JPS59198351A - Moisture content measuring apparatus - Google Patents

Abstract

PURPOSE:To perform moisture content measurement by online basis without exerting influence upon bulk density, by operating the ratio of an AC current having the same phase as applied voltages by applying AC voltages with difference frequencies between opposed electrodes through which an object to be measured flows. CONSTITUTION:AC voltage which are different in frequency but same in effective voltage are applied to the opposed electrodes 41, 42 of a detection part 4 through which an object to be measured such as grain flows and AC currents having the same phase as the applied voltages are detected by a detection circuit 6 to be respectively latched by a first and second hold circuits 7, 8 through a switch 9. This latch content is subtracted by a subtractor circuit 12 to determine a dielectric loss ratio uniquely change corresponding to a moisture percentage and moisture measurement is performed by online basis without exerting influence upon bulk density.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to the moisture content or moisture content (hereinafter referred to as moisture This invention relates to a moisture measuring device that can measure water content (sometimes referred to as ``water vapor'') online using the dielectric loss phenomenon without being affected by the density or moisture distribution.

[Prior art and its problems]

The moisture content of grains, etc. is an important factor that affects their economic quality and physical properties, so it has traditionally been measured using various methods.
Recently, the number of processes that continuously process large amounts of grain, etc. has been increasing, and in such processes, it is important to accurately measure the moisture content of grain, etc. online.

In general, the moisture in grains, etc. consists of bound water and free water in the substance, and this free water is often used as the purpose of moisture measurement. The resistance type, dielectric constant type, Janδ type, and microwave type are often used.

The electrical resistance formula, dielectric constant formula, and janδ formula (hereinafter sometimes referred to as the electrical resistance formula) require the sample to be filled between opposing electrodes because the electrical resistance, permittivity, or tanδ of grains, etc. depends on the amount of free water. The method attempts to estimate the amount of free water by measuring these quantities, and in both methods, the amount of voids between particles in grains, etc., that is, the bulk density of grains, etc., influences the measured value of moisture. It is clear from the measurement principle that the Therefore, in order to avoid the influence of these voids as much as possible, when measuring moisture using methods such as electrical resistance, powders are usually compressed as they are, and granules are crushed and compressed to a specified size. The sample is filled between opposing electrodes for measurement, but for this reason measurement methods such as the electrical resistance type require intermittent measurement operations and -
The disadvantage is that it takes time to measure because it is necessary to prepare a sample and clean the electrodes for each measurement operation, and accurate measurements cannot be made because the sample is small.As a result, this measurement method is This method cannot be applied to online measurements in continuous processes. In the microwave method, when microwaves of approximately 1 cm, which is the characteristic absorption wavelength of water molecules, are projected onto grains, etc., the water molecules in the grains absorb the energy of the microwaves in proportion to the amount, and the intensity of the transmitted microwaves increases. This method measures the moisture content of grains, etc. by measuring this intensity.As is clear from the above operating principle, this method is an electrical non-contact method, so it can be used for online measurement in continuous processes. , 1a'n has the advantage that it is not affected by components other than water that have microwave absorption wavelengths different from the wavelengths of 1a'n. However, in this microwave method, on the other hand, the intensity of the transmitted microwave is affected by the degree of umbrella, similar to the electric resistance method, and the measured value is a value that corresponds to the sum of bound water and free free water. However, as the amount of grain increases, energy absorption increases, making it difficult for microwaves to pass through.

[Purpose of the invention]

The present invention eliminates the shortcomings of the moisture measuring device using the conventional measuring method as described above, and makes it possible to measure the amount of free water on-line without being affected by bulk density. Seven purposes are to provide a measuring device.

[Key points of the invention]

The present invention provides a moisture measuring device which has opposing electrodes, and has a very small part between the electrodes that allows grains or other objects to be measured to flow or accumulate, and two alternating current voltages of different frequencies are applied between the electrodes. The voltage is applied alternately, and the component in the alternating current flowing at this time that is in phase with the applied voltage is detected and the ratio of the two phase currents is calculated.
The device is configured to measure the water content in the object to be measured based on this calculation result, and for reasons explained later, the above calculation result is based on the amount of free water in the object to be measured. Since the amount is not affected by falsification, if the moisture measuring device is configured in this way, it can be applied to online measurement.

