A Voltmeter or a Voltage Meter is a measuring instrument that is used for measuring voltage or potential difference between two points in a circuit. Voltmeters are an important piece of equipment that is associated with any kind of electronics project. They are used in the measurement of both AC and DC voltages.
Voltmeters are again classified into two types namely Analog Voltmeter and Digital Voltmeter. Analog Voltmeter consists of a pointer that moves across a scale and the movement is proportional to the voltage measured.
Analog Voltmeters are further classified based on their principle of construction. Some of the commonly known analog voltmeters are Permanent Magnet Moving Coil Voltmeter, Rectifier Type Voltmeter, Electrostatic Type Voltmeter, Moving Iron Type Voltmeter etc.
Analog Voltmeters generally have an error percentage of 5% and the parallax error is often an issue. But analog voltmeters can be used to measure ranging from few volts to several thousand volts.
To overcome the defects of analog voltmeters, Digital Voltmeters are introduced. Unlike analog voltmeters, which scale and a pointer to show the measured voltage, digital voltmeters directly display the measured voltage numerical on a digital display.
The percentage of error in digital voltmeters is usually less than 1% and the accuracy can be increased in precision digital voltmeters with high-speed measurement and the option of storing the values in memory.
In this project, an Arduino based Digital Voltmeter which can measure voltages up to 50V is designed.
The aim of the project is to build a digital voltmeter using Arduino UNO. The components required and the construction of the project is very simple. The working of the project is explained here.
In a digital voltmeter, the voltages to be measured, which are in analog form, are converted to digital form with the help of Analog to Digital Converters (ADC). Hence, the ADC feature of the Arduino UNO is utilized in this project.
In the first circuit, which is used to measure a maximum voltage of 5V, the input voltage is given to the analog input pin of the Arduino. The reference voltage of the ADC is 5V. The ADC in Arduino UNO is of 10-bit resolution. Hence, the input voltage is calculated by multiplying the analog value at the analog pin with 5 and dividing the value with 210 i.e. 1024.
The range of voltages for Arduino UNOs analog input is 0V to 5V. Hence, in order to increase this range, a voltage divider circuit must be used.
In the second circuit, the range of the analog input of Arduino UNO is increased up to 50V by using a voltage divider consisting of 100KΩ resistor and 10KΩ resistor. With the help of the voltage divider circuit, the input voltage being measured is brought down to the range of Arduino UNOs analog input.
The rest of the calculations are made in the programming part of the Arduino UNO.
For circuit diagram and Arduino code check this link DIY Simple Arduino Digital Voltmeter 0V-50V