Moisture Measurement Device and Moisture Measurement Method

Abstract

To provide a moisture content measuring device and a moisture content measuring method capable of accurately measuring the moisture content of a measurement object.SOLUTION: A moisture content measuring device 1 according to an aspect of the present invention includes: a weight scale 20 that measures weight of a measurement container 10 containing a powder and granular material-like or liquid-like measurement object 2; an oscillation circuit 30 that has a transmitting antenna 31 for transmitting electromagnetic waves and a receiving antenna 32 for receiving the electromagnetic waves transmitted by the transmitting antenna 31, and that feeds back an output of the receiving antenna 32 to an input of the transmitting antenna 31; and a calculation unit 40 that calculates a moisture content of the measurement object 2, based on mass of the measurement container 10 containing the measurement object 2 and a characteristic value indicating electrical characteristics of the oscillation circuit 30 in a state that the measurement container 10 is placed between the transmitting antenna 31 and the receiving antenna 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a moisture content measuring device and a moisture content measuring method.

Background Art

[0002] There is a technique for measuring physical properties such as the moisture content of a measurement object using electromagnetic waves. Generally, since the absorption rate, phase delay, etc. of electromagnetic waves when the electromagnetic waves pass through a substance change according to the moisture content, the moisture content of the measurement object can be estimated by measuring the attenuation amount, etc. of the electromagnetic waves by the measurement object. However, the change in the attenuation rate, etc. of electromagnetic waves with respect to the change in the moisture content of the measurement object is not so large. For this reason, a technique for highly sensitively measuring the change in the moisture content of a measurement object using a resonance circuit is also known.

[0003] Since the absorption rate of electromagnetic waves also depends on the size of the measurement object, it is necessary to create a calibration curve using a sample having the same shape as the measurement object. However, since agricultural products, etc. have a non-uniform shape of the measurement object, a measurement error occurs due to the difference in the shape of the measurement object. Therefore, as a method for measuring the moisture content of a measurement object without depending on the amount of the measurement object, based on the ratio of the change rate of the amplitude at the resonance frequency and the change rate of the phase at a specific frequency between the state where the measurement object is not placed inside the cavity resonator and the state where it is placed, a technique for estimating the moisture content of rice grains, etc. has also been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When calculating the moisture content based on the ratio of the rate of change of amplitude to the rate of change of phase, as described in Patent Document 1, there is a possibility that the error may be relatively large. For this reason, an object of the present invention is to provide a moisture content measuring device and a moisture content measuring method capable of accurately measuring the moisture content of a measurement object.

Means for Solving the Problems

[0006] A moisture content measuring device according to an aspect of the present invention includes a weighing scale that measures the weight of a measuring container containing a granular or liquid measurement object, a transmitting antenna that transmits electromagnetic waves, and a receiving antenna that receives the electromagnetic waves transmitted by the transmitting antenna. An oscillation circuit that feeds back the output of the receiving antenna to the input of the transmitting antenna, the mass of the measuring container containing the measurement object, and a characteristic value indicating the electrical characteristics of the oscillation circuit in a state where the measuring container is disposed between the transmitting antenna and the receiving antenna. And a calculation unit that calculates the moisture content of the measurement object based on the above.

[0007] In the above moisture content measuring device, the calculation unit may preset a calibration curve indicating the relationship between the characteristic value and the moisture content for each of a plurality of weights of the measuring container.

[0008] In the above moisture content measuring device, the transmitting antenna and the receiving antenna may be disposed to face each other vertically.

[0009] In the above moisture content measuring device, the weighing scale may have a conveyor that conveys the measuring container, and may measure the weight of the measuring container being conveyed by the conveyor.

[0010] In the above moisture content measuring device, the calculation unit may calculate the moisture content of the measurement object using the extreme value of the characteristic value that changes as the measuring container is conveyed.

[0011] In the above moisture content measuring device, the measuring container having a substantially constant horizontal cross-sectional area and a height smaller than the horizontal width may be provided.

