WO1988003273A1 - Appareil de detection/identification - Google Patents

Appareil de detection/identification Download PDF

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Publication number
WO1988003273A1
WO1988003273A1 PCT/US1987/002684 US8702684W WO8803273A1 WO 1988003273 A1 WO1988003273 A1 WO 1988003273A1 US 8702684 W US8702684 W US 8702684W WO 8803273 A1 WO8803273 A1 WO 8803273A1
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WO
WIPO (PCT)
Prior art keywords
field
phase
vector
signals
range
Prior art date
Application number
PCT/US1987/002684
Other languages
English (en)
Inventor
Bruce F. Beaudry
Lawrence H. Holten
Lauren R. Bandler
Original Assignee
Peerless-Winsmith, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Peerless-Winsmith, Inc. filed Critical Peerless-Winsmith, Inc.
Publication of WO1988003273A1 publication Critical patent/WO1988003273A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
    • G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
    • G01V3/105—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
    • G01V3/107—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops using compensating coil or loop arrangements

Definitions

  • the present invention relates generally to sensing 5. devices, and more particularly to an apparatus for detecting and/or identifying an article.
  • Detection devices have typically been used in the food industry where it is desired to detect the presence of
  • Such food product may comprise discrete items such as packages of bread, dry bulk items such as potato chips or other types of food items.
  • detection devices utilize a transmit coil which receives an excitation voltage and generate an alter-
  • such detectors are relatively insen ⁇ sitive to certain contaminants or articles which cause a small phase shift in the alternating electromagnetic field.
  • the vector defining the field during sensing of such contaminants or articles may have an imaginary cora ⁇ s ponent less than the predetermined reference but may in fact lie outside the range of vectors defining the field when uncontaminated product is being sensed.
  • con ⁇ taminated product or other articles may escape detection and/or identification.
  • a detec ⁇ tion/identification apparatus is not only highly sensitive to the presence of contaminants in product but is also capa ⁇ ble of identifying such contaminants or distinguishing dif- 5 ; ferent items.
  • the apparatus of the present invention is particularly useful to detect the presence of an item at a certain point in space.
  • the apparatus includes means for establishing an alternating electromagnetic field 0 in a volume of space containing the point using a field ex ⁇ citation signal and means for defining a field voltage vec ⁇ tor representing the voltage induced by the electromagnetic field relative to a base vector representing the excitation signal.
  • Means are responsive to the defining means for de ⁇ termining whether the field voltage vector is outside of a range of vectorial values wherein such determination is in- - dicative of the presence of the item at the particular point.
  • the defining means includes first and second phase detectors which detect the amplitude of the voltage induced by the electromagnetic field along the real and imaginary axes relative to the field excitation signal.
  • the signals developed by the phase detectors are converted by a micro ⁇ processor into signals representing the amplitude and angle of the field voltage vector, which signals are compared with the range of vectorial values to determine whether the item - is present at the particular point.
  • the microprocessor may be operated in one of two modes of operation, the first mode of operation being a learning mode in which samples of uncontaminated product are utilized to develop an indication of the range of vectorial values and the second mode being a processing mode of operation wherein subsequent samples of product are analyzed to determine whether contaminant is present therein.
  • samples of each dif ⁇ ferent type of item are sensed when the microprocessor is operated in the learning mode to develop several distinct ranges of vectorial values. Subsequently, when the micro ⁇ processor is operated in the processing mode to identify items, signals derived from the sensing of the items are compared against each of the vectorial ranges to determine whether such signals define a vector falling within one of the ranges to thereby permit identification of the item.
  • the apparatus utilizes sensitive electronic compo ⁇ nents which, in conjunction with the sensing of field ampli ⁇ tude along the real and imaginary axes, leads to a desired increase in the sensitivity thereof.
  • Fig. 1 is a block diagram of a detection/identifi ⁇ cation apparatus according to the present invention disposed adjacent a conveyor;
  • Fig. 2 is a waveform diagram illustrating a sample 10 output of one of the phase detectors shown in Fig. 1 when product is passing on the conveyor between the coils;
  • Fig. 3 is a diagram of the phase angle relation ⁇ ships illustrating the phase shift in an alternating elec ⁇ tromagnetic field caused by three different articles on the 15 " conveyor shown in Fig. 1;
  • Figs. 4A and 4B when joined along the dashed lines, together comprise a more specific block diagram of the detector illustrated in Fig. 1;
  • Figs. 5A-5D when joined at the similarly-lettered 201 lines, together comprise a flowchart of a portion of the programming executed by the microprocessor illustrated in Fig. 4;
  • Figs. 6A-6C when joined at the similarly-lettered lines, together comprise a flowchart of another portion of 5 ⁇ the programming executed by the microprocessor illustrated in Fig. 4;
  • Fig. 7 is a schematic diagram of one of the bridge circuits shown in Fig. 4A.
  • a detection/identifica ⁇ tion apparatus 10 which may be used as a metal detector according to the present invention includes transmit cir ⁇ cuitry 12 comprising an RF oscillator 14 which develops a field excitation signal in a transmit or field excitation winding or coil 16.
  • the winding 16 in turn develops an al ⁇ ternating electromagnetic field in space occupied by pro ⁇ duct, here shown as box 18, which is disposed on a conveyor 19.
  • the detector of the pre ⁇ sent invention need not be operated in conjunction with a " . conveyor but may be used to detect the presence of or iden ⁇ tify an item at any particular point or volume of space.
  • the alternating electromagnetic field established by the transmit coil 16 extends about a pair of receive windings or coils 20a,20b which are disposed on opposite sides of the transmit coil at equal distances therefrom.
  • the receive coils 20a,20b sense the electromagnetic field and are connected in electrical opposition as shown in Fig. 1 so that they generate a differential signal.
  • the number of turns of each receive coil 20 and the position of the coils relative to one another and to the transmit coil 16 are adjusted so that a substantially zero amplitude signal is developed by the receive coils when no product is present in the space therebetween.
  • the transmit coil 16 and the receive coils 20a,2Ob are typically enclosed in a rigid housing or head illustrated by the dotted lines 21 which may be filled with epoxy or another potting compound to maintain the precise spacing and relative positioning of the transmit coil 16 and the receiving coils 20a,20b. This reduces noise caused by vibration of the housing 21. Electromagnetic shielding in the head 21 further minimizes noise due to ex ⁇ ternal electromagnetic fields or by metal in the vicinity of the head which may cause erroneous readings. The head may be remote from the balance of the circuitry of the apparatus 10, if desired.
  • metal slugs, screws or other metal items may be placed between the receiving coils 20a, 2Ob so 5 that the combined output of the coils 20 is maintained at a null valve.
