Sensor Instruments
Entwicklungs- und Vertriebs GmbH
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D-94169 Thurmansbang
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23.04.2024 Optical spray jet control
01.09.2023 Sensor systems for recyclate control in the plastics industry for laboratory and inline use
31.08.2023 Checking the plastic type of recyclates and virgin material using NIR technology
22.12.2020 SPECTRO-M-10-MIR - Inline control of thin oil layers on metal



Optical spray jet control

When designing spray systems, it is important to ensure that the sensor technology is matched to the size of the spray cone and the spray volume of the application in question. Furthermore, the geometry of the spray cone and the spray quantity depend on the medium used (primer, adhesive, solvent, water, alcohol, paint, etc.) as well as on the spray nozzle opening, the overpressure and the spray quantity dosage. Particularly when using tough, adhesive media (glue) as a spraying agent, it can happen that part of the spray nozzle opening sticks, which leads to a change in both the spray quantity and the spray geometry. As a result, the spray jet can be changed in terms of direction as well as opening angle.

When designing a spray jet control system, it is important to address some key questions:
  1. Is the qualitative evaluation of the spraying process (yes/no or spraying process is ok/not ok) sufficient, or is a more detailed analysis (jet geometry, spray quantity) also required?
  2. Which medium (primer, adhesive, solvent, water, alcohol, paint, etc.) is sprayed and how is the medium optimally scanned (interaction with optical scanning: droplet size and distribution)?
  3. Which influencing variables determine/disturb the quality of the spray jet in the process? What are the general conditions for optical scanning of the spray process?
The aim of inline spray jet control is automated quality control of the spray process during the production process

The following document describes briefly the measurement principle, and, in the second section, the methods that can be used for inline control of spray jets in transmitted light. The final section deals with spray jet control in explosive areas.

► Whitepaper (pdf)
► Product overview



Sensor systems for recyclate control in the plastics industry for laboratory and inline use

While downcycling of plastic products still predominated in the past, the form of recycling in which the reused plastic is put to the same or a comparable use is now becoming increasingly important. This in turn means considerable additional technical effort in separating and sorting the items delivered to the recycling plant throughout the recycling process

After separation of as many non-plastics as possible, for example by means of metal separators and wind separation, sorting is currently primarily by color (color sorting systems) and type of plastic (NIR cameras). Despite pre-sorting, where mainly whole articles are checked, as well as post-sorting (after shredding the plastic articles and subsequent washing) of the plastic particles known as flakes, it is not possible to achieve 100% grade purity. Certain variations in color must also be expected..

In order to allow unrestricted use of the recyclates produced in this way, they must be checked for purity before the next processing step, at the very latest immediately before extrusion. Typically, this could be done by a metering system equipped with appropriate sensors. The degree of purity of both the color and the type of plastic is monitored. If the purity falls below a certain level, less recycled material is added and more virgin material is added, so that the deviations in the final article in terms of color and plastic type are within the required tolerances.

Furthermore, additional sensors can be used to detect a marker from the TAGTEC family contained in the recyclate (contained in the masterbatch from Gabriel Chemie). In the case of articles of the same color and plastic type, markers are used, for example, to distinguish between a clear PET ketchup bottle and a clear PET shampoo bottle. In addition to the actual sensor technology for testing the color, the type of plastic and the presence of any TAGTEC markers, the company Sensor Instruments also offers test systems for the laboratory, including the appropriate accessories for calibrating the devices, as well as inline devices, which will be explained in more detail below.
► Whitepaper (pdf)
► Product Overview (pdf)

              Color                  Plastic type              Marker    


Checking the plastic type of recyclates and virgin material using NIR technology

Open spectrographs, designed as hyperspectral cameras, are usually used in the recycling sector to perform the separation of different plastics. Working in combination with a broadband NIR light source (e.g. built up from high-intensity halogen spotlights), these cameras combine a moderate spatial resolution with a good spectral resolution of the objects. A further procedure directs a high-intensity NIR light source onto a surface to be scanned via a polygon mirror, whilst an optical unit is directed onto the polygon mirror. This means that part of the NIR light impinges on it after it has impinged on and been reflected from the object via the rear optical path, from where it is directed onto the aperture of an NIR grating spectrometer. Both procedures enable the spectral detection of a relatively large NIR wavelength range with simultaneous spatial resolution. This means for example, that different objects adjacent to each other on a conveyor belt and which pass through the detection area simultaneously are detected as separate objects, whilst being spectrally differentiated.

Plastic granulates on the other hand, do not require individual spectral differentiation. Instead, an integral process should record as many plastic pellets as possible at the same time, thereby obtaining reliable information about the quality or purity of the product. The complex technology that would be necessary to determine the spatial resolution is unnecessary and can be dispensed with. In principle however, an NIR spectrometer with optics and NIR illumination could be considered, but would represent a cost-intensive solution.

A more cost-effective alternative is a system that works in accordance with the three-range procedure. This measuring procedure directs three different NIR LED types (each LED type covers a specific wavelength range in the NIR) at the plastic granulate to be investigated, and a broadband NIR receiver detects the light reflected diffusely by the pellets. This is converted and passed on to an evaluation unit.
► Whitepaper (pdf)

   (NIR sensor fixed optics version)

   (NIR sensor fiber optics version)


SPECTRO-M-10-MIR - Inline control of thin oil layers on metal

The MIR measurement procedure deployed in the SPECTRO-M sensors was developed by Sensor Instruments in order to measure very thin organic layers on metal surfaces. As such, SPECTRO-M sensors are highly suited to the detection and inline control of thin oil films on metal.

In practice, it is necessary to control the de-oiling process of parts and monitor the homogeneity of an oil application. Within of the course of tests accompanying the development, we ascertained that the system can be used to measure the evaporation characteristics and oil residues of cutting oils on metal surfaces performed under realistic application conditions (thin layers).

To this end, we have also performed tests on special punching oils from the CLF series from Raziol; the results are summarized in section 6 of this document.

This document described the sensor principle of the SPECTRO-M-10-MIR/(MIR1+MIR2) inline sensor from Sensor Instruments. Further SPECTRO-M sensors of the type with other measurement geometries are currently in development. As the developer of special sensors, we are also able to adapt the technology to match special applications and customer requirements.
► Whitepaper (pdf)




Participation at trade fairs:

 •   Sensors Converge 2024
 •   SKZ Innovation Day 2024
•   SKZ Network Day 2024
 •   SKZ Technology Day 2024
 •   PRS Middle East & Africa 2024
 •   Plastics Recycling World Expo
Europe 2024
 •   Plastics Recycling World Expo
North America 2024
 •   PRS Asia 2024
 •   PRS India 2024
 •   European Coatings Show 2025


Press releases:

Determination of layer thicknesses between and on plastic films
(MIR transmitted light measurement)

Spray jet control in reflected light mode
(Measurement of the lowest spray quantities in the Ex area)



  Sensor systems for the plastics recycling industry
Color measurement of recyclates



Specialists article:

  Testing Recyclates Directly during Injection Molding and Extrusion
NIR Process for the Inline Inspection of Recycled Plastics
Plastics Insights 3/2024




Sensor systems for recyclate control in the plastics industry for laboratory and inline use
Checking the plastic type of recyclates and virgin material using NIR technology



Detection of dents and bumps on metal punching strips
(N° 801)
Differentiation of leather, fabric and synthetic interior components
(N° 802)
Plastic cap color measurement
(N° 803)


... surface tension?
... oil evaporation?
... oil layer thickness


Software news:

SPECTRO3-MSM-DIG-Scope V1.5 (2021.10.20)



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