[Embodiments of the invention]

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the moisture measuring device according to the present invention, and FIG. 2 is a perspective view of the detection section 4 in FIG. 1. In both figures, 1 and 2 are first and second voltages that generate sinusoidal AC voltages of equal effective value E at different angular frequencies W1 and W2, respectively.
A power supply unit, 3 is a first switch that switches the voltage generated by the picture power supply units 1 and 2, 4 is a cylindrical detection unit into which the object to be measured 5 such as grain is inserted, and 41 and 42 are the cylinders thereof. The counter electrodes 41a and 42a provided on the side surfaces are terminals of the counter electrodes 41 and 42, respectively. In some cases, the detection part 4 is formed without a bottom, and the object to be measured 5 flows continuously through it [
7. The detection part 4 may be formed with a bottom, and the object to be measured 5 may be accumulated therein.

The output side of the switch 3 is connected to the detection section 4, and the voltage generated by the power supply section 1 or 2 is applied between the opposing electrodes 41 and 42. Reference numeral 6 denotes a detection circuit connected to the detection section 4, and this circuit 6 outputs a signal corresponding to a current flowing between the opposing electrodes 41 and 42 that is in phase with the voltage applied between the two electrodes. 7 and 8 are respectively operation signals 1
0a.

10b is input, the first .10b holds and outputs the input signals 9a and 9b. The second holding circuit 9 switches the output signal of the detection circuit 6 into two signal paths 10a and 10b, respectively. Reference numeral 11 denotes an operation signal generating circuit for supplying the second holding circuit 7.8 to the first holding circuit 7.8. A switching operation drive circuit 12 is a switching operation drive circuit that repeatedly performs switching operations of the second switches 3 and 9 and the operation signal generation circuit 1o at a predetermined cycle;
12a is a division circuit to which each output signal of the second holding circuits 7 and 8 is input and calculates the ratio thereof; 12a is its output signal;

Next, the operation of this example will be explained. When the amount of grain, etc. is increased between the grains and the grains, voids caused by the grains, etc. coexist here. Therefore, the apparent dielectric constant ε between the electrodes can be calculated by simple division based on some assumptions: (1)
Expressed by the formula. Here, VD, Vl, and V2 are the volume between the electrodes, the volume of the void in VO, the volume of the gas in vOO, etc., and Vo = V1 + v2. ε1
．． ε2 is the dielectric constant of air, grain, etc., respectively.

VI V2 1? w・ε1−1−yy・ε2 ・・・・・・・・・
(1) Dielectric constant is expressed as a complex number, and the dielectric loss factor of air is considered to be zero, so ε1=ε11, ε2=ε21−Jε
22, equation (1) is transformed into equation (2).

VI V2, V2C
−(Vu・ff +1 +−H・62+)−3・W・6
22.・(2) Therefore, when a sine wave AC voltage with an angular frequency W% effective value E is applied between these electric plates with grain etc. inserted between the electrodes 41 and 42, the current expressed by equation (3) The work is flowing. Here, CO is the capacitance when there is a vacuum between the electrodes. ε11. ε21. ε22 is a function of the frequency of the applied voltage.

28 wC0E■-22 (3) In this embodiment, as mentioned above, the component in phase with the applied voltage E in the current generator, that is, w Co E (V2/VOν22 is detected by the detection circuit 6 is detected, and a signal corresponding to this component current is sent to the second
It is held in holding circuit 7 or 8 via switch 9 and output. In other words, in this embodiment, the switching operations of the switches 3 and 9 and the operation signal generating circuit 10 are configured to be linked, and when the voltage E generated by the first power supply section is applied between the electrodes by the switch 3, it is detected. The output signal of the circuit 6 is held in the holding circuit 7 and outputted, and the 21st signal is outputted by the switch 3.
! When the generated voltage E of the source section is applied between the electrodes, the output signal of the detection circuit 6 is held in the holding circuit 8 and outputted, so each output signal of the holding circuits 7 and 8 is WlCOE(V2/Vo)ε221. w2
The signal corresponds to coB'(V2/Vo)'g222. Here ε221. ε222 is the power supply section 1
This is the dielectric loss factor of grains, etc. corresponding to the angular frequency Wi, W2 of each generated voltage of °2. Therefore, the output signal 12a of the division circuit 12 becomes a signal corresponding to the value of R shown in equation (4). Here, Bt-ε221/ε222.

