JPH0643970B2 - Microwave water content measuring device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave-based moisture value measuring device for measuring while continuously supplying a sample.

2. Description of the Related Art A water content measuring device using microwaves includes a device for measuring the amount of attenuation of microwaves (Japanese Patent Laid-Open No. 56-92435) and a device for measuring the delay of the propagation velocity of microwaves (Japanese Patent Laid-Open No. 59-59). 102146).
The former measures the energy difference between the microwave propagating in the sample and the reference microwave, and the latter measures the phase difference between the microwave propagating in the sample and the reference microwave.

In these measuring devices, the sample transfer device normally transfers the supplied sample in a uniform layer, and when the supply amount is constant, the transfer speed fluctuates, or conversely, the transfer speed is constant. When the supply amount also changes, the amount of the sample staying in the measurement region changes and the sample thickness also changes. On the other hand, the amount of change in attenuation, propagation velocity, etc. related to microwaves depends mainly on the amount of water, and if the amount of sample in the measurement area is different, the measurement result will be the same even if the sample has the same water content (water content per sample unit). Therefore, any of the above-mentioned water content measuring devices adopts a correction means such as setting a fixed amount of sample placed in the measurement area or dividing the detected value by the sample weight. ing.

Correction by weight is an effective and practical means, but despite this correction, there are still variations in the measurement results. This is because when the amount of the sample in the measurement area at the moment of measurement, that is, the amount of the sample retained in the measurement area changes, the thickness of the sample changes and the microwave reflection status (degree of interference with the traveling wave). Change), the position of the sample relative to the electric field distribution in the microwave propagation path, and the amount of change in the microwave changes. .

For example, the sample is continuously supplied to the microwave propagation path, the sample weight and the amount of microwave attenuation are accumulated for a certain period of time, and the average value obtained by dividing each accumulated value or transmitted value by the cumulative number of times. There is a device to determine the water content of the sample from. In such an apparatus, even if the water content of the sample is the same and the cumulative value of the sample weight (the supply amount of the sample) is the same, the sample in the measurement range at the time of measurement as shown in FIGS. If there is a variation in the retention state, the cumulative value of the attenuation amount of the microwave does not always become the same value due to the influence of a fluctuation factor that is not proportional to the supply amount of the sample such as a standing wave.

In this case, the water content of the sample may be different from that of (a) and (b).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention uses a microwave that keeps the amount of the sample at the time of measurement in the measurement range, that is, the retention amount, almost constant, and suppresses the occurrence of fluctuation factors that cannot be eliminated by correction by weight as much as possible. An object is to provide a water content measuring device.

Means for solving the problems Moisture value output means for calculating and outputting a moisture value from the detected retention amount of the sample and its variation amount related to the microwave, and a sample transport device capable of transporting the supplied sample in a uniform layer as feedback Control means is provided to control and constantly maintain the sample conveyance amount constant.

The control means stores the standard staying amount of the sample, and controls so as to eliminate the difference between the value and the detected staying amount in the sample transport device.

The working feedback control means keeps the amount of sample retention in the measurement area almost constant.

The moisture value output means calculates the moisture value of the sample and outputs the value to the display device or the control device of the industrial equipment.

Example FIG. 1 is a block diagram showing a moisture value measuring device 1 utilizing microwaves. This device is of a type that employs the amount of attenuation of microwave energy due to water in the sample as the amount of change related to the microwave.

The moisture value measuring device 1 includes a microwave projection device 2, a sample transport device 3, a transport amount control means 4, and a moisture value output means 5.

As shown in FIG. 2, the microwave projection device 2 has a transmission horn (transmission antenna) vertically arranged with the sample transport device 3 in between.
6 and a transmitter / receiver having a reception horn (reception antenna) 7, and a microwave propagation path 8 between the transmitter / receiver is arranged so as to penetrate a carrier path 9 in the sample carrier 3.

The transmission horn 6 is connected to a power supply circuit 10 and a microwave oscillator 11 which mainly includes a Gunn diode and which generates a microwave of 9.4 GHz.

The receiving horn 7 includes a microwave receiver 12 and a receiving circuit 1.
3. The detection value processing device 14 is connected, and the detection value device 14 is connected with the moisture value display device 15 and the driver 16 for driving the industrial equipment corresponding to the measured value.

The microwave receiver 12 is mainly composed of a detection diode, and the receiving circuit 13 logarithmically converts the voltage value sent from the microwave receiver 12 and increases / decreases it and further A / D converts it to a value that can be easily processed later. is there.

