FR2552875A1 - Sensor for a physical quantity with a permanent local indication of the reading, fitted with proximity contacts for switching on or off an electrical circuit solely by the presence of the needle and requiring no physical effort - Google Patents

Abstract

Proximity switches are placed on the sensors for the physical quantity. The switches are of the inductive or capacitive type and no force is required to change their state.

Description

 The present invention relates to the equipment of physical quantity sensors with permanent measurement indication, such as thermometer, manometer, vacuometer, hydrometer, counter, tachometer, meter, voltmeter, wattmeter, equipped with electronic type adjustable contacts, therefore directly usable in a telematics chain.

 These sensors can equip production machines in manufacturing units or technical equipment in buildings, such as boiler rooms, elevators, smoke detection and theft protection.

 We already know many physical quantity sensors with permanent and local reading. The addition of mechanical contacts has the following disadvantages - to activate the contact, a certain force must be developed.

The energies deployed by the probes are generally very low and the
force used to activate this contact distorts the reading and affects the
reliability of the device.

- the value of the resistance of the contacts varies with time and condition
of oxidation of the contact surface.

- the bouncing of the contacts on closing causes false indica
tions, in particular for metering devices.

- external vibrations can cause closing or opening
untimely contacts.

 The use of inductive contactors overcomes these various drawbacks.

These inductive contacts operate on the following principle
The inductive proximity sensor signals the presence of a metallic object near its sensitive face.

 It essentially consists of an oscillator whose coils constitute the sensitive face. At the front of it is created an alternative magnetic chomp.

 When a metallic screen is placed in this field, the induced currents constitute an additional throat which causes the oscillation to stop.

 After shaping, a switching circuit delivers an output signal equivalent to a closing or opening contact depending on the device models.

 There are three forms of inductive contactors; inductive contactors type I and inductive contactors type U or type 0.

 According to another form of the invention, the inductive contactors are replaced by capacitive contactors.

Capacitive contactors operate on the following principle
A capacitive position detector consists of an oscillator, the capacitors of which constitute the sensitive face.

 When a conductive or insulating material with permitivity / 1 is placed in this field, it modifies the coupling capacities and causes oscillations.

 There are also optical contactors placed on the physical measurement indicators, influenced by the passage of the needle in the light field. This type of device has the disadvantage of being sensitive to local lighting, darkness or artificial lighting.

 The present invention overcomes the various drawbacks mentioned. It consists of placing an inductive contactor or a capacitive contactor on the reading dial of the measuring device.

 The present invention consists in using the metallic mass of the indicator needle of a physical measuring device to actuate a contactor closing or opening a circuit.

 If a capacitive proximity switch is used, it is the presence of the needle in the contactor Qomp which must modify the state of the latter, open or closed.

 The needle can be metallic or not or any other material.

 According to one embodiment, the contactor is in the form of a U and the indicator needle moves inside the branches of the U.

 According to another embodiment, the contactor is in the form of an I and the indicator needle moves in front of the I at a short distance.

 According to another embodiment, the contactor is in the form of an O and the indicator column moves inside the O.

 According to another embodiment, several contactors are placed on the reading scale.

 According to another embodiment, the contactors are adjustable in the vertical position.

 The present invention will be better understood using a schematic representation of the sensor equipped in the 3 attached figures.

 Figure 1 shows a physical measurement sensor fitted with a U-shaped contactor.

 FIG. 2 represents a physical measurement sensor reading by rotation of the needle equipped with an I-shaped contactor.

 FIG. 3 represents a physical measurement sensor fitted with an O-shaped contactor.

 The device represented in FIG. 1 comprises a sensor for measuring by rotation of the needle (1), a graduated reading dial (2), an indicator needle (3), a proximity switch (4) in the shape of a U adjustable in position on the entire scale.

 The device can include several adjustable contactors (5).

The number of adjustable proximity switches depends on the size of the reading dial and is not limiting.

 The device represented in FIG. 2 comprises a sensor for measuring by rotation of the needle (6), a graduated reading dial (7), a needle (8) and a proximity switch (9) in the form of an adjustable I in position over the entire graduotion.

 The device can include several adjustable contactors. The number of contactors depends on the size of the reading dial.

 The device represented in FIG. 3 comprises a physical measurement sensor by linear displacement of the indication (10), a graduation (11), a proximity switch (12) in the form of 0 adjustable in position over the entire height of the reading scale.

 Since the reading column is generally not metallic, proximity capacitance contactors are used in this case.

 The devices according to the invention are particularly intended to equip physical quantity sensors with proximity switches intended to give information by opening or closing a circuit to a telematics, robotization or tele-information device.

Claims (7)

Claims  1) Device intended to install proximity switches on physical quantity measuring devices. These contactors having to open or close a circuit in an electronic telemotic system, characterized in that it comprises a sensor (1), a reading dial (2) an indicator hand (3). The indicator needle moves inside a U-shaped slot of a proximity switch (4). The operation of the contactor, opening or closing of the circuit requires no effort, only the presence of the metal needle acting on the inductive contactor.  2) Device according to claim 1 characterized in that the needle is not metallic and the inductive contactor (4) is replaced by a contactor of the capacitive type. Under these conditions, the needle can be of any material and in particular of plastic.  3) Device according to claim 1 characterized in that the proximity switch is an inductive contactor (9) in the form of I.  4) Device according to claim 3 characterized in that the inductive proximity switch (4) is replaced by a capocitive contactor. Under these conditions, the needle may not be metallic.  5) Device for installing proximity switches of the capacitive type (12) on physical measurement sensors (10) whose reading scale is linear. The reading element can be either metallic or not, solid or liquid.  6) Device intended to install proximity switches on a sensor acting on a movable member, either in rotation or in linear displacement, even without reading scale.  7) Device according to claims 3 and 4, characterized in that the proximity switches are fixed on transparent elements (18) and (19) allowing adjustment in position relative to each other.