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WO2000014552A1 - Dispositif servant a mesurer l'humidite au moyen de micro-ondes - Google Patents

Dispositif servant a mesurer l'humidite au moyen de micro-ondes Download PDF

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Publication number
WO2000014552A1
WO2000014552A1 PCT/US1999/019314 US9919314W WO0014552A1 WO 2000014552 A1 WO2000014552 A1 WO 2000014552A1 US 9919314 W US9919314 W US 9919314W WO 0014552 A1 WO0014552 A1 WO 0014552A1
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WIPO (PCT)
Prior art keywords
sample
moisture content
attenuation
moisture
cavity
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PCT/US1999/019314
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English (en)
Inventor
Danny S. Moshe
Alexander Greenwald
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Malcam Ltd
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Malcam Ltd
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Priority to AU55830/99A priority Critical patent/AU5583099A/en
Publication of WO2000014552A1 publication Critical patent/WO2000014552A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G01N22/04—Investigating moisture content

Definitions

  • the present invention relates to a device for determining the moisture content of material on an analytic scale and, more particularly, to a device for such analytical measurements for calibrating another moisture measuring device on- location.
  • Synthetic and organic materials whose behavior depends upon their moisture content include seeds, hay, tobacco, grains, wood chips and logs, cotton, paper, wool, seeds, pharmaceuticals, synthetic fibers, and other loose organic materials.
  • cotton can be considered, although it will be appreciated that similar examples could be given for any of the above materials.
  • Cotton is processed to separate the desired cotton from contaminating materials such as seeds, and is then spun into fibers for use in textile manufacture. For such pro- cessing and spinning to be successful, the cotton fibers should have an even moisture content that is neither too high nor too low. For example, fibers with low moisture content are weaker, breaking more frequently.
  • the optimum moisture content of the cotton fibers for the production of textiles is from 6.5 to 8% before spinning and between 6-10% on the cones or bobbins, depending upon the requirements of the subsequent processing steps.
  • effective moisture control in the textile mill depends upon accurate measurement of the moisture content of the fibers.
  • moisture measurements may be performed using microwave radiation.
  • a microwave radiation source is located on one side of the bobbin or other type of module which contains the material, and an antenna is located on the opposite side of the bobbin, as described in U.S. Patent No. 5,621,330.
  • the radiation source beam is transmitted through a portion of the bobbin and is received by the receiving antenna, which then produces a signal. This signal is used to determine the moisture content of that portion of the bobbin and the mass uniformity of the bobbin.
  • sample refers to an amount of material ranging from about 5 cubic centimeters to about 2000 cubic centimeters in volume. The moisture content of the sample is then compared to the measured moisture content of a large bulk of the material, and the device is then calibrated according to this comparison.
  • the process of calibration of these devices would be far more efficient and easier to perform, as well as more accurate, if the process were to be automated. Such automation would sharply reduce, or even eliminate, the potential for human error, as well as being less time consuming. In addition, less skilled workers could perform the calibration.
  • the process could be automated with a small, portable device, which could measure the moisture content of samples of material on- location, thereby obviating the need for collection and transport of samples to a remote laboratory site for testing.
  • an analytical scale device for the on- location measurement of the moisture content of material would clearly solve the problems engendered by the current method of calibration.
  • a portable device for measuring a moisture content of a sample of material comprising: (a) a sample holder for holding the sample of material; (b) a body with an interior space; (c) a cover for being hingedly attached to the body, such that when the cover is closed, the interior space of the body is covered; (d) a cavity for receiving the sample holder, the cavity being located within the body; (e) a transmitting antenna disposed on one side of the cavity for transmitting a source beam of microwave radiation through the sample of material, such that the source beam becomes an exit beam, the transmitting antenna being located within the body; (f) a receiving antenna disposed on a substantially opposing side of the cavity for receiving the exit beam and for producing an antenna signal according to the exit beam, the receiving antenna being located within the body; (g) an attenuation measurer for determining an attenuation of the antenna signal; and (h) a moisture determiner for calculating the moisture content of the sample
  • the device further features: (i) a phase shift measurer for measuring a phase shift of the antenna signal, such that the moisture determiner calculates the calculated moisture content from the phase shift and from the attenuation. More preferably, the device further features: j) a temperature sensor for measuring a temperature of the sample of material, the temperature sensor featuring a probe for insertion into the sample of material, such that the moisture determiner corrects the calculated moisture content for an effect of the temperature. Most preferably, the device further features: (k) a balance for measuring a weight of the sample of material, the balance being located at a bottom of the cavity, such that the moisture determiner corrects the calculated moisture content for an effect of the weight.
  • the device further includes: (1) a screen for displaying the calculated moisture content.
  • the device further features: (m) an information input unit for inputting information about a type of the material and a form of the material, such that the moisture determiner corrects the calculated moisture content for an empirical effect of the type of the material and the form of the material.
  • the information input unit is selected from the group consisting of a touch sensitive screen, a keyboard and a keypad.
  • the sample holder is constructed from a substance for reducing an effect of reflectance of the source beam.
  • the material is selected from the group consisting of cotton fiber, silk fiber, wool fiber, pharmaceutical material, seeds, paper, tobacco and synthetic fiber.
  • the source beam is repeatedly transmitted through the sample of material by the transmitting antenna such that a plurality of antenna signals is produced, such that the attenuation measurer determines the attenuation for each of the plurality of antenna signals to form a plurality of attenuation values, the plurality of attenuation values being filtered to form the attenuation for the calculation of the calculated moisture content by the moisture determiner.
  • the cavity is substantially triangular in shape.
  • the cavity is a microwave resonator
  • the transmitting antenna is a microwave radiation broadband generator-synthesizer for producing the source beam
  • the receiving antenna is a signal receiver for receiving the exit beam.