  • the pre-amplifier 22 " amplifies the differential signal, converts it into a single-ended signal and delivers the- signal to a narrow bandpass filter 23, a buffer ampli- Q" fier 24 and a summing amplifier or junction 25.
  • the summing junction 25 also receives a signal developed by an auto bal ⁇ ance circuit 26.
  • the summing junction 25 subtracts a con ⁇ trolled value fro the filtered and amplified signal from the circuit 22 to remove any signal components in the dif- 5 ferential signal resulting from drift or temperature effects.
  • the amplified and corrected signal from the sum ⁇ ming junction 25 is coupled to a pair of phase detectors 28a,28b which in turn develop signals representing the phase 0, shift of the electromagnetic field as sensed by the receive coils 20a,20b relative to the excitation signal. More par ⁇ ticularly, the phase detectors 28a,28b develop first and second signals representing the amplitude of the differen ⁇ tial signal developed by the receive coils 20a,20b in phase 55 with the field excitation signal and in phase quadrature relationship with the field excitation signal, respectively. These first and second signals define a resultant vector representing the electromagnetic field, and more particular ⁇ ly the voltage-induced by the electromagnetic field in the 0 receive coils 20a,20b, as noted more specifically below.
  • each phase detector When product 18 or another article is introduced in the space between the receive coils 20a,20b, each phase detector develops an unbalanced signal similar to that shown in Fig. 2.
  • the positive excursion of the waveform of Fig. 2 5 is developed in response to passage of the article between a the coils 20a and 16 and the negative portion is developed in response to passage of the article between the coils 16 and 20b.
  • the frequency of the waveform is depen ⁇ dent upon the speed of the conveyor 19. 5
  • the 28a receive a reference signal from the oscillator 14.
  • the reference signal is passed through a phase shifting circuit 29 and is applied to the auto balance cir ⁇ cuit 36 and the phase detector 28b.
  • the first and second signals from the phase detec ⁇ tors 28 are converted into digital signals by an analog-to- digital converter (ADC) 30 and the digital signals are cou ⁇ pled to a microprocessor 32.
  • ADC analog-to- digital converter
  • the microprocessor 32 includes suitable programming to convert the digital signals into
  • I 5 signals H representing the amplitude and phase of the re ⁇ sultant vector.
  • the microprocessor also compares ⁇ the sig ⁇ nals M, ⁇ with a range of vectorial values that represent signals which would be generated by the receiving coils when uncontaminated product is present in the space between the
  • the auto balance circuit 26 is controlled by the microprocessor 32 via one or more digital-to-analog conver ⁇ ters (DAC's) 33 so that the auto balance circuit develops the controlled value which is coupled to the summing junc-
  • a signal representing the speed of the conveyor is developed by a speed sensor 46 and is coupled to the micro ⁇ processor 32 to in part control a reject actuator 48 for discharging contaminated product from the conveyor 19.
  • a 0- reject verify sensor 49 is provided to inform the micropro ⁇ cessor 32 of whether a defective item has, in fact, been
  • the speed of the conveyor may alternatively be sensed by measuring the period of the waveform from one of the phase detectors 28a,28b, if de ⁇ sired.
  • the microprocessor 32 receives inputs from a terminal 50 (shown in greater detail in Fig. 4B) which may be remote from the other components in the detec ⁇ tor and which includes a further microprocessor 51, an in ⁇ terface 52 coupled between the microprocessors 32,51, an alphanumeric display 53 and a set of pushbuttons 54. If de ⁇ sired, the microprocessor may be controlled by a remote sup ⁇ ervisory control unit (not shown) over lines 55a,55b.
  • the microprocessor may control one or more indica ⁇ tors 56 for indicating the presence of contaminated product on the conveyor 19 and/or may communicate over the lines 55a,55b with the remote supervisory control to generate an indication of contaminated product.
  • the display 53 may also develop messages prompting 1 a user to take certain action and to inform the user that a certain article has been detected on the conveyor 19.
  • the display may be a part of the remote terminal 50 or may be disposed atop a housing enclosing the coils 16,20, if desired.
  • the microprocessor 32 operates in one of two modes of operation.
  • the first mode of operation is a learning mode in which the microprocessor is "taught" to recognize and therefore disregard noise and uncontaminated product on the conveyor 19.
  • the microprocessor may be taught to recognize, and therefore distinguish between var ⁇ ious articles.
  • the microprocessor stores an indication of at least one range of vectorial values repre ⁇ senting the recognized product or articles.
  • the second mode of operation termed the process ⁇ ing mode, is the usual operating mode of the microprocessor and is the operational mode in which the microprocessor com ⁇ pares the signals from the A/D converters 30 against the range (or ranges) of vectorial values which are obtained during the learning mode.
  • the microprocessor is thus able to detect contaminants in product on the conveyor and/or identify different articles on the conveyor.
  • Fig. 3 there is illustrated one example of the phase angle relationships of the unbalanced signal from the receive coils relative to the ° field excitation signal for each of three conditions: (a) when conductive uncontaminated product is present on the conveyor between the receive coils 20a,20b; (b) when ferrous metal is present in the region between the coils 20a,2Ob; and (c) when nonferrous metal is present in the region be- tween the coils 20a,20b.
  • conductive un ⁇ contaminated product causes a phase shift of between -15° and +15° from the real axis with amplitude values from zero to approximately AT..
  • This region defines the boundaries of the expected vectorial values which would be obtained from the receive coils 20a,20b when uncontaminated product is present on the conveyor 19.
  • the region is in reality larger than the actual range of vectorial values generated by pro ⁇ duct on the conveyor 19 to minimize the chances of inadver- tently rejecting what turns out to be uncontaminated pro ⁇ duct.
  • fer ⁇ rous and nonferrous metal objects in product cause phase shifts in the sensed electromagnetic field which lead and lag, respectively, the field excitation signal in the coil 16.
  • Ferrous metals typically cause a phase shift of between 50° and 80° while nonferrous metals typically cause a phase shift of between -30° and -60".
  • the amplitude of the vector defining the sensed electromagnetic field var ⁇ ies with the size and orientation of the metal particles in the region between the coils 20a,20b.
  • the distinct phase shifts and vector amplitude varia ⁇ tions caused by different articles on the conveyor 19 permit not only the detection of contaminants or other unwanted items in product conveyed on the conveyor 19, but also per ⁇ mit the identification of articles on the conveyor by de- 0- tecting the phase shift and amplitude of the sensed electro ⁇ magnetic field and comparing the phase shift and amplitude against a series of predetermined ranges which identify the nature of the article.
  • the only requirement is that the various items which are expected to be encountered on the 53 conveyor 19 must produce phase shifts and vector amplitudes in regions which are distinct from one another so that the items can in turn be distinguished from one another.
