Advantages of Electronic Voltmeter


I. ADVANTAGES OF ELECTRONIC VOLTMETERS:


The following are the advantages of electronic voltmeter over conventional (ordinary) voltmeter:

(a) There is no circuit loading on voltage measurement.
(b) They have high sensitivity due to high input impedance.
(c) They have burnout resistance meter circuit.
(d) They have wide range of frequency response.
(e) When used as electronic test meters they offer wide range of resistance measurement.
(f) They are accurate and are dependable.

II. ADVANTAGES OF TRANSISTORIZED ELECTRONIC VOLTMETERS: 


Earlier versions of electronic voltmeters used vacuum tubes. Present day, electronic test instruments including electronic voltmeters use integrated circuits. The use of semiconducting devices has the following advantages:

(i) When semiconducting devices like transistors and integrated circuits are used, there is saving of the heating power as these do not require any heating power for their functioning.
(ii) The semiconducting devices are small in size. Hence compact instruments can be designed and manufactured.
(iii) The power supply requirements of the semiconducting device operated electronic voltmeters are not rigid. Low voltage battery operation is possible. They can be operated either from mains or using batteries.
(iv) They can be switched on for reading, hence there is no warming time.
(v) They can be used for accurate measurements under complicated conditions such as presence of ground loops. As they can be operated from batteries directly this is possible.
(vi) They are best suited for field work.

III. Factors to be considered in choosing a device for the Electronic Voltmeter:


(i) The input impedance of the device.
(ii) The output impedance of the device.
(iii) The frequency range in which the device can operate.
(iv) The stray capacitance and inductance of the device.
(v) The noise of the device.
(vi) The transit time.

The input impedance of the device must be very high. The output impedance also is to be moderate. The device should operate in the frequency range of usage. It should offer minimum stray capacitance and inductance. The device should present minimum noise. The transit time must be as small as possible. The maximum and minimum operating electrode voltages are in addition to the above factors are most important. They determine the design conditions and component values.

IV. Advantages of Using FETs in Electronic Voltmeters:


The following are the advantages in using FETs in electronic voltmeters:

(i) They offer very high input impedance of the order of several mega ohms.
(ii) The noise generated by a FET, is small compared to the noise generated by BJTs.
(iii) There is no offset voltage at zero drain current.
(iv) They are less effected by radiation.
(v) They have good thermal stability.


No comments:

Post a Comment