The detection value processing device 14 is capable of inputting and storing various set values and various constants from the outside, and uses a so-called personal computer.

The sample transport device 3 has a structure of a vibration conveyor and transports the sample supplied by vibration into a uniform layer in the measurement area. Specifically, as shown in the figure, the trough (trough) 17 is supported on a pedestal 18 via inclined leaf springs 19 provided on the front and rear of the left and right sides, and the frequency variation of the electric leaflet with the inclined leaf springs 19 is variable. The vibrator 20 is connected via a drive spring 21. The vibrator 20 first rotates the variable speed motor 22.
Is transmitted to the second bevel gear 24 via the bevel gear 23, and one end of the drive spring 21 is rotatably attached to the eccentric position of the second bevel gear 24.

The trough 17 is formed by integrally molding a thick plate (1 mm) of polypropylene material, and a hole is provided at a portion corresponding to the measurement area, and a styrene foam plate (foaming ratio 10) is attached to the portion. It should be noted that the material of the trough 17 may be a synthetic resin such as an acrylic resin that is hard and has a small absorption and reflection of microwaves.

Since polypropylene has high microwave transparency, the trough may be integrally formed without using another material for the measurement area.

The gantry 18 is a frame body in which a portion corresponding to the microwave propagation path 8 is cut out.
Is formed. The gantry 18 is supported in a floating state with respect to the machine frame of the measuring apparatus 1, and a load cell 25 is attached to the gantry 18.

The load cell 25 is a transport path weight detection device that detects the weight of the transport path 9 on which the sample 26 is placed, and the detected value is amplified and A / D converted by the receiving circuit 13 to be a value that can be easily processed later. Is transmitted to the detected value processing device 14.

The sample weight on the trough at that time can be calculated by subtracting the weight (constant) of the trough 17 from the detected value. Further, since the sample weight is an instantaneous value, the measurement for the trough 17 is performed. The retention amount of the sample can be calculated from the area ratio (detection retention amount).

Reference numeral 27 is a supply port end of the supply path of the sample 26 that is exposed from the industrial equipment and faces the trough 17.

The transport amount control means 4 is the load cell 25 and the receiving circuit 1 described above.
3, a detection value processing device 14, a D / A converter 28, and a variable speed motor 22.

The water content detecting means 5 is composed of a microwave receiver 12, a receiving circuit 13, and a detection value processing device 14.

When the vibrator 20 is driven, the trough 17 moves the inclined leaf spring 1
The elasticity of 9 and the inclination direction repeatedly vibrate upward in the direction of arrow u, and the sample supplied from the supply port 27 to the trough 17 is continuously swung upward while being shaken upward. The sample 26 on the trough 4 moves while uniformly spreading over the entire flow path, but the amount of movement per unit time, that is, the amount of conveyance is within a certain range (at least a vibration cycle of 0.07 to 0.12).
(Within the range of seconds), the trough 1
The retention amount of the sample on No. 7 is almost inversely proportional.

It should be noted that the conveyance by vibration is suitable when the irregular-sized small piece aggregates such as tea leaves and gravel or the granular material are evenly transported.

Simultaneously with the transportation of the sample 26, the transmission horns 6 to 9 are provided in the measurement area (the intersection of the sample transportation path 9 and the microwave propagation path 8).
A microwave of 4 GHz is projected and received by the reception horn 7 in a form of passing through the sample on the trough 17 and the trough. The microwave energy received by the reception horn 7 is
This is the microwave energy amount (reception microwave energy amount) after being absorbed by the water held by the sample on the trough 17 or attenuated by reflection / absorption by the equipment of the propagation path. Convert to voltage and use as detection value. The detection value passes through the receiving circuit 13 and the detection processing device 1
4 is transmitted.

It should be noted that among the attenuation of microwave energy, that due to reflection / absorption by the equipment of the propagation path is constant, and
Few.

Further, from the load cell 25 provided on the gantry 18, the weight of the transport path at any given time is transmitted via the receiving circuit 13 to the detection value processing device 1
4 is transmitted.

In the detected value processing device 14, for example, the processing shown in the flowcharts of FIGS.

In this treatment, tea leaves in the tea making process are used as samples, and the current weight (w) of the transport path and the amount of received microwave energy are reduced to 1 / under a preset standard sample retention amount (ws).
It is taken out every 50 seconds, and the transport path drive voltage (V) as the adjusted transport amount and the water content rate (G) of the sample are calculated and output about every 0.8 seconds. It is the basis.

This flow starts when the operation of the industrial equipment starts or at an appropriate time after the start. The variable speed motor 22 of the vibrator 20 is initially driven at V = 2.6 (v).

