I have been assigned the task to test and evaluate a sensor. The sensor I have chosen is a temperature sensor.

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Alex Willcocks

Sensing Coursework

        I have been assigned the task to test and evaluate a sensor. The sensor I have chosen is a temperature sensor. The sensor is a potential divider circuit. It consists of a power supply of e.m.f 2V, a variable resistor and a 15KΩ (ptc) thermistor. I will vary the resistance of the variable resistor to see if this will affect the sensitivity of my sensor.

   

        

To test my sensor I will measure the potential difference across the thermistor at varying temperatures. I will do this using a multimeter, connecting it in parallel across the thermistor. As it is a positive temperature coefficient (p.t.c.) thermistor I will expect the potential difference to increase as the temperature decreases.

 

These results were taken using a power supply with e.m.f. of 2.00V and the variable resistor at 1KΩ

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These results were taken using a power supply of e.m.f. 2.00V and the variable resistor at 1MΩ

These results were taken using a power supply of e.m.f. 2.00V and the variable resistor at 2MΩ

        For all values of the variable resistor my results fit the general expected pattern, the potential difference across the thermistor will increase as the temperature decreases. For each of the experiments I have drawn a scatter graph for the potential difference against the temperature and then drawn in a line of best fit. I have used excel to work out the equation ...

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