  • the microwave resonator is substantially cylindrical in shape. More preferably, the microwave resonator is constructed from metal. Most preferably, the microwave resonator features an entry for receiving the sample holder and a plurality of metal pieces being located substantially opposite from the entry.
  • the sample holder rotates within the microwave resonator for measuring the moisture content of the sample of material.
  • the term “material” includes any material which can be sampled and which has a moisture content measurable with microwave radiation.
  • material includes any material which can be sampled and which has a moisture content measurable with microwave radiation.
  • module refers to any structure of material, including bales and bobbins.
  • on-location refers to the ability of a calibration method to be performed at the site from which samples are taken, substantially without the need to transport the samples to a remote location.
  • the term “portable” refers to the ability to be transported from one location to another, without the need for special lifting and moving equipment.
  • FIG. 1A is a partially cut-away view of an exemplary portable device for performing a moisture measurement on a sample of material according to the present invention
  • FIG. IB shows an exemplary sample holder for the device of Figure 1A
  • FIG. 1C shows a series of exemplary calibration curves which could be obtained by using the device of Figure 1 A with the exemplary sample holder of Figure IB
  • FIG. ID shows a schematic block diagram of an exemplary embodiment with a reference signal
  • FIG. IE shows a schematic block diagram of a compensator according to the present invention
  • FIG. IF shows another preferred embodiment of a portion of the present invention
  • FIGS. 2A and 2B show two side views of the device of Figure 1 according to the present invention
  • FIG. 3 is a flow chart of the method of calculating the moisture content of the material
  • FIGS. 4A-4C show a third embodiment of the device of the present invention for moisture measurements with a resonator.
  • the present invention is of a device which can be used to measure the moisture content of a sample of material, and which can then perform the necessary calculations in order to calibrate an on-location device for performing such moisture measurements on a large scale.
  • the principles and operation of a device according to the present invention may be better understood with reference to the drawings and the accompanying description.
  • Figure 1A shows an exemplary device for performing the moisture measurement of a sample of material according to the present invention.
  • a device 10 for measuring the moisture content of a sample of material is shown.
  • Device 10 features a cavity 12 for receiving a sample holder 14.
  • Sample holder 14 holds a sample of material 16.
  • both sample holder 14 and cavity 12 are shown as being substantially cubic, substantially any suitable, complementary pair of geometrical configurations could be used, such that cavity 12 is able to receive sample holder 14, as described with reference to Figures IB and ID below.
  • Device 10 features a microwave radiation source 18, shown on one side of cavity 12, and at least one receiving antenna 20, shown on a substantially opposing side of cavity 12.
  • Microwave radiation source 18 preferably includes at least one source antenna 22 for transmitting a source beam.
  • one source antenna 22 and one receiving antenna 20 are shown, although preferably a plurality of different types of source antenna 22 and receiving antenna 20 are included, which are respectively capable of transmitting and receiving a plurality of different frequencies, as shown in Figure ID for example.
  • the source beam is directed through sample 16, sample holder 14 and cavity 12, and then exits as an exit beam.
  • the exit beam is then received by receiving antenna 20.
  • both source antenna 22 and receiving antenna 20 are high frequency, at least 1 GHz and optionally up to about 50 Ghz, according to the application.
  • both source antenna 22 and receiving antenna 20 have high gain for greater sensitivity.
  • Attenuation unit 24 includes an attenuation measurer 26, which measures the attenuation of the antenna signal.
  • Attenuation unit 24 includes an attenuation measurer 26, which measures the attenuation of the antenna signal.
  • the source beam passes through sample 16, sample holder 14 and cavity 12, the source beam is attenuated.
  • the attenuation caused by sample holder 14 and the material lining cavity 12 can be determined in the absence of any sample.
  • the extent of the remaining attenuation is determined by the elementary mass of sample 16, which is the mass of the material of sample 16 encountered by the source beam, and by the moisture content of the material of sample 16 encountered the source beam.
  • attenuation measurer 26 is actually correcting the measurement for the effect of sample holder 14 and the material lining cavity 12.
  • At least a part of the antenna signal also goes to a phase shift determiner 28, which determines the phase shift of the antenna signal.
  • the phase shift is the difference between the phase of the source beam and the phase of the exit beam, which is actually the phase shift caused by the passing of the source beam through sample 16, sample holder 14 and the material lining cavity 12.
  • the effect of sample holder 14 and the material lining cavity 12 on the phase shift can be determined in the absence of sample 16, so that the portion of the phase shift caused by sample 16 can then be calculated.
  • device 10 features a cover 30 which is shown as being hingedly connected to a body 32 of device 10, although other configurations are also possible.
  • Cover 30 can protect both the delicate electronics of device 10 and sample 16 while moisture measurements are being made.
  • cover 30 is made from a material which is substantially impenetrable to microwave radiation, such as Eccosorban-73TM (Millimeter Wave Technology Inc.)
  • body 32 is also lined with the same material, in order to reduce or substantially eliminate interference from ambient radiation, such as signals from cellular phones and other electronic devices in the environment.
  • sample holder 14 In addition to interference from ambient radiation, the measurement of moisture with microwave radiation can also be affected by reflectance of the microwaves within body 32 of device 10.
  • both the material and the structure of sample holder 14 is able to reduce reflectance of the microwave radiation.
  • sample holder 14 could be constructed from a suitable plastic or from a mixture of plastic and an absorbent material for absorbing microwaves.
  • absorbent material would tend to increase the signal to noise ratio
  • the geometrical placement of the sections of material would preferably tend to decrease reflectance of the microwave radiation, thereby increasing the proportion of radiation which passes through sample 16 within sample holder 14, thus increasing the signal to noise ratio by decreasing interference caused by the reflected waves.
  • the material lining cavity 12 is also able to reduce reflectance.
  • device 10 preferably also features a temperature sensor 34 and a balance 36, which can also be a touch sensor.
