SU1205004A1 - Moisture meter - Google Patents

Abstract

The invention relates to the field of radio engineering and m. used to determine the moisture content of bulk materials. The purpose of the invention is to improve measurement accuracy. The oscillations from the microwave generator 1 are supplied to the radiating antenna 2 mounted on the wall of the chamber 3 with the test material. Passing through the camera 3, an electromagnetic wave, weakened in power, enters the receiving antenna 4, and then into the detector 5 and the logarithmic amplifier 6. The prologized signal arrives at the 1st input of the analog multiplier 7. The output of the detector 5 is also connected to the 1st input of the comparator 8, the 2nd input of which is connected to the source of the reference voltage 22, which ensures that the comparator 8 switches to a single state. The output of the comparator 8 through the delay element 10 is connected to the input of the control unit (WU) II. The control unit 11 generates a pulse that zeroes the counters 14.15, and the signal I from the comparator 8 opens the 1st key 12, through which the pulses from the additional generator (DG) 16 arrive at the input of the counter 15. The frequency of the pulses corresponds to the capacitance i (L to oh oh oh 4ib

Description

the condenser formed by the cams of chamber 3 when it is not filled with the material under study. Upon expiration of this time interval, the 1st switch 12 is closed, while the counter 15 stores information corresponding to the frequency of DG 16, at which chamber 3 is not filled with the test material. After filling the test material with DG 16 through the 2nd key 13 at the input counter 15 (inlet.) pulses are received with a frequency corresponding to the case of the fallen chamber. KogL

The invention relates to a technique for measuring moisture by the method of absorbing microwave energy in a wet material and can be used to determine the moisture content of bulk materials.

The purpose of the invention is to increase the accuracy of moisture measurement by reducing the influence of the density of the material under study.

Fig. 1 shows the structural electrical circuit of the proposed device for measuring humidity; Fig. 2 is a structural electrical circuit of the control unit.

The device for measuring humidity contains a microwave generator 1 to which radiating antenna 2, camera 3, receiving antenna A, detector 5 and log amplifier 6, the output of which is connected to the first input of the analog multiplier 7, comparator 8, indicator 9, delay element 10, are connected in series. , the control unit P, the first key 12, the second key 13, the decimal and reversible counters 14 and 15, the additional generator 16, the oscillating circuit of which includes a capacitor, the plates 17 and 18 of which are two opposite walls chamber 3, the first and second digital to analog converters (DACs) 19 and 20, analogous govsh divider 21, a source 22 of support GO The voltages.

The moisture measuring device works nq to the next algorithm.

05004

Yes, the key 13 is closed, the information in the counter 15 is equal to the frequency difference of DG 16. At the same time, the output of the DAC 20 turned on at the output of the counter 15 is a voltage signal proportional to the frequency difference fo f |. The frequency f is converted to analog, the signal of the 1st DAC 19, and fed to the analog multiplier 7, where it is interchanged with a signal proportional to the attenuation in the wet test material, and hence humidity. 2 Il.

2

The attenuation measurements in the test material depend on the weight humidity W and on the bulk density P of the test material so that the ratio

N K p-W-d,

(one)

where K is the proportionality ratio, characteristic

for each specific material;

d is the thickness of the layer of material. The proposed device is free t ;; from this drawback due to the fact that the two opposite side walls of the chamber are plates 17 and 18 of a capacitor included in the oscillating circuit of an additional 20 generator 16, whose frequency depends on the capacitance of the capacitor formed by these plates 17 and 18 and filled with the test material.

25 If the frequency f of the operation of a capacitive sensor included in the circuit of the oscillatory circuit of the additional generator 16 is chosen so that the losses associated with the conduction and relaxation of the water dipoles are negligible, that the waves are. at a frequency of the order of 10 MHz, then the ratio is fulfilled with a high degree of accuracy

 35 YE-v / b5 -w- - c,), (2)

where is the dielectric constant of the wet material; L is the dielectric constant of the dry material; q - volume concentration of dry material}

g is the dielectric constant WATER1,

Let P, be the density of the dry material, which is a constant for each particular material. Then it is obvious that

H

Pd-w)

about

(3)

Substituting (3) in (2) and transforming

have

VF -i pw (i-i) (Vf; -iJ (m

Dividing equation (l) by (4) and entering the A-parameter, get

S

(Cb-1) P. (/ bo-1) (j (B

Thus, the A parameter is a monotonously increasing function of moisture content and does not depend on bulk density. Then the resonant frequency of the oscillating circuit, in which this capacitor is included, is determined by the ratio

-k

When the material under study is placed in the chamber, the frequency of the measuring contour changes by a factor of v and becomes equal to f, and

(7)

From comparison (6) and (7) it is found that

(eight)

° - 1. s. - one

From (8) and (5) finally found

BUT

,,

DG

(9) 1

Where

lg f - f.

