JP2000329748A - Ultrasonic sensor control circuit and ultrasonic densitometer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic sensor control circuit and to detect the sludge of a liquid having a wide usable temperature range and low in concentration. SOLUTION: An ultrasonic sensor part wherein a transmitter 1 for transmitting ultrasonic waves and a receiver 2 receiving ultrasonic waves are arranged in opposed relationship, an oscillation part forming a high frequency signal to be applied to the transmitter 1, a feedback control part inputting the output signal outputted from the receiver 2 and feeding back an AC voltage signal for driving the oscillation part to form an AC voltage signal having constant amplitude and a rectifying part for rectifying the output signal from the receiver 2 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor control circuit, and more particularly to an ultrasonic interferometer used for measuring the concentration of liquid, treating and treating sludge in a sewage treatment plant, and the like. The present invention relates to an ultrasonic sensor control circuit for a densitometer.

[0002]

2. Description of the Related Art In recent years, environmental problems have been widely taken up, and there is a concern that the pollution of rivers and oceans as well as the effects of environmental ecosystems due to pollution of rivers and oceans will occur. In order to measure and grasp the degree of pollution of such waterworks and rivers, interface meters and densitometers that have applied various measurement principles have been manufactured, but optical and ultrasonic types are mainly used. , Depending on the application.

[0003] Among them, the optical type uses a light emitting diode (LED) and a phototransistor as a light emitter and a light receiver, respectively, and detects the degree of contamination by the attenuation rate of light passing between them. However, in this optical system, the light transmittance may not correspond to the actual degree of contamination of the liquid due to contamination of the light projecting and light receiving surfaces by the contaminated liquid.

As a countermeasure for this, a light transmitter
Periodic maintenance is required, such as cleaning by spraying a water stream on the surface of the light receiver. In addition, since the characteristics of the light emitting diode greatly change with a change in temperature, there is a problem in measurement accuracy. Basically, the degree of light transmission varies depending on the color of the contaminant, the liquid, and the like, so that there is a large error in the concentration.

On the other hand, the ultrasonic type differs from the optical type in that the attenuation rate of the ultrasonic wave in the liquid is measured.
It is not affected by the color of the liquid. Further, since the transmitting and receiving surfaces of the ultrasonic waves are constantly subjected to micro-vibration by the ultrasonic waves, dirt hardly adheres thereto, and maintenance for cleaning is unnecessary. However, when detecting low-concentration sludge, it is necessary to increase the frequency of the ultrasonic wave, increase the distance between the transmitting and receiving sensors compared to the optical type, and increase the output difference with respect to the concentration difference. , Cannot detect low concentration sludge.

FIG. 6 shows a schematic configuration diagram of an ultrasonic sensor control circuit used in a conventional ultrasonic interface meter. Sign 1
Is an ultrasonic transmitter, 2 is an ultrasonic receiver, 4 '
Is an AC amplifier using a transistor, 20 is an oscillation circuit, 13 'is a diode rectifier, and 15 is a comparator. The transmitter 1 and the receiver 2 are fixedly arranged at a fixed interval, and are put into sludge or the like to be measured.

[0007] The resonance frequency of the oscillation circuit 20 is made to match the resonance frequency of the transmitter 1 and the receiver 2, and an ultrasonic wave is transmitted from the transmitter 1 to the receiver 2. The ultrasonic wave travels through the sludge and is attenuated due to contaminants in the sludge.
Is received. Part of the AC signal output from the oscillation circuit 20 is output to the rectifier 13 'as a detection signal, and is rectified into a DC signal. The rectified DC signal is supplied to the comparator 15
And outputs a judgment result of the sludge level.

[0008]

However, the ultrasonic sensor control circuit as shown in FIG. 6 has the following problems. Due to the temperature drift of the AC amplifier of the high-frequency transistor, the detection signal output to the rectifier 13 'changes according to the temperature change, and stable detection cannot be performed. To determine a lower concentration, it is necessary to use higher frequency ultrasonic waves. In particular, when discriminating between water and low-concentration sludge of about 0.5% or less, it is necessary to set the frequency of the ultrasonic waves so as to satisfy high oscillation conditions.

