Why do optical diffuse sensors not reach the parameters specified in the data sheets?

Very often our customers ask us about the parameters given in the data sheets of optical diffuse sensors.

In many applications, the sensors have a smaller switching distance.

We have to say, yes, this is normal, it is not a fault.

Why? Because the data given in the data sheets are related to the so-called „reference object“.

This „reference object“ is a 100 × 100 mm „measuring plate“, with 90% reflectivity. This plate is also known as the Kodak Gray Card.

White office paper has very similar properties, which can be used to quickly verify the properties of optical sensors.

In real applications, we will never encounter the detection of such an ideal object.

When designing optical diffuse sensors, it is good to count on sufficient margin.

The detection ability is affected by factors such as the size of the object, surface roughness, color, tilt, etc.

All of this can negatively affect the ability of the sensor to correctly and reliably detect the object.

Values for determining the range of a sensor which is dependent on the differing reflection properties of an object.

For example the range of the sensor is reduced with darker objects due to the greater light absorption.

For objects with different reflective properties the following correction factors can be applied (see table):