Wednesday, 14 May 2014

Thermistor resistance dependent on temperature

Two methods of measurement are presented here depending on the equipment you have available.

Equipment

NTC Thermistor
Hot water
Jug of cold water
Beaker
Thermometer
Digital Multimeter (option 1)
Ammeter and Voltmeter (digital or analogue - option 2)
12V d.c. Power supply (option 2)
Connecting leads

Method - Option 1

Connect the thermistor to the multimeter and set to read Ohms.
Immerse the thermistor in hot water in the beaker. Use the thermometer to measure the temperature and record this and the resistance.
Add a small amount of cold water to change the temperature by at least 5 degrees C and repeat the readings.
If you have time repeat the experiment twice more.
See image below for setup.

Method - Option 2

Connect the thermistor and ammeter in series to the power supply (set to 10V). Connect the voltmeter in parallel to the thermistor.
Immerse the thermistor in hot water in the beaker. Use the thermometer to measure the temperature and record this, the current and the voltage..
Add a small amount of cold water to change the temperature by at least 5 degrees C and repeat the readings.
Divide the voltage by the current to find the resistance.
If you have time repeat the experiment twice more.
See image below for setup.

Safety

Care should be taken with the hot water and a stack of paper towels should be kept handy to mop spills up straight away. You should also be aware that hot water can cause scalds so should work standing up to allow you move away quickly if there is a spill. leads should be prevented from wrapping around the beaker causing extra chance of a snag and spill occurring. If performing option 2 extra care should be taken to ensure that the water and power supply are kept as far away from each other as possible.

Option 1 Setup

Option 2 setup