CA2629408A1 - Induction balance sensor - Google Patents
Induction balance sensor Download PDFInfo
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- CA2629408A1 CA2629408A1 CA002629408A CA2629408A CA2629408A1 CA 2629408 A1 CA2629408 A1 CA 2629408A1 CA 002629408 A CA002629408 A CA 002629408A CA 2629408 A CA2629408 A CA 2629408A CA 2629408 A1 CA2629408 A1 CA 2629408A1
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- signal
- mineral
- software program
- balance sensor
- induction
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- 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
- G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
- G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
- G01V3/28—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device using induction coils
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
Abstract
The present invention consists of an induction-balance type sensor system an d method for detecting and recording electrical characteristics of conductive media, specifically low grade nickel ore and other conductive ores. The system comprises an arbitrary waveform generator, signal electronics, a sensing coil and a matched balancing coil with extension cables, data acquisition hardware, a computer running a software package, and power electronics. The base functionality of the sensor system finds use in differing applications, such as sample characterization, bore hole mapping, and automated ore sorting.
Description
INDUCTION BALANCE SENSOR
BACKGROUND OF THE INVENTION
The present invention is in the field of conductivity sensing, specifically the conductivity evaluation of ore samples, including low grade base metal sulphide ores. More particularly, the present invention is in the technical field of induction balance sensing, with applications in down the hole sensing and conductivity based sorting.
BRIEF SUMMARY OF THE INVENTION
The present invention consists of an induction-balance type sensor system and method for detecting and recording electrical characteristics of conductive media, specifically low grade nickel ore and other conductive ores. The system comprises an arbitrary waveform generator, signal electronics, a sensing coil and a matched balancing coil with extension cables, data acquisition hardware, a computer running a software package, and power electronics. The base functionality of the sensor system finds use in differing applications, such as sample characterization, bore hole mapping, and automated ore sorting.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a block diagram of the system components;
Fig. 2 is a signal flow diagram representing implemented circuitry;
Fig. 3 is an isometric view of a coil and coil housing block;
Fig. 4 is a drawing of a down-the-hole sensing application; and Fig. 5 is a drawing of a sorting application.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the invention in more detail, in Fig. 1 there is shown a block diagram of the system components. An arbitrary waveform generator 10 provides an input signal to the signal electronics 11, where it is applied to a pair of matching inductor coils 12a and 12b. Output from the coils 12 is sent back through the signal electronics 11 and is captured by the data acquisition hardware 13. The captured data is processed and analyzed by a computer software package 14. A regulated DC
power supply 15 provides power to the integrated circuits in the signal electronics 11. The dashed lines indicate one exemplary arrangement of the components; the waveform generator and data acquisition hardware are implemented on a single PCI card mounted in a computer 16, and the power supply and signal electronics are housed together within an enclosure 17. Other equivalent arrangements are easily conceivable, and the invention is not limited to the above described arrangement.
Waveform generation control is performed by the software package 14. The waveform generation hardware 10 is capable of producing user selectable arbitrary waveforms, including single frequency signals of specifiable shape, amplitude and frequency, composite signals of multiple frequencies, and frequency sweep signals with specifiable range. A generated waveform is applied at the input of the signal electronics 11, where it is conditioned to drive the matched coils 12a and 12b.
The input signal is filtered and amplified by the signal electronics 11 before being applied to the coils 12a and 12b as an excitation signal.
One coil functions as a sensing coil 12a used to examine samples, and the other as a balancing coil 12b used as a reference to the sensing coil. The balancing coil 12b is subject to the same static environmental conditions as the sensing coil 12a, but is kept isolated from the samples to be examined.
In the presence of conductive media, the impedance of the sensing coil 12a no longer matches that of the balancing coil 12b . This impedance change unbalances the signal electronics 11, producing a voltage signal of magnitude and phase related to the change in resistive and reactive components of the sensing coil impedance.
The unbalanced signal, along with a reference of the excitation signal 18, are sent back through the signal electronics 11, where they are conditioned for output to the data acquisition hardware 13.
BACKGROUND OF THE INVENTION
The present invention is in the field of conductivity sensing, specifically the conductivity evaluation of ore samples, including low grade base metal sulphide ores. More particularly, the present invention is in the technical field of induction balance sensing, with applications in down the hole sensing and conductivity based sorting.