  • Temperature sensor 34 is attached to cover 30, and features a probe 38 which is inserted into sample 16 when cover 30 is closed. Temperature sensor 34 then determines the temperature of the material of sample 16, which can be used to compensate for the effect of temperature on the measurement of the moisture content of sample 16, as described in more detail in Figure 3 below.
  • Balance 36 is located at the bottom of cavity 12 as shown, such that when sample holder 14 is placed within cavity 12, balance 36 is able to determine the weight of sample holder 14 and sample 16 together. Since the weight of sample holder 14 is known, the weight of sample 16 can be calculated. The weight of sample 16 can then be used to compensate for the effect of the weight of the material on the measurement of the moisture content, as described in more detail in Figure 3 below.
  • balance 36 is a touch sensor.
  • cavity 12 is lined with teflon or another surface which has reduced friction, which would permit an optical balance to be used to determine the weight of sample 16 (not shown).
  • substantially any device for measuinrg the weight of sample holder 14 and sample 16 could benefit from the inclusion of teflon in the lining of cavity 12.
  • Information input unit 44 could be a small keypad or even a keyboard, as shown, or a touch sensitive screen, for example.
  • Information input unit 44 preferably enables the user to enter identifying information about sample 16, such as the name of the user, the date and time, the type of the material, and the location of the bulk of material, for example.
  • Other useful and preferred information includes, but is not limited to, the type of material of the sample, and the form of the material of the sample.
  • the sample could be in the form of a powder, fibers, leaves, seeds, or threads, for example. If the material includes some type of fibers, the information also preferably includes the direction of the fibers, whether parallel or perpendicular.
  • the type and form of the material of the sample are particularly important as compensating factors for the calculation of the moisture content of the material, as shown in Figure 3 below.
  • sample holder 14 is preferably substantially triangular in shape in order to enable measurements to be made dynamically down the length of sample of material 16 with varying widths, as shown in Figure IB.
  • the variation of the width of sample of material 16 enables the effect of the amount of sample of material 16 to be removed from the calculations of the moisture content as sample holder 14 is moved past a microwave radiation source 18 (described in greater detail below).
  • the moisture content of sample of material 16 can then be determined from a series of calibration curves, as shown in Figure 1C. Briefly, a plurality of exemplary calibration curves are shown, each of which is a graph of the amplitude of the received microwave radiation (y-axis) against time (x-axis). As sample holder 14 of Figure 1A is moved between source 18 and receiving antenna (receiver) 20, multiple moisture measurements are made. As shown, each moisture measurement ⁇ corresponds to a different portion of sample of material 16 being measured. Each such portion has a different thickness and therefore a different attenuation coefficient ⁇ , which can be determined according to the calibration curves. Thus, the true moisture content of the material can be determined according to a plurality of such calibration curves.
  • the moisture content of the material could be determined from an equation, in which the moisture content is a function of the attenuation coefficient, as described in further detail below.
  • a similar effect can be obtained by rotating sample holder 14 within cavity
  • sample holder 14 is preferably a cylindrical resonator cell rotating between microwave radiation source 18 and at least one receiving antenna 20, as described in further detail below.
  • Figure ID shows a schematic block diagram of a preferred configuration of the device of the present invention, which features microwave antennas capable of transmitting or receiving a plurality of frequencies, including at least a first frequency of microwaves denoted F h and a second frequency of microwaves denoted F 2 .
  • this embodiment features a reference signal for correcting the measured moisture values.
  • the physical configuration of the device is substantially similar to that of Figure 1A, although certain components have been omitted for the sake of clarity.
  • a multiple- frequency system 46 has a multiple-frequency transmitter 48 for sequentially transmitting microwave radiation at a plurality of frequencies.
  • the frequency to be transmitted is selected by a frequency controller 50.
  • Transmitter 48 then causes a transmitting antenna 52 to transmit microwave radiation at the desired frequency.
  • the transmitted microwave radiation then passes through a sample of material 54, which is contained with a sample holder substantially as described above (not shown). This radiation is received by a receiving antenna 56.
  • Receiving antenna 56 sends a signal to a signal receiver 58.
  • Signal receiver 58 is preferably a heterodyne receiver.
  • a reference signal is sent from transmitter 48 to a reference receiver 60, which is also preferably a heterodyne receiver.
  • Signal receiver 58 sends a measurement signal ( "I.F.
  • Detector 62 uses the reference signal to determine the correct attenuation of the measurement signal, and then passes both signals to a phase detector 64, which determines the correct phase shift for the measurement signal.
  • the phase shift is obtained by sequentially transmitting microwave radiation of at least two different frequencies Fj, F 2 through the material, and "hopping" or alternating at least between these two frequencies at each point in the material.
  • Fj, F 2 are the frequencies of the microwave radiation, as described above; Pj is the phase shift of microwave radiation at frequency F , P 2 is the phase shift of microwave radiation at frequency F 2 ; K is the difference between the phase shift of the radiation at frequencies F, and F 2 ; P m P m are the measured phase shifts with frequencies F h F 2 , respectively; Pg is the gross phase shift difference; and nj and n 2 are greater than 0.
  • the two frequencies of microwave radiation should be chosen in order to enable sufficient dynamic range such that measurements of different ranges of moisture content can be made substantially without saturation. Thus, if saturation occurs with the higher of the two frequencies, the measurements can be made at the lower of the two frequencies, thereby avoiding saturation.
  • the values of Fj and F 2 are substantially greater than 24 Ghz.
  • the values of Fj and F 2 are substantially less than 16 Ghz.
  • FIG. IF a particularly preferred embodiment of the present invention for increasing the sensitivity of the measurement is shown in Figure IF.
  • This preferred embodiment shares certain features which multiple-frequency system 46 shown in Figure ID, as indicated by the identical reference numerals. However, certain features have also been added.
