Project Report: Temperature
Monitoring System with ADC Interface
1. Introduction
This project presents a prototype temperature monitoring system that senses ambient
temperature and converts it into a digital signal for monitoring and control. The system
includes five key stages: measurand, sensing element, variable conversion, variable
manipulation, and analog-to-digital conversion (ADC). The chosen application demonstrates
how environmental temperature is measured using a thermistor and processed using
Arduino's built-in ADC.
2. System Block Diagram
1. Measurand (Temperature)
2. Sensing Element (NTC Thermistor)
3. Variable Conversion (Voltage Divider)
4. Variable Manipulation (Op-Amp Amplifier or Filter)
5. ADC (Arduino Uno)
6. Digital Output (Serial Monitor or Display)
3. Component Explanation
**3.1 Measurand**
The physical quantity measured in this project is ambient temperature. The expected range
is 0°C to 100°C.
**3.2 Sensing Element: Thermistor**
A Negative Temperature Coefficient (NTC) thermistor is used. Its resistance decreases with
increasing temperature. This property allows temperature measurement through
resistance variation.
**3.3 Variable Conversion: Voltage Divider**
The thermistor is part of a voltage divider circuit that converts resistance changes to
voltage changes, which can then be read by an analog input.
Voltage Divider Formula:
Vout = Vcc * (R_thermistor / (R_thermistor + R_fixed))
**3.4 Variable Manipulation: Operational Amplifier (optional)**
An op-amp can be used to amplify or filter the output signal from the voltage divider to
ensure it fits within the 0-5V range required by the Arduino's ADC.
**3.5 Analog to Digital Conversion (ADC)**
The Arduino Uno has a 10-bit ADC which converts the analog signal (0-5V) into a digital
value ranging from 0 to 1023. This digital value is then used to estimate the temperature.
4. Circuit Design
- Thermistor connected in a voltage divider configuration with a fixed 10kΩ resistor.
- The midpoint is connected to Arduino analog pin A0.
- Optionally, an op-amp is used for signal conditioning.
5. Arduino Code
const int thermistorPin = A0;
float adcValue, voltage, temperature;
void setup() {
Serial.begin(9600);
}
void loop() {
adcValue = analogRead(thermistorPin);
voltage = (adcValue / 1023.0) * 5.0;
// Example conversion
temperature = (voltage - 0.5) * 100;
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.println(" °C");
delay(1000);
}
6. Results and Discussion
This prototype successfully monitors temperature by converting analog voltage from a
thermistor into a digital value using the Arduino’s ADC. Experimental results align with
expected trends where voltage decreases as temperature increases. The linear
approximation used provides a rough estimate, and accuracy can be improved through
calibration or by using the Steinhart-Hart equation.
7. Conclusion
The project demonstrates a simple yet effective temperature monitoring system using a
thermistor and Arduino. It covers the full sensor signal chain: measurand, sensing,
conversion, manipulation, and digital conversion. Future improvements can include
wireless transmission of data, improved sensor calibration, and adding a graphical display.
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Prepared for: [Insert Your Course Name]
By: [Insert Student Name & Reg No.]
Date: [Insert Date]