BRIEF SUMMARY OF THE INVENTION
The present invention consists of an induction-balance type sensor system and method for detecting and recording electrical characteristics of conductive media, specifically low grade nickel ore and other conductive ores. The system comprises an arbitrary waveform generator, signal electronics, a sensing coil and a matched balancing coil with extension cables, data acquisition hardware, a computer running a software package, and power electronics. The base functionality of the sensor system finds use in differing applications, such as sample characterization, bore hole mapping, and automated ore sorting.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a block diagram of the system components;
Fig. 2 is a signal flow diagram representing implemented circuitry;
Fig. 3 is an isometric view of a coil and coil housing block;
Fig. 4 is a drawing of a down-the-hole sensing application; and Fig. 5 is a drawing of a sorting application.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the invention in more detail, in Fig. 1 there is shown a block diagram of the system components. An arbitrary waveform generator 10 provides an input signal to the signal electronics 11, where it is applied to a pair of matching inductor coils 12a and 12b. Output from the coils 12 is sent back through the signal electronics 11 and is captured by the data acquisition hardware 13. The captured data is processed and analyzed by a computer software package 14. A regulated DC
power supply 15 provides power to the integrated circuits in the signal electronics 11. The dashed lines indicate one exemplary arrangement of the components; the waveform generator and data acquisition hardware are implemented on a single PCI card mounted in a computer 16, and the power supply and signal electronics are housed together within an enclosure 17. Other equivalent arrangements are easily conceivable, and the invention is not limited to the above described arrangement.
Waveform generation control is performed by the software package 14. The waveform generation hardware 10 is capable of producing user selectable arbitrary waveforms, including single frequency signals of specifiable shape, amplitude and frequency, composite signals of multiple frequencies, and frequency sweep signals with specifiable range. A generated waveform is applied at the input of the signal electronics 11, where it is conditioned to drive the matched coils 12a and 12b.
The input signal is filtered and amplified by the signal electronics 11 before being applied to the coils 12a and 12b as an excitation signal.
One coil functions as a sensing coil 12a used to examine samples, and the other as a balancing coil 12b used as a reference to the sensing coil. The balancing coil 12b is subject to the same static environmental conditions as the sensing coil 12a, but is kept isolated from the samples to be examined.
In the presence of conductive media, the impedance of the sensing coil 12a no longer matches that of the balancing coil 12b . This impedance change unbalances the signal electronics 11, producing a voltage signal of magnitude and phase related to the change in resistive and reactive components of the sensing coil impedance.
The unbalanced signal, along with a reference of the excitation signal 18, are sent back through the signal electronics 11, where they are conditioned for output to the data acquisition hardware 13.
2 The data acquisition system 13 is capable of real-time data streaming into a computer and is used to digitize the output signals for analysis by the software package 14. Data from the two measured signals 18 undergoes Fast Fourier Transform operations to extract and display spectral information. The change in impedance of the sensing coil 12a is then calculated, and magnitude and phase values are displayed. Depending on the application, the data can be recorded as individual values, stored in a database and correlated to previous entries, plotted as a positional map, or used to make a decision and generate a control signal.
The power supply 15 is a common component with internal operations and design non-critical to the invention, with the sole purpose of providing a DC voltage as required by integrated circuits in the signal electronics 11. The power supply is controlled by an ON/OFF switch and indicated by a light when operational. With the switch in the off position, no signal is applied to the coils 12a and 12b, and the data acquisition system 13 will only receive noise.
Referring now to the individual system components in more detail, in Fig. 2 there is shown a signal flow diagram of the signal electronics 11 previously described, and how they interact with the waveform generator 10 and data acquisition hardware 13. The signal electronics 11 comprise an input filter stage 19, a signal splitter stage 20, a power amplifier with differential output 21, a balanced bridge network 22 incorporating the matched coils 12a and 12b, and on each of the output channel lines, amplification 23, and filtering stages 24.
Output from the arbitrary waveform generator 10 is applied as an input to the signal electronics 11. The input filter 19 is a low pass filter with a cutoff frequency greater than the highest frequency component of the input signal. The filter is used to smooth the generated signal and remove spectral images produced by the waveform generator 10. The signal splitter stage 20 then produces inverted and non-inverted versions of the original signal, which are used as inputs to the power amplifier 21.
The differential outputs of the power amplifier 21 are used as the driving current to excite the bridge network 22, providing a balanced source of positive and negative signals.
Variable gain incorporated into the power amplifier 21 circuit allows for hardware level control of the excitation signal amplitude.
