Transmission Photometer

The transmission photometers of PIER-ELECTRONIC have a wide field of applications:

  • Contamination detection: Online measurements of components in liquid or gaseous substances
  • Online Moisture detection: Online measurements of the water content of brake fluid or the humidity of various other substances
  • Intensity measurements for the colour of a solution, of colour changes, and the detection of red, yellow, or blue hues in the visible spectrum
  • Detection of residues of organic substances in water or other liquids in the ultraviolet spectrum

These photometers work without contact to the target substance. The measured data are available within fractions of a second (in the case of continuous measurements) or after a few seconds (in the case of singular measurements). This does not only provide you with a quick display or data recording: It also becomes possible to directly control the production process in automated facilities to adequately react to the real-time data. This measurement principle is also suitable for random samples or serial measurements in laboratories attached to production facilities. The measurement technology of PIER-ELECTRONIC contributes to notable improvements of quality in production processes and helps to reduce the costs of operation. 

The measurement principle
Your sample (a gas or a liquid) flows through a flow cell with transparent sides. The light from a lamp is focused to penetrate the flow cell and then to enter the receiver housing. There, the measurement wavelengths are selected with filters on a filter wheel. The filter wheel rotates (motor M) to create an AC signal that can be filtered from stray and background light. The filtered light is detected by a photosensitive element. The signal is amplified and the processed by the analyser to produce the required measurement data.
The transmission photometers can be operated in the wavelength range between 200 and 4700 nm. Our method of alternating light leads to a high stability over time. As a result, many interfering factors have a negligible influence on the measured data.

Transmission measurements are perfectly suited for the analysis of liquids and gases in process and laboratory applications. In mixtures of several components, each component absorbs light of different wavelengths differently. Therefore, it is sufficient to know the absorption properties of a component in order to select the best wavelengths for detection and reference measurements. It is also possible to detect gases at all wavelengths. Due to the lower density, deeper layers are required depending on pressure and temperature. If pressure and temperature cannot be held constant. Deviations caused by their variation can be compensated during the measurements.

Our staff will select the most suitable wavelength for your application by spectral analysis of the substances in question. The wavelengths can be chosen from any of these spectral ranges of electromagnetic radiation:

Ultraviolet (UV) 200–400 nm
Visible light (VIS) 400–700 nm
Near infrared (NIR) 700–2500 nm
Infrared (IR) 2500–4700 nm

Transmission measurements are based on a beam of light that passes through the sample in a flow cell and then through a filter wheel. Finally, it is detected by a photo sensor. After pre-amplification and digital processing, the measured data are displayed and stored in the analyser. Other optical designs can be manufactured on request, such as measurement sensors on periscopic arms or flow cells connected to optical fibres.

The open assembly of the measurement sensor has several important advantages. One of them is safety: the flow cell, which may contain hazardous liquids or gases, is located separately between the lamp case and the receiver unit. In the case of a leakage, no liquid or gas will penetrate into the photometer housing. Furthermore, the flow cell is freely accesible for maintenance.

Applications: Component analysis
One of the most common applications of our transmission photometer is the online moisture easurement in various materials. The detection of other substances (liquids or gases) is a popular reason to apply our photometers, too.

For some examples, see the list of TMK applications.

Other Applications
In the visible spectrum, the colour intensity of solutions can be determined. This includes the detection of colour changes, e.g., during titration procedures, or blue/red/yellow hues.
In the ultraviolet spectrum, residues of organic substances can be detected in water or other liquids, e.g., to derive the TOC value (total organic carbon).

Suitable for Ex conditions
For applications in rooms an explosive atmosphere, a pressure-proof version of the measurement sensor and a pressurised housing is available. Sensors are available for Ex zones 1 and 2 according to the ATEX directive.