The galvanometer refers to a zero-point meter used to check the presence of a small current or a small voltage in the electromagnetic measurement comparison method, or a meter that indicates its magnitude after being temporarily calibrated.
Types of galvanometer
Loop galvanometer
An galvanometer made by the principle of the action of a magnetic field of a permanent magnet on a current-carrying coil. Its main structure has fixed permanent magnets and moving coils. In Figure 1, the moving coil is suspended by a suspension wire (or belt). In addition to providing a small recovery torque, the suspension wire is also used as a lead for the current of the moving coil, and the other lead of the moving coil is a lower spiral at the moving coil. The upper end is equipped with a reflective mirror that uses the reflection of the light to indicate the deflection of the active portion. A scale is installed at a distance from the small mirror, and the narrow beam generated by the small lamp is directed to the small mirror and reflected by the small mirror onto the scale to form a clear cursor to indicate the deflection angle of the movable portion. This galvanometer is highly sensitive, but it is highly susceptible to external vibrations. It should be mounted in a stable position or on a solid wall when used, so it is also called a wall galvanometer. Often used as a balance indicator for sensitive bridges and potentiometers. Generally, the galvanometer mounted on the bridge is essentially a sub-amplifier with a subscript value.
Impulse current meter
Its structural principle is the same as that of a circulator, which can be used to measure the amount of charge that a small transient pulse current migrates. It is widely used in magnetic measurement, and can also be used to measure capacitance and high resistance. The moment of inertia of the movable part of the galvanometer is large, and the free oscillation period is long, and the passage of the pulse current is much shorter than the oscillation period of the ammeter. It can be considered that the current meter only starts after the pulse current flows through the ammeter. deflection. As a result, the amount of pulse charge passed is proportional to the first maximum swing angle. The technical characteristics of the galvanometer are generally explained by the charge amount sensitivity (or the charge amount constant, which is equal to the reciprocal of the charge amount sensitivity) and the oscillation period. The charge amount constant can reach 10-9 banks/division, and the oscillation period can reach 20-30 seconds.
Photoelectric amplification galvanometer
The structural characteristics of the eddy current meter itself and the influence of Brownian motion in the air limit the sensitivity. The photoelectric amplification galvanometer made by the principle of photoelectric amplification can further improve the current sensitivity. The galvanometer constant is 10-11 ampere/division, and it has the advantages of stability, reliability, convenient use, etc., and has been widely used in precision electric measurement technology.