The power supply 15 is a common component with internal operations and design non-critical to the invention, with the sole purpose of providing a DC voltage as required by integrated circuits in the signal electronics 11. The power supply is controlled by an ON/OFF switch and indicated by a light when operational. With the switch in the off position, no signal is applied to the coils 12a and 12b, and the data acquisition system 13 will only receive noise.
Referring now to the individual system components in more detail, in Fig. 2 there is shown a signal flow diagram of the signal electronics 11 previously described, and how they interact with the waveform generator 10 and data acquisition hardware 13. The signal electronics 11 comprise an input filter stage 19, a signal splitter stage 20, a power amplifier with differential output 21, a balanced bridge network 22 incorporating the matched coils 12a and 12b, and on each of the output channel lines, amplification 23, and filtering stages 24.
Output from the arbitrary waveform generator 10 is applied as an input to the signal electronics 11. The input filter 19 is a low pass filter with a cutoff frequency greater than the highest frequency component of the input signal. The filter is used to smooth the generated signal and remove spectral images produced by the waveform generator 10. The signal splitter stage 20 then produces inverted and non-inverted versions of the original signal, which are used as inputs to the power amplifier 21.
The differential outputs of the power amplifier 21 are used as the driving current to excite the bridge network 22, providing a balanced source of positive and negative signals.
Variable gain incorporated into the power amplifier 21 circuit allows for hardware level control of the excitation signal amplitude.
3 The implemented bridge network 22 is a conventional Wheatstone bridge, used to measure impedance differences between bridge components in the form of a voltage signal. Variations of the Wheatstone bridge, and other bridge networks, provide equivalent methods of detecting impedance differences, and as such, the invention is not limited to one specific network arrangement.
In an ideal rest state with no conductive samples present, the bridge network 22 is perfectly balanced, and no voltage is seen across the bridge. Error tolerances in real components create an inherent imbalance in the bridge network 22, producing an unbalanced voltage signal even in the rest state. Local environmental factors also affect the bridge balance, such that the rest state unbalanced voltage of a given sensor system may differ between operating locations. The software package 14 calibrates the system by interpreting this rest state signal as a baseline response against which successive readings are measured.
Since the bridge network 22 is driven by an alternating current signal, the unbalanced voltage signal is measurable not only in magnitude, but also in phase with respect to the driving signal.
Measurement of these two components of the unbalanced signal makes the sensor system responsive to conductive and reactive properties of samples. Depending on the type of sample examined, the bridge network 22 may produce an unbalanced signal with a change in magnitude only, a change in phase only, or a combination of magnitude and phase changes. From these parameters, the sensor system can determine the amount and type of conductive media present in the sample.
Output channels 18 are taken from a reference of the excitation signal and an unbalanced signal from the bridge network 22. The output channels pass through variable gain differential amplifiers 23 for common mode rejection of any induced circuit noise. Low pass anti-aliasing filters 24 remove high frequency noise from the signals to prevent sampling errors. Buffer stages condition the signals for driving the data acquisition hardware.
Referring now to the individual system components in more detail, in Fig. 3 there is shown an isometric view of a coil and coil housing. The coil 26 rests in a base 27 comprising a solid block of high density polyethylene with a circular groove 28 routed around a center spindle 29. The coil 26 is produced by feeding one end of the wire though a cable hole 30 in the side of the base 27 and
In an ideal rest state with no conductive samples present, the bridge network 22 is perfectly balanced, and no voltage is seen across the bridge. Error tolerances in real components create an inherent imbalance in the bridge network 22, producing an unbalanced voltage signal even in the rest state. Local environmental factors also affect the bridge balance, such that the rest state unbalanced voltage of a given sensor system may differ between operating locations. The software package 14 calibrates the system by interpreting this rest state signal as a baseline response against which successive readings are measured.
Since the bridge network 22 is driven by an alternating current signal, the unbalanced voltage signal is measurable not only in magnitude, but also in phase with respect to the driving signal.
Measurement of these two components of the unbalanced signal makes the sensor system responsive to conductive and reactive properties of samples. Depending on the type of sample examined, the bridge network 22 may produce an unbalanced signal with a change in magnitude only, a change in phase only, or a combination of magnitude and phase changes. From these parameters, the sensor system can determine the amount and type of conductive media present in the sample.
Output channels 18 are taken from a reference of the excitation signal and an unbalanced signal from the bridge network 22. The output channels pass through variable gain differential amplifiers 23 for common mode rejection of any induced circuit noise. Low pass anti-aliasing filters 24 remove high frequency noise from the signals to prevent sampling errors. Buffer stages condition the signals for driving the data acquisition hardware.
