A brief note on Digital Voltmeter

Let’s understand the various components of a digital voltmeter and its working.

• Input Signal – The signal or voltage to be monitored is known as the input signal.
• Pulse Generator – A pulse generator is a voltage source that generates a rectangular impulse using analog, digital, or both methods. The frequency and width of the rectangular pulse are controlled by the controller’s digital circuitry. 
• AND – It produces a high output when both inputs are high. When a train pulse and a rectangle pulse are fed to it, the AND gate produces a train pulse output. They have the same duration as the pulse generator’s rectangular pulses.
• Decimal Display – The decimal display keeps track of the number of impulses and their duration. The voltage value is then displayed on a display screen, which can be LCD or LED, after it has been calibrated.

 The steps are as follows –

1. The pulse generator receives an unknown voltage signal and generates a pulse with a width proportionate to the input signal.
2. One leg of the AND gate receives the pulse generator’s output.
3. A train of pulses is used as the input signal to the AND gate’s opposite leg.
4. The AND gate produces a positive triggered train with the same duration as the pulse generator’s pulse width.
5. The inverter receives this positive triggered train and changes it to a negative triggered train.
6. The inverter’s output is sent into a counter, which counts the number of triggers in a time period proportional to the input signal, i.e. the voltage under measurement.
7. As a result, the counter can be calibrated to directly indicate voltage in volts.

Input Signal →   Attenuator →   ADC  →   Counter  →    Read out System

Based on the above A/D Conversion, there are many types of digital voltmeters such as – Ramp type digital voltmeter, Integrating type voltmeter, Potentiometric type digital voltmeters, Successive approximation type digital voltmeter and Continuous balance type digital voltmeter. 

Digital voltmeters are being phased out in favour of digital multimeters but not completely due to their multitasking capabilities, which include the ability to measure current, voltage, and resistance.

Advantages of digital voltmeter

1. Unlike analog voltmeters, you don’t have to work out the readings manually to acquire the voltage, ohm, or ampere reading.
2. Digital voltmeters display a precise and computer-generated reading on the screen, obviating the possibility of human reading errors.
3. When compared to readings obtained from an analog voltmeter, they deliver accurate and quick results.
4. Digital voltmeters are more steady, dependable, and reliable since they do not require you to make calculations.
5. Unlike analog voltmeters, digital voltmeters produce correct results and do not rely on the readers’ ability to understand them.
6. Digital voltmeters are less expensive and smaller, making them easier to hold and operate.
7. Both AC and DC voltages can be measured with digital voltmeters.
8. Microcontrollers are included in some of the most recent digital voltmeters, allowing you to save readings for later processing.

Disadvantages of digital voltmeter

1. The display of digital voltmeters is dependent on an external battery or power source.
2. Digital voltmeters can overheat while measuring voltage, resulting in inaccurate readings.
3. In the event of fluctuating readings, a digital voltmeter will not be able to quantify the variations and will instead display an incorrect measurement or error. An analog voltmeter, on the other hand, can detect these fluctuations.
4. Digital voltmeters are susceptible to harm if the voltage rises or climbs beyond the limit.
5. Digital voltmeters have a hard time detecting transient voltage spikes.
6. Digital voltmeters have a digitising circuit, which slows down operations.

Voltmeter Vs Multimeter

While a digital voltmeter serves the single purpose of ascertaining voltage, a multimeter is a comprehensive tool that can ascertain not only voltage but also resistance, current, amps, and ohms. Multimeters are often referred to as VOM, which is an abbreviation for Voltage-Ohms-Amperes or DMM, or Digital Multimeter. So, they can be multifunctional, digital and analog, and also accurate, but the limitation is the multimeter price. They tend to be expensive.

Conclusion

Digital voltmeters come with a high resolution and are more programmed than analog voltmeters. They offer more speed of operations and also give an overload indication. Though voltage potential can be ascertained through analog and digital type of voltmeters, they are being replaced nowadays by multimeter. But again, this has not been done completely, it is just a matter of fact that a multimeter is a handy electronic device which serves a comprehensive use not only for voltage but also for current and resistance. The only issue is that of the multimeter price.

DVMs are commonly used to determine whether a circuit, such as a mains outlet, has power and is used to determine the voltage of various components.