The oscillations from the microwave generator 1 are supplied to the radiating antenna 2 mounted on the wall of the chamber 3 s.

,

m

AT)

-

20500/44

the test material. Pass through the research material, an electromagnetic wave, weakened in power, enters the receiving antenna5, 4, and then into the detector 5, the output of which is connected to the input of the logarithmic service1liter 6. The output signal of the logarithmic amplifier 6 is proportional to the humidity of the material to be followed. Prologue signal is fed to the first input of the analog multiplier 7. The output of the detector 5 is also connected to the first input of the comparator 8,

15, the second input of which is connected to the source 22 of the reference voltage, which has a value. The voltage ensuring the switching of the comparator 8 to one state at

20 filling chamber 3 with material. The output of the comparator 8 is connected via a delay element 10 to an input of the control unit 11, the delay Element 10 provides a time delay

25 necessary to completely fill the chamber with the test material. The control unit 11 performs the following functions: it makes the initial setting of the decimal and reversible

 counters 14 and 15, forms a time interval during which the first key 12 is opened, forms a time interval during which the second key 13 is opened. When the device for measuring

 moisture control unit I1 generates and shulk, nulling the decimal and reversible counters 14 and 15, and on signal 1 from the comparator 8 opens the first

 key 12, through which the input of the reversible counter 15 receives pulses from an additional generator 16, and their frequency corresponds to the capacitance of the capacitor,

 formed by the walls of chamber 3 when it is not filled with the material under study. The first key 12 is in the open state during the interval specified by the control unit 50, and the pulses through the second key 12 are sent to the summing input of the reversible counter 14. After this time interval has expired, the first key 12 closes - 55 s, while reversing the counter 15 stores information corresponding to the frequency of the additional generator 16, at which chamber 3

not filled with the test material. After filling the test material into the chamber 3, the comparator 8 switches to state 1 and the time key determined by the delay element Yu switches the second key 13 into the open state. At the same time, from the additional generator 16 and the second key 13 to the input of the reversible counter 15 (subtracting input) pulses are received at a frequency corresponding to the case when chamber 3 is filled with the material under study. After the time interval formed by the control unit P has expired, the second key 13 is closed and in the reversible counter 15 is recorded information equal to the frequency difference of the additional generator 16, which generated a frequency corresponding to the capacitor capacity filled with the material under study when there was no test material in chamber 3. In this case, an analog signal in the form of a voltage proportional to the frequency difference ff, appears in the code of the second ACA 20 switched on at the output of the reversible counter 15 - f At the input of the decimal counter 24 with the second key 13 open, the frequency arrives. f- /, which is converted into an analog signal by the first ACD 19 and supplied in the form of voltage to the second input of the analog multiplier 7, where it multiplies with a signal proportional to the attenuation in the wet material under study, and consequently, humidity.

The control unit 1 consists of a pulse shaping unit in a decimal counter 14 and a reversible counter 15, which contains an inverter 23, shapers of measurement intervals during which the first and second orders 12 and 13 are open, made from D-flip-flops 24-27; generator 28 of these pulses and standby multivibrator 29 (Fig2),

The control unit 1i operates as follows.

When the power is turned on (when the measuring device switches on, the nozzles are connected) the output of the inverter 23 produces a positive reset pulse of the decimal and reversible counters 14 and 15, which simultaneously starts the waiting multivibrator 29 "The duration of the pulse is determined by the time constant of the circuit consisting of the resistor 30 and the capacitor 31, When the capacitor 31 is charged, the output potential of the inverter 23 is set to the potential of a logical zero, at which the decimal and reversible counters G4 and 15 are ready for counting pulses LS starts the waiting multivibrator 29, from the inverse output of which the C-input of the D-flip-flop 26 receives a pulse delayed in relation to the reset pulse. The time delay is determined by the time constant of the circuit consisting of the resistor 32 and the capacitor 33. A logic level G is applied to the input of the trigger 26. Therefore, when a pulse appears at the C input, the D flip-flop 26 changes from O to state 1,