[0012] In the above-described moisture content measuring device, the characteristic value may be the attenuation amount of the output of the receiving antenna with respect to the input of the transmitting antenna, the phase difference of the output of the receiving antenna with respect to the input of the transmitting antenna, or the oscillation frequency of the oscillation circuit.

[0013] In the above-described moisture content measuring device, the oscillation circuit may include a tuning circuit unit that resonates the oscillation circuit by adjusting the phase of the feedback from the transmitting antenna.

[0014] Further, a moisture content measuring method according to an aspect of the present invention includes a step of measuring the weight of a measurement container containing a measurement object in a granular or liquid state, and a transmitting antenna that transmits electromagnetic waves and a receiving antenna that receives the electromagnetic waves transmitted by the transmitting antenna. While the measurement object is disposed between them, by driving an oscillation circuit that feeds back the output of the receiving antenna to the input of the transmitting antenna, a step of detecting a characteristic value indicating the electrical characteristics of the oscillation circuit, and based on the mass of the measurement container and the characteristic value. And a step of calculating the moisture content of the measurement object.

Effect of the Invention

[0015] According to the present invention, the moisture content of a measurement object can be accurately measured.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a moisture content measuring device 1 according to an embodiment of the present invention. The moisture content measuring device 1 is a device that implements an embodiment of the moisture content measuring method according to the present invention.

[0018] The moisture content measuring device 1 measures the moisture content (water content rate) of a measurement object 2 in a powdery, granular or liquid state. The moisture content measuring device 1 includes a measurement container 10 that houses the measurement object 2, a weighing scale 20 that measures the weight of the measurement container 10 housing the measurement object 2, a transmission antenna 31 that transmits electromagnetic waves, and a reception antenna 32 that receives the electromagnetic waves transmitted by the transmission antenna 31. The oscillation circuit 30 is configured to feedback the output of the reception antenna 32 to the input of the transmission antenna 31. The calculation unit 40 calculates the moisture content of the measurement object 2 based on the mass of the measurement container 10 housing the measurement object 2 and the characteristic value indicating the electrical characteristics of the oscillation circuit 30 in a state where the measurement container 10 is disposed between the transmission antenna 31 and the reception antenna 32.

[0019] The measurement container 10 houses the measurement object 2 such that the thickness in the facing direction of the transmission antenna 31 and the reception antenna 32, that is, the transmission direction of the electromagnetic wave, is substantially constant. The measurement container 10 preferably has a substantially constant horizontal cross-sectional area. Thereby, the projected area of the measurement object 2 is kept constant regardless of the amount of the measurement object 2 housed in the measurement container 10, and the measurement error can be reduced. Note that "substantially constant" means that there may be fluctuations within a range where the technical effect is achieved. Further, as the measurement container 10, a container having a height smaller than the horizontal width (minor axis length) is preferably used. Thereby, the interval between the transmission antenna 31 and the reception antenna 32 can be reduced, and the transmission efficiency of the electromagnetic wave from the transmission antenna 31 to the reception antenna 31 can be improved. Therefore, the S / N ratio can be improved and the measurement error can be reduced.

[0020] The weighing device 20 preferably has a weighing conveyor 21 that conveys the measurement container 10 and is configured to measure the weight of the measurement container 10 being conveyed by the weighing conveyor 21. Specifically, the weighing device 20 may have a configuration similar to that of an in-line inspection weight checker having a load cell 22 that measures the weight of the weighing conveyor 21, a supply conveyor 23 that is slower than the weighing conveyor 21 and supplies the measurement container 10 to the weighing conveyor 21, and a discharge conveyor 24 that discharges the measurement container 10 from the weighing conveyor 21. Thereby, it becomes possible to continuously weigh a plurality of measurement containers 10 containing different measurement objects 2 and quickly measure the moisture content of the measurement object 2 contained in each measurement container 10.

