Design, prototyping, calibration, testing and evaluation of an electronic measurement system

Abstract. This paper reports on the design of a prototype electronic measurement system to meet a specific requirement. The first task was to measure the force in the top link of a moving tractor by using a force sensor. We chose a resistance based sensor. The resistance of the gauges changes due to strain. The Wheatstone bridge is one of the most convenient and accurate resistance measurements. The second task was to measure the ground speed of the tractor. There were many methods that we could choose to measure the speed. Velocity measurement is not usually direct. A tachogenerator can be used to test velocity. Velocity is usually derived from position differentiating with respect to time or acceleration integrating with respect to time. Therefore, we used an encoder to measure the distance and then differentiated the distance to obtain the velocity. Another method we chose was using the accelerometer to test the acceleration and then we integrated it to gain the velocity.

Every sensor was calibrated before conducting experiments to ensure the accuracy of the data and this was performed accordingly. Sensors were then connected to a data logger to extract the data. We chose DEWE43 which was very efficient and the information was accessed by using the DEWE soft. This data logger could receive both analogue and digital signals and likewise, the output could be both analogue and digital signals. After collecting the data, analysis was carried out and it was found that there were some signal noises with the data which might make readings greater than or less than the true value. It was necessary to filter before dealing with the data. Matlab was used to deal with the data to obtain the force and velocity.

The results showed that the speed obtained by integrating from the acceleration was not accurate enough. The force was close to the true value after filtering. Some parts of the experiment could be improved by adapting more accurate methods.