Contrast sensors

Contrast sensors detect and compare contrasts very precisely through the use of different light sources such as white light, laser-generated red light or RGB light. The detected contrasts marks are then reported to the process with minimal signal jitter. Through the automatic selection of the right transmitter colors, various color or gray value combinations can be reliably detected. Bar graph indicators offer additional ease in making adjustments during manual setup.

Extension of the KRT 18B contrast sensor product range by the addition of white-light models with additional teach process

Now also in white light – and with static 1-point teach

The task of contrast sensors is to scan an object for a predefined marking which differs in color only slightly from the rest of the background. In many packaging processes, these contrast markers must be reliably detected on film, bag and blister packaging or on labels. The KRT 18B series contrast sensors combine ease-of-use thanks to permanent signal indicators with high performance. Apart from our established models with RGB light source, contrast sensors with white light are now also available and add another teach variant to our product range. They offer fast and intuitive adjustment via potentiometer or teach button, remotely via cable or IO-Link, and feature a unique bar graph indicator that provides permanent feedback about the contrast quality. The highly precise contrast detection is performed with an extremely short response time and minimum signal jitter. The RGB devices are also available with analog output for particularly challenging marker detection applications.



Advantages for you

  • Models in multicolor (RGB) or white light (W) offer optimum performance for marker detection on colorfully printed or glossy films
  • White light provides greater reliability in the case of contrast markers on glossy surfaces
  • Multicolor (RGB) provides better performance with colorfully printed films
  • Free selection of adjustment method: intuitively using removable potentiometers, quickly and precisely by means of teach buttons. Also of course remotely through teach via cable or IO-Link
  • IO-Link with dual channel: for monitoring, diagnosis, easy changeover in the case of format change
  • Three teach levels ensure the perfect adjustment routine for every application
  • Static 2-point teach with stationary conveyor belt based on marker and background
  • Dynamic 2-point teach with running conveyor belt
  • Static 1-point teach detects any contrast markers in front of a homogeneous background
  • Permanent signal indication through self-adjusting bar graph on the rear side of the sensor
  • Tracking function with threshold tracking for fading contrast markers
  • Fine adjustment of the switching threshold through "near-to-marker" teach or EasyTune (T)
  • Light spot variants with horizontal or vertical alignment
  • Flexible operating range of 13 mm +- 3 mm
  • Maximum switching frequencies up to 22 kHz / response time 20 µs
  • Small, compact housing made of nickel-plated metal, IP67 and IP69K and ECOLAB



Highlights

Twice as much choice: Contrast sensors in white light and RGB

Depending on the packaging characteristics, white light or RGB may be of advantage for contrast detection. In order to provide our customers with full flexibility in the choice of their contrast sensor solution, we are doubling our KRT 18B product range and extending our innovative series by adding an intelligent 1-point teach to our white-light models. In addition to the high degrees of protection IP67 and IP69K, the extremely small and elegant housing also has ECOLAB certification for use in harsh environments. This ensures that our contrast sensors also withstand intensive cleaning cycles without problem.

IO-Link inside

The KRT 18B series contrast sensors feature an innovative, dual operating concept: Depending on the customer preference, all sensor functions can be configured via IO-Link or a simple, manual sensitivity adjustment can be carried out via potentiometer or teach button.
IO-Link can be used to implement innovative machine concepts with remote maintenance, diagnosis or sensor configuration.

Three different teach processes via IO-Link

Each application requires a different adjustment routine for the sensor. Easy to adjust via teach button, remotely via cable or IO-Link:

  • Static 2-point teach: With the conveyor belt stationary, the sensor is taught to the marker and then to the background – or vice versa. The switching threshold is set between the two signal values and can be set closer to the marker by means of a subsequent teach.
  • Dynamic 2-point teach: With the conveyor belt running, a measurement window is opened by pressing the teach button. As soon as multiple markers have passed under the sensor, the window is closed by pressing the teach button again. Here too, the switching threshold can be set closer to the marker by means of a subsequent teach.
  • Static 1-point teach: With the conveyor belt stationary, the sensor is aligned with the background and then taught to it. Each marker that deviates from this signal is detected as a contrast marker. The switching threshold can be moved by performing the teach again.

Applikation

Cut mark detection on packaging film in the film feed

Requirement:
A product is wrapped in a horizontal form-fill-seal (FFS) system. The packaging film must be cut to the exact size. The feed rate of the packaging film is controlled through the detection of contrast markers, which can have different colors and in some cases differ only slightly from the print on the film.

Solution:
The new KRT 18BW contrast sensor in the white-light version reliably detects contrast markers in a wide variety of colors, even on a glossy background. Here, the dynamic 2-point teach offers the possibility of configuring the sensor even while the film is moving. Fading print marks, e.g. towards the end of the film roll, can be compensated by the tracking function.

Color mark detection for tube alignment in a filling system

Requirement:
In a packaging system, plastic tubes are filled with toothpaste. The tubes must be correctly aligned before the fold is made at the end of the tube. The distance from the object to the sensor can vary by a few millimeters when the tube is rotated.

Solution:
The KRT 18BW also operates reliably even if the operating range relative to the object changes by 20%. With a homogeneous background, the white-light model also detects differently colored contrast markers, which saves time and effort particularly in the case of a format change.

Technical properties

Feature KRT 18B Standard KRT 18B Teach KRT 18B Multiturn KRT 18B Tracking KRT 18B Speed KRT 18B Analog
Setting Teach-In Teach-In Spindle Teach-In Teach-In Spindle
Bar graph No Yes Yes Yes Yes Yes
Light source RGB (red/green/blue)
White light
RGB (red/green/blue)
White light
RGB (red/green/blue)
White light
RGB (red/green/blue)
White light
RGB (red/green/blue)
White light
RGB (red/green/blue)
Switching frequency 15 kHz 15 kHz 15 kHz 15 kHz 22 kHz 15 kHz
Response time 33 µs 33 µs 33 µs 33 µs 22,5 µs 100 µs
IO-Link version No Yes No Yes Yes No
Operating range 13 ± 3 mm 13 ± 3 mm 13 ± 3 mm 13 ± 3 mm 13 ± 3 mm 13 ± 3 mm
Switching output PNP, NPN Push-Pull (IO-Link) Push-Pull (IO-Link) Push-Pull (IO-Link)    
IO-Link - V1.1 (COM2) V1.1 (COM2) V1.1 (COM2)    
Operation 2 potentiometers:
  • Sensitivity adjustment
  • Light/dark switching
2 potentiometers:
  • Sensitivity adjustment
  • Light/dark switching
2 potentiometers:
  • Sensitivity adjustment
  • Light/dark switching
2 potentiometers:
  • Sensitivity adjustment
  • Light/dark switching
   
Degree of protection IP 67 IP 67 IP 67 IP 67    
Certifications CE, UL CE, UL CE, UL, ECOLAB CE, UL, ECOLAB    
Connection M12 4-pin M12 4-pin M12 4-pin M12 4-pin M12 4-pin M12 4-pin
Temperature range –40 to +60 °C –40 to +60 °C –40 to +60 °C –40 to +60 °C –40 to +60 °C –40 ro +60 °C