Next, the significance of Rt in equation (4) will be explained based on the experimental results of the present inventors.

Figure 3 shows an example of the dielectric loss factor measurement results conducted by the present inventors on dry rice grains with a dry surface.
It is a figure which shows an example of the relationship between the moisture content of paddy and Bt created based on the figure. Here, H and t are the measurement frequency IMH
It is the ratio of the dielectric loss factor when the measurement frequency is 2 MHz and the dielectric loss factor when the measurement frequency is 2 MHz.

As is clear from FIG. 4, this Rt uniquely corresponds to the moisture content of paddy. Therefore, by measuring R and t, the moisture content of paddy can be determined. According to the experiments conducted by the present inventors, the angular frequency W
The ratio Bt of the dielectric loss factor C222 measured by applying a voltage of angular frequency W2 to the same grain, etc. as ε221 is a measure of the moisture content of the grain, etc. becomes.

Therefore, since R in equation (4) is an amount corresponding to the moisture content of grains, etc., the moisture measuring device of this example can measure the moisture of grains, etc. based on the output signal 12a. As mentioned above, ε221. Since ε222 depends on the amount of free free water, Bt also depends on the amount of free free water.
Furthermore, as shown in equation (4), R does not include V2/VO, that is, a quantity related to the force density of grains, etc. Therefore, according to the moisture measuring device of this example, the amount of free water in grains, etc. can be measured without being affected by the bulk density, and this measurement is performed by interlocking the switching operations of the switches 3 and 9 and the operation signal generating circuit 10. Since the measurement is carried out continuously by repeatedly performing the gauging at a predetermined short G) period, it is possible to use such a measuring device to detect the G grain flowing inside the force 3 detection section 4! /1 can be accurately measured even if it remains in the detection part 4, and it can be applied to online measurement of the fixed device. The dielectric loss factor measurement result is different from that shown in Figure 3, which was carried out by placing rice inside the detection unit 4. This figure shows the dielectric loss measured by applying a voltage of a certain frequency to the rice whose surface is dry. The paddy was sealed for a predetermined period of time at rate A, and when the surface of the paddy was abraded by evaporated water, snow and pressure of the same frequency were applied and measured, and the dielectric loss factor B was subtracted by 1.7. B/A...
: Indicates the relationship with the measurement frequency. As is clear from this figure, A and B are not equal. In other words, even for the same paddy, the value of the reading rate measured by the detection unit 4 is determined by the fact that the surface of the paddy is dry.
It depends on the degree of dryness of the surface of the paddy, whether it is covered or submerged. Furthermore, as is clear from the figure, B/A changes depending on the measurement frequency.

In other words, this means that the ratio of the electric loss factor when the surface of the rice is wet to the dielectric loss factor when the surface of the rice is dry differs depending on the measurement frequency. Therefore, any two Set one measurement frequency and use it to induce lightning.

The Bt value obtained by measuring the loss rate is generally different depending on whether the surface of the rice is dry or wet. Therefore, if we use R in equation (4) obtained with the two constant frequencies set in this way, the measured moisture value of the paddy will be a different value depending on the degree of dryness of the surface. An error occurs.

Therefore, in the measuring device shown in FIG. 1, when determining the moisture content Ij of paddy, the circumferences Mt@'1 Wl of the two power supply units 1 and 2,
For example, the frequencies corresponding to points C and D in FIG. 5 are selected as W2. These points C and D are the two intersections of the straight line parallel to the horizontal axis that intersects the song IU of B/'A and the curve of B/A. Points C and D are formed in this way, so the surface force S of the rice grains is equal to the dielectric constant loss in the wet state and the dielectric constant loss in the dry state. .Therefore, for the paddy ζ, it is equal to the measurement frequency corresponding to points C and D.'It source frequency W1. Using W2 (4)
When the Ishita 12a corresponding to R in the equation is obtained using the measuring device shown in FIG.
). In other words, when the value is set, such a moisture measuring device ζ has the effect of being unaffected by the degree of dryness of the surface of the grain (1, 1, G).