  • the device shown in Figure IF also features a splitter 49 for splitting the microwave radiation from transmitter 48 into two portions. A first portion, indicated as A 0meas , is transmitted by transmitting antenna 52. A second portion, indicated as A r ⁇ is passed to a bridge summation apparatus 63. Bridge summation apparatus 63 also receives the signal from receiving antenna 56, shown as A meas . The combined signal, A res , is then passed to a detector 65.
  • the performance of the device according to this preferred embodiment of the present invention could be described according to the following set of equations.
  • a res is the amplitude of the resultant signal, after corrections for the effect of the material lining the cavity have been made;
  • a re f is the amplitude of the reference signal;
  • a meas is the amplitude of the measured signal;
  • a omeas is the amplitude of the signal from the receiving antenna;
  • a*(W) is the attenuation coefficient, which depends upon the moisture content of the material;
  • ⁇ *(W) is the phase coefficient, which also depends upon the moisture content of the material;
  • / is the length of the material; and re/ -is the phase shift of the reference signal.
  • the sensitivity of the amplitude vector which results from the moisture content of the material (W) is as follows.
  • Figure 1 E is a schematic block diagram of an exemplary compensator 66, which receives the known attenuation caused by sample holder 14 and the mate ⁇ al lining cavity 12 (shown as "Attenuat ⁇ on 2 "), as well as the measured attenuation (shown as "Attenuation ! ”)
  • the measured attenuation is affected by the known attenuation caused by sample holder 14 and the mate ⁇ al lining cavity 12, as well as by the attenuation caused by sample 16 alone and by the attenuation caused by the moisture withm sample 16.
  • Compensator 66 removes the effect of the known attenuation caused by sample holder 14 and the mate ⁇ al lining cavity 12 from the measured attenuation in order to obtain the true attenuation (shown as
  • Attenuat ⁇ on 3 which only includes the attenuation caused by the matenal itself and by the moisture content of the matenal.
  • Figures 2 A and 2B show two side views of device 10 of Figure 1 A
  • Figure 2 A shows a view of the exte ⁇ or of one side of device 10, with cover 30 closed Screen 42 and information input unit 44 are shown attached to the exte ⁇ or of one side of body 32 of device 10, for easy access by the user (not shown)
  • two handles 46 are attached as shown for facilitating transport of device 10.
  • Figure 2B shows a cut-away side view of device 10, showing sample holder 14 inside cavity 12.
  • Balance 36 is also shown.
  • Figure 3 shows a flow chart of the calculations for determining the moisture content of the sample.
  • the attenuation is used to determine the raw moisture content of the material.
  • the phase shift is used to correct the raw moisture content to calculate the moisture content of the material more accurately.
  • the attenuation, and the phase shift if measured are used in combination with empirically determined correction factors to calculate the final moisture content of the material.
  • the first step in the flow chart is the transmission of microwave radiation through the material, which can be performed using the device essentially as described above. Microwaves are transmitted through the sample so that they pass through the sample and are received on the other side. Preferably, this step is repeated at least once so that a plurality of transmissions through the sample is done. More preferably, microwaves of a plurality of different frequencies are transmitted in order to eliminate at least part of the interference, for example as shown and described with reference to Figure IB above.
  • the attenuation and optionally the phase shift are calculated, as shown in step 2, by an attenuation measurer and a phase shift measurer, respectively.
  • the flow chart now branches into two parts.
  • the right branch shows the steps used in calculating the raw moisture content of the material
  • the left branch shows the steps for the determination of the density of the material.
  • steps in the right (moisture content) branch will have the letter “a” appended; e.g., "3a”, “4a”, etc.
  • steps in the left (density) branch will have the letter "b” appended; e.g., "3b", "4b”, etc.
  • step 3a an algorithm is used to filter the data points obtained for the attenuation.
  • Each transmission of microwaves through the sample enables a separate measurement of the attenuation to be made as described above in Figure 1.
  • Each such measurement is a separate data point.
  • These data points must be filtered, since otherwise artefacrual data could be obtained. Filtering can be done by averaging the data points, or by selecting the median of the points, for example, since all measurements are replicates.
  • the attenuation is preferably corrected for the effect of the weight of the material and the sample holder, more preferably according to the vector of multiple measurements made for each sample, as shown in step 4a.
  • This correction is preferably performed by compensating the attenuation with the ratio of a standard weight to the actual weight, for example by multiplication when the material is tobacco, and produces a weight-corrected attenuation value.
  • the weight-corrected attenuation value is preferably corrected for temperature, to produce a temperature-corrected attenuation value.
  • the correction is performed by adding the weight-corrected attenuation value to the factor a(l - Ts/Te), where Ts is the standard temperature, and Te is the measured temperature of the material, in order to produce the temperature-corrected attenuation value.
  • the value of a is empirically determined according to the type of material. More preferably, the temperature is substantially continuously monitored by the temperature sensor, so that each measurement of the attenuation can be corrected with the temperature value taken as the transmission of microwaves was made. The temperature-corrected attenuation value thus is compensated for the effect of measurements at different temperatures.
  • the temperature-corrected attenuation value is used to calculate a raw moisture value for the material.
  • various empirical factors are included in the calculation, such as the type of material being examined and the form of the material.
  • This raw moisture value will be used in the determination of the final moisture value for the material.
  • the final moisture value is preferably determined by also incorporating the density of material into the calculations.
  • the density of the material is preferably calculated as shown in the left branch of the flow chart. Turning back now to the left and optional branch of the flow chart, in step
  • the data points are preferably filtered as for step 3a.
  • the density is calculated from the phase shift, in accordance with empirical information from a database.
  • the empirical information includes the type of material and the form of the material.
  • the database preferably contains "fuzzy descriptors" which are used to find the correct phase region and to determine the proper relationship between measured phase shift values and calculated density values, such that fuzzy logic is used to determine the density of the material.
