JPH0268829A - Lead relay for micro-signal - Google Patents

Abstract

PURPOSE:To make it possible to reduce or completely eliminate the leak current flowing over the surface of an insulation sleeve by forming a conductive layer on the external surface of the insulation sleeve, and installing a power source means to equalize the potential of the conductive layer with that of a lead switch contact point. CONSTITUTION:Conductor belts 3, 4 for guard having lead wires 9, 10 are wound around the surface of insulation sleeves 7, 8 in a way not to leave any gap between them respectively. The conductor belt 3 and a relay contact point 5 and the conductor belt 4 and a relay contact point 6 are respectively maintained at a same potential by applying a voltage of a same potential to the lead wires 9, 10 and relay contact points 5, 6. Since electric current does not flow between two conductors with the same potential, any leak current from a contact point lead 12 does not flow to the surface of the insulation sleeve 7. Similarly, no leak current flows from the contact point lead 13 to the surface of the insulation sleeve 8 which is held between the conductor belt 4 and the relay contact point 6. This enables to reduce the flow of leak current from contact points to the surface of insulation sleeves of relays.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a reed relay for minute signals, and in particular, to reducing leakage current flowing through the surface of an insulating sleeve of a reed switch and reducing thermoelectromotive force generated at the joint of dissimilar metals. This invention relates to a reed relay for minute signals that reduces fluctuations.

[Conventional technology]

As a conventional reed relay, for example, JP-A-57-76
There is one shown in Publication No. 730. This reed relay has an electrostatic shield made of copper foil or the like placed between the excitation coil and the reed switch. By providing the electrostatic shield portion in this manner, the excitation coil and the reed switch can be electrostatically separated, and the plurality of reed switches can be prevented from being electrostatically coupled.

[Problem to be solved by the invention]

However, when attempting to open and close minute signals using conventional glued relays, the leakage current of the relay and the generation and fluctuation of thermoelectromotive force may become a problem.

Leakage current mainly flows through the outer surface of an insulating sleeve made of an insulating material such as glass that encloses the relay. This current changes depending on the surface condition of the insulating sleeve,
It becomes larger due to dirt, moisture, etc. When using a relay in a microcurrent circuit, if the leakage current that flows when the contacts are opened cannot be ignored compared to the signal current that flows when the contacts are closed, the effect on the circuit will be significant.

Thermoelectromotive force occurs when there are dissimilar metals in the reed relay and its connecting conductors and there is a temperature difference between these connecting points. Conventional reed relays open and close their contacts by interrupting the current in the excitation coil, but this interruption changes the heat generation temperature of the coil, causing a temperature change in the reed relay, which also causes thermoelectromotive force. fluctuate.

Therefore, an object of the present invention is to provide a reed relay for minute signals that reduces or eliminates leakage current flowing on the surface of an insulating sleeve.

Another object of the present invention is to provide a reed relay for minute signals that reduces or eliminates fluctuations in thermoelectromotive force.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention, as a first means, makes the surface of the insulating sleeve conductive and applies a voltage having the same potential as the contact.

As a means for making it conductive, for example, a copper foil is wrapped around an insulating sleeve so that there are no gaps.

As a second means, two or more excitation windings are provided and current continues to flow there. The contacts open and close depending on the direction of the current flowing through them. For example, if two excitation windings are provided and current is applied so that the magnetic fluxes generated by these two windings are added to each other, the contacts close, the direction of the current in one winding is reversed, and the winding is generated. When energized so that the magnetic fluxes cancel each other out, it becomes open. Since the winding is always energized and the total current is constant, the heat generation state is constant,
The temperature of the contacts becomes stable. Therefore, changes in thermoelectromotive force due to temperature changes are reduced.

When a reed relay having the above two means is configured with two circuits and the contacts of each circuit are thermally coupled to each other, the thermoelectromotive force of the pair of contacts becomes equal to each other. By connecting a pair of inputs of a differential amplifier with a high common-mode rejection ratio to the terminal under test via this pair of contacts, it becomes possible to cancel out the thermal electromotive force, and its influence is further reduced.

By implementing the means described above, the reed relay can be used to open and close minute signals.

〔Example〕

Hereinafter, the reed relay for minute signals of the present invention will be explained in detail.

FIGS. 1 and 2 show an embodiment of the present invention, which shows a relay contact 5 in which a guard conductor band 3 made of copper foil, for example, is wrapped around an insulating sleeve 7 made of glass, and an insulating sleeve 7 made of glass or the like. 8, a guard conductor band 4 made of copper foil, for example.
Excitation windings 1 and 2 for contact opening/closing having the same characteristics are attached to a relay contact 6 which is wound with a wire, and the excitation windings 1 and 2 are housed in a single exterior case 11 made of, for example, a molded plastic body. Insulating sleeve 7 enclosing relay contact 5
A guard conductor band 3 having a lead wire 9 and a guard conductor band 4 having a lead wire 10 are wound around the surface of the insulating sleeve 8 enclosing the relay contact 6, respectively, so as not to form a gap. Furthermore, the conductor band 3.4 protrudes from the outer case 11 to the outside. By applying a voltage with the same potential as the relay contact 5 to the lead wire 9 and a voltage with the same potential as the relay contact 6 to the lead wire 10, the conductor band 3 and the relay contact 5, and the conductor band 4 and the relay contact 6 are at the same potential. Becomes electric potential.

