This article provides detailed information about Galvanometers. You can get all the information about the galvanometer from here. The working principle of the galvanometer, theory of galvanometer, parts of the galvanometer, and all uses of galvanometer are explained.
Galvanometers
A Galvanometer is an absolute electronic device that can
accurately measure the amount of current passing through a circuit. It did not
need to be calibrated with any other standard device. This meter is also called
a moving magnetic meter. The angle at which the pointer of this meter moves is
multiplied by the constant Tan of an angle K to find the current passing
through the coil of this meter. Therefore it is called a Tangent galvanometer.
Galvanometer Theory
Suppose there is a circular coil whose number of cycles is
"n" and whose radius is 'r'. If an electric current is passed through
this coil, the magnitude and direction of the magnetic field formed by it will
vary in different places.
The magnetic field in the center of the coil's sphere will
be uniform and perpendicular to the plane of the coil. As shown by the shape
"a”. If a short length of the magnetic needle is placed in the middle of
the coil, so that it can rotate freely on its axis, it will indicate the
direction of the magnetic field. When the current is not passing through the
coil, this magnetic needle aligns itself with the horizontal component
"H" Horizontal of the Earth's magnetic field. This horizontal
component is called the Magnetic Meridian. As shown by figure "b".
(Remember that the earth itself is a great magnet).
 |
| Galvanometer Diagram |
Now, if the current is passed through the coil, the resulting magnetic field will be perpendicular (90) to the ground magnetic field, as shown by figure "c". The force "F" applied by the coil's magnetic field depends on the following.
F = 2Ï€ni / r (Oersted) ........ (1)
In this case, the following two magnetic
forces act on this magnetic needle.
- The magnetic force created by the current passing through the coil
- The magnetic force generated by the horizontal component H of the ground magnetic field
As a result of the interaction of these
two forces, the magnetic needle rotates to a "Ѳ"
angle. The value of this force is as follows.
F = H TanѲ……… (2)
Galvanometer Working Principle
When a magnet is suspended freely in a
magnetic field, the magnetic field forces a magnetic force on the bar magnet,
forcing it to remain parallel (i.e. in alignment). So a magnetic field is
created. Which affects the magnetic needle placed
in the middle of the coil. And she tries to keep it aligned. The horizontal
component "H" of the earth's magnetic field is already aligned by
affecting the magnetic needle (Figure b above). When the two forces on
the magnetic needle (which are at 900 on each other) are permeated, the magnetic
needle rotates to an angle of "Ѳ".
Construction/Parts of Galvanometer
The following figure shows the parts of a
galvanometer. It has a round plastic frame. In the middle of which there is a
groove. In this groove, there are usually three galvanometer coilers consisting
of three turns of insulated copper wire. One of these coils consists of just
one turn of thick wire.
The second coil bar consists of 50 turns
of a single wire while the third coil bar consists of 500 turns of a single
wire. Each coil has its own two terminals. A total of six terminals of these
three coils are made on the front of the instrument. Sometimes there are four
terminals, one of which is common and the other three are used to detect
different amounts of current. The size of the coil wire is kept different so
that different amounts of current can be measured. For measuring high current,
a thick wire with fewer cycles is used and for low current, a single wire coil
with more cycles is used.
 |
| Galvanometers Parts and Construction |
The round frame is mounted on a
horizontal platform so that the coils (including their terminals) can rotate
horizontally at some angles in a circular circle. There is vertical support in
the middle of the gum frame. Above which the horizontal scale of the
galvanometer is applied in such a way that it falls right in the middle of the
coiled round frame. This scale is divided from zero to 900. A short length of
the magnetic needle is pivoted in the middle of the scale. A long pointer is
usually attached to this magnetic needle in such a way that when the magnetic
needle is aligned with the meridian then the pointer is at zero degrees.
Sometimes a mirror is also attached to the center of the galvanometer scale. To
avoid parallax error, a horizontal platform is formed under the vertical
platform. Below are three screwdrivers for leveling the instrument.
How to use a Galvanometer
The galvanometer is first leveled with
the help of adjustable screwdrivers. The frame is then rotated to align the magnetic
needle with the ground magnetic meridian. Then, with the help of a Daniel cell,
the current is passed through the coils of the frame so that the pointer moves
at an angle of less than 90. Now the coil radius "r" is noted from
the galvanometer information data plate. The amount of current is determined in
amperes by applying the number of angles and angles of the previously known
horizontal component "H" in the following formula.
i = 10Hr tanѲ / 2πN.......... in Amperes
Uses of Galvanometers
Galvanometers are used in standard
laboratories for the following purposes:
- For absolute measurement of current
- To measure the horizontal component "H" of the earth's magnetic field at some point.
- For Calibration of Laboratory Standard Instruments
- (Instruments that are used for calibration of common instruments are called laboratory standard instruments.)
Importance of balancing the moving system of instruments
The moving system of Spring Control
Instruments is attached to a spindle and it is the pivot between the jewels. It
is very important to balance the spindle of the moving system. If it is not
balanced then the amount of wear on different parts of the Pivot and Jewel will
vary due to tilting to one side. This way the jewel will penetrate more from
one side. This will cause the spindle to move permanently off its axis of
rotation (as shown by the following shapes and b) and the pointer of the
instrument will not display the correct reading. That is, the reading will not
be reliable. Therefore, the rotating axis of the moving stem of the instrument
must be in the exact alignment of the center of gravity for all the positions
of the pointer.
 |
| Galvanometers G |
See About: Controller Modes
1 Comments
Informative❤️❤️
ReplyDeleteThank You.