Metal detector

 

The invention relates to measuring technique and can be used in the food and wood processing industry to identify the metal. The technical result consists in the simplification of the electrical circuit. The generator sends a signal to the induction sensor, which in the presence of metal in the zone of control signals to the amplifier. Through the key, two phase detector, amplifier, filter, comparator, the trigger is fired the Executive body. During normal operation, temperature and other detuning of induction coils of the sensor is compensated by supplying in-phase and orthogonal components at the amplifier input from the multiplier products, managed signals offset through the integrators. Futuremouse device provides shift 90to obtain orthogonal voltage. Thus the output of the induction coil sensor are located on two sides of the input coil and are connected in series and a counter. 7 C.p. f-crystals, 9 Il.

The invention relates to measuring technique and can be used in the food and wood processing industry for detecting metal in a useful product.

Izviskovy detector, amplifier-filter, a comparator, an Executive body. A disadvantage of devices of this type is relatively low sensitivity, due to lack of temperature compensation and temporary changes in sensor design.

It is also known device-prototype [2], which contains a series generator, transformer, induction sensor, containing the transmitting coil and geometrically equidistant from the transmitting coil and the output coil to ensure zero potential in the area of the sensor in the absence of metal, pre-amplifier, two phase detector outputs are connected to the chain of series-connected amplifier-filter, comparator, trigger and Executive body, the first inputs of the detectors connected to the transformer output, respectively, directly and through the phase shifter, and their second inputs are combined.

The prototype is too complex, because it contains a lot of blocks. This reduces the reliability, costly to manufacture, debugging.

The aim of the present invention is to simplify and increase the sensitivity of the detector.

This goal is achieved due to the fact that he has two integrators and two transaction the outputs of the transformer and the phase shifter, respectively, the outputs of multiplier products are connected to summing inputs of the pre-amplifier, the output of which is connected to the second inputs of the detectors through the key, a control input connected to the trigger output, while the output induction coil sensor are located on two sides of the input coil and are connected in series and oppositely, and their outputs are connected to different conclusions of the pre-amplifier.

An additional difference is that the inputs of the integrators are connected to the outputs of the phase detectors through the amplitude limiter.

Goal - improvement of the sensitivity is also achieved due to the fact that the active part of the input and output Pawcatuck placed at an angle to each other, and the angle between the output coils two times greater than the angle between any of them and the input coil.

The same goal is achieved due to the fact that interconnected the conclusions of the output coils of the induction sensor is connected to the communication unit, the second terminal of which is connected to ground.

The goal of the invention is the implementation of the communication unit by one of the following: a resistor, a capacitor, a parallel connection of a resistor and capacitor or wire.

The scheme of the detector pikelny power,

5 key

6, 7 and phase detectors,

8 - amplifier-filter,

9 comparator,

10 - trigger

11 is an Executive body,

12 - Phaser (shift 90),

13, 14 - multiplier products,

15, 16, integrators,

17 - amplitude limiters.

Generator 1, a transformer 2, an induction sensor 3, a preamplifier 4, key 5 is connected in series so that the output of the previous element is connected to the input of the next. Exit key 5 is connected to the two inputs of the phase detectors 6 and 7, and their outputs connected to inputs of the amplifier-filter 8. Each of the detectors 6 and 7 is connected to the output with the corresponding integrator 15 and 16. Amplifier-filter 8, a comparator 9, the trigger 10, the Executive body 11 form a series circuit.

The detector operates in this way.

Generator 1 generates a high-frequency voltage (tens of kilohertz), which through the transformer 2 is fed to the transmitting induction coil sensor 3. The output coil of the sensor geometrically equidistant from the transmitting coil. Therefore, in the absence of metal in the zone of the sensor output of the sensor 3 has a zero signal. The key 5 is closed, the output of the phase detectors 6 and 7, the signal is also equal to zero. The trigger 10 is in a disabled status the size of the induction sensor under the influence of temperature, etc.

Due to the interference balance sensor 3 may be broken. Signals, which appeared under the influence of noise on the outputs 4, 5, 6, 7, lead to the accumulation of signals at the output of the integrator 15, 16. These signals are multiplied together in multiplier products 13, 14 with sinusoidal output signal of the transformer 1 and the phase shifter 12. Obtained at the output of the multipliers sinusoidal signals serves to sum the inputs of the pre-amplifier 4 to compensate for the interference. The time constant of the integrators few seconds when the duration of the useful signal of the order of 0.1-0.25 s, so when the useful signal caused by the presence in the control area of the metal, the feedback circuit has no effect, since the integrators 15 and 16 during this time practically does not change its output signal.

The signal causes the output of the phase detectors of large signals, which are summed, filtered and amplified by amplifier 8. Since this signal exceeds the trip point of the comparator 9, the latter triggers 10, which includes, in turn, the Executive body 11. The body 11 stops the mechanism (conveyor, etc.,). For the next start after removal of metal you need to reset the trigger 10. The reset circuit not shown integrator 15, 16 "freezes", keeping the previously accumulated signal and providing compensation offset at the input of the amplifier 4.

