Scribd
Upload
987 views3 pages

Digital Voltmeter

Digital voltmeters use analog to digital conversion to measure and display voltages in digital form. There are several types of digital voltmeters including ramp type, integrating type, potentiometric type, successive approximation type, and continuous balance type. Ramp type DVMs work by converting the input voltage to a digital equivalent by measuring the time taken for a ramp wave to decrease from the input voltage to zero. Integrating type DVMs measure the true average value of the input voltage over a fixed period. Potentiometric and successive approximation types employ voltage comparison techniques to compare the unknown voltage to a reference voltage. Continuous balance type DVMs drive a potentiometer arm to zero any difference between the input voltage and a reference,

Uploaded by

Firsts Middles Lasts
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
987 views3 pages

Digital Voltmeter

Digital voltmeters use analog to digital conversion to measure and display voltages in digital form. There are several types of digital voltmeters including ramp type, integrating type, potentiometric type, successive approximation type, and continuous balance type. Ramp type DVMs work by converting the input voltage to a digital equivalent by measuring the time taken for a ramp wave to decrease from the input voltage to zero. Integrating type DVMs measure the true average value of the input voltage over a fixed period. Potentiometric and successive approximation types employ voltage comparison techniques to compare the unknown voltage to a reference voltage. Continuous balance type DVMs drive a potentiometer arm to zero any difference between the input voltage and a reference,

Uploaded by

Firsts Middles Lasts
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 3

Digital Voltmeter (DVM)

- Used to measure the ac and dc voltages and displays the result in


converted digital form with decimal point, polarity, and the unit for V, A,
or Ω.
- Uses ADC conversion techniques to convert analog values to digital
display
Types:

 Ramp type DVM


Principle:
 Input voltage is converted into digital equivalent by counting the
time taken for the ramp wave to decrease from the magnitude of
input voltage to 0V.

Construction:
The block diagram of the Ramp-type ADC can be divided into two
sections as follows:
1. Voltage to time conversion section
2. Time measurement section

 Integrating type DVM


 The voltmeter measures the true average value of the input
voltage over a fixed measuring period.
• In contrast the ramp type DVM samples the voltage at the end of
the measuring period.
• This voltmeter employs an integration technique which uses a
voltage to frequency conversion.
• The voltage to frequency (VIF) converter functions as a feedback
control system which governs the rate of pulse generation in
proportion to the magnitude of input voltage.

 Potentiometric type DVM


• A potentiometric type of DVM employs voltage comparison
technique. In this DVM the unknown voltage is compared with
reference voltage whose value is fixed by the setting of the
calibrated potentiometer.

• The potentiometer setting is changed to obtain balance (i.e. null


conditions).
 Successive approximation type DVM
The successive approximation type DVM is special type of
potentiometric DVM in which a digital divider is used in the place of linear
divider. The servomotor replaced by electromagnetic logic. The
comparator compares the output of digital to analog converter with
unknown voltage. The digital to analog converter successively generates
the sequence of digits. The signal is sent to the output for display, when
the output of digital to analog converter becomes equal to the unknown
voltage.

 Continuous balance type DVM


The input voltage is applied to one side of a mechanical chopper
comparator, the other side being connected to the variable arm of a
precision potentiometer. The output of the chopper comparator, which is
driven by the line voltage at the line frequency rate, is a square wave
signal whose amplitude is a function of the difference in voltages
connected to the opposite side of the chopper. The square wave signal
is amplified and fed to a power amplifier, and the amplified square wave
difference signal drives the arm of the potentiometer in the direction
needed to make the difference voltage zero. The servo-motor also drives
a mechanical readout, which is an indication of the magnitude of the
input voltage.

Advantages of Digital Voltmeters:

 Outputs on the screen are accurate without any errors


 Readings are taken faster
 Parallax error and approximation is entirely eliminated.
 Output can be stored in memory devices
 Versatile and accurate
 Power consumption is less
 Portable instrument
 Cheap cost and compact
Resolution and Sensitivity of Digital Meters

Resolution

If n= number of full digits, then resolution (R) is 1/10n.

The resolution of a DVM is determined by the number of full or active digits used,

Sensitivity is the smallest change in input which a digital meter is able to detect.
Hence, it is the full-scale value of the lowest voltage range multiplied by the
meter’s resolution.

General Specifications of a DVM

You might also like