The flow of FIG. 4 can be summarized as shown in FIG. 3, and Sa (step a ...
Sb to S3 to S7, Sc to S13 to S25, S
d corresponds to S10 to S12, and the sample conveyance amount is adjusted every time data is accumulated 40 times in Sb (Se), and the water content is calculated every time this accumulation exceeds 3000 times. This is a configuration for outputting (Sd).

Specifically, in S1 (step 1 ... The same hereafter), T, U, M, W
Registers 1, W2 and W3 are initialized.

T, U ... Repeat count register.

M ... Integrated value of the detected amount of microwave energy in a large unit time (described later).

 W1, W2, W3 ... Weight related registers.

Note that, hereinafter, the register name and its stored content will be described with the same reference numerals.

In S2, w0, ws, and m0 are read and stored in appropriate registers.

w0 ... initial weight of transport path. It is based on the output of the load cell 25 when there is no sample in the transport path 9 of the sample transport device 3.

ws: sample standard retention amount (weight). To control the sample transfer amount,
This is a standard value, which is appropriately set based on the type of sample, estimation of water content, etc. before starting the measurement, and is input in advance from the keyboard. It is a value around the sample retention amount when the initial transport amount when 2.6 (v) is applied to the variable speed motor 22 continues.

m0 ... initial received value. Based on the output of the microwave receiver 12 when there is no sample in the transport path 9 of the sample transport device 3.

a: Area ratio of the measurement area to the trough.

In S3, the 1/50 second timer is reset and then started,
When it is determined in S4 that 1/50 second has elapsed, w and m1 are read in S5 and stored in an appropriate register.

w: Current weight of the transport path. It depends on the current output of the load cell 25.

m1 ... Currently received value. It depends on the current value of the microwave receiver 12.

In S6, the current weight (w) of the transport path is added up and stored in the register W1. In addition, the number of times is integrated and stored in the register T.

In S7, the current weight (w) of the transport path is added up, and the register W2
And the current amount of microwave energy received (m
1) is integrated and stored in the register M. Then, the number of times of these processes is integrated and stored in the register U.

In S8, it is determined whether or not the current weight (w) of the transport path has been accumulated 40 times. If NO, S3 to S8 are repeated via S9. This process monitors the sample retention volume to about 0.
This is because the time unit is about 8 seconds (called a small unit time). This value is determined by the response capability of the sample transport device and the characteristics of the sample (such as relatively easy supply), and can be changed as appropriate from keyboard input.

When it is determined that T = 40 in S8, the process proceeds to S13, proceeds from S14 to S25, moves from S25 to S9, and transfers the present weight (w) of the transport path and the detected microwave value (m
It is determined whether the integration in 1) has been performed 3000 times.
If NO, S3 to S25 and S9 are repeated, and U ≧ 3.
Wait for 000. This is because the water content output to the industrial equipment is performed in a time unit of about 60 seconds (referred to as a large unit time). This value is determined in consideration of the response capability of the moisture value control device provided in the industrial equipment, and can be changed appropriately from the keyboard.

Now, in S13, the average value (W
1 / T-w0) is calculated and the register W1 is replaced with this value. A value obtained by multiplying this value by the area ratio a of the trough and the measurement area is defined as the detected retention amount of the sample.

In S14, it is determined whether or not the value of the register W3 is 0, that is, whether or not the flow is the first cycle, and if YES, the value of the register W3 is replaced with W1 in S15 and the process proceeds to S16. If NO, Goes directly to S16. This processing is to set the second term on the right side of the calculation formula in S16 to 0 in the first execution of the flow.

Therefore, when the flow cycle is the first, only the first term in S16, that is, the primary adjustment by multiplying the difference between the standard retention amount (ws) and the detected retention amount in a small unit time (a · W1) by the coefficient k1. The voltage V1 is calculated, and the coefficient k3 is multiplied in S17 to calculate the secondary adjustment voltage V2.

W3 is not 0 after the second flow cycle (S
24), the second term on the right side of the calculation formula in S16 is used, and the detected retention amount in the small unit time at the time of the previous execution of the flow and the detected retention amount in the current small unit time (a · W
By multiplying the difference from 1) by the coefficient k2, a part of the primary adjustment voltage is obtained. Therefore, the primary adjustment voltage is calculated from the variation amount (absolute variation amount) with respect to the standard retention amount (ws) according to the first term and the variation amount (relative variation amount) with respect to the previously detected retention amount according to the second term. It is calculated.

k1 to k3 are constants determined from the transfer capability of the sample transfer device 3 and the response of the transfer amount control. For example, k1 = 1 and k2.
= 1 and k3 = 0.182.