  • Figs. 4A and 4B there is illus ⁇ trated in greater detail the block diagram of Fig. 1.
  • the 0 receive coils 20a,20b are coupled to a resonant variable capacitor network including capacitor Cl across which the differential signal is developed.
  • the capacitor Cl is adjusted so that the receive coils 20 and the capacitor network Cl form a resonant circuit having a resonant fre- 5 quency equal to the operational frequency f_ of the RF os ⁇ cillator 14.
  • the operational frequency f_ of the oscillator 14 is in turn determined by adjustment of a variable capacitor C2.
  • the differential signal across the capacitor Cl is coupled to a differential input amplifier 70 and D thence to a differential line amplifier 72 which develops a differential output that is coupled over a shielded twisted pair transmission line 74.
  • the twisted pair 74 is in turn coupled to a differential input amplifier 76 which converts the differential output of the amplifier 72 into a single-ended output on a line 78.
  • the differential line amplifier 72 is used to can ⁇ cel common mode noise which may be present in the signal : from the receive coils 20a,20b and to permit transmission of the differential signal over a relatively long distance by means of the twisted pair 74.
  • the line 78 is coupled to the narrow bandpass fil ⁇ ter and the buffer amplifier 24 described previously in con- - nection with Fig. 1.
  • the center frequency of the filter 27 is tuned to the resonant frequency f_ of RF oscillator 14.
  • the bandpass filter eliminates spurious signals at frequen ⁇ cies other than the resonant frequency f_ to minimize the occurrence of false alarms due to noise. By placing the bandpass filter before the summing junction 25, phase shifts in the filtered differential signal due to temperature ef ⁇ fects or aging do not result in significant errors in the detection process.
  • the output of the summing junction 25 is amplified by an amplifier 79 and is coupled to first inputs of first and second multipliers 80a,80b which are part of the phase detectors 28a,28b, respectively.
  • the second inputs of the multipliers 80a,80b receive precision phase reference sig ⁇ nals developed by reference signal circuitry 82.
  • the reference signal circuitry 82 includes a line amplifier 90 coupled to the capacitor C2 and a twisted pair transmission line 92.
  • the output of the transmission line 92 is coupled to a differential input amplifier 94.
  • the amplifier 94 is in turn coupled to the second input of the multiplier 80a by a line 96.
  • the multiplier 80a thus re ⁇ ceives a phase reference signal which is in phase with the differential signal.
  • the multiplier 80b re ⁇ ceives a phase reference signal displaced 90° with respect to the differential signal from a phase shift circuit 98 which is coupled to the amplifier 94.
  • phase shift circuits may be used to introduce a controlled offset in the phase of the signals coupled to the
  • the multipliers 80a,80b multiply the signals at their inputs and provide DC outputs which are proportional to the magnitude of a field voltage vector representing the voltage induced in the receive coils 20 by the electromagne ⁇ tic field along the real and imaginary axes, respectively,
  • the outputs of the multi ⁇ pliers 80a,80b represent the amplitude of the detected elec ⁇ tromagnetic field vector components at 0° and 90" with re ⁇ spect to the excitation signal in the winding 16, as repre-
  • the outputs of the multipliers 80a,80b are fil ⁇ tered by low pass filters 120a,120b, respectively, (Fig. 4B) each having a cutoff frequency of 100 hertz. These filters extract the DC component of the output of the multipliers
  • phase detectors 28a,28b which develop first and second signals defining a resultant
  • the low pass filters 120a,120b remove the oscillator fundamental and higher harmonic frequencies from the output of the mul ⁇ tipliers 80a,80b.
  • the cut off frequency of the low pass filters 120a,120b is selected so that information at a fre ⁇ quency higher than that corresponding to the maximum product speed on the conveyor is removed. This in turn results in a high signal to noise ratio of the apparatus which in turn increases the sensitivity thereof.
  • the analog multiplexer 126 is operated by control logic 128 which is in turn coupled to the microprocessor 32.
  • the multiplexer 126 is coupled to a unipolar level shifting circuit 130 which converts the bipolar signals on the lines : 84a,84b into signals which vary between zero and some posi ⁇ tive value.
  • the multiplexer 126 also receives a signal devel ⁇ oped by an amplifier 100 and a level detector 102 which are in turn coupled to the output of the differential amplifier 94.
  • the level shifting circuit 132 is coupled to an A/D converter 134 which samples the signal from the circuit 130 at a predetermined rate.
  • the microprocessor 32 instructs the control logic 128 to operate the multiplexer 126 at a frequency equal to three times the sampling rate of the analog-to-digital con ⁇ verter 134 so that the signals from the low pass filters 120a,120b and the level detector 102 are sequentially con ⁇ nected to the level shifting circuit 130 at a frequency which allows the sampling of such signals at the desired sampling rate by the A/D converter 134.
  • the amplifier 100 and level detector 102 develop signals which inform the microprocessor of whether the transmit coil is actually transmitting a field. This infor- mation may be used by the microprocessor 32 for diagnostic purposes. O 88
  • the A/D converter develops digital signals which are utilized by the microprocessor 32 to detect and/or iden ⁇ tify contaminants or other products on the conveyor.
  • the RF oscillator 14 (Fig. 4A) includes a level - regulator 140 and a power amplifier 142 which is coupled to the capacitor C2 and .to the transmit coil 16.
  • the level regulator 140 insures that the amplitude of the output from the oscillator 14 is maintained at a constant level.
  • the resonant frequency of the resonant 0 circuit comprising the capacitor C2 and the transmit coil 16 may be adjusted by varying the capacitance of the capacitor C2.
  • the choice of operational frequency fo of the oscillator 14 is dependent upon the sensitivity desired and the size of the : coils 16,20. The size of the coils is in turn selected tak ⁇ ing into account the desired sensitivity and the size of the product which is to pass through the coils.
  • the auto balance circuit 26 includes first and second bridge circuits 143,144 which are controlled by the 0 microprocessor 32 via D/A converters 33a,33b and first and second control circuits 145,146.
  • Each bridge circuit as seen in Fig. 7, includes input terminals Tl and T2 which are coupled to the output terminals of the transmission line 92 and output terminals T3 and T4.
  • First and second resistors 5 R1,R2 are coupled in two legs of the bridge while first and second pairs of variable-capacity diodes (or "varicaps") D1,D2 and D3,D4 are coupled in the remaining legs of the bridge.
  • the cathodes of the varicaps in each leg are con ⁇ nected together and receive a control voltage CTL1 and CTL2 from the control circuit 145 or 146 through resistors R3,R4.
  • the microprocessor develops control signals which are coupled to the D/A converters 33a,33b and which are then delivered as analog signals to the control circuits 145,146.
