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Informationen für:

Fakultät Life Sciences
Fakultät Life Sciences

Smartphone Photometer

Here, a photometer is described that can be manufactured at low cost by people with little prior knowledge of electronics, computers and software.


A general description can be found as a technical article in the GIT Labor Fachzeitschrift (issue 5/2017 p. 20 - 22) which is also available online (http://www.git-labor.de/forschung/chemie-physik/smartphone-photometer-zum-selbstbau).

The online portal Heise-Online published a report on October 4,2017 (https://heise.de/-3845435).

A report on the photometer was published in issue 5/2017 p. 100-101 of Make magazine (https://www.heise.de/select/make/2017/5/1508789914032591).

The issue 3/2018 of the journal GIT Laboratory Jurnal has published a review article, which is also available online. (https://www.laboratory-journal.com/science/chemistry-physics/diy-low-budget-smartphone-photometer)

 

The photometer was/is also to be seen "Life".

Maker Faire Hannover 2017 - Exhibition Stand School Lab Mobile Analytics - August 25-27,2017 (https://maker-faire.de/hannover/).

Night of Knowledge Hamburg - Campus Bergedorf - 4 November 2017 (https://nachtdeswissens.hamburg.de/index.php?article_id=161&id=16284).

Maker Fair in the north of 2017 (Kiel) - exhibition stand for the school laboratory mobile analytics - (https://makerfaireimnorden.com/).

Concept Idea


Within the scope of this project, a photometer is to be developed that can be manufactured for low costs by people with little previous knowledge of electronics, computers and software.

The basic components of a photometer include

  • a light source
  • a monochromator
  • a measuring cuvette/measuring vessel
  • a light sensor
  • a system that prepares the measured data
  • something for operating and visualizing measurement data (user interface)
  • as well as a holder for the measuring vial to enable reproducible measurements

 

An essential characteristic of a photometer is the measurement of the light attenuation (light absorption) at a certain wavelength of the light. Many commercially available photometers allow the preselection of this wavelength. Technically, this is often achieved by spreading a broadband beam and selecting a small narrowband area or by a color filter. This optical assembly - the so-called monochromator - is a considerable cost factor. In this project a monochromator should therefore become unnecessary through the use of LEDs. LEDs have a more or less narrow-band light spectrum. By selecting the LED color, a "suitable" light for the measurement task can be selected. The width of the spectrum of the respective LED varies from manufacturer to manufacturer. On the one hand, a narrower band would be desirable to achieve high wavelength selectivity. On the other hand, the overlapping of the individual bands also allows the limitation to a few LEDs in order to cover a wide range of wavelengths.

The following criteria are desirable when selecting a suitable light sensor:wide wavelength measurement range to measure ultraviolet to infrared light

  • high resolution to be able to distinguish light intensities finely graduated
  • little cross sensitivities against environmental influences (e. g. temperature)
  • Low electro-technical complexity in order to obtain the measurement results

 

The last point in particular suggests the use of a sensor with an integrated digital interface. This eliminates the need for signal amplifying electronics and the associated expense.

The use of a small computer is recommended for controlling the LED and processing the data of the light sensor. In order to display the measurement data and to be able to start measurements, a display option and control buttons are required. If it is possible to select a small computer that can offer its data via a data interface that can be used by a tablet or smartphone, there is no need for a separate display and the control buttons. In order to be able to dispense with an additional program on the side of the smartphone, it is desirable to offer the data and the possibility of starting measurements in the form of a website, which can be called up by any internet-capable device, thus also by smartphones. The integration of a smartphone into the concept saves costs for display and control elements and is suitable to increase the acceptance of the project among young people. The required computer should therefore have a WLAN / WIFI interface and the possibility to implement a small web server.

The individual components of the photometer should also be manageable for beginners in the electronics sector. Soldering work should also be carried out by "first solderers" and can be inspected and corrected by briefly instructed project supervisors. Soldering work on sensitive or very small components is therefore out of the question.

Letzte Änderung: 05.06.18

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