In S18, the adjustment voltage V obtained by subtracting the secondary adjustment voltage V2 from the current applied voltage to the variable speed motor 22 is calculated, and in S19 to S22, the value is changed from a minimum value of 1.5 (v) to a maximum value of 3 (v). It fits in the range and is output in S23. This voltage is applied to the variable speed motor 22 via the D / A converter 28, and the motor 22 is feedback-controlled.

That is, the adjustment voltage V is the adjustment conveyance amount expressed as a voltage.

The range of the adjustment voltage V is limited because if V <1.5, the sample is not transported at all, and if V> 3.0, the durability of the vibrator 20 becomes a problem. Is. Actually, the output shaft of the variable speed motor 22 is 1000 to 1700 in the range of 1.5 to 3.0 (v).
rpm, and with the reduction ratio of the first and second bevel gears being 1/2, the vibration cycle of the trough 17 is finally 0.12 to 0.07.
Seconds.

Further, in S24, after storing the average value (W1) of the sample weight in this small unit time in the register W3 and storing it,
The used W1, T used this time is initialized at 25, and the process returns to S3 for the next cycle.

Therefore, the adjustment voltage V is output every time this cycle is repeated, and the rotation speed of the variable speed motor 22 is controlled with respect to the weight of the transport path at intervals of about 0.8 seconds. Also, during this period, S
In FIG. 7, the current weight (w) of the transport path and the microwave detection value (m1) are continuously accumulated in the registers W2 and M without being updated even if the flow cycle changes, and the number of times the register U has been accumulated. Will increase.

When U ≧ 3000 (60 seconds for 1/50 second data accumulation) is satisfied in S9, the process proceeds to S10, and the sample water content (G) is calculated by the notation formula, and S11 is calculated.
With industrial equipment driver 11 or moisture value display device 15
Is output to. Therefore, this output is performed at intervals of about 60 seconds.

Next, in S12, the registers U, W2 which have been used this time are finished.
M and G are initialized and the process returns to S3, and the calculation and output process of the adjustment voltage V is continued.

Formula for calculating the sample moisture value G in S10, Is a well-known sample obtained by statistically processing the moisture value of the same sample and the microwave energy attenuation value per unit weight by the same sample by a highly reliable dry method. Of microwave energy attenuation, sample weight,
It is a correlation expression of water content. The constants k4 and k5 are
For example, k4 = 72.17 and k5 = 0.17.

Although the embodiments have been described above, the present invention is also applicable to a moisture value measuring device using microwaves other than the type that detects an attenuation amount of microwave energy as a variation amount relating to microwaves.

For example, the microwave propagated in the sample as described above,
It can also be applied to an apparatus of a type that measures the water content by detecting the phase difference from the reference microwave as the amount of change in the microwave. In this type of device, the propagation velocity of microwaves in the dielectric changes with respect to the relative permittivity of the dielectric (delay), N ... Propagation velocity c ... Light velocity ... Specific permittivity Further, since the relative permittivity of the sample is related to its water content, the delay of the propagation velocity of the microwave is obtained from the phase shift with respect to the reference wave and corrected by the sample weight. This is based on the fact that the water content of a sample can be estimated from a calculation formula obtained by experiments in advance.

The block diagram of the moisture measuring device 1 in this case is as shown in FIG. 6, and the configurations of the power supply circuit 10, the microwave projecting device 2, and the sample transporting device 3 are the same as those in the first embodiment, and The configurations of the load cell 25, the vibrator 20, and the D / A converter 28 attached to these are also the same.

However, in this embodiment, the phase detector 30 is provided, and the reference wave propagation path (from the microwave oscillator 11 to the demultiplexer 31,
The detected wave propagation path (from the microwave receiver 12) is connected to the phase shifter 32). And the phase detector 3
The output of 0 is connected to the detected value processing device 14.

The phase shifter 32 is for synchronizing the reference wave reaching the phase detector 30 and the detected wave.

Therefore, the microwave oscillated from the microwave oscillator 11 is divided into the reference wave propagation path and the detection wave propagation path by the demultiplexer 31. The phase detector 30 detects and compares the phases of the microwaves propagated through the two paths, converts the phase difference into data that is easy to handle, and sends the data to the detection value processing device 14.

The water content is calculated by detecting the phase difference between the reference wave and the detected wave in the absence of a sample before the start of measurement and setting this value as the initial reception value m0 in the first embodiment, and then supplying the sample. The value of the phase difference detected in this state is set as the current received value m1, and the processing is performed in the same manner as in the case of the first embodiment.