  • Each control circuit develops a pair of outputs from the single input, one of which is identical to the input and the other of which is complementary to the input. For example, if the output of the D/A converter 33a varies between 10 volts and 0 volts, the first output of the control circuit 45 likewise varies between 10 volts and 0 volts while the second output varies between -0 volts and 10 volts.
  • These signals are applied to different legs of a bridge so that the bridge output varies with changes in the output from the control circuits 145,146.
  • the first and second bridge circuits 143,144 are coupled to inverting inputs of the summing junction 25.
  • the bridge circuits 143,144 develop signals which are combined by the summing junction 25 with the filtered output of the differential amplifier 76 to compensate for drift due to aging, temperature effects or the like. More specifically, the auto balance .circuit develops a pair of signals which, when combined, are equal in magnitude to but 180° out of phase with respect to the signal from the differential input amplifier 76 when no product is present in the region be ⁇ tween the coils 20a,20b. Hence, the output of the summing junction 25 is near zero when no product is disposed between the coils 20a,20b.
  • the auto balance circuit re ⁇ sponse is relatively slow so that the summing junction 25 develops an error signal when an unbalanced signal is devel ⁇ oped by the receive coils 20 due to the presence of product in the space between the coils 20a,20b.
  • the response time of the auto balance circuit 26 is selected to be longer than the period of time it takes for product to • traverse the space between the coils 20a,20b at the slowest conveyor speed.
  • the auto balance circuit 26 the summing junction 25, the microprocessor 32, the converters 33 and the control -16-
  • circuits 145,146 are the main elements of a servo system which provides high sensitivity and maintains stable opera ⁇ tion over time.
  • the auto balance circuit 26 under control of the microprocessor 32 shifts the phase and amplitude of its combined output signal until the digitized output of the phase detectors 28a,28b is again near zero so that accuracy is preserved.
  • the microprocessor 32 is coupled to an input in- terface circuit 150 which in turn receives the signals from the speed sensor 46 and the reject verify sensor 49.
  • An output interface circuit 152 is coupled between the micro ⁇ processor 32 and one or more actuator relays 154 for con ⁇ trolling the reject actuator 48 and additional optional " sorting actuators.
  • the indicator 56 is also coupled to the output interface 152.
  • the microprocessor 32 energizes the fault relay 156 via the output * interface circuit 152 when a fault is detected during a self-test sequence described in greater detail below. When the fault relay 156 is ener- gized, a light or other alarm may be actuated to alert the user to the existence of a possible malfunction.
  • the microprocessor 32 may be coupled to a communi ⁇ cations interface circuit 160 which permits the generation of hard copy reports by a report printer 162 and which also allows supervisory control by an optional supervisory compu ⁇ ter.
  • An optional programmable controller interface 164 may be provided to permit communication with and control over one or more programmable controllers by the icropro- cessor 32.
  • the microprocessor also controls a self-test gene ⁇ rator 170 which verifies that the electronics of the detec ⁇ tor are working.
  • the self-test generator 170 generates high -17-
  • the microprocessor includes software which detects the high frequency pulses that are picked up by the receive coils 20a,2Ob and which are processed by the receive cir ⁇ cuitry. As long as the microprocessor 32 receives the puls ⁇ es, no fault indication is generated. However, if these 1° pulses are interrupted for any reason, a fault indication is generated by means of actuation of the fault relay 156 to actuate the light and/or alarm so that the user is alerted to the possibility of defective circuitry.
  • the self-test generator 170 15 receives the signal on the line 96, the signal from the phase shifting circuit 98 and a pulse rate signal from the microprocessor 32.
  • the phase reference signals are alter ⁇ nately gated and applied to the auxiliary winding 172. Spe ⁇ cifically, a number of cycles, e.g. ten, of the signal from 20 the line 96 are applied to the winding 172. This sequence is followed by a pause for a predetermined time interval, and then ten cycles of the signal from the phase shifting circuit 98 are applied to the winding 172.
  • the microprocessor 32 may include an internal mem ⁇ ory, such as a random access memory 176 (RAM) , and is also coupled to a nonvolatile memory 180 which may be a read only memory (ROM) and/or an erasable programmable read only mem ⁇ ory (EPROM) together with an electrically erasable program ⁇ mable read only memory (EEPROM) and/or a RAM with battery backup.
  • the RAM 176 stores the various flags and intermed ⁇ iate and final results of calculations and program opera ⁇ tions.
  • the nonvolatile memory 180 contains the control pro ⁇ gram executed by the microprocessor and further stores set up information and processing parameters used during execu ⁇ tion of the control program, as noted in greater detail be ⁇ low. It should be noted that the particular form of the memory 180 is not critical, it being understood that other i types of memory elements may be used instead.
  • Figs. 5A-5D there is illustrated a portion of the programming contained in the nonvolatile memory 180 which is executed by the microprocessor 32.
  • the control program illustrated in Figs. 5A-5D is run as a back- : ground program, i.e. it is executed continuously except when an interrupt is received, at which time program execution is halted so that a different program may be executed.
  • One of the latter programs which is executed on such an interrupt basis is a data acquisition and computation routine illus- ; trated in Figs. 6A-6C and described in greater detail here ⁇ inafter.
  • This program is executed upon expiration of a re ⁇ petitively reset timer and is thus executed on a real time basis once every Xs milliseconds, where Xg is a selected or desired value.
  • the background program starts at a block 200 which initiates a self-diagnostic routine to check the operative status of the microprocessor 32. In the event that any faults in the microprocessor 32 are found, a fault routine -19-
  • a block 204 is executed by a block 204.
  • the operation of the fault rou ⁇ tine 204 and other fault routines noted hereinafter is not important to an understanding of the instant invention and hence will not be described in detail.
  • an indication of the operative status of same may be developed by a -pair of blocks 206,208 which cause the operator display 54 to develop a copyright notice and to illuminate an indicator 56.
  • a block 209 causes the microprocessor 32 to load into its internal memory a series of set up values stored in the nonvolatile memory 180.
  • the set up values are obtained during a learning mode of opera ⁇ tion of the microprocessor 32 which is described in greater detail hereinafter.
  • the set up values define the vectorial' range(s) of product(s) which is (are) to be tested for contaminants and/or identified.
  • a block 210 fetches a pair of values from the nonvolatile memory 180 which are the last values that were coupled to the D/A converters 33a,33b. These values are again provided to the D/A converters by a block 211 so that the bridge circuits 143, 144 are con ⁇ trolled to accomplish the auto balance function described previously.