  • fuzzy descriptors are obtained by collecting phase shift data from an analysis of material with known density, and then comparing the calculated density values with the true, known density values of the test material. From this analysis, the proper correlation between the measured phase shift values and the calculated density values can be determined. Since this correlation depends upon the material or materials from which the test shape is constructed, such an analysis must be performed for substantially every desired material in order to obtain these essentially empirical correlations.
  • step 7 the optional density value, and the raw moisture value, which is calculated in step 6a, are combined to determine the final moisture value by a moisture determiner.
  • the equation for calculating the final moisture value includes the density, as well as an empirically determined correlation factor. The correlation factor depends upon the type and form of material, and was empirically determined through experimentation.
  • the final moisture value is then output, for example by displaying on the display screen of the device of Figures 1 and 2.
  • An example of specific coefficients and moisture values for the material cotton is as follows.
  • the measured signal from the receiver antenna can be determined according to the following equation:
  • Kj and K 2 depend upon the type of material and can be empirically determined. For example, for cotton fibers, when the measured temperature was 20 °C, the density was 100 kg/m , and the frequency was 10 GHz, the resultant value of K] was 0.18 dB per one percent of moisture, and the resultant value of ⁇ was 10 degrees per one percent of moisture.
  • This final moisture value can be then be used to calibrate the on-location device.
  • the advantage of the device of the present invention is that the entire process of obtaining the final moisture value, after the sample has been placed into the sample holder and then into the cavity, is entirely automatic.
  • the device of the present invention can be operated by a relatively unskilled user, yet gives highly accurate and sensitive results.
  • the device of the present invention is far less sensitive to the presence of chemicals in the sample of material than the prior art method, which requires heating of the material to remove the moisture.
  • the small size of the sample within a known sample holder volume reduces sensitivity to temperature and moisture deviations within the material.
  • the closed nature of the device of the present invention reduces sensitivity to other ambient factors.
  • a resonator cell is featured as shown in Figures 4A-4C, described briefly below.
  • a more extensive description is provided in U.S. Patent Application No. 08/xxx,xxx, entitled "Method And Device For Highly Accurate, High Speed, Real Time, Continuous Or Stationary, In-Line, Non- Invasive, Three Dimensional, Multi-Slice Density Deviation And Density Measurements And Calculations Of Homogeneous Or Non-Homogeneous Fibrous Yarn, Slivers, Or Pad Material", filed on xx, xx, 1998, the teachings of which are incorporated by reference as if fully set forth herein.
  • FIG 4A is a schematic diagram of a preferred embodiment which features a resonator cell for receiving the sample holder containing the sample of material.
  • Sample of material 16 is placed within sample holder 14, in a substantially similar manner as previously described above for Figure 1A. However, instead of placing sample holder 14 into a cavity which features transmitter and receiver antennas as in Figure 1A, sample holder 14 is now placed into a cylindrical microwave resonator 68.
  • Microwaves of controllable, specified frequencies are generated by a microwave radiation broadband generator- synthesizer 70. Broadband generator- synthesizer 70 continuously generates, in a sweeping mode, microwave radiation of frequencies within pre-set ranges, and feeds the microwaves through a microwave input port 72, into resonator 68.
  • the range of frequencies of microwave radiation passes through material 16 such that the radiation becomes transmitted microwaves.
  • the transmitted microwaves are continuously received by and further transmitted through a microwave output port 74, into signal receiver 76.
  • the microwave signals go to an attenuation measurer 78, simultaneous to continuously received values of material temperature received from a strategically located external temperature sensor 80.
  • Attenuation measurer 78 is similar in function to the attenuation measurer of Figures 1A and 3.
  • the attenuation values are corrected substantially as described for Figure 3, for example according to the value of the measured density.
  • FIG. 4B shows a close-up of resonator 68 with sample of material 16 in holder 14.
  • This embodiment illustrates and describes, but is not limited to, a microwave resonator of substantially cylindrical shape, it being understood that other such shapes are possible within the scope of the present invention.
  • Resonator 68 is comprised of a hollow piece of cylindrically shaped metal, having typical dimensions of 44 mm height and 38 mm diameter, preferably constructed of high purity copper or invar alloy, or an equivalent material thereof.
  • the entire inner surface of resonator 68 is preferably anodized with high purity gold or silver. Gold and silver are the preferred anodizing metals for their superior conductivity and anti-corrosive properties compared to base metals, such as copper or invar.
  • Resonator 68 features a resonator cover 82 having a typical diameter of about 20 mm for a base plate diameter of 38 mm.
  • resonator cover 82 is composed of the same anodized metal as the principle microwave resonator.
  • resonator cover 82 is composed of teflon. Resonator cover 82 acts as a cutoff waveguide for preventing leakage of microwave radiation outside resonator 68.
  • Resonator cover 82 is critically important for containing the microwave radiation inside resonator 68, thereby maintaining high quality, Q, of resonator 68 (i.e., high amplitudes of the electromagnetic field associated with the microwave signals inside resonator 68).
  • the type of resonance modes are preferably double-degenerate, whereby each double-degenerate mode of the microwave radiation has two different electromagnetic distributions at the same resonance frequency, f r , i.e., A m and A' m .
  • f r resonance frequency
  • a m and A' m resonance frequency
  • these components exhibit different resonance frequencies, f r and f r , in addition to different amplitudes, A m and A' m , respectively, due to structural and/or material imperfections, asymmetries, and/or non-homogeneities of the resonator and/or cutoff waveguides.
  • This phenomenon leads to error in resonance frequency bandwidth received by signal receiver 76, in that 2(delta)f ⁇ 2(de)f, which leads to error in the determination of the quality, Q, of resonator 68, ultimately causing error in measurements of moisture content and in calculations (compensated) of the density of sample of material 16. Elimination of this error is accomplished with metal pieces 84.