In the measurement of sludge concentration, the ultrasonic sensor control circuit is generally installed outdoors. However, it is difficult to guarantee normal operation throughout the year because the oscillation output changes with temperature changes. . In order to accurately determine the concentration difference between water and sludge in the predetermined temperature range by the detection signal, the deviation of the measured value due to the temperature change of the control circuit in FIG. 6 corresponds to the difference in concentration between water and sludge. It is necessary to keep the difference between the detection signals as small as possible.

In the ultrasonic sensor control circuit, an AC amplifier 4 'using a transistor amplifier circuit, an oscillation circuit 20 combining an inductor and a capacitor, and a transmitter 1 and a receiver 2 each having a ceramic piezoelectric body bonded to a diaphragm. Can be made to be somewhat unaffected by temperature changes.However, when detecting an object having a low concentration of sludge water, the temperature change cannot be ignored and the desired measurement temperature It is difficult to guarantee sufficient measurement accuracy in the range. Conversely, the temperature range of the measured object, which can guarantee sufficient measurement accuracy, is very narrow, and cannot meet the specifications required for low-concentration sludge measurement.

When detecting the concentration of sludge by ultrasonic waves, the attenuation rate of ultrasonic waves corresponds to the concentration of sludge. However, the attenuation rate of ultrasonic waves sometimes depends on the degree to which solids in the sludge shield the ultrasonic waves. It changes every moment. Sludge is generally a mixture of liquid and solid matter, so it partially varies from place to place, and the mixing ratio of liquid and solid matter is rarely uniform everywhere, even in the same place. The concentration of sludge varies over time. That is, even if a temporary concentration is measured at a certain place, the measured value often cannot be said to reflect the concentration of the entire sludge. In addition, when the concentration of sludge varies around the set threshold value, a device that performs various controls based on the output of the densitometer repeats unstable operations and cannot perform stable operations.

Accordingly, the present invention has been made in view of such circumstances, and is hardly influenced by a temperature change, and is capable of detecting low-concentration sludge in a temperature range as wide as possible. The task is to provide Another object of the present invention is to provide an ultrasonic densitometer capable of performing stable detection of sludge concentration by subjecting a signal corresponding to the measured sludge concentration to digital processing.

[0013]

According to the present invention, there is provided an ultrasonic sensor unit in which a transmitter for transmitting an ultrasonic wave and a receiver for receiving the ultrasonic wave are arranged opposite to each other, and an oscillator for generating a high-frequency signal applied to the transmitter. And a feedback control unit that receives an output signal output from the receiver as input, generates an AC voltage signal having a constant amplitude by feeding back an AC voltage signal for driving the oscillation unit, and an output from the receiver. And a rectifying unit for rectifying the output signal. This makes it possible to transmit a more stable ultrasonic wave without depending on the temperature change, and further to widen the temperature range in which sludge can be detected, and to detect low-concentration sludge. Also,
The present invention provides an ultrasonic densitometer including the ultrasonic sensor control circuit.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a transmitter and a receiver constituting an ultrasonic sensor section have at least a diaphragm and a piezoelectric element, and may have the same configuration. The transmitter and the receiver are opposed to each other with a certain distance therebetween, but the diaphragms are configured to face each other. As the piezoelectric element, a ceramic plate such as PZT is used. The diaphragm is a metal plate such as Cu, stainless steel, etc., and the piezoelectric element is adhered to the diaphragm in close contact with the diaphragm in order to transmit high-frequency vibration to the diaphragm. At the time of measurement, a space to be measured is filled in a space portion of the pair of diaphragms arranged opposite to each other. That is, the ultrasonic sensor unit is put into the liquid to be measured, and the ultrasonic wave output from the transmitter passes through the object to be measured and is input to the receiver.

As the oscillating section, for example, an LC oscillating circuit including an inductor and a capacitor can be used. In addition, a crystal oscillator or the like can be used. The feedback control unit may rectify the fed-back AC voltage signal to detect a DC voltage, and multiply the detected DC voltage by an output signal output from the receiving unit to provide a constant value. And a gain control unit that generates an AC voltage signal having an amplitude of

Here, the rectifying unit and the detecting unit may use rectifiers that are usually used. To reduce the influence of temperature change, two rectifying transistors are provided. Are preferably configured so that the bases thereof have the same potential. Further, in terms of simplification of the circuit configuration, it is preferable to use an AGC operation circuit for the gain control unit.

Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this. FIG. 1 shows a configuration diagram of one embodiment of a sludge interface meter including an ultrasonic sensor control circuit of the present invention.