  • a block 212 checks to determine whether an operator has entered a command by actu ⁇ ating one or more of the pushbuttons 54. Such commands may be, for example, to change the stored set up values, to change the parameters which are used during the learning mode of operation, to generate a hard copy printed report, to request help messages or to enter the learning mode of operation. Each of these functions is initiated by blocks 214, 216, 218, 220 and 222, respectively. In the event that W
  • a block 224 oper ⁇ ates the display. 53, Fig. 4, to indicate the currently stored set up values. If desired, the operator may be re- ⁇ quired to enter a valid password before the block 224 is executed. The operator is then prompted by the display 53 to enter a set up identifying number by means of the push ⁇ buttons 54. Once the operator has done this, a block 226 reads the set up number and a block 228 loads the selected 0- set up values which are stored in the nonvolatile memory 180.
  • the change of parameter function is accomplished by prompting the operator to enter one or more parameter values via the pushbuttons 54. Once this is accomplished and the parameter values are read by a block 230, the para ⁇ meter values are stored by a block 232 . in the internal mem ⁇ ory of the microprocessor 32.
  • the hard copy printed report function is accom ⁇ plished by blocks 234,236,238 (Fig. 5B) which prompt the : operator to ready the printer 162 and print the hard copy report once the operator has acknowledged that the printer 162 has been readied.
  • the help function is implemented by a block 210 which causes the display to generate appropriate help mes- ' sages, as needed. This function is entirely optional and may be omitted, if desired.
  • the learning mode begins at a block 250 (Fig. 5C) which checks the pushbuttons 54 to determine whether the operator has requested a sorting operation or a detection operation.
  • the sorting operation also referred to as the identification or classification operation, re ⁇ sults in the storage of two or more vectorial range indica ⁇ tions in the internal memory of the microprocessor 32 and/or the nonvolatile memory 180, such indications defining the ranges of expected signals which would be developed in the receive coils by passage of different products on the con ⁇ veyor 19.
  • the detection operation results in the storage of a single vectorial range in the internal memory of the mi ⁇ croprocessor 32 or in the nonvolatile memory 180 which de ⁇ fines the signals which would be expected to be developed in the receive coils 20 when uncontaminated product is present on the conveyor 19.
  • a block 252 operates the display 53 to inform an operator that learning is to occur for a certain period of time fol- lowing actuation of a start button which is one of the push ⁇ buttons 54.
  • a block 254 then operates the display 53 to in turn prompt the operator to pass samples of uncontaminated product through the coils 16,20 on the conveyor 19.
  • a block 255, Fig. 5D sets the value of three var ⁇ iables ZLEVELMAX, ZALPHAMAX and ZALPHAMIN to zero. These variables, as described in greater detail hereinafter, are used to derive representations of the maximum amplitude, maximum angle and minimum angle, respectively, of one or more learned vector ranges.
  • a block 256 then sets a flag LEARN which is stored in the RAM 176 and a timer maintained in the RAM 176 is started' by a block 257.
  • a portion of the data acquisition and computation routine illustrated in Fig. 6C is enabled by setting of the LEARN flag.
  • the programming illustrated in Figs. 6A-6C is repetitvely executed on an real time interrupt basis to generate vectorial values for each of the samples which are passed through the coils 16, 20. These vectorial values in turn determine values for the -22-
  • ALPHA2 ZALPHAMAX-(ZALPHAMAX/8)
  • the values ZLEVEL, ALPHA1 and ALPHA2 define the bounds of a final vectorial range.
  • a block 263 checks to determine whether sorting has been selected. If so, a block 264 determines whether additional items are to be learned. If this is also the case, a block 265 stores the values ZLEVEL, ALPHA1 and ALPHA2 in the RAM 176 and control returns to the block 252, Fig. 5C so that such items may be learned. When this oc ⁇ curs, additional values ZLEVEL, ALPHA1 and ALPHA2 are de- termined and stored in the RAM 176.
  • con ⁇ trol passes to a block 266 which identifies the stored val ⁇ ues resulting from execution of the blocks 252-265 as the -23-
  • This set up defines the vectorial range(s) stored in the internal memory of the microprocessor 32 against which subsequent vectors are compared.
  • a block 267 then prompts the operator to enter an identifying number or name under which this set up may be stored and recalled.
  • a block 272 operates the dis ⁇ play 53 to prompt the operator to actuate the start button and to note that the learning mode is to be operative for a particular length of time. Once the start button has been actuated, the operator is prompted to pass through a series of samples of an item. Control then passes to the block 255, Fig. 5D.
  • the tolerance band estab ⁇ lished by the blocks 260-262 is empirically determined and should be selected to be sufficiently large to reduce or minimize the chance of rejecting good product or to minimize the chance of mistakenly not identifying a product but should not be so large as to allow contaminated product to pass undetected or to result in misidentification of an item.
  • the block 290 obtains data from the data acquisition and computation routine to determine the field voltage vector magnitude and angle resulting from passage of such product between the coils 20a, 20b.
  • a block 292 (Fig. 5B) then checks to determine whether the sorting or detection operation has been selected.
  • a block 294 com ⁇ pares the vector against the stored indication of vectorial ranges as defined by the determined series of values ZLEVEL, ALPHAl and ALPHA2 to determine whether the vector falls within any of the ranges. If this is not the case, the dis ⁇ play is operated to indicate that no match has been found for the item, and control passes to a block 298 which imple ⁇ ments a fault routine.
  • a block 300 operates the display to identify the product by number or name.
  • a block 302 then operates one of the actuator relays 154 which in turn controls an appropriate sorting device similar to the reject actuator 48 so that the item is placed with other like items.
  • a block 304 checks to determine whether the vector magnitude and angle are within the single prestored vectorial range represented by the single set of determined values ZLEVEL, ALPHAl and ALPHA2. If this is the case, the. display is operated by a block 306 to indicate that the item is not defective. On the other hand, if the vector does not fall within the prestored range indication, the display is operated by a block 308 to alert the operator that a defective item is present on the conveyor.
  • a reject indicator is actuated by a block 310 and the reject actuator 48 is operated by a block 312 (Fig. 5C) after the time delay required to place the item adjacent the actuator 48 on the conveyor. The item is thereby rejected and the output of the reject verify sensor 49 is checked to determine whether the rejection operation has been carried out.
  • a block 313 which checks to determine whether a time Ti has elapsed since the signals passed to the D/A converters 33a,33b were last updated. If .this is not the case, control returns to the block 212, Fig. 5A, which checks to determine whether an operator command has been entered. On the other
  • the block 314 analyzes the digitized phase detec ⁇ tor output to determine whether such outputs are at substan ⁇ tially a zero voltage level plus or minus a small tolerance
  • Control passes to a block 315 which checks to determine whether the D/A converters are already at their
  • Control also passes to the block 318 directly from the block 315 if the latter determines that the D/A converters 33a,33b are not at their limits.