Since no current flows between two conductors of the same potential, an insulating sleeve 70 is sandwiched between the conductor band 3 and the relay contact 5.
No leakage current from the contact lead 12 flows on the surface, and similarly no leakage current from the contact lead 13 flows on the surface of the insulating sleeve 8 sandwiched between the conductor band 4 and the relay contact 6. Further, since the conductor band 3 protrudes from the outer case 11, no leakage current flows from the contact lead 12 to the outer case 11. Similarly, since the conductor band 4 also protrudes from the outer case 11, the leakage current does not flow from the contact lead 13 to the outer case 11. Leakage current to case 11 does not flow.

The excitation windings 1.2 of the relay have exactly the same conditions such as the number of turns and the diameter of the wire. When closing the contacts 5 and 6 of the relay, each excitation is turned in a direction such that the magnetic flux φ1 generated by the excitation winding 1 and the magnetic flux φ2 generated by the excitation winding 2 are added to each other, as shown in FIG. 3(a). When a current ■1°I2 is applied to the winding and the contact 5.6 is opened, the magnetic flux φ generated by the excitation winding 1 and the magnetic flux φ2 generated by the excitation winding 2 are separated as shown in FIG. 3(b). Flow the current in such a direction that they cancel each other out. Therefore, a constant current always flows through the excitation winding 1.2 regardless of the opening/closing operation of the contacts 5.6, and the amount of heat generated in the winding due to energization is also constant, and the temperature of the relay contacts 5 and 6 is kept constant. Sagging and fluctuations in thermoelectromotive force are less likely to occur.

Further, these two relay circuits are thermally coupled to each other by the outer case 11, and their temperature environments are the same, so that the thermoelectromotive force generated by each relay circuit is the same.

Therefore, when two relay circuits are connected to the positive and negative terminals of a differential amplifier with a large common-mode rejection ratio, the signal current is
Although the difference between the two circuits is amplified, the thermal electromotive force is canceled out and its influence can be further reduced.

〔Effect of the invention〕

As described above, according to the redo relay for minute signals of the present invention, the following effects can be achieved.

(1) For example, by wrapping a conductor band around the insulating sleeve of the relay and applying a voltage of the same potential as the contacts,
Leakage current from the contacts can be reduced.

(2) By making two excitation windings and constantly energizing them to stabilize the temperature of the relay contacts, fluctuations in the thermoelectromotive force generated there are reduced, and thermoelectromotive force is generated in response to minute voltage signals that are opened and closed at the contacts. It is possible to reduce the influence of

(3) Since the two relay circuits are thermally coupled and the thermoelectromotive force generated at each contact point is made equal to each other, this can be canceled out by using a differential amplifier, etc., and the influence on minute signals can be reduced. can.

In order to make the outer surface of the insulating sleeve conductive, copper foil was used in the embodiment, but aluminum foil or the like may be used, or metal may be vapor-deposited. Further, the number of excitation windings may be two or more.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, and FIG. 1 is a partially cutaway perspective view. FIG. 2 is a partially expanded explanatory diagram. FIGS. 3(a) and 3(b) are explanatory diagrams showing the operation of the present invention. Explanation of symbols ■, 2...--- Excitation winding 3, , t---
--- Conductive layer 5.6- - Relay contact 7,
8...--Insulating sleeve 9, 10--1--
Conductive layer lead wire 1 piece...-Exterior mold 12, 13...--Relay conductor patent applicant Japan EM Co., Ltd. agent
Patent Attorney Taira 1) Tadashi Exciting winding Exciting winding Conductive layer Conductive layer Thread colored edge sleeve Conductive layer lead wire Conductive layer lead wire Exterior mold relay Conductor relay Conductor Exciting winding Exciting winding Conductive layer 4 conductive layer Relay contact Relay contact Insulating sleeve Insulating sleeve Conductive layer Lead wire Conductive layer Lead wire Exterior mold Relay conductor Relay conductor Figure 2 L-11111 Figure 3

Claims (3)

[Claims] (1) A reed relay for minute signals, comprising a conductive layer formed on the outer surface of an insulating sleeve enclosing a reed switch, and a power supply means for making the potential of the conductive layer equal to the potential of the reed switch contact. . (2) a pair of conductive layers formed on the outer surfaces of a pair of insulating sleeves each enclosing a reed switch; and a power supply means for equalizing the potential of the pair of conductive layers to the potential of the corresponding reed switch contact. Two or more excitation windings are provided for opening and closing the reed switch contacts, and the two or more excitation windings are constantly excited, and the reed relay contacts are opened and closed based on a combination of directions of the magnetic fields. Features: Reed relay for minute signals. (3) The reed relay for minute signals according to claim 2, wherein the pair of insulating sleeves covered with the conductive layer are covered with a molded body serving as a thermal bonding body.