Characteristics of a thermistor

Experiment to determine the characteristics of a thermistor.

1. SENSORS AND INSTRUMENTATIONS


Aim: To determine the characteristics of a Thermistor.
Components Used:
1.Thermistor
2.Resistor (22 ohm)
3.Breadboard
4.Battery 9V
5.Connecting wires
6.Multimeter


Procedure followed:
1. We first took a 22-ohm resistance and a thermistor with unknown resistance.
2. With the help of multimeter we first found out the resistance of thermistor at room
temperature.
3. Then we set up circuit on bread board as given in the circuit diagram.
4. We then found out the output voltage across the known resistance by changing the
thermistor temperature.
Note: We changed the thermistor resistance first by touching it with cold water to
decrease the temperature and then we rubbed it to increase the temperature.
5. Then using the known formulas, we found out the thermistor resistance and
temperature.

2. Circuit Diagram:






Formula used for temperature:



Results:

3. We took Rb = 22ohms, for the thermistor taken we have B = 4190K.

For decreasing temperature:

Vin(V) Vout(V) Ra(ohms) Temperature(K)
9 0.0032 61854.37 299.6
9 0.0030 65978.00 298.5
9 0.0023 86058.26 293.25


For increasing temperature:
Vin(V) Vout(V) Ra(ohms) Temperature(K)
9 0.0034 58233.09 301.2
9 0.0037 53491.51 302.7
9 0.0040 49478.00 304.4
Graphs:




Inferences:
0
1
2
3
4
5
6
7
8
9
10
292 294 296 298 300 302 304 306
R(Ω)*10^4

4. From the observed trend from the table as well as from the graph we found that as the
temperature increases or decreases, the corresponding resistance also increases or decreases
respectively. Therefore, it is a P.T.C (Positive Temperature Coefficient) Thermistor.