  • the block 318 checks to determine whether one or both of the digitized phase detector outputs are above or below a tolerance band. If a phase detector output is a- bove, a block 319 reduces the D/A converter values and, if a
  • a block 320 increases the D/A converter values.
  • a block 321 then replaces the old D/A converter values with the values determined by the blocks 319,320.
  • An interrupt procedure is also provided by a block
  • 10. 322 which stores the set-up values and other data needed for power-up of the microprocessor 32 in the nonvolatile memory 180 when a power interruption occurs.
  • FIG. 6A-6C there is illustrated in greater detail the data acquisition and computation rou-
  • the routine begins at a block 323 which reads a pair of values that are the digital equivalents of the out ⁇ puts of the low pass filters 120a-120b illustrated in Fig. 4.
  • a block 324 then checks to determine whether these val-
  • a block 325 adjusts the gain of the amplifiers 70,79 so that the output signals from the A/D converter 134 are brought within the range. Also, the gains of the variable gain amplifiers 147,149 are adjusted so that
  • the blocks 324,325 comprise an automatic gain control (or autoranging) which prevents saturation of the electrical components by reducing the amplifier gain when a large metal object is detected. These blocks also increase the gain of the amplifiers when
  • the output of the A/D converter 134 is too low so that sen ⁇ sitivity is increased.
  • these blocks keep the signal levels within the dynamic range of the amplifiers so that wide dynamic response is obtained with high sensitiv- ity.
  • a block 326 then obtains and stores a predeter ⁇ mined number (called a "block") of pairs of output values from the A/D converter 134 representing the output of both low pass filters 120a,120b. These values are referred to as a "time series pair" of values .to denote that the values are stored along with an indication of the time at which they were detected.
  • a block 327 checks to determine whether the entire block of time series pair values has been acquired. If this is not the case, control returns to the block 323 where ad ⁇ ditional pairs of values are detected. On the other hand, if all of the pairs of values have been detected, a block 328 determines whether any of the values exceeds an upper limit value of a noise band. If none of the values exceed this upper limit value, then it is assumed that the pairs of values were generated by noise, and hence control returns to the blocks 323-327 until a new block of values has been ob- tained.
  • the block 330 analyzes the values received from the A/D converter 134 to determine whether the analog sig ⁇ nals represented by these values contain two or three peaks of alternating polarity. If neither satisfies this condi ⁇ tion, then it is assumed that the data from the A/D conver ⁇ ter has resulted from noise in the system, and hence an er- ror message is displayed by a block 332 indicating that the noise is excessive. Control then passes to a block 334 ' which implements a fault routine. It should be noted that the alternating current signal may have two or three peaks, depending upon the length of the items on the conveyor. Generally, shorter items will develop only two peaks while longer items will be
  • a further test for noise is undertaken by a block 336 which senses the periods of time ti and t 2 between the
  • the block 338 senses the period of the alternating
  • Control then passes to a block 342 which exe ⁇ cutes a fault routine.
  • a block 344 (Fig. 6B) checks the state of a self-test flag stored in memory.
  • the self-test generator (Fig. 6B) checks the state of a self-test flag stored in memory.
  • 30" 170 is continuously operated to provide the series of pulses via the auxiliary winding 172, Fig. 4, to in turn check the operative status of the electrical components. If the self- test is not passed, the self-test flag is set low and is detected by the block 344. The display 53 is then operated by a block 346 to indicate the fault and control passes to a block 348 where a fault routine is executed.
  • a block 354 analyzes the data from the A/D conver ⁇ ter 134 to determine the magnitude and sign of the second peak of each of the alternating current waveforms and stores an indication of same in the internal memory of the micro ⁇ processor 32.
  • a block 356 detects and stores the time of the zero crossing between the first and second peaks of each of the waveforms. The magnitude of the second peaks of the waveforms are used to develop values X and Y indicating the real and imaginary components of the voltage vector defining the field sensed by the receive coils 20a,2Ob. The time of the zero crossing is used to determine the position of the item on the conveyor so that the item can be rejected, if necessary, or sorted by actuators downstream on the convey ⁇ or.
  • a block 358 then checks to determine whether the magnitude of one of the waveforms represented by the data from the A/D converter is within the noise band. If this is the case, then the vector defining the field sensed by the receive coils 20 is very close to the real or imaginary ax ⁇ is.
  • a pair of blocks 360,362 compute the polar magnitude and angle of the field vector using a predetermined lower limit value of the noise band for one of the values X or Y and by using the upper limit value of the noise band for the same value X or Y. These upper and lower limit values cor- * respond to the amplitude boundaries of the noise band.
  • the blocks 360,362 establish a range of possible field vectors representing the sensed field which is stored by a block 364 in the internal memory in the microprocessor 32.
  • a block 366 com- putes the polar magnitude and angle of the field voltage vector defining the sensed field and a block 368 stores an indication of this vector in the internal memory in the mi ⁇ croprocessor 32.
  • the blocks 360,362,366 compute the polar magnitude and angle of the field vector using the following equations:
  • the block 370 checks to determine whether the LEARN flag is set. If not, control returns directly to the appropriate spot in Figs. 5A-5D. On the other hand, if the LEARN flag is set, a block 372 determines whether the magnitude MAG of the vector representing the most recent sensed item is the largest mag- nitude of the vectors representing all of the items sensed up to the present time. If so, the variable ZLEVELMAX is established at the following value:
  • ZLEVELMAX (ZLEVELMAX 0 LD + MAG)/2
  • ZLEVELMAXOLD s the previously determined- value of ZLEVELMAX.
  • phase angle (denoted ANGLE) of the most recent vector is compared against the highest and lowest phase angles of the previously sensed items. If ANGLE is larger than the previous largest phase angle, the value ZALPHAMAX is established by a block 378 according to the first equation below. If ANGLE is smaller ' than the previous smallest phase angle, the value ZALPHAMIN is established by a block 382 according to the second equa ⁇ tion below. If ANGLE is equal to or between the previous smallest and largest phase angles, the values ZALPHAMAX and ZALPHAMIN remain unchanged.
  • ZALPHAMAXOLD and - ZALPHAMINoLD are tne previously de ⁇ termined values of ZALPHAMAX and ZALPHAMIN, respectively.
  • the blocks 374, 378 and 382 establish the values ZLEVELMAX, ZALPHAMAX and ZALPHAMIN as running averages. These values, therefore, are based on at least one, and likely more than one of the vectors deter ⁇ mined in the learn mode. This in turn limits the vectorial range(s) to a certain extent so that the chances of mistak- enly identifying an item or wrongly accepting bad product are minimized.
  • Control from the programming illustrated in Fig. 6C returns to the appropriate spot in Figs. 5A-5D.
