Digital voltmeter project

My first project during my Engineering days!

1. DIGITAL
VOLTMETER WITH
LED DISPLAY.
By Kaushik Bandopadhyay
NSEC, BME.

2. What is a Voltmeter?
A Voltmeter is an instrument used for
measuring the electrical potential
difference between two points in an
electrical circuit.
Technically speaking, all voltmeters are
basically ammeters (device that measures
current in an electrical circuit), as they
measure current rather than voltage.

3. What’s so special being
“Digital”?
General purpose analog voltmeters may have an
accuracy of a few percent of full scale, and are
used with voltages from a fraction of a volt to
several thousand volts. Digital voltmeters can be
made with high accuracy, typically better than
1%. Specially calibrated test instruments have
higher accuracies, with laboratory instruments
capable of measuring to accuracies of a few
parts per million!

4. CLASSIFICATION OF VOLTMETERS
Voltmeters can be classified as:
1) Analog Voltmeter
2) Digital Voltmeter
3) Electrostatic Voltmeter
4) Oscilloscope Voltmeter
5) Micro-Voltmeter
6) Vacuum Tube Voltmeter
7) Solenoid Voltmeter

5. DIGITAL VOLTMETER
Digital Voltmeter is an electronic testing
equipment that is used for measuring the
electrical potential difference between two
conductors in a circuit.
 Andrew Kay invented and produced the
first digital voltmeter in 1954.

6. Advantages of Digital Voltmeter
Digital format display aids visual
convenience.
They are very accurate and have high
resolution
They are robust and precise than their
analog counterparts.

7. Classification of Digital
Voltmeter
On the basis of analog-to-digital converter
(ADC) used the digital voltmeter, digital
voltmeters can be classified into the following
four broad categories:
Ramp-type digital electronic voltmeter.
Integrating-type digital electronic voltmeter.
Continuous-balance or Servo-balance digital
electronic voltmeter.
Successive-approximation digital electronic
voltmeter.

8. DIGITAL VOLTMETER WITH LED
DISPLAY
A standard Digital Voltmeter is discussed which
can be used in DC power supplies. The circuit
employs the ADC (Analog to Digital Converter)
I.C. CL7107. This IC incorporates in a 40 pin
case and the circuitry necessary to convert an
analog signal to digital and can drive a series of
four seven segment LED displays directly.

9. FEATURES
Salient Features of the DVM:
Small size
Easy construction
Low cost
Simple adjustment
Easy to read from a distance
Few external components

10. Salient Features of the IC L7101:
Great accuracy.
It is not affected by noise.
No need for a sample and hold circuit.
It has a built-in clock.
It has no need for high accuracy external
components.

11. Technical Specifications
Supply Voltage (Symmetrical) : +/- 5 V
Power requirements (maximum) : 200 mA
Measuring range: +/- 0 to 1,999 V DC in
four ranges.

Accuracy: ....................... 0.1 %

12. Circuit diagram of the DVM

13. CONCLUSION
The versatility, accuracy, precision, robustness of Digital electronic
devices cannot be matched with that of Analog devices as the
former ones are far more superior. Digital Voltmeter is a very simple
example of a digital electronic device, science today has expanded
by leaps and bounds for the better and has given us an array of
devices based on digital electronics which otherwise would not have
been possible if Man had held on to his analog knowledge and its
limited application. One still should not undermine the power and
concept which analog electronics has ushered upon our minds
when we started our initial steps in the electronics/electrical world. It
has impregnated its basic principles into our minds which should
never be forgotten. Science will continue its exponential progress in
this millennium with its digital facet blazing and we hope to enlighten
ourselves with inventions and technologies that will come across us.