PL190436B1 - Highly sensitive d'arsonval galvanometer - Google Patents

Abstract

1. A magnetoelectric galvanometer, containing an induction coil located in a magnetic field, suspended on a thin thread equipped with a mirror and fixed to a spring. It is characterised in that the inductive coil (1) is fixed to a float (4) immersed in a liquid (3), while the spring (6) rests against the tip of the regulating screw (7).

Description

The subject of the invention is a magnetoelectric galvanometer, used in particular for measuring very low currents, or as a neutral instrument.

There is known a magnetoelectric galvanometer having an induction coil in the form of a frame in a magnetic gap. The coil is suspended on a very thin phosphor-bronze thread, which is connected to a flat spring with its other end, fixed at its free end. Thin phosphor-brown threads are characterized by a small steering moment D, causing it to twist, as this moment decreases with the fourth power of the thread radius. The twist angle of the thread is read by the light reflected from the mirror located at the end of the thread. The galvanometer sensitivity C also depends on the magnetic induction B, the number of turns N and the surface S of the induction coil according to the relationship:

C = BNS / D

The value of the magnetic induction B is limited by the properties of magnetic materials and for the best it does not exceed 1 T. When using the thinnest copper wire from which the most suitable inductor can be made, the number of turns N and their area S cannot be increased further due to the increase in the weight of the coil, which causes increase in the thickness of the phosphor-brown thread so that it does not break, under the weight of the inductor. An increase in the thickness of the phosphor-brown thread causes an increase in the steering moment D and a decrease in sensitivity.

The known solutions do not allow increasing the sensitivity.

The essence of the solution according to the invention consists in the fact that the induction coil is connected with a float immersed in the liquid, and the spring rests on the end of the adjustment screw. The liquid, preferably mercury, is contained in the cavity of the ferromagnetic core constituting the core around which the induction coil is wound. The induction coil is situated in the magnetic gaps between the poles of opposite polarity, formed between the poles of a permanent magnet and two additional magnetic cores located opposite the magnetic poles of the ferromagnetic core.

The invention is characterized in that the sensitivity of the galvanometer according to the invention is increased by at least an order of magnitude.

The subject matter of the invention is illustrated in an embodiment in the drawing which schematically shows the mechanism of a highly sensitive magnetoelectric galvanometer in side view.

190 436

The galvanometer has an induction coil 1 suspended on a Wollestone 5 thread connected at its other end to a flat spring 6. The other end of the spring 6 is fixed. The induction coil 1 in the form of a rectangular frame is mounted on a float 4 that floats freely in the liquid 3, which is mercury. The liquid 3 is in the cavity of the ferromagnetic core 2 in the form of a permanent magnet, constituting the core around which the induction coil 1 is wrapped. On both sides of the induction coil 1 there are additional ferromagnetic cores 2a with magnetic poles opposite to the poles of the ferromagnetic core 2 and opposite the poles magnetic core of the ferromagnetic core 2. Thus, the induction coil 1 is positioned in the magnetic gap with opposite poles. The spring 6 rests in its central part on the end of the adjustment screw 7.

The thread 5, through the screw 7 and the spring 6, is slightly taut so that the thread 5 is in the optimal range of its tension. The mirror 8 located at the end of the thread reflects the light, which is used to read the angle of rotation of the inductor 1.

According to the formula below, the sensitivity of the galvanometer C is:

C = BNS / D where:

B - magnetic induction value,

N - number of turns,

S - entrusting the coil of the induction coil 1,

D - thread steering moment proportional to their thickness.

The weight of the coil 1 has been balanced by the buoyancy force obtained by the liquid 3 and the float 4, which makes the number of turns N and their surface S can be increased by many orders of magnitude, and therefore the sensitivity of the galvanometer C is increased to the same extent. .

Due to the fact that the vibration period of the galvanometer is very long, it is used to study very subtle, slowly changing electrical phenomena.

190 436

Publishing Department of the UP RP. Circulation of 50 copies. Price PLN 2.00.

Claims (3)

Patent claims 1. A magnetoelectric galvanometer containing an induction coil situated in a magnetic field, suspended on a thin thread equipped with a mirror and connected to a spring, characterized in that the induction coil (1) is connected to a float (4) immersed in the liquid (3), and the spring ( 6) rests on the end of the adjustment screw (7). 2. The galvanometer according to claim A process as claimed in claim 1, characterized in that the liquid (3), preferably mercury, is contained in a cavity of the ferromagnetic core (2) constituting the core around which the induction coil (1) is wound. 3. The galvanometer according to claim 1 1 or 2, characterized in that the induction coil (1) is located in the magnetic gaps between the poles of opposite polarity, formed between the poles of the permanent magnet (2) and two additional magnetic cores (2 a) located opposite the magnetic poles of the ferromagnetic core (2) .