[0021] By arranging the measurement container 10 between the transmission antenna 31 and the reception antenna 32, the oscillation circuit 30 detects, as a characteristic value indicating the electrical characteristics of the entire circuit, the transmission characteristics of electromagnetic waves from the transmission antenna 31 to the reception antenna 32 that change particularly according to the weight and moisture content of the measurement object 2 contained therein. In the illustrated example, the transmission antenna 31 and the reception antenna 32 are arranged to face each other with the weighing conveyor 21 interposed therebetween so that the characteristic value in a state where the measurement container 10 is arranged between the transmission antenna 31 and the reception antenna 32 can be detected substantially simultaneously with the measurement of the weight of the measurement container 10 by the weighing device 20. Note that "substantially simultaneously" means that there may be a time difference within the range where the technical effect is achieved.

[0022] As the transmission antenna 31 and the reception antenna 32, in order to improve the transmission rate of electromagnetic waves from the transmission antenna 31 to the reception antenna 32, it is preferable to use an antenna with high directivity such as a horn antenna. Further, the transmission antenna 31 and the reception antenna 32 are preferably arranged to face each other vertically so that the projected area of the measurement object 2 in the electromagnetic wave transmission direction does not change depending on the amount of the measurement object 2 accommodated in the measurement container 10. Thereby, the transmission characteristics of electromagnetic waves from the transmission antenna 31 to the reception antenna 32, and thus the value of the measured characteristic value, are determined by the three of the material, weight, and moisture content of the measurement object 2. Therefore, by considering the material of the measurement object 2 set at the time of measurement and the weight measured by the weight meter 20, the moisture content can be accurately calculated from the characteristic value of the oscillation circuit 30.

[0023] The oscillation circuit 30 may have an amplifier 33 that amplifies the output of the reception antenna 32, and may be configured to feedback the signal amplified by the amplifier 33 to the input side of the transmission antenna 31. The oscillation circuit 30 may be configured to self-excite simply by amplifying the feedback from the reception antenna 32 and re-inputting it to the transmission antenna 31, but may be configured to have a tuning circuit unit 34 that actively resonates the oscillation circuit 30 by adjusting the phase of the feedback from the reception antenna 32. By providing the tuning circuit unit 34 that actively resonates, the oscillation circuit 30 can operate stably in a resonant state, so that the moisture content of the measurement object 2 can be measured accurately.

[0024] As the synchronization circuit unit 34, a well-known circuit can be adopted. In the illustrated embodiment, it is configured to include a low-frequency oscillator 341, a low-frequency phase modulator 342, a circulator 343, a phase comparator (mixer) 345, a filter 346, and a phase controller 347. This synchronization circuit unit 34 phase-modulates the feedback signal of the output of the receiving antenna 32 by the phase modulator 342 according to the low frequency generated by the low-frequency oscillator 341, and when the frequency of the feedback signal does not match the resonance frequency of the oscillation circuit 30 mainly determined by the transmission characteristics of the electromagnetic wave from the transmitting antenna 31 to the receiving antenna 32, the reflected wave from the transmitting antenna 31 is detected by the frequency detection circuit unit 344 via the circulator 343. Then, the synchronization circuit unit 34 obtains the difference between the detected low frequency and the low frequency of the low-frequency oscillator 341 by the phase comparator (mixer) 345, and controls the phase controller 347 using the control signal generated by passing this difference through the filter 346, thereby performing frequency synchronization so that the frequency input to the transmitting antenna 31 matches the resonance frequency of the oscillation circuit 30.

[0025] Also, in order to ensure the adjustment by the synchronization circuit unit 34, for example, a phase shifter 35 for adjusting the phase of the feedback signal of the output of the receiving antenna 32 may be provided to perform rough phase adjustment by manual operation.