Referring now to the individual system components in more detail, in Fig. 3 there is shown an isometric view of a coil and coil housing. The coil 26 rests in a base 27 comprising a solid block of high density polyethylene with a circular groove 28 routed around a center spindle 29. The coil 26 is produced by feeding one end of the wire though a cable hole 30 in the side of the base 27 and
4 alternating between winding layers from the outer edge of the groove 28 inward to the spindle 29, then outward from the spindle 29 to the outer groove edge 28. The free ends of the coi126 exit the base through the cable hole 30, are twisted together to prevent crosstalk interference, shielded with braided cable 31 to prevent external electromagnetic interference, and finally sealed in a protective insulating layer 32. A flex relief grommet 33 affixed to the base 27 around the cable prevents damage from sharp bends in the wire. An XLR connector 34 is used to connect the coi126 to the signal electronics 11 either directly or through an extension cable. Shield plates 35 are placed above and below the coil 26 to limit electromagnetic interference. The shields 35 are implemented with two-sided printed circuit boards, each side bearing a comb of 0.3mm thick copper traces, spaced 0.3mm apart, which are connected together and grounded. The entire sensor block is sealed by casting it in a polyester resin.
When excited, the coils 26 each produce a dynamic magnetic field in the surrounding environment, related in frequency and strength to the applied excitation signal. Electric currents are induced in conductive media present within the field. These currents, and their respective magnetic fields, alter the impedance of the coil-conductor system as seen across the sensing coil terminals. This change in impedance works to unbalance the bridge network 22, causing a potential difference across the center bridge nodes. The magnitude and phase of this signal is dependent on the conductive material present within the magnetic field.
To make the coils 26 less prone to internal, self-induced eddy currents, and more responsive to external influences, the coils 26 are wound from a conductor with minimum skin effect characteristics.
The coils are wound using Litz wire, a multi-stranded cable with each strand individually insulated.
This type of wire also reduces the proximity effect, an increase in resistance of adjacent conductors caused by field interactions.
Regardless of application, the system must undergo a startup and calibration routine before use.
In use, power is supplied to the signal electronics 11, and the desired operating mode and corresponding excitation signal are selected via the software package 14.
Initiating signal generation streaming does not necessarily initiate data acquisition streaming, depending on the selected operating mode. A rest state calibration reading is taken in the absence of conductive media and used as a baseline reading to compensate for any inherent imbalances in the bridge network 22. Once calibrated, the system is ready for use. Recalibration may occur at desired intervals to compensate for any changes in the local operating environment.
In operation, readings can be produced using a variety of generated signals and data acquisition methods. Useful signals include a frequency sweep and a multi-frequency composite signal. Data acquisition can function in snapshot mode, where a set of readings are recorded on demand, or streaming mode, where a continuous flow of data is recorded. Exemplary signals are a repeating frequency sweep up to 1Mhz, and a composite of 8 frequency components between 10kHz and 1MHz.
Each of these signals have their own use in application and can function with either snapshot mode or streaming mode data acquisition. The sweep signal produces a detailed set of readings for each sample but requires the sample to remain motionless for at least one sweep period.
The composite signal produces a set of readings with lower frequency resolution, though all readings for one sample are captured in a single instant.
In one implementation, readings from a group of samples are recorded before the samples are analyzed for mineral content. The readings are then correlated to their respective mineral content. A
sample database can then be constructed containing magnitude and phase readings from the sensor system along with the mineral analysis results. For this application, the more detailed sweep function is a preferable input signal, and snapshot mode data acquisition can be triggered manually. With a database in place, the sensor system can be used to judge characteristics of unknown samples without performing the mineral analysis process. The magnitude and phase readings produced by an unknown sample can be compared to similar entries in the database, thus the mineral content of the sample can be inferred.
Characterization of unknown samples can be performed by several conceivable means, not limited to desktop systems, conveyor systems, and down the hole systems. In a desktop system, the user manually places a sample above the sensing coil 12a, instructs the software 14 to take a reading, then removes the recorded sample and replaces it with a new sample, repeating the reading process.
For the desktop application, a sweep input signal is used with manually triggered snapshot mode data acquisition. In a conveyor system, the sensing coil 12a is mounted beneath a conveyor belt that moves samples along. For this application, a multi-frequency composite signal is used with streaming data acquisition. The software 14 streams the data signals and determines when a reading should be taken based on a specified threshold value. In a down the hole system, the sensing coil 12a is lowered down a bore hole while a continuous streaming signal is recorded. A composite input signal is used since the sensing coil is constantly in motion. The recorded data can be used to map conductive media distribution down the bore hole. An exemplary down the hole system is shown in Fig. 4. The sensing coil 12a is lowered down a bore hole while the computer 16, power and signal electronics 17, and the balancing coil 12b remain on the surface. As the sensing coil 12a passes through regions of non-conductive earth 35, slightly conductive deposits 36, and highly conductive deposits 37, a vertical mapping of the regions is created.
