Resistance =Voltage/Current, which will allow me to work out the resistance of the strain gauge.
To measure the temperature of the wooden block, I shall use 2 thermocouple devices , one of which I shall attach to the wooden block by using a substance called araldite 2024, which has a good thermal conductivity and a high melting point. ref1.
I will use general purpose thermocouples as they can be used to measure high temperatures and are responsive enough to a temperature of 400ºC.
The ranges of temperature that I will be using are 0ºC to 40 º, as these are the extremes the temperatures are likely to be in an average household.
I will attach the thermocouple to a millivoltmeter to read the potential difference across it. First I will have to calibrate the thermo couples by heating them up and measure temperature against PD and plot a calibration graph.
I shall have to stick the wood block on to the strain gauge using a substance called Cyanoacrylate, ref 2 or more commonly known as super glue, as this is a very strong adhesive it will stick to the wood strongly.
On the strain gauge I shall attach the second thermo couple device, this way I shall always have a reading of the resistance of the strain gauge.
In order to get the range of temperatures I shall use both an oven and a freezer.
I do not want the wires of the strain gauge to get stretched too much whilst being heated, as this will increase the overall resistance and affect the final results. At high temperatures the wire will expand, and at low temperature they will shrink.
In order to keep the experiment fair, all other factors must be kept constant. Humidity is an important factor that can have an impact on my results, so I shall have to be careful and keep it as constant as possible by not allowing too much water near the apparatus when the experiment is being conducted in the freezer.
In order to get a reliable experiment it would be best to execute this experiment at least 3 times and making an average of the results and using them to make a graph. I will plot a graph of resistance versus temperature for each of the thermocouples to show the resistance at the two points of contact.
For safety I will handle the wood, wires with gloves as they will be very hot after being heated. Also make sure that I connect the wires in the correct way to prevent the malfunction of components.
Reference:
1. http://www.huntsman.com/advanced_materials/Media/Aral_2000_(English).pdf
2. http://en.wikipedia.org/wiki/Cyanoacrylate
