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LM 20

Luminance meter for vehicle license plate lighting

LM 20

LM 20

Luminance meter for vehicle license plate lighting

Universal solution for conformity analysis conforming to standards ECE R4 and SAE J587

The LM 20 was developed for die standard-compliant measurement of luminance of vehicle registration lighting (license plates) in conjunction with an AMS goniophotometer system from the Optronik line from Instrument Systems.

The luminance meter consists of a tube with special measurement optics for stray light reduction, a digital DSP 10 photocurrent amplifier and an LED alignment device for precise focusing on the reference surface on the test object. It meets the requirement of classification A (high accuracy) pursuant to DIN 5032-7 for luminance meters.

The instrument focuses precisely on a measuring field with a diameter of 25 mm at a distance of 3.162 m. It is fully integrated via CAN-bus into the other components of an AMS goniophotometer system, ensuring convenient operation of the measurement set-up in positioning on the measuring fields.

The LM 20 luminance meter is normally used in conjunction with a goniophotometer of the AMS series for automated measurement procedures, in order to determine the illumination of license plates in accordance with current standard specifications.

Accessories optimized for measurement task are available for the LM 20, e.g. license plate holder with dummies in compliance with ECE, SAE and GB standards.  

Key Features

- Display range 1,000,000 cd/m² with a resolution of 0.02 cd/m² in the most sensitive measuring range

- Connection to the AMS goniophotometer via CAN-bus; display of readings directly on the AMS controller

- LED alignment device facilitates targeting on measuring points

- Special measurement optics for the suppression of stray and extraneous light

Technical data and specifications

Instrument parameters

           LM 20 properties                                                   

Class notation

A in acc. with DIN 5032-7 (2017)

Measuring scope

0.02 (resolution in the most sensitive measuring range) 

up to 1.000.000 cd/m2

Measuring ranges


V (λ) correction

f1‘ ≤ 2 % (typ ≈ 1.5 -2.0%) (full filtering)

Linearity errors

f≤ 1 %

Total errors

fges ≤ 7.5 %

Influence of ambient luminance

f(u) ≤ 1.5

Viewing angle


Measurement distance

3.162 m


Sample system