26-02-2013, 10:42 AM
Study of instruments and their symbols
Study of instruments.docx (Size: 11.48 KB / Downloads: 19)
APPARATUS:
•All laboratory instruments
THEORY:
Any device that converts the physical variable of interest into a form that can be recorded
is termed as measuring instrument.
The instrument that records or measures an electrical quantity is called an Electrical
Instrument.
The two major categories of measuring instrument are:
1. Absolute Measuring Instruments
2. Secondary Measuring Instruments
Absolute instruments are those instruments that indicate the quantity to be measured in
terms of the instrument constant. In order to convert these quantities into practical unit it
is necessary to multiply the deflection of such instrument by the instrument constant. No
previous calibrations or comparison is required in this case. The most typical absolute
measured instrument is the tangential galvanometer, which gives the measuring current in
terms of tangent of the deflected angle, the radius and the number of turns of the
galvanometer. Such instrument rarely used today (In laboratories these instruments are
used for standardizing other lab Instrument).
Secondary instruments are those that give the value of the electrical quantities by their
deflection, but only after they have been previously calibrated with the absolute
instrument.
Secondary instruments are further classified into following categories:
1. Indicating instruments
2. Recording instruments
3. Integrating instruments
PROCEDURE:
Note the symbols made on each instrument and study them