro

The RXS-SOG-15 gives pulses out per travelled meter, comparable with a tachometer. This module comes with an additional serial connector to give the user the flexibility to adjust the amount of pulses per travelled meter (16 pulses per travelled meter = correction factor 1.00, the duty cycle of the pulse is 50%)

Again a 10 degree tilt is used to ensure accurate measurements:

Installed on the metro (sideview):

Front view of the radar installed on the metro:

The metro used for this test is considered by the customer as their reference; the pulses from the tachometer (attached to a set of wheels) and therefore the speed, is assumed to be correct. In order to see if the radar corresponds, the pulses from the tachometer should align with the pulses from the radar.

The pulses from the radar (in yellow) align well with the pulses from the metro’s tachometer (in blue). Conclusion is that the radar matches exactly the metro system.