To reduce the influence of the useful signal on the output signals of the integrators 15, 16 during his rise, Fig.2 are the amplitude limiter 17. Setting the last several times (in relative units) is lower than the setpoint comparator 9. This is an even greater extent weakens the influence.

The above scheme is different from the prototype structure, in comparison with the known scheme changed the installation location of the key. Instead of two keys used in a known schema, uses a single key. In addition, there are no complex key management schemes through the use of other relations. This significantly simplifies both structural and schematic diagram of the device and increases its sensitivity.

In Fig.3, 4 shows diagrams that illustrate paragraph 3, of the formula of the invention, and Fig.5 - p. 4. These figures depict: 1 - generator, 2 - transformer, 3 - induction sensor, 4-pre-amplifier 18 to the input coil, 19 - output coil, 20 - detecting unit 21, the communication unit.

The generator 1 through the transformer 2 is connected to the input of the induction sensor 3 - reel - the output of the sensor 3, which is connected to the input of the amplifier 4. The output of the amplifier 4 is connected to the input of the detecting unit 20. In block 20 includes elements of Fig.1 or 2 numbers 5-17. This preserves the same structure of relations between elements. In Fig.3 presents a General view of the induction sensor 3, and Fig.4 is a view of the same sensor on top of the arrow a of Fig.3. The structure of the sensor 3 is not different from the known. However, the active part of the output coils 19 in relation to the input coil 18 is placed at an angle (of the order of 10-30). Coil 19 connected counter and are located on either side of the entrance, the exciting coil 18. In the prototype these coils active parts (upper and lower) geometrically parallel between themselves. Therefore, when passing through the window of the sensor oblong object (such as a nail), placed parallel to the plane of the coil 18, the sensor signal will be the same as for a sphere of diameter equal to the diameter of the nail. The oblique placement of the coils 19 such situation is impossible, since the latter is the subject of any accommodation will be located at an angle to one of the receiving coils 19. This circumstance increases the sensitivity. In the presence of a metal object in the window of the sensor in its output to cat the accordance of such item signals, inductively in the coils 19, due to the transformation from the input coil 18, equal and vzaimokompensiruyutsya.

Therefore, the output of the sensor 3 has a zero signal. In the circuit of Fig.5 interconnected conclusions of the output coils of the induction sensor 3 is connected to the communication unit 21, the second terminal of which is connected to ground.

The operation of the device is similar to the device depicted in Fig.3. The detectors operate in conditions of high electromagnetic fields that are generated thyristor drive, by welding, by circulating currents, etc., These interferences can penetrate into the output coil 19 and further into the amplifier 4, the detecting unit 20. This leads to increase the threshold of the comparator, that is, to reduce the sensitivity. The relationship of the middle node of the sensor to ground leads to the reduction of noise due to snapping on circuits, bypassing the inputs of the amplifier 4.

In Fig.6, 7, 8, 9 communication units in the expanded form. Here: 22 - resistor 23 and capacitor, 24 - jumper (wire). A particular type of communication unit depends on the placement of the sensor 3 and the source of the interference. The choice of the type of block 21 is held in commissioning robots by sorting options.

The noise reduction provides an opportunity to increase justprint UK No. 2025630, G 01 V 17/06, Appl. 10.11.77, publ. 23.01.80.

Claims

1. Metal detector containing series-connected generator, transformer, induction sensor, containing the transmitting coil and geometrically equidistant from the transmitting coil and the output coil to ensure zero potential in the area of the sensor in the absence of metal, pre-amplifier, two phase detector outputs are connected to the chain of series-connected amplifier-filter, comparator, trigger and Executive body, the first inputs of the detectors connected to the transformer output, respectively, directly and through the phase shifter, and their second inputs of the joint, characterized in that it has two integrators and two multiplier products, the first inputs of which are connected respectively to the outputs of integrators, their second inputs connected to the outputs of the transformer and the phase shifter, respectively, the outputs of the multiplier products are connected to summing inputs of the pre-amplifier, the output of which is connected to the second inputs of the detectors through the key, a control input connected to the trigger output, while the output induction coil sensor located on duyvendak preamplifier.

2. Metal detector under item 1, characterized in that the inputs of the integrators are connected to the outputs of the phase detectors through the amplitude limiter.

3. Metal detector according to any one of paragraphs.1 and 2, characterized in that the active part of the input and output Pawcatuck placed at an angle to each other, and the angle between the output coils two times greater than the angle between any of them and the input coil.

4. Metal detector according to any one of paragraphs.1 and 2, characterized in that the interconnected conclusions of the output coils of the induction sensor is connected to the communication unit, the second terminal of which is connected to ground.

5. Metal detector under item 4, characterized in that the communication unit is made in the form of a resistor.

6. Metal detector under item 4, characterized in that the communication unit is made in the form of a capacitor.

7. Metal detector under item 4, characterized in that the communication unit is made in the form of a parallel connection of a resistor and a capacitor.

8. Metal detector under item 4, characterized in that the communication unit is made in the form of a wire.

 

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2 dwg, 1 tbl

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