SU890333A2 - Metal detector - Google Patents

Description

I

The invention relates to a measurement technique and can be used to detect metal particles in a process product stream.

According to the main auth. No. 798669, a metal detector is known that contains a series-connected sensor with two coils connected in opposite planes, an oscillator, a detector, an amplifier, a dual-channel circuit with a clock generator, each channel of which consists of a series-connected comparator, shift register and element, the OR element and the actuator, while the output of the clock generator is connected to the shift inputs of the shift registers of the two-channel circuit whose outputs of the comparators additionally connected with su inputs of elements And opposite channels. The required response of the actuator of the metal detector is the coincidence of the first pulse delayed by the shift register by time tjQ mi-, where m is the number of shift bits, f is the frequency of the generator clock, and the second pulse is the signal from the passage of the metallic object . When using the known metal scooter 10 in the process lines, for example in the case of continuous dosing, the speed of movement of the product being monitored can be continuously varied over a wide range. In that

In case of a change in the speed of movement of the monitored product, the impulse delayed by the shift register, which constitutes the signal from the metallic object moving through the first coil of the sensor, has been taken into account up to the value tjo corresponding to the minimum movement speed of the monitored product to. The purpose of the additional invention is to increase the noise immunity of the metal detector at varying speeds of the monitored product. The goal is achieved by the fact that a metal detector containing a series-connected sensor with two oppositely switched on and parallel coaters, a generator, a detector, an amplifier, a two-channel circuit with a clock pulse generator, each channel of which consists of a series-connected comparator, shift register and element And, the OR element and the actuator, the output of the clock generator is connected to the shift inputs of the shift registers of the dual channel circuit, the outputs omparatorov which are further connected to the inputs of the AND protivopolozhnk channels additionally introduced product moving speed sensor, whose output is connected to the control input teneratora clock channel scheme. The drawing shows a block diagram of a metaplorer. The metal detector contains successively connected sensor 1, generator 2, detector 3, amplifier 4, the output of which is connected to the channels of a two-channel circuit, each channel of which contains series-connected comparator 5, shift register 6, element AND 7. The channels are connected to the inputs element OR 8, the output of which is connected with the input of the actuating device 9, and the output of the clock pulse generator 10 is connected to the shift inputs of the registers 6 of both channels, and the outputs of the comparators 5 are additionally connected to the electrical inputs cops and 7 opposite channel. The output of the motion sensor of the controlled product is connected to the control input of the clock pulse 0 generator. The metal detector operates as follows. Randomly moving metallic objects into the technological mass together with the mass passes the first and second coils of the inductive sensor 1 in succession. The interaction of the metal object with the sensor modulates the oscillations of the generator 2. The envelope is separated by detector 3 and amplified by the measuring amplifier 4. At the output of the amplifier, the signal is a sequence of two different-polarized pulses, one after the other, with a time equal to the time of movement of the metal object from the first coil to the second. The polarity of the pulses is due to the fact that the coil of sensor 1 is turned on counter and their magnetic fields are balanced in order to increase the sensitivity of the metal detector. A metal object passes sensor 1, breaking this balance. Two cases are possible: the first case, when a metal object with magnetic permeability (steel, cast iron, etc.) Passes through the sensor coils. At the output of amplifier 4, the signal is a sequence of positive and negative pulses; the second case, through coil sensor passes a metal object with magnetic permeability (brass, copper, aluminum, etc.). At the output of the amplifier, the signal is a sequence of negative and positive pulses. Both cases are equally They are equal to the probability of falling into the technological mass of metallic inclusions of ferrous or non-ferrous metals controlled by a metal detector. In the first case, the amplified signal from the output of amplifier 4 goes to the inputs of two comparators 5. The first positive pulse that constitutes the signal from a moving metallic object through a sensor passes through the first channel of the comparator 5, where its amplitude is estimated (the sensitivity level of the metal detector is set by the comparators), and is fed to the counting input of the shift register 6, apoln his bits. The clock pulse generator 10 provides a delay of the pulse arriving in the register for the time it moves through all bits. The delay time is proportional to the frequency of the clock pulses of the generator 10 and depends on the speed of movement of the process product monitored by the speed sensor. The delayed signal is fed to the first input of the logic element 7 of this channel. The second pulse (a negative component of the movement of a metal object through the second sensor head) is not transmitted by the comparator of the first channel, passes through the inverted comparator 5 of the second channel and goes to the second channel without delay. the input of the logical element And 7. The first channel. Since the delay time of the first pulse corresponds to the time of movement of the metal object between the coils of the sensor, then, therefore, the delayed The pulse and the second, the component signal to the element And 7, the arrival simultaneously at any speed of movement of the product. At the output of the circuit And 7, a pulse is formed that passes through the element ShchSh 8 and uses the -fl control executive device 9. The first (positive impulse is The output signal from the output of the comparator 5 of the first channel is directed to the second input of the second channel element I. However, the second (negative pulse, pass the comparator 5 of the second channel, and, having reached the counting input of the shift register 6 of the second channel, is delayed in m at the same time t, which eliminates the coincidence of the pulses on the second channel on the element And 7 of the second channel.

In the second case, the operation of the metal detector occurs similarly with the only difference that the first negative pulse is inverted by the inverting comparator 5 of the second channel, delayed in shift register 6 and fed to the first input of the second channel element 7.

The clock pulse generator 10 is made with an adjustable frequency, and the frequency of the clock pulses is automatically set depending on the speed of movement of the controller.

roll product With an increase in the speed of movement of the product, the signal at the output of the sensor of the speed of movement of the monitored product 11 increases, and, consequently, the frequency of the generator of clock pulses 10 increases proportionally and, as a result, the frequency of the generator of clock pulses decreases

10 10 and the delay time increases.

Thus, at varying speeds of the monitored product, the inserted sensor of the product speed allows an automatic change in the delay time tj of the first pulse in accordance with the change in the speed of the product.

The outcome of this is not required.

20 expansion of the delayed pulse, which constitutes a signal from the movement of a metal object through the first coil of the sensor, which increases the noise immunity of the metal detector, and

25 it also becomes possible to significantly reduce the duration of both the first and second pulses. the element arriving at the OR element, which reduces the likelihood of a false e-

30 battalions of a metal detector.

Claims (1)

1. USSR author's certificate No. 798669, cl. G 01 V 3/10, 01.21.79.