Here, the AGC arithmetic circuit 3, the DC amplifier 11, and the AC amplifier 1 are different from the conventional configuration of FIG.
2. The difference is that a rectifier 10 for level detection is provided. The detection signal input to the rectifier 13 is a signal obtained by amplifying the output of the receiver 2 via the AC amplifier 12, and the signal input to the AC amplifier 4 is obtained by changing the output of the receiver 2 to AG.
The difference is that the signal is stabilized via the C operation circuit 3. Further, the present invention is characterized in that the amplitude of the signal output from the O port, which is the output terminal of the AGC operation circuit 3, is constant regardless of the temperature change. By providing such a configuration, it is possible to detect sludge in a wider temperature range using the signal output from the rectifier 13.

In FIG. 1, an ultrasonic transmitter 1, an ultrasonic receiver 2, and a comparator 15 may be the same as those in the conventional art. The resistor 5, the inductor 6, the capacitor 7 and the buffer 8 of FIG. The buffer 8 is provided for amplitude adjustment.

The inductor 6 and the capacitor 7 constitute a so-called resonance circuit. The resonance frequency of the resonance circuit is adjusted in advance so that the resonance frequencies of the transmitter 1 and the receiver 2, which are ultrasonic sensors, match. You. However, it is difficult to completely match them from the beginning of manufacture due to variations in circuit components and the like. Therefore, it is preferable that at least one of the inductor 6 and the capacitor 7 is configured to be finely adjusted. For example, the capacitor 7 may be configured by a combination of a rotary variable condenser or a rotary switch and some capacitor groups.

The changeover switch 9 is provided for adjusting the resonance frequency of the resonance circuit. When adjusting the resonance frequency, the changeover switch 9 is connected to the contact A and used. When operating as
Used to connect to.

Reference numeral 14 denotes a monitor terminal for the output signal of the rectifier 13, reference numeral 16 denotes a threshold setting resistor for setting the detection level of sludge, and reference numeral 17 denotes a relay. This is for notifying the result of the sludge determined by the vessel 15 to an external display device or the like.

In FIG. 1, the output signal 13 of the rectifier 13
b, that is, the signal output from the monitor terminal 14 is “P”, and the threshold signal set by the threshold setting resistor 16 is “P ₀ ”. At this time, P> P ₀
The relay 17 is turned on by the output signal of the comparator 15 at the time of
N, and the relay 17 operates so as to be turned off by the output signal of the comparator 15 when P ≦ P ₀ . That is, the output signal of the relay (ON / OFF) with P ₀ as the boundary
Thereby, the interface of the degree of the liquid sludge can be determined.

If the output signal of the relay 17 is given to the LED, it is possible to determine whether the sludge concentration of the liquid to be measured is lower or higher than the preset sludge concentration by turning on and off the LED. The same determination can be made even when the two LEDs of red and green are switched on and off according to the output signal of the relay 17. Furthermore, by connecting the output signal of the relay 17 to the drive circuit of the drainage pump, the drive / stop of the drainage pump can be controlled depending on the degree of sludge to be measured. Further, by giving a DC output voltage value output from the monitor terminal 14 to a digital display circuit or the like,
A numerical value of the sludge concentration proportional to the output voltage value can be displayed.

FIG. 2 is a sectional view of an ultrasonic transmitter 1 and a receiver 2 of the present invention. Here, reference numeral 21 denotes the ultrasonic wave 3
Reference numeral 22 denotes a piezoelectric element that transmits or receives 0, a piezoelectric element 22 converts an electric signal into vibration and transmits the vibration to the vibration plate 21, a reference numeral 24 denotes a ground lead, a reference 25 denotes a positive lead,
Reference numeral 23 denotes a case, and reference numeral 26 denotes a sound absorbing damper. The piezoelectric element 22 is formed by forming electrodes on both sides of a ceramic plate such as PZT, and is subjected to a polarization process so that vibration at a predetermined resonance frequency occurs.

The transmitter 1 and the receiver 2 having the above configuration
The diaphragms 21 are assembled such that the diaphragms 21 face each other at regular intervals so that the central axes of the diaphragms 21 coincide. The distance between the surfaces of the pair of diaphragms 21 is, for example, 2
At the time of measurement, the space between the transmitter 1 and the receiver 2 is filled with a liquid to be measured, such as sewage.