〔Effect of the invention〕

As explained above, in the present invention (1), C is water ml
A first switch for switching between two sinusoidal AC voltages with different frequencies and equal magnitudes, a detection circuit with a detection section having a counter electrode, a second switch, and the first and second sine wave AC voltages. In this device, the magnitude and force are equal to 5 and the frequency is Wl.
, w2, different sinusoidal AC voltages are switched by the first switch and applied between the opposing electrodes, and this applied voltage causes a current to flow between the opposing electrodes when an object to be measured is inserted. A detection circuit detects a component in the current that is in phase with the applied voltage, outputs a signal corresponding to this component current, and the output signal is increased by 1 with a second switch to be used in the first holding circuit or the second holding circuit. Either one of the switches ζ is held and outputted, and each switching operation of the first and second switches is continuously repeated at a predetermined period in conjunction with the switching operation drive circuit ζ. The division circuit calculates the ratio of the Okayama force signals of the first and second holding circuits, and a signal corresponding to the result is output from the division circuit, so this output signal can be used when the object being measured is grain, etc. The signal corresponds to the amount of free water and is not affected by the bulk density of grains or the like. Therefore, according to the present invention, there is an effect that the amount of free water in grains, etc. can be measured without being affected by the bulk density, and as a result, online measurement is also possible.

Furthermore, in the present invention, the dielectric loss factor of the object to be measured is calculated at the first measurement frequency for both cases where the surface of the object to be measured is wet and dry. Measure and find the ratio between the measured value in the former case and the measured value in the latter case, and determine if the surface of the object to be measured is wet or dry at the second measurement frequency. Measure the dielectric loss factor of the measured object in each case, find the ratio between the measured value in the former case and the measured value in the latter case, and calculate the value of the ratio at the first measurement frequency ζ and the second The first and second measurement frequencies are set at the first and second measurement frequencies such that the ratio values at the measurement frequencies are equal to each other.
Since the frequency of each voltage generated by the i-source is set, such a moisture measuring device has the advantage that the measured value is not affected by the degree of dryness of the surface of the object to be measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the moisture measuring device according to the present invention, FIG. 2 is a perspective view of the detection unit 4 in FIG. 1, and FIG.
The figure shows an example of the measurement results of the sleep loss rate of paddy, and Fig. 4 is an example of the relationship between the moisture content of paddy and Rt, which was created based on Fig. 3.
FIG. 5 shows another example of the measurement results of the dielectric loss factor of rice. In each figure, 1...first power supply section, 2...
...Second power supply section, 3...First switch, 4...
...Detection unit, 5...Measurement object, 6...
...Detection circuit, 7...First holding circuit, 8...
...Second holding circuit, 9...Second switch, 9
a... Input signal of the first holding circuit 7, 9b...
...Input signal for second holding circuit 8, 10...Operating signal generation circuit, 10a...Operating signal for first holding circuit 7, 10b...Second holding Operation signal of circuit 8, 11... Switching operation drive circuit, 12...
. . . Division circuit, 12a . . . Output signal of division circuit 12, 41.42 . . . Counter electrode. Patent Attorney Yamaguchi (Fig. 1 @ 2)

Claims (1)

[Scope of Claims] A first switch that switches and outputs two sinusoidal AC voltages having different frequencies and equal magnitudes, and an opposing Ng to which the output voltage of the first switch is applied, between the electrodes thereof. a detection section into which an object to be measured is inserted; and a detection section connected to the detection section that detects a current in phase with the applied voltage among the currents flowing between the electrodes and outputs a signal corresponding to the current. A detection circuit, a second switch that switches and outputs the output signal of the detection circuit, first and second holding circuits that respectively hold the output signal No. of the second sentry switch, and each front tl'r2 first: #Switching operation in r6 and v, 2 switches, 11! A dividing circuit calculates the ratio between the output signal of the first holding circuit and the output signal of the second holding circuit. A moisture measuring device 2, characterized in that the output signal of the weeping circuit described in IJ is a measure of moisture in the object to be measured, the device according to claim 1, wherein each of the The frequency of the sine wave AC voltage is measured at a first measurement frequency when the surface of the object to be measured is wet, and when the surface of the object to be measured is dry when measured at the first measurement frequency. of the dielectric loss factor measured at the second measurement frequency when the surface of the object to be measured is wet, and when the surface of the object to be measured is dry when measured at the second measurement frequency. A moisture measuring device characterized in that the frequency is set to be equal to the first and second measurement frequencies such that the ratio of the frequency to the dielectric loss factor is equal.