AVL OTR On-The-Road Opacimeter

The AVL OTR Opacimeter is a pressure-filled and compact partial-flow Opacimeter for continuous measurement of exhaust gas opacity on board a vehicle.

AVL Approach

The OTR Opacimeter is mounted with a special box close to the open tail pipe and draws its power from the cigarette lighter via a 12V/24V voltage converter. The software runs on a standard notebook PC and makes it easy to control the instrument, displays the online data and supports data post-processing.

Benefits at a Glance

  • Easy installation
  • Built-in calibration (linearity check)
  • Easy handling through small dimensions and low weight
  • Low power demand (can draw its power from cigarette lighter)
  • Easy control and data display via standard notebook PC

Technical Data

Easy installation and compact dimensions

The OTR Opacimeter is characterized by its compact dimensions and low power demand. The mounting box, which houses the measurement chamber, can be installed very easily on a trailer hitch.

Measurement value output Opacity N [%] or
Absorption k [m-1]
Measurement range N = 0 ... 100 % or
k = 0 ... 99,99 m-1
Resolution 0.1 % Opacity or
0.01 m-1 Absorption
Additional Output USB – Analog Converter:
Two user-defined channels (e.g. 0...+5 V = 0... 100% Opacity)
Effective length
(optical path length of the measurement chamber in the sensor unit)
0.215 m +/- 0.002 m
Operating conditions

+5 ... +45°C
Adhering to measurement accuracy
Max. 90% relative humidity, non-condensing

Power supply 24V DC (via 12 V/24 V converter)
Power consumption Approx. 60W (with heating)
Mechanical dimensions

Sensor unit: 395 x 285 x 136 mm
(W x H x D)
Mounting box: 500 x 340 x 250 mm
(W x H x D)

Weight Sensor unit: approx. 3.5 kg
Sensor unit and mounting box: approx. 12.5 kg



Measuring Principle

Pressure filled, partial flow Opacimeter

The AVL OTR Opacimeter measures the opacity of contaminated air in particular of diesel exhaust emissions. The measuring chamber with a non-reflecting surface is pressure filled with exhaust gas. The opacity of the exhaust gas is determined based on the loss of light intensity between a light source and a receiver. The specific absorption of the exhaust gas is calculated based on the opacity. The calculation is based on the Beer-Lambert law.