Contrast sensor FT 20 WT

Contrast sensors are mainly used in the packing industry, in assembly/handling and in the printing industry; it is their task to detect or distinguish colours of products, labels or printed marks based on their grey value.  A (colour-) neutral vision of objects is essential here: the FT 20 WT therefore functions with white light, which enables the detection of many more colour differences in comparison to a single-coloured LED light source. It also has a high resolution of 30 contrast levels. The result is an unusually high sensitivity: the sensor switches quickly and reliably even at the slightest difference in contrast and this over the entire colour spectrum.

The scanning range of the FT 20 WT is 17 mm, with a depth of focus tolerance of ± 2 mm. The sharp, rectangular light spot of 1.5 x 4 mm² also enables the detection of small objects. With its maximum pulse frequency of 5 kHz, the sensor is also suitable for fast applications– e.g. reliable detection of printed marks is guaranteed with a belt speed of up to 900 m/min.

SensoPart has succeeded in fitting all these performance characteristics into a very compact (32 x 20 x 12 mm³), robust plastic casing. The FT 20 WT is thus the smallest contrast sensor on the market (some competitive products with comparable characteristics are over three times its size).

Three teach-in modes: static, dynamic, external

Many users are not just taken with the sensor’s compact design but also with its easy use: instead of time-consuming fiddling with potentiometers, which is often to be encountered in this sensor class, the FT 20 WT offers user-friendly teach-in.  Fine adjustment of contrast in particular - virtually impossible with a potentiometer - is no longer a problem.

Three teach-in modes are available:

• With static teach-in, either the object / marking colour and background colour or only the object / marking colour can be taught. First the marking is taught, then the background. The microprocessor automatically determines the optimum switch level from the receiving signals. This ensures that reliable detection is guaranteed even with colour fluctuations, as can for example occur with printed marks due to a fluctuating printing quality.
• The second control mode available is dynamic teach-in, in which objects can be virtually taught on a “running conveyor belt”. This dynamic method is recommended for example with quick product change-overs. The order in which the marking/object and background is taught is of no importance as the output can subsequently be inverted.
• The external teach-in mode is particularly helpful with sensors which are difficult to access: all operating steps can also be carried out via an external control cable here in addition to use of the sensor buttons.

Quality made in Germany: F 20 sensor family

The white-light contrast sensor FT 20 WT is SensoPart’s latest addition to its F20 sensor family, which has now been successfully established on the market for roughly ten years due to its excellent price/performance ratio. Last but not least, users also value the elaborate conceptual design and the excellent quality of these sensors developed and manufactured entirely in Germany.

The F 20 family offers a wide choice of sensors of identical design which share the same connection cables and fixing brackets; the teach-in programming concept is also the same for all F20 sensors. This makes the new FT 20 WT even easier to use for those users already familiar with other F20 products.