Martin Popik e-mail Martin Popik Slovensky Michal Holub Michal Holub e-mail
Gymnasium of Ladislav Novomesky, Bratislava, SLOVAKIA Gymnasium of Jur Hronec, Bratislava, SLOVAKIA
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CONSTRUCTION PART

Measuring Cylinder

  • Material: PMMA (polymethyl meta acrylate)

  • Thickness: 3 mm

  • External diameter: 80 mm

  • Internal diameter: 74 mm

  • Height: 560 mm

  • Exploited height: 460 mm

  • Exploited capacity: 2 000 cm3

  • Heating body: commonly available heating spiral taken from a boiling pot

  • Wattage of heating body: 800 W to 900 W

  • We selected the transparent material for better clearness and higher didactical value.

Structural Arrangement of the Device

We filled the sensors that we created from NTC's with Dentakryl. We disposed them equally into measuring cylinder and we glued them up with the special glue for acrylate. This worked well in the experiments with clear tap water. As it turned out in the experiment with highly concentrated salt solution this arrangement was not sufficient as well as many previous experiments such as filling the sensors with waxy glue or filling them with wax. It was insufficient because the salt solution worked as an outstanding insulator and a bubble with high temperature was created in the lower layer of the cylinder. We decided to use materials specially suited to this purpose instead of the frequently used and easily available ones. We used Dentakryl again to fill in the tips of the sensors and we glued them up with glue for PMMA. We painted the contacts over with a Protective varnish. This solution allowed us to use this device also for the tests with substances that have completely different thermal features than water.

Used Chemicals

DENTAKRYL: Technical dentakryl is a binary methyl meta acrylate synthetic resin for casting that is designated for technical use. It is commonly used in engineering because of its good process ability, dielectric properties, rigidity and solidity. It is resistant to acids, alkalines, and salts.

PROTECTIVE VARNISH: It also is commonly used in engineering for a variety of reasons. It is completely dielectric and so it is optimal for painting over and protecting the cables and links. We used it by the experiments for the protection of the links that come out of the heads of the sensors and for the protection of the contacts by the links.

SYLGARD: It is a low-viscously thermally conductive silicone thermosetting elastomer. This binary material creates a sticky bond after hardening. It is used for the protection to moisture, influences of the environment, mechanical and thermally influences and oscillations. Typical application of this material is to protect the sensors and transformers. It has also good dielectric properties.