Using knowledge gained from correlating recorded readings to mineral analysis data, the system is able to discriminate between the amount and type of conductive material producing the readings.
Discrimination parameters can be set so the system only acknowledges samples containing a specified amount of a specified material. An application of this function is the ability of the system to sort a group of unknown samples depending on the type and grade of their mineral content. Sorting can be implemented in a user controlled desktop system or in an automated conveyor system where the software decision drives a conveyor mounted deflector.
In an automated sorting system, a composite input signal is used with streaming data acquisition. In Fig. 5 there is shown an exemplary automated ore sorting system. Ore samples 38 are transferred across the sensing coil 12a by a conveyor belt 39. The balancing coil 12b is kept away from the passing samples 38. Output from the signal electronics 17 is processed on a computer 16, which in turn controls a deflector arm 40. Samples containing desirable ore fall to one side of a divider 41, while undesirable samples fall to the other side.
Multiple coils can be arranged in an array to augment system performance. One application of a sensor array involves placing a row of sensors across the width of a conveyor. By monitoring the response from each sensing coil, the location of a conductive sample on the conveyor can be determined. It is conceivable that a sensor array may be used in conjunction with an optical sensor to correlate sample readings from the two sensor systems and better distinguish multiple samples in a single image. Such a combination would result in a more robust sorting system.
Alternatively, placing a row of sensors along the length of a conveyor would allow for taking multiple readings of each sample, which could then be averaged to produce a more accurate reading.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.
When excited, the coils 26 each produce a dynamic magnetic field in the surrounding environment, related in frequency and strength to the applied excitation signal. Electric currents are induced in conductive media present within the field. These currents, and their respective magnetic fields, alter the impedance of the coil-conductor system as seen across the sensing coil terminals. This change in impedance works to unbalance the bridge network 22, causing a potential difference across the center bridge nodes. The magnitude and phase of this signal is dependent on the conductive material present within the magnetic field.
To make the coils 26 less prone to internal, self-induced eddy currents, and more responsive to external influences, the coils 26 are wound from a conductor with minimum skin effect characteristics.
The coils are wound using Litz wire, a multi-stranded cable with each strand individually insulated.
This type of wire also reduces the proximity effect, an increase in resistance of adjacent conductors caused by field interactions.
Regardless of application, the system must undergo a startup and calibration routine before use.
In use, power is supplied to the signal electronics 11, and the desired operating mode and corresponding excitation signal are selected via the software package 14.
Initiating signal generation streaming does not necessarily initiate data acquisition streaming, depending on the selected operating mode. A rest state calibration reading is taken in the absence of conductive media and used as a baseline reading to compensate for any inherent imbalances in the bridge network 22. Once calibrated, the system is ready for use. Recalibration may occur at desired intervals to compensate for any changes in the local operating environment.
In operation, readings can be produced using a variety of generated signals and data acquisition methods. Useful signals include a frequency sweep and a multi-frequency composite signal. Data acquisition can function in snapshot mode, where a set of readings are recorded on demand, or streaming mode, where a continuous flow of data is recorded. Exemplary signals are a repeating frequency sweep up to 1Mhz, and a composite of 8 frequency components between 10kHz and 1MHz.
Each of these signals have their own use in application and can function with either snapshot mode or streaming mode data acquisition. The sweep signal produces a detailed set of readings for each sample but requires the sample to remain motionless for at least one sweep period.
The composite signal produces a set of readings with lower frequency resolution, though all readings for one sample are captured in a single instant.
In one implementation, readings from a group of samples are recorded before the samples are analyzed for mineral content. The readings are then correlated to their respective mineral content. A
sample database can then be constructed containing magnitude and phase readings from the sensor system along with the mineral analysis results. For this application, the more detailed sweep function is a preferable input signal, and snapshot mode data acquisition can be triggered manually. With a database in place, the sensor system can be used to judge characteristics of unknown samples without performing the mineral analysis process. The magnitude and phase readings produced by an unknown sample can be compared to similar entries in the database, thus the mineral content of the sample can be inferred.
