Design, make, test and evaluate a strain gauge sensor Essay

These are my preliminary results that helped me to understand the physics and approach needed to make my experiment successful. In exp1, 3 and 4 I used the same wire and exp2 was a fresh wire. Clearly u can see the set of results obtained in exp2 were different to the other sets of data. After a wire stretches the wire Changes State and becomes a harder material, meaning it will stretch less the next time u apply a strain. Therefore in my real experiment I used fresh wire for each experiment. Trend In Graphs: From the graphs u can see a general trend formed in exp2, as weight is applied the voltage across the rest of the circuit decreases, therefore increasing across the wire. In the other three experiments u can see weight has little or no effect on voltage, thus showing the wire has already been stretched. This can be seen in ‘Chart 1’. Results I have used ‘Ohm’s law’ which is a formula, to get a resistance for my results. R= V/I Experiment one Experiment 2 Experiment 3 Length of Constantine wire (cm) Voltage (v) Resistance (ohms) Voltage (v) Resistance (ohms) Voltage (v) Resistance (ohms). Experiment 4 Experiment 5 Length of Constantine wire (cm) Voltage (v) Resistance (ohms) Voltage (v) Resistance (ohms) 1The anomalies are in red. I have also carried out a further experiment to find out how there is a general increase in voltage and resistance across a wire as it becomes longer. These results support the prediction I have made before hand. I predicted that the longer the wire the greater the resistance will be and then more energy will be needed to push the electrons through. Now I can carry out my experiment, knowing current and voltage will increase as strain is applied on the wire. Results: 1st Set†¦ Length Of Wire/(mm) Current/(milliamps) Weight/(grams) Power, voltage/(millivolts) [Start]8off scale 700 254 This is my first set of results, which I believe to be the most accurate. As u can see there is a clear trend in the increase of current and voltage. There are no anomalies in this experiment. 2nd Set†¦ Length Of Wire/(mm) Current/(milliamps) Weight/(grams) Power, voltage/(millivolts) [Start]8Observations: There was only one major observation and that was to see how the wire stretched as more weight was applied. As more weight was applied the wire slowly stretched until its deformation point. The deformation point is where the wire is stretched or re-shaped so much it cannot return to its original state. Accuracy of Results: The accuracy that I achieved was very high even though I had very little time. Also I got lots of results to make a good analysis. The level of accuracy in this investigation was as high as I could get. The only thing I could of improved was to use more weights and measure every 50grams however this may have taken too long to achieve. I got someone else to check the reading on the meters to be sure I was reading them correctly. Before taking each reading I would also check the connections were crisp between the wire and the rest of the circuit. I could change one or two thing during this experiment. A few examples of these could be the thickness of the wire, the type of wire for example copper and gold. We made sure to limit out systematic error by valuing all the results a 0 for 0 weight. This way only my own human judgement can effect the quality of the results. A random error could of included, when I was reading the results someone knocked or a change in the gravitational field, effected the weight. Also a slight wind could of pushed on the weights for that precise second, tiny chance, but possible! Analysis: First Experiment: The first experiment clearly went much better then the second as I have a significant and clear trend between the strain, current and voltage. From ‘Chart 2’ u can clearly see that as u stretch the wire the current and voltage increase. The voltage only grows very slowly until the wire is deformed, then the electrons need much more energy to move across the wire (large increase in resistance). The sharp slope proves this in ‘Chart 2’. Chart 3 and Chart 4 show this in much more detail. In ‘Chart 3’ u can see where the wire snaps because the stain is too much for it to withstand. Therefore from the first experiment we can see that my theory and hypothesis is proven. Chart 8 shows the general pattern between voltage and current and how resistance increases. Between point 6 and 7 on the X-axis the wire has deformed and resistance has greatly increased. The wire has stretched 45mm, which also increase resistance. Second Experiment: There is one major anomaly in experiment 2 and that is when 100grams were placed on. The reading of power/voltage and current are much too high. On Chart 5 and 6 I have draw a pencil line which I believe should have been the results gained. The general trend again shows that as u stretch the wire the resistance across it increases. Chart 7 shows the general pattern between voltage and current and how resistance increases. Evaluation: A strain gauge can predict when a wire or something with applied stress or stain will deform or even break. When the voltage and current increases in a wire it must mean resistance has also increased. Improvements: If I were to do the experiment again, I could make some improvements to make the level of accuracy better. For example, I could make sure that the joints/connections were jointed properly and would have to make sure I use the same equipment every time. I could also get a machine to measure the length of the fine wire. I would also take more than two sets of results, which would eliminate any factors of anomalies and would therefore make the experiment a lot more reliable.