DIGITAL VOLTMETER WITH LED DISPLAY.By Kaushik Bandopadhyay

NSEC, BME.

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.

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!

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

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.

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.

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.

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.

FEATURES

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

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.

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 %

Circuit diagram of the DVM

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.