Characterization of unknown samples can be performed by several conceivable means, not limited to desktop systems, conveyor systems, and down the hole systems. In a desktop system, the user manually places a sample above the sensing coil 12a, instructs the software 14 to take a reading, then removes the recorded sample and replaces it with a new sample, repeating the reading process.
For the desktop application, a sweep input signal is used with manually triggered snapshot mode data acquisition. In a conveyor system, the sensing coil 12a is mounted beneath a conveyor belt that moves samples along. For this application, a multi-frequency composite signal is used with streaming data acquisition. The software 14 streams the data signals and determines when a reading should be taken based on a specified threshold value. In a down the hole system, the sensing coil 12a is lowered down a bore hole while a continuous streaming signal is recorded. A composite input signal is used since the sensing coil is constantly in motion. The recorded data can be used to map conductive media distribution down the bore hole. An exemplary down the hole system is shown in Fig. 4. The sensing coil 12a is lowered down a bore hole while the computer 16, power and signal electronics 17, and the balancing coil 12b remain on the surface. As the sensing coil 12a passes through regions of non-conductive earth 35, slightly conductive deposits 36, and highly conductive deposits 37, a vertical mapping of the regions is created.
Using knowledge gained from correlating recorded readings to mineral analysis data, the system is able to discriminate between the amount and type of conductive material producing the readings.
Discrimination parameters can be set so the system only acknowledges samples containing a specified amount of a specified material. An application of this function is the ability of the system to sort a group of unknown samples depending on the type and grade of their mineral content. Sorting can be implemented in a user controlled desktop system or in an automated conveyor system where the software decision drives a conveyor mounted deflector.
In an automated sorting system, a composite input signal is used with streaming data acquisition. In Fig. 5 there is shown an exemplary automated ore sorting system. Ore samples 38 are transferred across the sensing coil 12a by a conveyor belt 39. The balancing coil 12b is kept away from the passing samples 38. Output from the signal electronics 17 is processed on a computer 16, which in turn controls a deflector arm 40. Samples containing desirable ore fall to one side of a divider 41, while undesirable samples fall to the other side.
Multiple coils can be arranged in an array to augment system performance. One application of a sensor array involves placing a row of sensors across the width of a conveyor. By monitoring the response from each sensing coil, the location of a conductive sample on the conveyor can be determined. It is conceivable that a sensor array may be used in conjunction with an optical sensor to correlate sample readings from the two sensor systems and better distinguish multiple samples in a single image. Such a combination would result in a more robust sorting system.
Alternatively, placing a row of sensors along the length of a conveyor would allow for taking multiple readings of each sample, which could then be averaged to produce a more accurate reading.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.
Claims (13)
1. An induction-balance sensor comprising:
a. a matched pair of wound induction coils, one being a sensing coil and the other being a balancing coil;
b. a device for the generation of a range of excitation signals;
c. a variable gain power amplifier circuit to drive the coils;
d. a bridge network to compare the impedance of the sensing coil to the impedance of the balancing coil;
e. a signal conditioning circuit to amplify and filter the bridge network output;
f. an analog to digital converter to digitize both the signal in (b) and the signal in (e);
g. a pair of shielded RF signal cables connecting said signal conditioning circuit to said analog to digital converter; and h. a software program for signal analysis, data recording, and process control.
a. a matched pair of wound induction coils, one being a sensing coil and the other being a balancing coil;
b. a device for the generation of a range of excitation signals;
c. a variable gain power amplifier circuit to drive the coils;
d. a bridge network to compare the impedance of the sensing coil to the impedance of the balancing coil;
e. a signal conditioning circuit to amplify and filter the bridge network output;
f. an analog to digital converter to digitize both the signal in (b) and the signal in (e);
g. a pair of shielded RF signal cables connecting said signal conditioning circuit to said analog to digital converter; and h. a software program for signal analysis, data recording, and process control.
2. The induction coils of Claim 1 each comprising:
a. a coil wound from stranded signal wire;
b. an upper electrostatic shielding plate;
c. a lower electrostatic shielding plate;
d. a molded casing of high density polyurethane; and e. a shielded signal cable connecting the coil to the bridge network in 1(d).
a. a coil wound from stranded signal wire;
b. an upper electrostatic shielding plate;
c. a lower electrostatic shielding plate;
d. a molded casing of high density polyurethane; and e. a shielded signal cable connecting the coil to the bridge network in 1(d).
