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# Investigate the variation of the resistance of a thermistor with different temperatures.

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Introduction

Kiron Nandhra 12KFA

Sensor Project

Introduction

For this experiment I am going to investigate the variation of the resistance of a thermistor with different temperatures. The resistance will be tested at every 5 degrees, with a range from 90 C down to 5 C, and these results will be recorded. After recording the results, the experiment will be repeated at a total of 3 times, this is so we can get an average that should be correct and accurate.

Plan: Sensor circuit

The following below, are what are needed for me to complete my task:

• One thermistor
• Digital multi-meter with a setting to read resistance in Ohms to 2 decimal places

The sensor circuit’s purpose is to sense the change in temperature in a domestic water tank. For example it will be able to sense and recognise when the water is very close to boiling point and if it has dropped to close to freezing point. If it gets to hot, the sensor would cause the heater to be switched off. If it gets too cold, the sensor would cause the heater to be switched on, so avoiding the risk of burst pipes due to freezing. On separate circuits there will be many thermistors flooded in the water at different points, so we are able to find an overall temperature in the tank.

Middle

Hypothesis

I predict, therefore that the resistance in any experiment will rise as the temperature of the water falls.

Results

 Temperature Resistance Resistance Resistance Resistance (C) (Ohms) (Ohms) (Ohms) (Ohms)

Conclusion

To improve this, we would use an Amplifier, which alerts the danger much faster. A thermistors response time is usually slow, however, with the aid of an Amplifier, problems will be alerted much sooner. It works by sensing on small changes in resistance through the thermistor. The amplifier then picks up on this, then amplifying the current at a much faster speed so the circuit responds quicker. When the temperature exceeds 65 C or drops below 25 C, my circuit will recognise this and respond by passing the information to an additional circuit, which will respond by cooling or heating the water. Heating if below 25 C, or cooling if above 65 C.

My circuit would look like this. It’s a circuit from ‘Advancing Physics A1, IOP Publishing’

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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