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Digital Voltmeter

Digital voltmeters measure voltage through an analog to digital conversion process. They were first invented in 1954 and offer advantages over analog voltmeters like increased accuracy, readability, speed, and portability. A digital voltmeter works by attenuating the input voltage, converting it to a digital signal via an ADC, counting the digital pulses with a counter, and displaying the numeric output on a digital readout. Digital voltmeters can be classified based on their ADC conversion method, such as ramp-type, dual slope integrating type, or successive approximation type.

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173 views7 pages

Digital Voltmeter

Digital voltmeters measure voltage through an analog to digital conversion process. They were first invented in 1954 and offer advantages over analog voltmeters like increased accuracy, readability, speed, and portability. A digital voltmeter works by attenuating the input voltage, converting it to a digital signal via an ADC, counting the digital pulses with a counter, and displaying the numeric output on a digital readout. Digital voltmeters can be classified based on their ADC conversion method, such as ramp-type, dual slope integrating type, or successive approximation type.

Uploaded by

Nazma
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Digital Voltmeter

Digital Voltmeters (DVM)


• Digital Voltmeter is a voltage sensitive device.
• It measures AC or DC voltage and displays the value
directly in numeric form instead of pointer
deflection.
• DVM was first invented in 1954 by Andrew Kay.
Block Diagram of Digital Voltmeter

• The block diagram consists of attenuator with an


analogue to digital converter after it.
• The ADC unit basically distinguishes between various
types of Digital Voltmeters.
• A counter section is also employed in the circuitry that
is usually a decade counter.
• The read-out system is used to display the digital
voltage of the input signal.
Working of Digital Voltmeter
• Let us now have a look at the detailed diagram of a Digital Voltmeter.

• The attenuator section consists of a series resistance that attenuates the input
signal. The voltage at point A will be exactly same as the input voltage Vin.
• By voltage division rule it is clear that voltage at B will be less than the voltage at A.
Similarly, the voltage at C will definitely be less than the voltage at both the points A
and B. So, in this way an attenuator section works.
• The attenuator minimizes the excess voltage that can damage the other
components of the device. It is basically a predefined resistive network that
performs attenuation for circuit protection.
• Here, the attenuation is termed as decade attenuation. That means if attenuation
occurs it will be in powers of 10. (N = 10, 100, 1000)
• So, at the input of ADC, we will have Vin/N as the input voltage.
• The ADC employed in the circuit converts analogue signal into
digital one in order to provide the digital output. A digital signal is
the one having 2 levels i.e., 0 and 1.
• So, the input at ADC Vin/N gets converted into digital signal. This will
provide a sequence of digital pulses. One pulse for 1 mV as at the
ADC we have taken resolution as 1 mV/step.
• These digital pulses are then fed to the counter unit. Here, we have
used a decade counter. A decade counter counts in decimal.
• The counter unit on a whole consist of 3-decade counters that are
cascaded together. These decade counters have the ability to count
from 0-9 i.e., 10 counts. Hence the three will count up to 1000.
• IC 7447 converts the BCD value into 7 segment display. That means
now the input value will be displayed here in digital format. The
decimal point selector at the end of the circuit will select the
position of decimal according to the magnitude of the voltage.
Types of Digital Voltmeter
• The classification of DVM is based on different
ADC conversion methods-

(a)Ramp-type DVM
(b)Dual Slope Integrating type DVM
(c) Integrating type DVM
(d) Successive-approximation type DVM
Advantages of Digital Voltmeter
• DVM provides numerical readouts that eliminate
observational errors. Thus providing better
readability.
• DVM offers better accuracy and versatility as
compared to analogue voltmeters.
• DVM has a greater speed of taking voltage
readings as compared to analogue instruments.
• The decreased size of DVM increases the
portability.

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