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How to design a Temperature to Voltage Converter using Thermistor & 741

Thermistor and 741 Op-Amp IC are used in this simple temperature to voltage converter circuit. The temperature range for this circuit is 0 to 24 degrees Celsius (32 to 75 degrees Fahrenheit). The conversion output rate is 500mV per degree Celsius. Any standard voltmeter can readily interpret the output.

You may precisely measure the room temperature with this simple Temperature to Voltage Converter utilizing Thermistor and 741 circuits. The circuit is powered by a 6V battery. A sensor with a strong temperature dependence is an NTC (Negative Temperature Coefficient) thermistor or a Temperature Variable resistor. If the Thermistor detects a temperature rise in this circuit, the output voltage climbs by 0.5 V every 1 degree Celsius.

The type of thermistor resistance employed determines the temperature to the voltage conversion factor. If you wish to read the temperature directly on a universal measurement device, you’ll need to choose the value of feedback resistor R17 680K to reach the desired sensitivity.

Components Required

  • 741 Op-Amp IC
  • Resistor 10K – 4
  • Resistor 100K – 2
  • Resistor 680K – 1
  • Potentiometer 10K
  • Thermistor 10K
  • Capacitor 0.1uF
  • 6V Power Supply

Temperature to voltage converter circuit using thermistor

The temperature sensed by a thermistor is converted into a voltage level by this temperature to voltage converter circuit. Within a reasonable temperature range, the conversion can be called linear. The thermistor’s features are to blame for the conversion’s nonlinearity. Between 0 and 24 degrees Celsius, the circuit performs well.

What is Thermistor & How do they Work?

Thermistors are thermally sensitive resistors whose primary role is to modify electrical resistance dramatically, predictably, and precisely in response to a change in body temperature.

When exposed to an increase in body temperature, Negative Temperature Coefficient (NTC) thermistors experience a decrease in electrical resistance, while Positive Temperature Coefficient (PTC) thermistors experience an increase in electrical resistance. Thermistors are often regarded as the most advantageous sensor for many applications, including temperature monitoring and control, due to their highly predictable properties and exceptional long-term stability.

Thermistor

The most important feature of a thermistor is its extraordinarily high coefficient of resistance at high temperatures. Modern thermistor technology produces devices with exceptionally exact resistance versus temperature properties, making them the best sensor for a wide range of applications.

Temperature to Voltage Converter Circuit using Thermistor & 741

The following is a circuit diagram for the Temperature to Voltage Converter Project that has been thoroughly tested. You may either put the circuit together on a breadboard or create a PCB for it.

Temperature to Voltage Converter

The 741 Op-Amp IC is used as the difference amplifier. There are inputs as a bridge circuit, with R11 to TH1 and constant arms of the bridge at R11, R12, R13, and PR1. Bridget’s fluctuating values are controlled by the thermistor TH1.

At 0 degrees Celsius, the voltage across R11 and R12 is roughly 3.4V. The PR1 is set to 0V at the output of the op-amp. There are NTC circumstances in which the resistance of the NTC decreases at increasing temperatures and the voltage drop across the NTC decreases. Increasing the voltage of the Op-output.  The NTC is a standard thermistor with a resistance of 10K, but the values of R13 and PR1 can be changed to make it proportional.

How Do you calibrate the temperature to the voltage converter circuit?

We lower the thermistor temperature to 0°C to achieve a 0-volt output, then tweak the RV1 potentiometer to confirm that the output voltage is accurate.

741 Op-Amp Pin Configuration and Function

Conclusion

I hope you understand how to design a Temperature to Voltage Converter using Thermistor & 741. We MATHA ELECTRONICS will be back soon with more informative blogs soon.

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