CP12 Calibrate a Thermistor in a Potential Divider circuit as a Thermostat

Question 1

What equipment is used?

Answer 1

Boiling water (bunsen burner)
Fixed resistor
NTC thermistor
Ohmmeter (around the thermistor)
Beaker
Ice
Stirring rod

Question 2

How?

Answer 2

Boil water
Put thermistor in water
Put ice in water to vary temperature until it reaches close to 0
Stir constantly
Measure the resistance of the thermistor
Make a curve of resistance against time
Use the potential divider formula with the temperature at any given time to calibrate the thermistor

Question 3

Safety

Answer 3

Boiling water/ so don’t handle hot beaker
Do not exceed the voltage limit of the thermistor
Keep leads away from hot things to stop them from melting
Use a heat proof mat

Question 4

Reducing uncertainty

Answer 4

Heat up slowly to allow the semiconductor to adjust to the temperature of the water
Use a data logger with temperature and resistance probes
Measure the temperature at eye level to avoid parallax errors
Make sure that the fixed resistor’s resistance isn’t too high
Use a small current to avoid heating up the system.

Question 5

What formula is used for this experiment?

Answer 5

R =R(0)e^(b/T)