Potentiometric type dvm, Electrical Engineering

Potentiometric type DVM: A potentiometric type of DVM, employs voltage comparison technique. In this DVM the unknown Voltage is compared with a reference voltage value is fixed by the setting of the calibrated potentiometer. The potentiometer setting is changed to obtain balance (i.e. null condition).When null conditions are obtained the value of the unknown voltage, is indicated by the dial setting of the potentiometer.

In potentiometric type DVMs, the balance is not obtained manually but is arrived at automatically. Thus, this DVM is in fact a self-balancing potentiometer .The potentiometric DVM is provided with a readout which displays the voltage being measured.

The block diagram of basic circuit of a potentiometric DVM is shown in.

The unknown voltage is filtered and attenuated to suitable level. This input voltage is applied to a comparator (also known as error detector). This error detector may be chopper. The reference voltage is obtained from a fixed voltage source. This L voltage is applied to a potentiometer R. The value of the feedback voltage depends upon the position of the sliding contact; the feedback voltage is also applied to the comparator.

The unknown voltage and the feedback voltages are compared in the comparator. The output voltage of the comparator is the difference of the above two voltages. The difference of voltage is called the error signal. The error signal is amplified and is fed to a potentiometer adjustment device which moves the sliding contact of the potentiometer. This magnitude by which the sliding contact moves depends upon the magnitude of the error signal. The direction of movement of slider depends upon whether the feedback voltage is larger or the input voltage is larger. The sliding contact moves such a place where the feedback voltage equals the unknown voltage. In that case, there will not be any error voltage and hence here will be no input to the device adjusting the position of the sliding contact and therefore it (sliding contact) will come to rest. The position of the potentiometer adjustment device at this point is indicated in numerical form on the digital readout device associated with it. Since the position at which no voltage appears at potentiometer adjustment device is the one where the unknown voltage equals the feedback voltage, the reading of readout device indicates the value of unknown voltage. The reference voltage source must be extremely stable and generally consists of a standard cell or a Zener diode sources.

 

Posted Date: 7/12/2012 6:12:33 AM | Location : United States







Related Discussions:- Potentiometric type dvm, Assignment Help, Ask Question on Potentiometric type dvm, Get Answer, Expert's Help, Potentiometric type dvm Discussions

Write discussion on Potentiometric type dvm
Your posts are moderated
Related Questions
The rectangular pulse train of Figure (a) consists of pulses of height A and duration D. Such pulse trains are employed for timing purposes and to represent digital information. Fo

Since past few decades, telecommunication systems are continuously evolving from 2G to 3G to 4G etc. This has resulted in multiple technologies and many types of receivers which do

Q. What do you understand by common control? In some switching systems, control subsystem may be an integral part of switching network itself. Such system iscalled direct contr

Q. A certain 10-hp, 230-V motor has a rotational loss of 600 W, a stator copper loss of 350 W, a rotor copper loss of 350 W, and a stray load loss of 50 W. It is not known whether

Q. Define Memory For a digital computer? For a digital computer which stores both programs and data, memory can be divided into three types: random-access memory, mass storage,

Normal 0 false false false EN-IN X-NONE X-NONE

Power Distribution System The Distribution System contains: - Sub-transmission system in voltage ranges from 33 kV to 220 kV. The energy goes from power subs

Q. Show that any amplifier represented by the model of Figure of the text can also be represented by themore general hybridmodel of Figure. Evaluate the four parameters of the hybr

The goal of this project is to model a system and to design a controller for the system so that the closed-loop system performs satisfactorily.

when i/p voltg is grater than battery diode is clse or open