Reflectometer Calibration by AWTA Product Testing

The importance of calibrating instruments so that these measurements are meaningful is an integral part of providing road users with a safe readily identifiable road infrastructure.

Optical measurements made by reflectometers provide assurance to relevant authorities that road markings are within designated limits and can be seen by motorists.

The simplified principle of how reflectometers make measurements once the trigger is pressed is the projection of a defined illuminant at a defined temperature onto a reflective substrate and the reception of the same retroreflected light which is then mathematically weighted into the number displayed on the LED screen.

Whilst the operation of reflectometers is fairly simple, the measurements they make are a function of both the angular geometry of the measurement being made and the angular geometry and alignment of the mirrors and lenses within the equipment. Measurement of angular geometry is determined by the operator, who ensures that the base of the reflectometer is aligned parallel with the marking being measured. A poor alignment results in measurement error. The alignment of mirrors and lenses within a reflectometer is achieved by disassembling the equipment and re-establishing correct geometric alignment using a special optical bench that is accurate to an angular second.

Reflectometer measurements should be regularly checked to calibration tile sets in order to validate the suitability of equipment for the measurement range intended, prior to field use measurement.

Calibration of reflectometers is necessary at regular intervals to validate the equipment operation and the suitability of the equipment for making measurements within the range intended.

Calibration also validates the measurement being made. There is little point measuring anything if the number you arrive at is either outside defined measurement boundaries for the equipment, or not related to what has been measured.

Litigious implications arising from erroneous measurements made from poorly maintained or uncalibrated equipment may be severe, especially where potential loss of life is the result.

It is recommended that reflectometers are checked yearly, with a view to adjustment if instrumental measurement is in error, and replacement of components that may have been damaged during use.

The Roadmarking Industry Association of Australia (RIAA) as the representative body for the road marking industry has deemed at its February 2012 Board meeting that it becomes a recommended requirement for all reflectometers to be calibrated at least once yearly in order to ensure their accuracy of measurement. This calibration should be performed by a recognised and accredited laboratory and that each individual unit should have a current calibration certificate at all times.

AWTA Product Testing is the only Australian laboratory that calibrates reflectometers and offers a quick turnaround service for calibration.