Reflection Photometer

The reflection photometers of PIER-ELECTRONIC are used to analyse solid materials, such as wood, minerals, or grains. The product is illuminated with light of a suitable wavelength. The photometer spectrally analyses the light that is reflected by the target:

Reflection photometer

Reflection photometer over a conveyor belt

The measured raw data are transferred to an analyser which computes the required data, e.g., moisture, concentration, or thickness.

The photometers of PIER-ELECTRONIC are used in different industrial sectors for the quality control of various products. Typical applications include:

  • Moisture measurements (water content) of sand, grains, wood, polymers, etc.
  • Concentration measurements of certain minerals in raw salt
  • Thickness measurements of coatings, foils, and films
  • Whiteness control of sugar
See our full application list for details.

Reflection photometer

Reflection photometer for sample analysis

The measurement principle
The illuminated sample reflects light in a typical pattern. The human eye detects this as the colour of the object. Our detectors are able to observe more wavelengths than the human eye, if required by the application. For example, moisture is detected using near-infrared light.

The optics of the photometer focus the reflected light onto an adequate photodetector. The signal from that detector is then amplified and combined with the calibration parameters to display the required data.

Principle of operation of reflection photometers

The optical principle of a reflection photometer

If necessary, additional environmental parameters can be taken into account, as some measurements are sensitive to the temperature or to other components of the product.

A special method using modulated light ensures a high stability over time, and leads to a neglible influence of various interfering factors on the measured data.

The wavelengths for the measurement depend on the material and are selected from these sections of the electromagnetic spectrum:
Ultraviolet (UV) 190–400 nm
Visible light (VIS) 400–700 nm
Near infrared (NIR) 700–2500 nm
Infrared (IR) 2500–4700 nm

Reliable measurements require a good calibration of the system. That is achieved with well-characterised product samples, the composition of which is known either due to their production process or from independent measurements. With such calibration samples, the characteristic function of the photometer is determined which then relates any measurement within the valid range to a certain value of the required physical quantity, such as the product moisture.

Traversing units for wide targets
When the product is very wide, such as paper, glass, or sheet metal, measurements are often required over the entire width of the production line. Therefore, the photometer has to be able to move across the material. We at PIER-ELECTRONIC can offer you custom-made traverses for that purpose.

Fibre optics
Point measurements at short distances (5 mm) to the target are possible with flexible fibre optics. This option is used when space is tight and the environmental conditions are difficult.