[0026] Furthermore, the moisture content measuring device 1 is configured to be able to detect characteristic values indicating the electrical characteristics of the oscillation circuit 30. The illustrated moisture content measuring device 1 is configured to detect, as characteristic values, the attenuation amount of the output of the receiving antenna 32 with respect to the input of the transmitting antenna 31, the phase difference of the output of the receiving antenna 32 with respect to the input of the transmitting antenna 31, and the oscillation frequency of the oscillation circuit 30. For this reason, the moisture content measuring device 1 includes an input detection circuit unit 36 that detects the input of the transmitting antenna 31, an output detection circuit unit 37 that detects the output of the receiving antenna 32, a phase difference detection circuit unit 38 that detects the phase difference between the input of the transmitting antenna 31 and the output of the receiving antenna 32, and a frequency detection circuit unit 39 that detects the frequency of the output of the amplifier 33. Note that the attenuation amount of the output of the receiving antenna 32 with respect to the input of the transmitting antenna 31 is calculated in the calculation unit 40 as the difference between the detection value of the input detection circuit unit 36 and the detection value of the output detection circuit unit 37.

[0027] The calculation unit 40 may be configured to include a weight acquisition unit 41 that acquires the weight of the measurement container 10, a characteristic value acquisition unit 42 that acquires the characteristic values of the oscillation circuit 30, a calibration curve setting unit 43 that presets a calibration curve indicating the relationship between the characteristic values and the moisture content, and a moisture content specifying unit 44 that specifies the moisture content of the measurement object 2 using the calibration curve set in the calibration curve setting unit 43 based on the weight acquired by the weight acquisition unit 41 and the characteristic values acquired by the characteristic value acquisition unit 42. The calculation unit 40 can be realized by causing a computer device including, for example, a memory, a processor, an input / output interface, etc. to execute an appropriate control program. Note that the above-described weight acquisition unit 41, characteristic value acquisition unit 42, calibration curve setting unit 43, and moisture content specifying unit 44 are classifications of the functions of the calculation unit 40, and do not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration.

[0028] The weight acquisition unit 41 includes the weighing scale 20 and the measurement object 2. The characteristic value acquisition unit 42 acquires the characteristic values from the oscillation circuit 30 by performing an operation on the detection values as necessary.

[0029] The calibration curve setting unit 43 presets a calibration curve showing the relationship between the characteristic value and the moisture content for each of the plurality of weights of the measurement container 10 for each type of the object to be measured 2. The calibration curve can be set by performing the steps of adjusting the moisture content of the sample of the object to be measured 2, weighing a predetermined weight into the measurement container 10, and acquiring the characteristic value from the oscillation circuit 30 a plurality of times while changing the moisture content. Further, the calibration curve setting unit 43 may be configured to be able to import the calibration curve data set in another moisture content measuring device 1. The calibration curve data of a typical type of the object to be measured 2 may be preset at the time of shipment of the moisture content measuring device 1, or the calibration curve data of a desired type of the object to be measured 2 may be configured to be downloadable via a recording medium, a network, or the like.

[0030] FIG. 2 and FIG. 3 illustrate calibration curves showing the relationship between the characteristic value and the moisture content when the object to be measured 2 is polished rice. FIG. 2 shows the relationship between the attenuation amount of the output of the receiving antenna 32 with respect to the input of the transmitting antenna 31 and the moisture content of the object to be measured 2 in each case where the weight of the polished rice (excluding the weight of the measurement container 10) is 450 g, 500 g, and 550 g. FIG. 3 shows the relationship between the frequency (oscillation frequency) of the output of the amplifier 33 and the moisture content of the object to be measured 2 for the same object to be measured. As is clear from these graphs, a correlation is recognized between the slope of the calibration curve and the weight of the object to be measured 2.