  • Metal pieces 84 are positioned inside the resonator at the point of highest electric field strength of the component having the lower amplitude.
  • the presence of metal pieces 84 causes a decrease in the resonance frequency of the component with the smaller amplitude, A' m , resulting in separation of the two resonance curves, enabling a correct reading of the resonance frequency full width half amplitude bandwidth, 2(delta)f, and thus enabling the true quality of the resonator signal to be processed.
  • this correction enables the calculation of highly accurate values of moisture content.
  • the preceding corrective design in resonator 68 is an example only; each microwave resonator configuration requires its own corrective design, based upon the specific material and structural imperfections, asymmetries, and/or non-homogeneities.
  • Measurement and monitoring of temperature of sample of material 16 are accomplished by employing a strategically located in-line temperature sensor 80.
  • a thermocouple, thermoresistor, or alternatively, an infrared device can be used as temperature sensor 80.
  • Temperature sensor 80 is strategically positioned to monitor, in a real time, continuous or stationary, in-line, and non-invasive mode, the temperature of sample of material 16.
  • the temperature sensor output lead of 80 is connected to attenuation measurer 78.
  • the relative geometry of the microwave resonator device illustrated in Figure 4B is such to enable the rotation of either sample of material, microwave resonator, or the direction of the microwave radiation in the resonator, during real-time, in an in-line, non-invasive mode of density measurement and control.
  • the ability to rotate the sample holder is also an optional but preferred feature of the other embodiments of the device of the present invention, as previously described, since such rotation allows multiple moisture measurements to be made at different locations or "slices" of the sample of material.
  • Microwave radiation generator-synthesizer 70 can optionally include a number of features which are designed to maximize the sensitivity of resonance frequency shift (density) and resonator quality (moisture content) measurements of fibrous materials.
  • One such feature is an electric field director which determines the mode of the electric field strength, established by the microwave source, through input port 72 relative to sample of material 16 inside microwave resonator 68, such that the mode of the electric field partially determines the magnitudes of frequency shifts and changes in resonator quality (i.e., changes in signal amplitude).
  • FIG. 4C is a flow chart of the method of calculating density and moisture content of samples of material for the resonator of the present invention.
  • the overall calculation method used in achieving the objectives of the present invention is based on the evaluation of two arrays (of time samples), D and W, representing an array of resonator resonance frequency shift / density, and an array of resonator quality / moisture content, respectively.
  • Numerical evaluation of the arrays D and W is determined from evaluation of iterative correlation functions, F ; (i.e., F, through F 8 ), which in turn are functions of resonator frequency shift, resonator quality, material temperature, and four empirically determined structure sensitive (i.e., material shape and type) correlation functions, S harassment denoted by Si, S 2 , S 3 , and S 4 .
  • the correlation functions, F, and S forum represent sets of linear and non-linear functions, each functional form uniquely determined from correlations of calculated density and moisture content values to true, known density and moisture content values, for a variety of material structural shapes and types.
  • Correlation data are obtained from calibration plots and numerical analysis of density vs resonance frequency shift or moisture content vs resonator quality data, made from data generated during calibration measurements recorded at standard conditions, using reference materials of known densities, moisture content, temperatures, and of well characterized structure shapes and types.
  • the correlation functions, F, and Song provide proper correlations between calculated and known density and moisture content values, according to different sample material structural peculiarities or uniqueness, and are critical in achieving high accuracy and reproducibility in calculations of final density and moisture content shown on the display unit. Numerical results of these calculations represent averages and standard deviations of density (and optionally, moisture content) of n slices of material, whereby n is an adjustable parameter proportional to the scan rate of the resonator device.
  • Both arrays, D and W are used in calculating density and moisture content averages and standard deviations.
  • the D and W arrays are directly proportional to material density, and moisture content, which in turn are functions of resonator resonance frequency, f r , resonator quality, Q, respectively, material temperature, T m , and all four of the empirically determined structure sensitive correlation functions, S, , (Si, S 2 , S 3 , and S 4 ).
  • array W providing structural and temperature compensated average and standard deviation values of moisture content, i.e., W A and W SD , are themselves used in compensating and correcting initial average and standard deviation values of density, i.e., D A and D S , leading to highly accurate moisture content compensated values of density average and standard deviation, i.e.,
  • the first step in the flow chart represents the real time, in-line, continuous or stationary mode, multi-slice scanning of n slices of the test material using one of the preferred embodiments (a) or (b) (Fig. 1 and 3, or 4) of the device of the present invention.
  • Multi-slice scanning of the test material, positioned inside the microwave resonator/waveguide device is performed by continuously transmitting a sweeping set of microwaves of known frequencies into the resonator, and identifying and detecting the affected microwaves by the respective microwave receiver components.
  • the scanning step provides the necessary raw data for the initial determination of the resonator resonance frequency shift/density array, D 0 , and the resonator quality array, W 0 , step (1).
  • step (2) an algorithm is used to evaluate, filter and eliminate unreasonable data points from the calculations of initial frequency shift and resonator quality, step (2).
  • the raw frequency data must be filtered in order to eliminate system noise and/or artificial readings of resonance frequency and/or frequency bandwidths.
  • Values of density array, D and quality array, W b are calculated from the appropriate functions, F b and F 5 , respectively, following data filtering, step (3).
  • the flow chart now branches into two parts. The right branch shows the steps used in calculating the density of the material, while the left branch shows the steps used in calculating moisture content of the material.
  • steps in the right (density) branch, and steps in the left (moisture content) branch are assigned the numbers 3a - 3c, and 4a - 4c, respectively.
  • the next value of density array, D is evaluated from the function, F 2 , of D, and S[ (structure correlation function), step (3a). Calculated values of density can now compensated and adjusted for temperature.
