Colour sensors

The sensor operates by the three-stage principle, meaning that it emits the three colors red, green and blue and then measures the color proportions of the three colors reflected by the object.

The color of an object is programmed in the Teach-in procedure. If the sensor recognizes this color again during operation, it activates the corresponding output. Optional tolerances permit it to detect large or small differences in color.

Characteristics and advantages
Mounting and adjustment

The use of the color sensor is as simple as for a diffuse sensor. Only the points below must be observed.


Diffuse contrast sensors

Diffuse contrast sensors can detect finest differences in contrast. Contrasts arise when surfaces bear bright and dark areas (e.g. a dark color mark on a bright primary color), or by structures on a surface (e.g. a weld seam).

Diffuse contrast sensors are based on the intensity difference principle with a clearly defined small light spot. At the ideal operating distance the sensor is optimized so that the finest contrast differences are detected almost independent of small changes in distance.

Characteristics and advantages
Mounting and adjustment

The sensor should usually be mounted inclined by 5° to 20° to the object surface, especially when shiny material is scanned. When scanning edges, grooves or indentations, the sensor must be aligned so that the direct reflection is detected when the indentation, groove, or edge enters the light beam.


Difference sensors

The range of difference sensors opens new perspectives in the field of sensing. The patented functions provide the user with new, innovative solutions in the detection of objects, monitoring of tolerances or the comparison of object sizes and object positions. With the fine laser beam and the high insensitivity of the sensor to colors, objects are accurately detected. Five different sensors with different functions are available according to the application:  

Characteristics and advantages
Difference sensors with step analysis

In step analysis, objects are detected by their height difference (stage) and reported in the form of a digital output signal. The sensor evaluates the positive or negative height difference within a specified time window of max. 5 ms. If the height difference is greater than 50 % of the taught-in value, an impulse of at least 10 ms is issued at the output. When the value is less than 50 %, the sensor switches back to the OFF state. If height differences are smaller than 50 % of the taught value within the time window (e.g. fluctuation of the conveyor belt), the sensor remains in the OFF state.

Advantages:

Difference sensors with min/max analysis

With min/max analysis, objects can be inspected and monitored according to their scanned contour or shape. The scanning of the objects is activated by an external control signal. At the end of detection sequence, the measured values are evaluated and the difference between the minimum and maximum values is determined. If the difference exceeds a nominal difference previously taught into the sensor, this is reported in the form of an ON signal. This signal remains active until a new detection sequence is started. When this starts, the output returns to the OFF state. If the difference is smaller than the nominal difference, the output remains in the OFF state.

Advantages:

Difference sensors with tolerance analysis

The dimensional tolerance of objects can be determined by tolerance analysis. In the continuous detection of object distances, all measured values are checked to determine if it is between the specified maximum and minimum tolerances. In the case of if being between, an ON signal is issued at the output. If the distance remains within the tolerance range, the sensor remains in the OFF state.

Advantages:

Difference sensors with window analysis

With window analysis, objects can be classified by a specified switching window. For this purpose, the switching window is specified in a simple Teach-in procedure with upper and lower limits. If an object is outside the defined limits, this is reported at the switching output.

Advantages:

Difference sensors with 2-point comparison

In a 2-point comparison, two distances detected at two specifically chosen times are measured and compared. The choice of the time is made using a sync signal. The first distance is measured at the rising flank of the signal and the second distance at the falling flank of the signal. After the second distance was measured, the sensor evaluates the difference between the two distances and compares this with a previously taught-in maximum permissible deviation. If this difference is exceeded, the output switches to the ON state.

Advantages:

Mounting and adjustment

The direct reflection from glossy or reflective objects must not impinge on the receiver. This can be avoided by slightly tilting the sensor.

For optimum measurement results, the sensor must be installed at right angles to the movement of the object.

To the top