  • the present apparatus achieves high sensitivity by : reducing the effects of noise. This is accomplished by the use of: (a) the resonant tank circuit comprising the re ⁇ ceive coils 20 and the capacitor C2; (b) the floating dif ⁇ ferential mode signals which are coupled over the transmis ⁇ sion line 74; ( ⁇ ) the bandpass filter 23 which filters spur- ious signals; (d) the low pass filters 120a,120b which remove signal components higher than that corresponding to the maximum product speed on the conveyor; (e) the extensive noise checking effected by the data acquisition subroutine shown in Figs. 6A-6C; and (f) the wide dynamic response ef- fected through the use of the autoranging function.
  • the reference signal for the phase detectors is de ⁇ rived from the output of the RE oscillator 14, and hence the outputs of the level shifting circuits 108,110 are maintain ⁇ ed at a precise 0° and 90" displacement with respect to the - excitation signal regardless of drift in operating frequency fo-
  • the phase detectors have wide dynamic range and have a low noise floor to allow high sensitivity.
  • the foregoing description of the present invention - assumes that the items on the conveyor are not in bulk form.
  • the instant apparatus can be used to detect product in pipeline or free-falling installations ' where the product is conveyed in bulk or fluid form. In this case, it may or may not be necessary to change opera- tion of the auto balance circuit 26 to obtain proper opera ⁇ tion of the apparatus. If a change is required, however, the apparatus is first turned on and the output of the auto balance circuit 26 is allowed to stabilize before product is introduced in the region between the coils 20a,20b. Then, the microprocessor generates a signal to cause the auto bal ⁇ ance circuit 26 to maintain the stabilized level of its out ⁇ put during subsequent operation of the apparatus.
  • microprocessor 32 to perform many of the functions of the detector permits features to be add- ed or deleted simply by modifying the program steps. This allows customization of the detector for a particular in ⁇ stallation with a minimum of expense and complexity.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Electromagnetism (AREA)
  • Environmental & Geological Engineering (AREA)
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Abstract

Un appareil de détection/identification permettant de détecter la présence d'un article en un point particulier dans l'espace comprend des moyens (14, 16) pour établir, à l'aide d'un signal d'excitation de champ, un champ électromagnétique alternatif dans un volume d'espace contenant le point, des moyens (28a, 28b) pour définir un vecteur de champ représentant le champ électromagnétique par rapport à un vecteur de base représentant le signal d'excitation, et des moyens (32) sensibles auxdits moyens de définition en vue de déterminer si le vecteur de champ se situe en dehors d'une plage de valeurs vectorielles, cette détermination signalant la présence de l'article en un point particulier. Si on le désire, on peut également utiliser l'appareil pour distinguer et par là-même identifier plusieurs articles différents.
PCT/US1987/002684 1986-10-23 1987-10-20 Appareil de detection/identification WO1988003273A1 (fr)

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US92218786A 1986-10-23 1986-10-23
US922,187 1986-10-23

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Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0337783A2 (fr) * 1988-04-13 1989-10-18 Yamato Scale Co., Ltd. Détecteur de matière étrangère
EP0353035A2 (fr) * 1988-07-26 1990-01-31 Yamato Scale Co., Ltd. Détecteur de matière étrangére
EP0375366A2 (fr) * 1988-12-20 1990-06-27 Loma Group Limited Procédé et dispositif utilisant un champ électromagnétique variable pour déterminer la nature ou une propriété d'un matériau conducteur non-métallique
US5034689A (en) * 1988-04-13 1991-07-23 Yamato Scale Company, Limited Detector for detecting foreign matter in an object by detecting electromagnetic parameters of the object
FR2708748A1 (fr) * 1993-08-02 1995-02-10 Azkoyen Ind Sa Procédé et dispositif pour la mesure et la caractérisation, à grande vitesse, de matériaux magnétiques.
DE19510114A1 (de) * 1995-03-21 1996-09-26 Forschungsgesellschaft Fuer In Einrichtung zum Messen magnetischer Remanenz
EP0862067A1 (fr) * 1997-02-28 1998-09-02 Laboratoires d'Electronique Angelidis et Sarrault Dispositif et méthode de détection, d'indentification et de tri d'emballages métalliques ou comprenant une partie métallique
WO2001051959A1 (fr) * 2000-01-12 2001-07-19 Willett International Limited Dispositif et procede permettant de detecter la contamination d'un objet par un metal
WO2006087510A1 (fr) * 2005-02-16 2006-08-24 Illinois Tool Works, Inc. Detecteur de metal
WO2009130018A1 (fr) * 2008-04-23 2009-10-29 Mesutronic Gerätebau GmbH Dispositif à fonctionnement numérique pour détecter des éléments conducteurs métalliques
GB2499239A (en) * 2012-02-10 2013-08-14 Illinois Tool Works Automatically balancing the detector coil system in a metal detector
WO2013119741A1 (fr) * 2012-02-10 2013-08-15 Illinois Tool Works Inc. Détecteur de métaux
EP2674791A1 (fr) * 2012-06-15 2013-12-18 Mettler-Toledo Safeline Limited Dispositif et procédé pour détecter les contaminants métalliques dans un produit
US9018935B2 (en) 2011-09-19 2015-04-28 Mettler-Toledo Safeline Limited Method for operating a metal detection apparatus and apparatus
US9665847B2 (en) 2009-12-22 2017-05-30 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
EP3158369A4 (fr) * 2014-06-19 2018-02-21 Metrotech Corporation Système de localisation de ligne pourvu d'un détecteur de métaux
DE102017111722A1 (de) * 2017-05-30 2018-12-06 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und vorrichtung zum charakterisieren eines objekts, verfahren und vorrichtung zum bestimmen einer zusammensetzung eines objekts sowie verfahren und vorrichtung zum erkennen eines elektrisch leitfähigen und/oder magnetisch permeablen objekts
DE102017124407A1 (de) 2017-10-19 2019-04-25 Minebea Intec Aachen GmbH & Co. KG Verfahren zur Signalauswertung, Auswerteeinheit sowie Metallsuchgerät
DE102018121762A1 (de) * 2018-03-20 2019-09-26 Sesotec Gmbh Verfahren und Vorrichtung zur Aussonderung von metallhaltigen Materialien