  • step (3b) the next value of density array, D 3 , is evaluated from the function, F 3 , of D 2 and T, where the dependency of F 3 on T is empirically determined, and as an example, is proportional to (1 - T m /T s ), where T m and T s are the 'actual' and 'standard' material temperatures, respectively.
  • step (3c) initial values of the magnitude of the material density array, D, including average density, D A and density standard deviation, D SD , are evaluated from the function, F 4 , of D 3 and S 2 , another structure sensitive empirical correlation function.
  • the above initial calculated values of density are to be compensated/corrected for moisture content of the material, determined from resonator quality data according to the left branch of the flow chart.
  • step (2) the initial value of the moisture content array, W 2
  • step (3) the initial value of the moisture content array, W 2
  • the next value of moisture content array, W 3 includes compensation and adjustment for temperature.
  • W 3 is evaluated from the function, F 7 , of W 2 and T, where the dependency of F 7 on T is proportional to (1 - T m / T s ), similar to that of F 3 , in the above density calculations.
  • step (4c) the corrected values of the magnitude of material moisture content array, W, including average moisture content, W A and moisture content standard deviation, W SD , are evaluated from the function, F 8 , of W 3 and S 4 . These values of moisture content are used to compensate the above initial calculated values of density, step (5), in order to obtain final moisture content compensated average and standard deviation values of mate ⁇ al density, D A and D SD , step (6), which are ready for display.
  • the resonator cell has high sensitivity for very small volumes of material, such as from about 5 cubic centimeters to about 50 cubic centimeters.
  • the resonator cell can aid in the measurement of the moisture content of pharmaceutical powders or synthetic materials.
  • the moisture content of pharmaceutical powders is particularly difficult to measure, since these powders tend to have low moisture content, such that the resonator is preferred over the antennas for measuring the moisture content of such material.

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Abstract

Dispositif portable servant à évaluer la teneur en humidité de petits échantillons de matériau. On introduit un porte-échantillon (14) dans une cavité couverte. Des antennes des deux côtés de la cavité dirigent un faisceau micro-ondes à travers l'échantillon de matériau. On utilise l'atténuation et les déphasages pour extraire les informations concernant la composition de l'échantillon. Dans un autre mode de réalisation, on soumet la cavité contenant l'échantillon à une résonance. La totalité de l'instrument est contenue en vase clos et prête à être utilisée soit en mode autonome, soit en tant que périphérique informatique.
PCT/US1999/019314 1998-09-03 1999-08-25 Dispositif servant a mesurer l'humidite au moyen de micro-ondes Ceased WO2000014552A1 (fr)

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AU55830/99A AU5583099A (en) 1998-09-03 1999-08-25 Moisture measurement device using microwaves

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Cited By (20)

* Cited by examiner, † Cited by third party
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WO2006048080A1 (fr) * 2004-11-06 2006-05-11 Sartorius Ag Balance secheuse
WO2008030162A1 (fr) * 2006-09-05 2008-03-13 Astrazeneca Ab Procédé et système destinés à être employés pour contrôler un processus de séchage
EP1980844A1 (fr) * 2007-04-12 2008-10-15 Manneschi, M. Alessandro Analyse de la composition du contenu d'un récipient par mésure des caractéristiques diélectriques complexes à plusieurs fréquences échantillonnées sur la plage d'excitation de quelques Hz à plusieurs GHz et par mésure d'au moins une donnée physique additionnelle comme par exemple de la masse du récipient avec son contenu
WO2009071143A1 (fr) * 2007-12-03 2009-06-11 Sartorius Ag Dispositif et procédé pour déterminer l'humidité d'un matériau par thermogravimétrie
WO2009071047A3 (fr) * 2007-12-05 2009-09-03 Forschungszentrum Jülich GmbH Procédé et dispositif de détermination de biomasse et de détermination de la teneur en humidité de sols à l'aide de mesures diélectriques dans un résonateur micro-ondes
US8088784B2 (en) 2005-10-28 2012-01-03 Astrazeneca Ab 4-(3-aminopyrazole) pyrimidine derivatives for use as tyrosine kinase inhibitors in the treatment of cancer
US8114989B2 (en) 2005-05-16 2012-02-14 Astrazeneca Ab Pyrazolylaminopyrimidine derivatives useful as tyrosine kinase inhibitors
US8129403B2 (en) 2005-02-16 2012-03-06 Astrazeneca Ab Chemical compounds
US8486966B2 (en) 2007-05-04 2013-07-16 Astrazeneca Ab 9-(pyrazol-3-yl)-9H-purine-2-amine and 3-(pyrazol-3-yl) -3H-imidazo[4,5-B] pyridin-5-amine derivatives and their use for the treatment of cancer
US20140210492A1 (en) * 2013-01-29 2014-07-31 Agratronix Llc Moisture Meter for Determining the Moisture Content of Particulate Material
CN105806732A (zh) * 2016-03-23 2016-07-27 江苏鑫源烟草薄片有限公司 索式抽提法测定再造烟叶原料极限提取率的方法