When the phase difference of the detected wave with respect to the reference wave becomes large, it may make one rotation and return to the original phase. Therefore, the phase shifter 32 is adjusted to set the received value when the phase is 0 to the initial received value m0. The measurement range is wide.

A means for measuring the water content of the sample by detecting the phase difference (delay) of the detected wave with respect to the reference wave as the change amount relating to the microwave is well known, for example, the above-mentioned JP-A-59-10214.
No. 6 publication.

In the above, the detection value processing device 14 in these examples is basically based on the comparison of the standard retention amount (ws) of the sample with the detection retention amount (a · W1). Not only by the amount of sample staying in the area, but also by setting a standard value (sample standard weight) for the sample weight on the trough (transport path) and comparing this with the detected sample weight, the transport path weight Even if a value (standard weight of sample transport path) is determined and directly compared with the detected current weight (w) of the transport path, the standard retention amount can be maintained substantially constant. It can be carried out. The cigarette and the coefficient a are unnecessary, and the values of the coefficients k1 to k5 need to be adjusted.

Note that the sample volume can be adopted as an “amount” such as a retention amount by further developing.

Further, the sample transfer device 3 is not limited to the vibration conveyor, and the rotation speed of the belt drive motor may be controlled by an ordinary belt conveyor, or the tilt angle is controlled by a trough having a variable tilt angle depending on the state of the sample. It can also be implemented by

Further, other appropriate formulas for calculating the adjusted transport amount and the moisture value calculation formula can be adopted, and these calculation processes can be performed in parallel using two processors.

Further, for example, initial values (m0, w0) in a state where there is no sample, for example, a part of the sample adheres to the trough 17.
If it is expected that the value will change over time, the supply of the sample will be stopped at regular time intervals in cooperation with the sample supply device of the industrial equipment, the process will return to S2, and the values of the microwave receiver 12 and the load cell 25 will be returned. May be read to update the initial value.

Effect of the Invention Since the amount of sample (residence amount) existing in the measurement region is always constant, the influence of error factors that are not proportional to the amount of sample from the measured value can be eliminated as much as possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment, FIG. 2 is a partial front view, FIG. 3 is a schematic flowchart of one embodiment, and FIG. 4 is a flowchart of the one embodiment.
FIGS. 6A and 6B are diagrams for explanation, and FIG. 6 is a block diagram of another embodiment. 1 ... Moisture value measuring device, 2 ... Microwave projection device, 3
...... Sample transport device, 4 ... Transport amount control means, 5 ... Moisture value calculation / output means, 6 ... Transmission horn, 7 ... Reception horn, 8 ... Microwave propagation path, 9 ... Transport path, 10 ……
Power supply circuit, 11 ... Microwave oscillator, 12 ... Microwave receiver, 13 ... Reception circuit, 14 ... Detection value processing device, 15 ... Moisture value display device, 16 ... Driver, 1
7 ... Trough, 18 ... Stand, 19 ... Inclined leaf spring, 2
0 ... Variable frequency vibrator, 21 ... Drive spring, 2
2 ... Variable speed motor, 23 ... First bevel gear, 24 ...
2nd bevel gear, 25 ... Load cell, 26 ... Sample, 2
7 ... Sample supply port, 28 ... D / A converter.

Claims (2)

[Claims] 1. A sample transport device equipped with a staying amount detection device and capable of transporting a supplied sample in a uniform layer, and a sample transporting device that stores a standard staying amount of a sample and eliminates the difference from the detected staying amount. An apparatus for measuring a moisture value by microwave, comprising: a conveyance amount control means for feedback-controlling the apparatus and a moisture value output means for calculating and outputting a moisture value based on a detected retention amount of a sample and a variation amount thereof with respect to a microwave. . 2. A microwave projection device is sent to a transfer path of a sample transfer device capable of transferring the supplied sample in a uniform layer.
The receiver is arranged so that the microwave propagation path penetrates the transport path, and a sample weight detection device is provided on the transport path.
Further, the microwave projection device is provided with a change amount detection device for microwaves, and
Sample weight value output means for storing a sample weight / moisture correlation expression and calculating and outputting the sample water value (G) from the amount of change in microwave and the sample weight value, and the sample weight for storing the sample standard weight. A moisture value measuring device using microwaves, which is provided with a transport amount control means for calculating an adjusted transport amount (V) that approximates to a standard unit amount and outputting the adjusted transport amount (V) to a drive device of the sample transport path.