Optical Instruments

Last change: 15.11.2019

Maintenance Retroreflectometer


In order to ensure the long-term accuracy of DELTA measuring instruments, they must be handled with care and well looked after. As well as regular cleaning of the window in front of the lens and the calibration standard, the battery should also be used in accordance with the manufacturer's instructions.

The majority of units are used by publicly appointed and sworn surveyors, experts, and test institution employees or in quality management. These units should therefore be subjected to an  inspection/maintenance and recalibration every two years.

Important notice:
In 06/2019, 15 years after the end of production, Delta terminates providing spare parts and support for LTL 2000/S/SQ, Qd30 and RetroSign 4000/4500 systems. Batteries, lamps and calibration standards may be vailable for a certain time on. This must be checked individually.

Recalibration of Standards


DELTA is accredited by DANAK and has the status of a national reference laboratory for testing and calibration in the fields of photometry, radiometry and colorimetry. The Danish accreditation body DANAK is a member of the EA (European Cooperation for Accreditation), which guarantees international recognition of the calibration certificates produced by the testing and calibration laboratory.

Every DELTA instrument is delivered from the factory with a calibration standard which has been verified in Delta's DANAK-accredited calibration laboratory for photometry. The origin and knowledge of the precise reflectivity of the standard are the basis for accurate and above all reproducible measurements.

A calibration certificate guarantees that the calibration of the standard has been produced in accordance with the quality criteria of the DELTA quality manual which has been assessed by DANAK.

In the long term the values of calibration standards can change (e.g. due to UV radiation). Therefore the standards should be recalibrated every two years.

In agreement with DELTA, we offer to recalibrate the standards every spring (February/March) at a special rate. The standards are recalibrated at DELTA in the DANAK-accredited calibration laboratory for photometry. There is a certificate relating to the recalibration for every standard.

Maintenance Works LTL-X LTL-XL RetroSign
Cleaning of instruments and standards
Check of system functions
Installation of software updates
Check of light sources
Check of batteries
Check of illumination angle
Check of observation angle
Check / adaption of hardware settings
Check / adaption of softare settings
Calibration RL standard optional optional optional
Conformity check of Qd standard optional optional optional
Stability test
Calibration of instrument
Check of printer -
Check of interfaces
Check of charger

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ZTV M 13, BASt, Federal Highway Research Institute, service, maintenance, recalibration, DANAK, PTB, calibration standard, RL, Qd, LTL, RetroSign, Delta light & Optics, testing institute, DIN 1436, ASTM E 1710, EN 1463-1:1997