WO2016025569A3 (fr) * 2014-08-14 2016-08-25 Dickey-John Corporation Dispositif de mesure et capteur d'humidité à hyperfréquences
CN107064178A (zh) * 2017-06-16 2017-08-18 默斯测控技术（长沙）有限公司 槟榔水分测量设备
CN107102011A (zh) * 2017-06-06 2017-08-29 默斯测控技术（长沙）有限公司 多频谱微波水分仪
US10379065B2 (en) 2015-10-30 2019-08-13 Mesdan S.P.A. Measuring method and device for measuring the moisture content, the length and/or at least one dynamometric characteristic of textile fibers, in particular cotton fibers
CN111323322A (zh) * 2020-04-13 2020-06-23 黑龙江北草堂中药材有限责任公司 一种中药材终端浸润程度检测装置
WO2020216528A1 (fr) * 2019-04-24 2020-10-29 Rheinmetall Waffe Munition Gmbh Procédé et dispositif de détermination de la teneur en humidité d'un matériau
CN115876809A (zh) * 2022-12-01 2023-03-31 张家港扬子纺纱有限公司 一种快速检测纱线回潮率的方法
CN118010763A (zh) * 2024-02-28 2024-05-10 四川聚元药业集团有限公司 一种白芍饮片微波水分快速检测方法
US12000788B1 (en) 2020-01-10 2024-06-04 Gold Bond Building Products, Llc Inline detection of gypsum panel calcination

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Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7441443B2 (en) 2004-11-06 2008-10-28 Sartorius Ag Drying balance
WO2006048080A1 (fr) * 2004-11-06 2006-05-11 Sartorius Ag Balance secheuse
US8129403B2 (en) 2005-02-16 2012-03-06 Astrazeneca Ab Chemical compounds
US8114989B2 (en) 2005-05-16 2012-02-14 Astrazeneca Ab Pyrazolylaminopyrimidine derivatives useful as tyrosine kinase inhibitors
US8088784B2 (en) 2005-10-28 2012-01-03 Astrazeneca Ab 4-(3-aminopyrazole) pyrimidine derivatives for use as tyrosine kinase inhibitors in the treatment of cancer
WO2008030162A1 (fr) * 2006-09-05 2008-03-13 Astrazeneca Ab Procédé et système destinés à être employés pour contrôler un processus de séchage
EP1980844A1 (fr) * 2007-04-12 2008-10-15 Manneschi, M. Alessandro Analyse de la composition du contenu d'un récipient par mésure des caractéristiques diélectriques complexes à plusieurs fréquences échantillonnées sur la plage d'excitation de quelques Hz à plusieurs GHz et par mésure d'au moins une donnée physique additionnelle comme par exemple de la masse du récipient avec son contenu
FR2914998A1 (fr) * 2007-04-12 2008-10-17 Alessandro Manneschi Dispositif d'analyse de la composition du contenu d'un recipient comprenant des moyens pour l'obtention d'au moins une donnee physique additionnelle relative au recipient
US8030948B2 (en) 2007-04-12 2011-10-04 Manneschi Alessandro M Device for analyzing the composition of the contents of a container comprising means for obtaining at least one additional physical datum relating to the container
US8486966B2 (en) 2007-05-04 2013-07-16 Astrazeneca Ab 9-(pyrazol-3-yl)-9H-purine-2-amine and 3-(pyrazol-3-yl) -3H-imidazo[4,5-B] pyridin-5-amine derivatives and their use for the treatment of cancer
US8046176B2 (en) 2007-12-03 2011-10-25 Sartorius Weighing Technology Gmbh Device and method for determining material moisture by thermogravimetry
WO2009071143A1 (fr) * 2007-12-03 2009-06-11 Sartorius Ag Dispositif et procédé pour déterminer l'humidité d'un matériau par thermogravimétrie
WO2009071047A3 (fr) * 2007-12-05 2009-09-03 Forschungszentrum Jülich GmbH Procédé et dispositif de détermination de biomasse et de détermination de la teneur en humidité de sols à l'aide de mesures diélectriques dans un résonateur micro-ondes
US9459225B2 (en) * 2013-01-29 2016-10-04 Farmcomp Oy Moisture meter for determining the moisture content of particulate material
US20140210492A1 (en) * 2013-01-29 2014-07-31 Agratronix Llc Moisture Meter for Determining the Moisture Content of Particulate Material
US9874535B2 (en) 2013-01-29 2018-01-23 Farmcomp Oy Moisture meter for determining the moisture content of particulate material
US10094789B2 (en) 2014-08-14 2018-10-09 Tsi, Incorporated Microwave moisture meter and sensor
US10613039B2 (en) 2014-08-14 2020-04-07 Tsi, Incorporated Microwave moisture meter and sensor
WO2016025569A3 (fr) * 2014-08-14 2016-08-25 Dickey-John Corporation Dispositif de mesure et capteur d'humidité à hyperfréquences
EP3180602A4 (fr) * 2014-08-14 2018-01-10 Dickey-John Corporation Dispositif de mesure et capteur d'humidité à hyperfréquences
US10379065B2 (en) 2015-10-30 2019-08-13 Mesdan S.P.A. Measuring method and device for measuring the moisture content, the length and/or at least one dynamometric characteristic of textile fibers, in particular cotton fibers
CN105806732A (zh) * 2016-03-23 2016-07-27 江苏鑫源烟草薄片有限公司 索式抽提法测定再造烟叶原料极限提取率的方法
CN107102011A (zh) * 2017-06-06 2017-08-29 默斯测控技术（长沙）有限公司 多频谱微波水分仪
CN107064178A (zh) * 2017-06-16 2017-08-18 默斯测控技术（长沙）有限公司 槟榔水分测量设备
WO2020216528A1 (fr) * 2019-04-24 2020-10-29 Rheinmetall Waffe Munition Gmbh Procédé et dispositif de détermination de la teneur en humidité d'un matériau
US11828716B2 (en) 2019-04-24 2023-11-28 Rheinmetall Waffe Munition Gmbh Method and device for determining the material moisture of a material
US12000788B1 (en) 2020-01-10 2024-06-04 Gold Bond Building Products, Llc Inline detection of gypsum panel calcination
CN111323322A (zh) * 2020-04-13 2020-06-23 黑龙江北草堂中药材有限责任公司 一种中药材终端浸润程度检测装置
CN115876809A (zh) * 2022-12-01 2023-03-31 张家港扬子纺纱有限公司 一种快速检测纱线回潮率的方法
CN118010763A (zh) * 2024-02-28 2024-05-10 四川聚元药业集团有限公司 一种白芍饮片微波水分快速检测方法

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