3. The device for generating the signal of excitation of Claim 1 comprising:
a. an arbitrary waveform generator;
b. a user defined mode of operation selectable between sweep, step, or composite signals;
c. user defined parameters for sweep time, step size, number of frequencies, and signal amplitude;
d. an adjustable gain output amplifier; and e. an output filter circuit.
a. an arbitrary waveform generator;
b. a user defined mode of operation selectable between sweep, step, or composite signals;
c. user defined parameters for sweep time, step size, number of frequencies, and signal amplitude;
d. an adjustable gain output amplifier; and e. an output filter circuit.
4. The signal conditioning circuit of Claim 1 comprising:
a. a DC power supply; a balanced bridge network;
b. a multi-channel adjustable gain amplification circuit; and c. a multi-channel output filter.
a. a DC power supply; a balanced bridge network;
b. a multi-channel adjustable gain amplification circuit; and c. a multi-channel output filter.
5. The software program of Claim 1 comprising:
a. a subroutine to perform spectral analysis on both digitized signals in 1(f), determining frequency content and amplitude;
b. a subroutine to calculate the magnitude and phase of the bridge network output signal in 1(d);
c. a subroutine to convert the magnitude and phase response in (b) into units of conductivity and magnetic susceptibility;
d. a subroutine to calibrate the system;
e. graphical and numerical displays of the frequency content in (a) and the calibrated magnitude and phase response in (b);
f. a subroutine to record the response data in (b) and (c) along with additional user defined fields;
g. a subroutine to compare sensor response data to previously recorded data from samples of known composition, grade, conductivity, and magnetic susceptibility;
h. a subroutine to generate a sort signal based on the comparison in (g); and i. a graphical user interface to control operation and data recording.
a. a subroutine to perform spectral analysis on both digitized signals in 1(f), determining frequency content and amplitude;
b. a subroutine to calculate the magnitude and phase of the bridge network output signal in 1(d);
c. a subroutine to convert the magnitude and phase response in (b) into units of conductivity and magnetic susceptibility;
d. a subroutine to calibrate the system;
e. graphical and numerical displays of the frequency content in (a) and the calibrated magnitude and phase response in (b);
f. a subroutine to record the response data in (b) and (c) along with additional user defined fields;
g. a subroutine to compare sensor response data to previously recorded data from samples of known composition, grade, conductivity, and magnetic susceptibility;
h. a subroutine to generate a sort signal based on the comparison in (g); and i. a graphical user interface to control operation and data recording.
6. The sensor of Claim 1 further comprising a winch that includes:
a. a cable drum attached to a steel wire cable graduated in metres;
b. the graduated steel wire cable in (a) attached to said sensing coil in Claim 1(a);
c. an electric motor and gearbox attached to the cable drum in (a); and d. a forward/reverse electric controller for controlling the electric motor in (c).
a. a cable drum attached to a steel wire cable graduated in metres;
b. the graduated steel wire cable in (a) attached to said sensing coil in Claim 1(a);
c. an electric motor and gearbox attached to the cable drum in (a); and d. a forward/reverse electric controller for controlling the electric motor in (c).
7. The sensor of Claim 1 further comprising a sorting mechanism that includes:
a. a steel shaft;
b. a steel deflector plate mounted on the steel shaft in (a);
c. a pneumatic piston attached to the deflector plate in (b);
d. a pneumatic valve controlled by the sort signal of 5(h) to actuate the piston of (c);
and e. a row of deflector mechanisms in (b,c,d) spanning the width of a conveyor belt.
We further claim:
a. a steel shaft;
b. a steel deflector plate mounted on the steel shaft in (a);
c. a pneumatic piston attached to the deflector plate in (b);
d. a pneumatic valve controlled by the sort signal of 5(h) to actuate the piston of (c);
and e. a row of deflector mechanisms in (b,c,d) spanning the width of a conveyor belt.
We further claim:
8. A method of determining the conductive or magnetic properties of a mineral sample using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system;
b. exposing said sensing coil to a mineral sample;
c. measuring the response of said sensing coil to said mineral sample by means of the signal conditioning circuit in Claim 1(e) and the software program in Claim 1(h);
d. converting the measured response (c) into units of conductivity by means of the software program described in Claim 1(h); and e. converting the measured response (c) into units of magnetic susceptibility by means of the software program described in Claim 1(h).
a. providing said induction balance sensor system;
b. exposing said sensing coil to a mineral sample;
c. measuring the response of said sensing coil to said mineral sample by means of the signal conditioning circuit in Claim 1(e) and the software program in Claim 1(h);
d. converting the measured response (c) into units of conductivity by means of the software program described in Claim 1(h); and e. converting the measured response (c) into units of magnetic susceptibility by means of the software program described in Claim 1(h).