[0031] The moisture content specifying unit 44 calculates the value of the moisture content at the characteristic value acquired by the characteristic value acquisition unit 42 at the weight acquired by the weight acquisition unit 41 from the calibration curves at the plurality of weights set in the calibration curve setting unit 43. As an example, the moisture content at the characteristic value acquired by the characteristic value acquisition unit 42 in a plurality of preset calibration curves is obtained, and the moisture content of the measured object to be measured 2 can be calculated by weighted averaging according to the weight acquired by the weight acquisition unit 41.

[0032] The water content specifying unit 44 may be configured to be able to select characteristic values used for calculating the water content of the object to be measured 2, and may be configured to specify the water content as, for example, the average value of a plurality of candidate values based on a plurality of candidate values of the water content calculated from a plurality of characteristic values.

[0033] The water content specifying unit 44 may calculate the water content of the object to be measured 2 using the extreme value of the characteristic value that changes as the measurement container 10 is conveyed. When the measurement container 10 is not sufficiently large with respect to the projected areas of the transmission antenna 31 and the reception antenna 32, it is not easy to specify the moment when the conveyed measurement container 10 faces the transmission antenna 31 and the reception antenna 32. However, since the characteristic value reaches an extreme value at the moment when the measurement container 10 faces the transmission antenna 31 and the reception antenna 32, by continuously monitoring the value of the characteristic value and using the extreme value, the water content of the object to be measured 2 can be accurately calculated.

[0034] As is clear from the above description, one embodiment of the water content measurement method according to the present invention implemented by the water content measurement device 1 includes a step of measuring the weight of the measurement container 10 containing the particulate or liquid object to be measured 2, and a step of placing the measurement container 10 containing the object to be measured 2 between the transmission antenna 31 that transmits electromagnetic waves and the reception antenna 32 that receives the electromagnetic waves transmitted by the transmission antenna 31, and driving the oscillation circuit 30 that feeds back the output of the reception antenna 32 to the input of the transmission antenna 31, thereby detecting a characteristic value indicating the electrical characteristics of the oscillation circuit 30, and a step of calculating the water content of the object to be measured 2 based on the mass of the measurement container 10 containing the object to be measured 2 and the characteristic value of the oscillation circuit 30.

[0035] In this way, in the measurement of the water content by the water content measurement device 1, it is only necessary for the object to be measured 2 to form a layer on the entire inner surface of the measurement container 10, and the measurement operation can be performed relatively easily. Further, since the water content measurement device 1 uses a layer of the object to be measured 2 that is an aggregate of a large number of particulate matters, it has high sensitivity to changes in the water content and can accurately measure the water content of the object to be measured 2.

[0036] As described above, the water content measuring apparatus and the water content measuring method according to an embodiment of the present invention have been described. However, the configuration and the effects of the water content measuring apparatus and the water content measuring method according to the present invention are not limited to those described above.

[0037] As an example, the water content measuring apparatus according to the present invention preferably includes a dedicated measuring container having a shape and a material suitable for measuring the water content of a measurement object. However, the measuring container is an arbitrary component, and calibration curve setting and water content measurement may be performed using an appropriate container not included in the water content measuring apparatus.

[0038] Further, in the present invention, only some characteristic values of the attenuation amount of the output of the receiving antenna with respect to the input of the transmitting antenna, the phase difference of the output of the receiving antenna with respect to the input of the transmitting antenna, and the oscillation frequency of the oscillation circuit may be detected, or other characteristic values may be detected. Further, the detection of the characteristic values may be realized by a circuit configuration different from that of the above-described embodiment.

