characteristics of a thermistor

D-and-C-book_098

D-and-C-book_099

Thermistor characteristics

The voltage & current of a thermistor
are measured as its temperature changes. Sensors allow graphs of voltage and current to be plotted against time. Not only can the resistance of the thermistor can be calculated but also the relationship of Ln(temperature) against 1/current.

Apparatus

TH7 thermistor, smoothed power supply, heater/stirring unit, interface, temperature, voltage and current sensors.

Setting up

Connect up the circuit as shown. Connect the current sensor to socket 1, the voltage sensor to socket 2 and the temperature sensor to socket 3.

If the sensors are adjustable, set a 1A range on the current sensor, a 5V range on the voltage sensor and a 0-100 range on the temperature sensor. Some systems recognise the sensors you attach automatically, in others you do this yourself.

You may be able to set up the software to plot the resistance (V / I) against temperature as the experiment proceeds.

Recording the data

Heat the beaker to almost boiling and then allow it to cool. Record for 20 minutes. You may need to do a test run to establish a suitable voltage for the power supply.

Using the results

What does the graph tell you about the change in temperature?

What does the graph tell you about the change in current?

What does the graph tell you about the change in potential difference?

How does the temperature affect the current and potential difference?

Use the software to calculate the resistance (V / I). Try to plot resistance against temperature.

Use the software to calculate Ln (Temperature)

Use the software to calculate 1/Current. Plot this against Ln(temperature).

Save your data on disk. Print the graphs.

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