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Abstract
To calibrate a press it is necessary to have a pressure sensor. We have built one that has a strain gauge as a sensing element and presents the value in a digital display. The sensor has been calibrated with known weights and the equivalence between the number and the weight to which the sensor is subjected has been established.
Description
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One of the projects of the group is the construction of a hot-plate press that we want to use to laminate different types of plastic materials. In this application the presses work at low pressures (less than 50 kg) and moderate temperatures (less than 120 ºC) so, instead of buying an expensive hot-plate press, we can consider the construction of a system in which we can measure and apply a precisely controlled pressure and temperature.
The first step of the project is to build a reliable pressure sensor and calibrate it to be able to apply known pressures through some device of weights, levers or springs.
The device uses a force sensor (strain gauge) with a large surface, which has a different electrical resistance depending on the pressure exerted on the sensor. This variable resistance is converted into a voltage value that can be read on a digital display. In order to calibrate the device with known weights, OFFSET and GAIN adjustments have been included for resistance-voltage conversion. The whole device is mounted in a box, having a single cable with the sensor at the end, and powered by a 9V battery. The box also houses the display and a power-on switch.
