Short Answer:

A digital voltmeter (DVM) works by converting an analog voltage signal into a digital value using an analog-to-digital converter (ADC). The measured voltage is first processed through electronic circuits and then displayed as numbers on a digital screen, usually in volts or millivolts.

Unlike analog voltmeters, which use a moving needle, a digital voltmeter provides clear and precise readings. It is commonly used for measuring both AC and DC voltages and is preferred for its accuracy, speed, and ease of use in modern electrical and electronic systems.

Detailed Explanation:

How digital voltmeter works

A digital voltmeter (DVM) is an instrument used to measure voltage and display the result in numeric form on a digital screen. It is widely used in laboratories, industries, service centers, and by electronics hobbyists due to its accuracy, portability, and fast response. The main function of a DVM is to take an analog voltage input and display the corresponding voltage value in digits using digital circuits.

Basic Principle:

The working of a digital voltmeter is based on the conversion of analog voltage into a digital value. This is done using an internal circuit called an Analog-to-Digital Converter (ADC). The ADC compares the input voltage with a known reference and generates a binary number that represents the voltage. This binary number is then decoded and shown as a readable voltage on the screen.

Step-by-Step Working Process:

1. Input Voltage Application:
   The voltage to be measured is applied to the input terminals of the DVM. This voltage can be DC or AC, depending on the DVM type.
2. Signal Conditioning:
   Before converting, the input voltage may go through conditioning circuits such as attenuators (to reduce voltage), amplifiers (to boost low voltage), or filters (to remove noise). This prepares the signal for accurate conversion.
3. Analog to Digital Conversion (ADC):
   The conditioned analog voltage is sent to the ADC. The ADC compares the input voltage with a reference voltage and assigns a digital value to it based on the comparison. There are different types of ADCs like successive approximation, dual slope, and flash type.
4. Digital Processing:
   The digital value from the ADC is processed by a microcontroller or logic circuit that calculates the actual voltage and formats the output.
5. Display:
   The processed voltage value is sent to a digital display, often a seven-segment or LCD screen, where the reading is shown in volts or millivolts.
6. Additional Features (in advanced DVMs):
   Many DVMs offer features like auto-ranging (automatically selecting the appropriate range), data hold (freeze the last reading), and overload protection.

Advantages of Digital Voltmeters:

• High Accuracy: Less human error due to digital readout.
• Fast Response: Quick measurement of changing voltages.
• Portability: Battery-powered models are easy to carry.
• Wide Range: Can measure from microvolts to kilovolts.
• Multifunction: Many DVMs also measure current, resistance, frequency, etc.

Limitations of Digital Voltmeter:

• Requires Power Supply: Cannot operate without battery or external power.
• Sensitive to Overvoltage: May get damaged if exposed to voltages beyond rated limit.
• Affected by EMI/Noise: In noisy environments, readings may fluctuate unless shielded properly.

Applications of Digital Voltmeter:

• Used in electronics labs for testing components and circuits.
• Helpful in home electrical maintenance.
• Common in industrial systems for equipment monitoring.
• Built into multimeters used by technicians and engineers.

Conclusion

A digital voltmeter works by converting analog voltage into a digital value using an ADC and displaying it as numbers on a screen. This allows fast, accurate, and easy measurement of voltage in both DC and AC circuits. Due to their reliability and ease of use, digital voltmeters have become essential tools in all fields of electrical and electronic work.