DE102020117243A1 (de) 2020-06-30 2021-12-30 Minebea Intec Aachen GmbH & Co. KG Metalldetektor mit digitalisierter Empfangsvorrichtung für simultane Demodulation

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US3676772A (en) * 1970-08-18 1972-07-11 Nasa Metallic intrusion detector system
US4006407A (en) * 1975-03-10 1977-02-01 Magnaflux Corporation Non-destructive testing systems having automatic balance and sample and hold operational modes
US4351031A (en) * 1980-11-07 1982-09-21 Magnaflux Corporation Nondestructive testing system having automatic set-up means

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3676772A (en) * 1970-08-18 1972-07-11 Nasa Metallic intrusion detector system
US4006407A (en) * 1975-03-10 1977-02-01 Magnaflux Corporation Non-destructive testing systems having automatic balance and sample and hold operational modes
US4351031A (en) * 1980-11-07 1982-09-21 Magnaflux Corporation Nondestructive testing system having automatic set-up means

Cited By (39)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0337783A2 (fr) * 1988-04-13 1989-10-18 Yamato Scale Co., Ltd. Détecteur de matière étrangère
EP0337783A3 (fr) * 1988-04-13 1991-04-03 Yamato Scale Co., Ltd. Détecteur de matière étrangère
US5034689A (en) * 1988-04-13 1991-07-23 Yamato Scale Company, Limited Detector for detecting foreign matter in an object by detecting electromagnetic parameters of the object
EP0353035A2 (fr) * 1988-07-26 1990-01-31 Yamato Scale Co., Ltd. Détecteur de matière étrangére
EP0353035A3 (fr) * 1988-07-26 1991-03-20 Yamato Scale Co., Ltd. Détecteur de matière étrangére
US5045789A (en) * 1988-07-26 1991-09-03 Yamato Scale Company, Limited Detector for detecting foreign matter in object by using discriminant electromagnetic parameters
EP0375366A2 (fr) * 1988-12-20 1990-06-27 Loma Group Limited Procédé et dispositif utilisant un champ électromagnétique variable pour déterminer la nature ou une propriété d'un matériau conducteur non-métallique
EP0375366A3 (en) * 1988-12-20 1990-09-05 Loma Group Limited Method and apparatus using a varying electromagnetic field for determining the nature, or a property of a material
US5189366A (en) * 1988-12-20 1993-02-23 Loma Group Limited Method and apparatus using a varying electromagnetic field for determining the nature, or a property of a non-metallic material
FR2708748A1 (fr) * 1993-08-02 1995-02-10 Azkoyen Ind Sa Procédé et dispositif pour la mesure et la caractérisation, à grande vitesse, de matériaux magnétiques.
DE19510114A1 (de) * 1995-03-21 1996-09-26 Forschungsgesellschaft Fuer In Einrichtung zum Messen magnetischer Remanenz
EP0862067A1 (fr) * 1997-02-28 1998-09-02 Laboratoires d'Electronique Angelidis et Sarrault Dispositif et méthode de détection, d'indentification et de tri d'emballages métalliques ou comprenant une partie métallique
FR2760276A1 (fr) * 1997-02-28 1998-09-04 Pechiney Recherche Dispositif et methode de detection, d'identification et de tri d'emballages metalliques ou comprenant une partie metallique
WO2001051959A1 (fr) * 2000-01-12 2001-07-19 Willett International Limited Dispositif et procede permettant de detecter la contamination d'un objet par un metal
WO2006087510A1 (fr) * 2005-02-16 2006-08-24 Illinois Tool Works, Inc. Detecteur de metal
US8473235B2 (en) 2005-02-16 2013-06-25 Illinois Tool Works Inc. Metal detector
WO2009130018A1 (fr) * 2008-04-23 2009-10-29 Mesutronic Gerätebau GmbH Dispositif à fonctionnement numérique pour détecter des éléments conducteurs métalliques
US11797512B2 (en) 2009-12-22 2023-10-24 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
US10380095B2 (en) 2009-12-22 2019-08-13 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
US10083197B2 (en) 2009-12-22 2018-09-25 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
US10019606B2 (en) 2009-12-22 2018-07-10 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
US9665847B2 (en) 2009-12-22 2017-05-30 Philip Morris Usa Inc. Method and apparatus for storage of data for manufactured items
US9018935B2 (en) 2011-09-19 2015-04-28 Mettler-Toledo Safeline Limited Method for operating a metal detection apparatus and apparatus
WO2013119741A1 (fr) * 2012-02-10 2013-08-15 Illinois Tool Works Inc. Détecteur de métaux
CN104246539A (zh) * 2012-02-10 2014-12-24 伊利诺斯工具制品有限公司 金属探测器
GB2499239B (en) * 2012-02-10 2014-02-12 Illinois Tool Works Metal detector
GB2499239A (en) * 2012-02-10 2013-08-14 Illinois Tool Works Automatically balancing the detector coil system in a metal detector
US10215875B2 (en) 2012-02-10 2019-02-26 Illinois Tool Works Inc. Metal detector
EP2674791A1 (fr) * 2012-06-15 2013-12-18 Mettler-Toledo Safeline Limited Dispositif et procédé pour détecter les contaminants métalliques dans un produit
US9448323B2 (en) 2012-06-15 2016-09-20 Mettler-Toledo Safeline Ltd. Device and method for detecting metallic contaminants in a product
CN103592339A (zh) * 2012-06-15 2014-02-19 梅特勒-托利多安全线有限公司 用于检测产品中的金属污染物的设备和方法
JP2014002149A (ja) * 2012-06-15 2014-01-09 Mettler-Toledo Safeline Ltd 製品中の金属汚染物質を検出するためのデバイスおよび方法
EP3158369A4 (fr) * 2014-06-19 2018-02-21 Metrotech Corporation Système de localisation de ligne pourvu d'un détecteur de métaux
US11156490B2 (en) 2017-05-30 2021-10-26 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Method and apparatus for determining a fill level of a storage container
DE102017111722A1 (de) * 2017-05-30 2018-12-06 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und vorrichtung zum charakterisieren eines objekts, verfahren und vorrichtung zum bestimmen einer zusammensetzung eines objekts sowie verfahren und vorrichtung zum erkennen eines elektrisch leitfähigen und/oder magnetisch permeablen objekts
DE102017124407A1 (de) 2017-10-19 2019-04-25 Minebea Intec Aachen GmbH & Co. KG Verfahren zur Signalauswertung, Auswerteeinheit sowie Metallsuchgerät
DE102017124407B4 (de) 2017-10-19 2020-07-02 Minebea Intec Aachen GmbH & Co. KG Verfahren zur Signalauswertung, Auswerteeinheit sowie Metallsuchgerät
DE102018121762A1 (de) * 2018-03-20 2019-09-26 Sesotec Gmbh Verfahren und Vorrichtung zur Aussonderung von metallhaltigen Materialien
DE102020117243A1 (de) 2020-06-30 2021-12-30 Minebea Intec Aachen GmbH & Co. KG Metalldetektor mit digitalisierter Empfangsvorrichtung für simultane Demodulation

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