Since the direct output of the D-flip Thera 26 is connected to the input of the D-flip-flop 27, the closest pulse from the tat generator 28 translates the D-flip-flop 27 to the state 1, At the same time the inverse output of the D-flip-flop 27 has the potential O is applied to the R input of the installation at the O of the D flip-flop 26. As a result, the 0-flip-flop 26 is set to the state O. and there it is held all the time while the D-flip-flop 24 is at one. Due to the fact that switching to zero O-flip-flop 26 leads to the appearance of the signal O at the D-input O-Flip-flop 27 5, the latter is set to O by the next pulse from the generator 28. 27 returns to its original state. As follows from the above, the duration of the positive impulse at the output of the D-flip-flop is equal to one period of clock pulses generated by the generator 27. -This period forms the measurement interval during which the first 1 switch 12 is opened, which passes the frequency ff to the summing reversing input counter-15. At the end of the measurement interval, the first key 12 is closed.

opposite side chamber walls comparator, delay element, first and second keys, control unit, reversible counter, decimal counter Jch, reference voltage source, n & pBbui and second digital-to-analog converters, logarithmic amplifier, analog multiplier and analog divider , and after the filling of the material under investigation into the chamber 3, the comparator 8, through the delay element 10, triggers the shaper of the measuring terminal on the D-flip-flops 2.4 and 25, which works exactly as the first one, a result generator generates a measuring interval during which the second switch 13 open, turn 0 che auxiliary oscillator frequency transmissive to the subtracting input of down counter 15.

To measure the humidity of the next sample, the device must be turned off, and when it is switched on again, the measurement is performed in the same order. The reset and start pulse of the first measuring interval can be produced by button 34. Manual start can also be entered into the trigger circuit 20 of the second measuring interval.

Claims (1)

Invention Formula the first key is connected to the summation of the reversible counter input, and through the second key to the input of the decimal counter and to the subtracting input of the reversible counter, the control inputs of the first and second keys are connected respectively to the first and second outputs of the control unit, the third output of which is connected with installed inputs of the reversing and decimeter counters, the input of the control unit is connected to the output of the comparator through an element of the delay, the output of the detector is connected to the input of the logarithmic amplifier and to the first input of the comparator - rator, and the second input of the comparator is connected to the source of the reference voltage, the output of the logarithmic force of the bodies is connected to the first input of the analog multiplier, the second input of which is connected to the outputs of the decimal counter via the first digital-to-analog converter the divider, to the second input of which is connected the second code of the second digital-analog reversible counter, and the output of the analog divider is connected to the indicator stroke. A device for measuring humidity, containing a radiation power: a receiving antenna and mounted on opposite walls of the chamber to accommodate the sample under study., A microwave generator connected to the input of a radiation, a antenna, a detector whose input is connected to the output of the receiving antenna, and an indicator This is due to the fact that, in order to increase the NIN accuracy of humidity measurement due to a decrease in the influence of the density of the material under study, an additional generator was introduced, the oscillator circuit of which included a capacitor Secondly, they are 1205004g opposite side camera walls, comparator, delay element, first and second keys, control unit, reversible counter, decimal counter J j, reference voltage source,, n & pBbui and second digital-to-analog converters, logarithmic amplifier, analog multiplier and analog divider , and you, 0, move the additional generator 0 stroke of additional generator tS 20 five about five the first key is connected to the summation of the reversible counter input, and through the second key to the input of the decimal counter and to the subtracting input of the reversible counter, the control inputs of the first and second keys are connected respectively to the first and second outputs of the control unit, the third output of which is connected with the inputs of the reversible and decimeter meters installed, the input of the control unit is connected to the comparator output through a delay element, the detector output is connected to the input of the logarithmic signal. The second input of the comparator is connected to the source of the reference voltage, the output of the logarithmic amplifier is connected to the first input of the analog multiplier, the second input of which is connected to the outputs of the decimal counter, the output of the analog variable connected to the first input of an analog divider, to the second input of which is connected the code of the second digital-analog reversing counter, and the output of the analog divider is connected to the indicator stroke. FIG. inside Thioazh 896 Order 8520/44 Subscription Branch of ShP Patent, Uzhgorod, Proektna St., 4