RU2509305C2 - Industrial metal detector for conveyor lines - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: in an industrial detector for conveyor lines the area of receiving coils is many times less than the area of a metal detector "window". Signals from receiving coils arrive to inlet amplifiers (separate for each coil), from the outlet of the amplifier the signal is sent to a summator, where it is summed with the "compensation" signal, arriving from a digital to analog converter (DAC), which makes it possible to compensate the signal x.x., then the signal arrives to an analog to digital converter (ADC). Data from all ADC, a speed sensor and another receiving coil connected in parallel to the transmitting one, and also data from the scales (optionally) is sent to a unit of a central processor, in which metal presence is detected. Also in parallel to the transmitting coil there is a calibration loop connected, which is periodically closed, making it possible for an instrument to independently perform automatic inspection and automatic calibration. In the considered metal detector the excitation coil connected to an AC generator creates unresolved magnetic field of excitation acting as the investigated object, moving through the control zone.EFFECT: increased sensitivity of a metal detector and reduced impact of external electromagnetic environment, which causes reduction of quantity of false actuations.1 dwg

Description

The invention relates to the manufacturing industry and can be used to detect and localize metal objects in finished products or in raw materials.

State of the art

To search for metal objects, metal detectors are used, consisting of transmitting and receiving coils designed to measure the magnitude of the magnetic field, for example, the invention SU 1078384a “Conveyor metal detector”, however, achieving high sensitivity of the device is not always possible, since it is limited by the actual magnetic environment. The signal from electromagnetic interference is proportional to the area of the receiving coil. Accordingly, to reduce the value of the "harmful" signal, it is necessary to reduce the area of the receiving coil.

The problem is solved:

- using multiple receiving coils;

- using a special processing algorithm taking into account the signal of an additional coil located parallel to the transmitting one.

In the metal detector under consideration, the following are applied: an excitation coil 1 connected to an alternating current generator, which creates an alternating magnetic field of excitation, acting on the object being examined, moving through the control zone. Receiving coils 2, located perpendicular to the transmitter, inside it, to compensate for the field of excitation from the transmitter coil and having a smaller size compared to the transmitter coil. The signals from the receiving coils are fed to the inputs of the amplifier 3 (separate for each coil). From the output of the amplifier, the signal is fed to the adder 4, where the signal is summed with the signal "compensation" coming from the DAC 5, which allows you to compensate for the signal x.x., then the signal goes to the ADC 6.

Data from all ADCs, a speed sensor 7, and another receiving coil connected in parallel with the transmitting coil, as well as data from the scales 8 (optional) are supplied to the central processor module 9, in which the presence of metal or its quantity is determined. Also, a calibration loop is included parallel to the transmitting coil, which is periodically closed, which allows the device to independently perform auto-testing and auto-calibration. Also in the signal processing module 15 there are: a band-pass filter 10, a synchronous detector 11, a tunable low-pass filter 12, a nonlinear tunable high-pass filter 13, a pulse shape processor 14. To control the signal processing module, a signal generation and compensation compensation signal generating module is used 16. Also to the central processor module connected: keyboard 17, indicator 18, computer interface 19, radiating element 20.

The main difference from similar devices is:

1. The diameter of the receiving coils is much smaller than the control zone, due to which the induced noise on them is much smaller.

2. The presence of an automatic compensation system x.x. receiving coils eliminates the time-consuming process of tuning the sensor, and also eliminates the effect of "aging" of the element base due to the constant automatic tuning of optimal parameters.

3. The presence of a “loop”, which is a periodically closed coil located parallel to the transmitting one, allows the device to independently perform auto-testing and auto-calibration.

4. Monitoring the speed of the conveyor to change the signal processing parameters can significantly reduce the influence of interference due to the fact that only a signal with a given rate of change is recognized as a useful signal.

5. The presence of an input for connecting the scales (mass information) allows you to programmatically reduce the likelihood of a false positive.

6. The programmable phase of the signal allows you to configure (tune) the device to the maximum (minimum) sensitivity on the desired metal.

Claims (1)

Industrial metal detector for conveyor lines, consisting of an excitation coil covering the control zone, an alternating current generator generating a magnetic field in the control zone, receiving coils located inside the control zone perpendicular to the transmitting amplifier, adder, DAC of the receiving coil unbalance compensation signal, ADC, speed sensor, additional receiving coil located parallel to the transmitter, weights (optional), central processor module, periodically closing calibration loop, laid parallel and in the plane of the transmitting coil, characterized in that the receiving coils are perpendicular to the transmitting one, inside it (to compensate for the excitation field from the transmitting coil) and have a smaller size (i.e., less external interference signal is induced in proportion to the decrease in area), and since they are located perpendicular to the control zone, they are parallel to the metal housing of the sensor, which, being an additional screen, further reduces the noise level, compensation signal x.x. It is developed taking into account the redistribution of harmonics of the fundamental frequency and compensates for the signal x.x. taking into account the changing environment (climatic, mechanical changes) dynamically, i.e. without loss of sensitivity in real time.