Description of Reference Numerals

[0039] 1 Water content measuring apparatus 2 Measurement object 10 Measuring container 20 Weighing scale 21 Weighing conveyor 22 Load cell 23 Supply conveyor 24 Discharge conveyor 30 Oscillation circuit 31 Transmitting antenna 32 Receiving antenna 33 Amplifier 34 Synchronization circuit section 35 Phase shifter 36 Input detection circuit section 37 Output detection circuit section 38 Phase difference detection circuit section 39 Frequency detection circuit section 40 Calculation section 41 Weight acquisition section 42 Characteristic value acquisition section 43 Calibration curve setting section 44 Water content specifying section

Claims

1. A weighing scale for measuring the weight of a measuring container containing a powdery or liquid object to be measured, An oscillation circuit having a transmitting antenna for transmitting electromagnetic waves and a receiving antenna for receiving the electromagnetic waves transmitted by the transmitting antenna, and feeding back the output of the receiving antenna to the input of the transmitting antenna, A calculation unit that calculates the moisture content of the object to be measured based on the mass of the measuring container containing the object to be measured and a characteristic value indicating the electrical characteristics of the oscillation circuit in a state where the measuring container is disposed between the transmitting antenna and the receiving antenna, Comprising: The oscillation circuit has a tuning circuit unit that resonates the oscillation circuit by adjusting the phase of the feedback from the receiving antenna, The tuning circuit unit includes a low-frequency generator, a phase modulator that phase-modulates the feedback signal from the receiving antenna according to the low frequency generated by the low-frequency generator and inputs it to the transmitting antenna, a circulator that separates the reflected wave from the transmitting antenna, a frequency detection circuit unit that detects the reflected wave separated by the circulator, a phase comparator that calculates the difference between the low frequency generated by the low-frequency generator and the reflected wave detected by the frequency detection circuit unit, a filter that filters the output of the phase comparator, and a phase controller that controls the phase of the feedback signal from the receiving antenna by the signal that has passed through the filter. A moisture content measuring device.

2. The calculation unit preset calibration curves indicating the relationship between the characteristic value and the moisture content for each of a plurality of weights of the measuring container. The moisture content measuring device according to claim 1.

3. The transmitting antenna and the receiving antenna are arranged to face each other vertically. The moisture content measuring device according to claim 1 or 2.

4. The weighing scale has a conveyor for conveying the measuring container, and measures the weight of the measuring container being conveyed by the conveyor. The moisture content measuring device according to any one of claims 1 to 3.

5. The calculation unit calculates the moisture content of the object to be measured using the extreme value of the characteristic value that changes as the measuring container is conveyed. The moisture content measuring device according to claim 4.

6. Comprising the measuring container having a substantially constant horizontal cross-sectional area and a height smaller than the horizontal width. The moisture content measuring device according to any one of claims 1 to 5.

7. The moisture content measuring device according to any one of claims 1 to 6, wherein the characteristic value is an attenuation amount of an output of the receiving antenna with respect to an input of the transmitting antenna, a phase difference of the output of the receiving antenna with respect to the input of the transmitting antenna, or an oscillation frequency of the oscillation circuit.

8. A step of measuring the weight of a measurement container containing a measurement object in a powder or granular state or a liquid state; A step of detecting a characteristic value indicating an electrical characteristic of the oscillation circuit by driving an oscillation circuit that feeds back an output of the receiving antenna to an input of the transmitting antenna with the measurement object disposed between a transmitting antenna that transmits electromagnetic waves and a receiving antenna that receives the electromagnetic waves transmitted by the transmitting antenna; A step of calculating a moisture content of the measurement object based on the mass of the measurement container and the characteristic value; comprising: The oscillation circuit has a tuning circuit unit that resonates the oscillation circuit by adjusting a phase of feedback from the receiving antenna; The tuning circuit unit includes a low-frequency generator, a phase modulator that phase-modulates a feedback signal from the receiving antenna according to a low frequency generated by the low-frequency generator and inputs the phase-modulated signal to the transmitting antenna, a circulator that separates a reflected wave from the transmitting antenna, a frequency detection circuit unit that detects the reflected wave separated by the circulator, a phase comparator that calculates a difference between the low frequency generated by the low-frequency generator and the reflected wave detected by the frequency detection circuit unit, a filter that filters an output of the phase comparator, and a phase controller that controls a phase of the feedback signal from the receiving antenna with a signal that has passed through the filter. A moisture content measurement method.

Images