9. A method of determining the conductive or magnetic properties of an exploration borehole and correlating these properties to the depth of the borehole using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system;
b. attaching said sensing coil to the winch described in Claim 6;
c. lowering said sensing coil down the length of an exploration borehole;
d. measuring the response of said sensing coil to said exploration borehole by means of the signal conditioning circuit described of Claim 1(e) and the software program described of Claim 1(h);
e. A method of converting the measured response of (d) into units of conductivity and magnetic susceptibility by means of the software program described in Claim 1(h), and f. correlating the data in (d) and (e) to the depth of the borehole by means of the graduations on the winch cable described in Claim 6;
a. providing said induction balance sensor system;
b. attaching said sensing coil to the winch described in Claim 6;
c. lowering said sensing coil down the length of an exploration borehole;
d. measuring the response of said sensing coil to said exploration borehole by means of the signal conditioning circuit described of Claim 1(e) and the software program described of Claim 1(h);
e. A method of converting the measured response of (d) into units of conductivity and magnetic susceptibility by means of the software program described in Claim 1(h), and f. correlating the data in (d) and (e) to the depth of the borehole by means of the graduations on the winch cable described in Claim 6;
10. A method of determining the mineral grade of an unknown sample using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system;
b. measuring the magnitude and phase response due to the unknown sample as described in Claim 8;
c. using the software program described in Claim 1(h) to compare the measured data in (b) to previously recorded response data from samples of known grade; and d. using said software program to assign a grade value to the unknown sample based on the comparison in (c).
a. providing said induction balance sensor system;
b. measuring the magnitude and phase response due to the unknown sample as described in Claim 8;
c. using the software program described in Claim 1(h) to compare the measured data in (b) to previously recorded response data from samples of known grade; and d. using said software program to assign a grade value to the unknown sample based on the comparison in (c).
11. A method of determining the mineral type of an unknown sample using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system;
b. measuring the magnitude and phase response due to the unknown sample as described in Claim 8;
c. using the software program described in Claim 1(h) to compare the measured data in (b) to previously recorded response data from samples of known type; and d. using said software program to assign a mineral type to the unknown sample based on the comparison in (c).
a. providing said induction balance sensor system;
b. measuring the magnitude and phase response due to the unknown sample as described in Claim 8;
c. using the software program described in Claim 1(h) to compare the measured data in (b) to previously recorded response data from samples of known type; and d. using said software program to assign a mineral type to the unknown sample based on the comparison in (c).
12. A method of discriminating mineral samples based on conductive, magnetic, mineral type and mineral grade parameters using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system b. determining the conductivity, magnetic susceptibility, mineral type, and mineral grade of the mineral sample as described in Claims 8, 10 and 11; and c. using the software program in Claim 1(h) to compare the values determined in (b) to predefined values of conductivity, magnetic susceptibility, mineral type, and mineral grade.
a. providing said induction balance sensor system b. determining the conductivity, magnetic susceptibility, mineral type, and mineral grade of the mineral sample as described in Claims 8, 10 and 11; and c. using the software program in Claim 1(h) to compare the values determined in (b) to predefined values of conductivity, magnetic susceptibility, mineral type, and mineral grade.
13. A method of automatically rejecting or accepting mineral samples based on conductive, magnetic, mineral type or mineral grade parameters using said induction balance sensor comprising the steps of:
a. providing said induction balance sensor system;
b. discriminating between sample materials as described in Claim 12;
c. using the software program in Claim 1(h) to generate a sort decision based on the discrimination in (b);
d. effecting the sort based on the decision in (c) by means of the sorting mechanism described in Claim 7.
a. providing said induction balance sensor system;
b. discriminating between sample materials as described in Claim 12;
c. using the software program in Claim 1(h) to generate a sort decision based on the discrimination in (b);
d. effecting the sort based on the decision in (c) by means of the sorting mechanism described in Claim 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002629408A CA2629408A1 (en) | 2008-05-01 | 2008-05-01 | Induction balance sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002629408A CA2629408A1 (en) | 2008-05-01 | 2008-05-01 | Induction balance sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2629408A1 true CA2629408A1 (en) | 2009-11-01 |
Family
ID=41265494
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002629408A Abandoned CA2629408A1 (en) | 2008-05-01 | 2008-05-01 | Induction balance sensor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2629408A1 (en) |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |
Effective date: 20140501 |