Pradctical- 12 :- Experiment to Identify and Test Thermistors ( NTC , PTC )

 

Aim :- How to Identify and Test Thermistors

1. Safety First: Ensure the thermistor is disconnected from any powered circuit before you begin.

2. Initial Resistance Measurement:

   • Set your multimeter to measure resistance in ohms (Ω).

   • Connect the probes of the multimeter to the thermistor's leads.

   • Record the resistance reading at room temperature (approximately 25°C). 

1. Apply Heat:

   • Use a heat source like a heat gun, soldering iron, or even just your fingers to gently warm the thermistor.

2. Observe Resistance Change:

   • NTC Thermistor: If the resistance reading on your multimeter decreases as the temperature of the thermistor increases, it's an NTC type. This is because NTC thermistors are designed so their resistance is inversely proportional to temperature.

   • PTC Thermistor: If the resistance reading on your multimeter increases as the temperature of the thermistor increases, it's a PTC type. PTC thermistors are used as resettable fuses because they can quickly increase their resistance to limit current flow when a certain temperature is reached.

3. Record and Analyze: For a more formal experiment, you can use a thermometer to measure the temperature at various points and record the corresponding resistance values. Plotting a graph of resistance vs. temperature for both thermistors will visually demonstrate their distinct characteristics.


The experiment demonstrates the fundamental characteristic that differentiates NTC and PTC thermistors: their temperature coefficient. NTC thermistors have a negative coefficient, while PTC thermistors have a positive one.