FIG. 3 is a block diagram showing a schematic configuration of the AGC operation circuit 3 used in the ultrasonic sensor control circuit according to the present invention. Here, the AGC operation circuit 3 is not a special one, but may be a high-frequency one generally used in the field of information equipment. The I port is a terminal for inputting a signal output from the receiver 2, the GAIN port is a terminal for inputting a DC voltage from the DC amplifier 11, and the FB port is a proportionally attenuated output signal output from the O port. Terminal for inputting signals.

In the AGC operation circuit 3, an output signal (AC) of the receiver 2 input to the I port is multiplied by a DC voltage signal which is a constant voltage input to the GAIN port. A proportional attenuation signal (alternating current) input to the FB port is added. Then, the result of the amplification is output from the O port. The output signal output from the O port is an AC voltage having a constant amplitude that is not affected by a temperature change.

The AC voltage signal having a constant amplitude is supplied to the AC amplifier 4 and amplified, and then drives the oscillation circuit 20. Therefore, the oscillation circuit 20 performs stable oscillation which is hardly affected by a temperature change. It can be carried out. As a result, stable ultrasonic waves 30 which are hardly affected by a temperature change are transmitted from the transmitter 1 by stable oscillation, so that the output signal 13b received by the receiver 2 and obtained through the rectifier 13 has a temperature characteristic. Can be improved. That is, the change in the measured value of the sludge is small in a wider temperature range, and low-concentration sludge can be detected.

FIG. 4 shows the rectifier 1 shown in FIG. 1 of the present invention.
3 shows a circuit diagram of one embodiment. Here, reference numeral 13a is
The signal 13b corresponds to the input signal of the rectifier 13 in FIG.
This corresponds to the output signal output from the rectifier 13 in FIG.
Further, R ₄ R ₁ to resistors, Tr _1, Tr ₂ are transistors, C1 is a smoothing capacitor. Here, it is assumed that two transistors Tr ₁ and Tr ₂ use NPN transistors having the same characteristics.

In FIG. 4, the bases of these two NPN transistors Tr ₁ and Tr ₂ are connected so as to have the same potential. By connecting in this way, the output signal 1
3b can be a signal with a small voltage fluctuation with respect to a temperature change. The specific circuit configuration of the rectifier is shown in FIG.
However, the present invention is not limited to this, and other rectifier circuits may be used in addition to simple diodes.

Also, the circuit of FIG. 4 can be used for the level detection rectifier 10 of FIG. The level detection rectifier 10 performs half-wave rectification on the AC voltage signal output from the AC amplifier 4 and detects the level thereof, and corresponds to the above-described detection unit.

Next, the operation of the ultrasonic sensor control circuit shown in FIG. 1 will be described. First, the changeover switch 9 is connected to the contact A side, and the resonance frequency of the inductor 6 and the capacitor 7 and the resonance frequency of the transmitter 1 and the receiver 2 (for example, 3.8
MHz) and adjust so as to set the resonance frequency of the maximum efficiency. Specifically, the capacity of the capacitor 7 is adjusted while observing the output waveform of the transmitter 1, and when the amplitude of the output waveform becomes maximum, the capacity of the capacitor 7 is fixed as the optimum capacity. Thereafter, the changeover switch 9 is connected to the contact B side.

When the oscillating circuit 20 is in an oscillating state, the piezoelectric element 22 of the oscillator 1 resonates, and the diaphragm 21 of the oscillator 1 disposed in close contact therewith also vibrates at the same time. An ultrasonic wave 30 is output. After the adjustment of the resonance frequency as described above, the ultrasonic sensor unit including the transmitter 1 and the receiver 2 is put into sludge or the like, which is an object to be measured.

When the oscillating circuit 20 is in an oscillating state, the ultrasonic waves 30 excited by the vibration of the diaphragm 21 reach the receiver 2 through the water. In the receiver 2, the vibration plate 21 is vibrated by the ultrasonic waves 30, and the vibration plate 21
The piezoelectric element 22 in close contact with vibrates at the same time to generate a transmission voltage. This transmitted voltage is an AC signal, and is input to the I port of the AGC operation circuit 3 and the AC amplifier 12.

Here, the signal input to the I port of the AGC operation circuit 3 is arithmetically processed with the feedback signal input to the FB port and the GAIN port as described above.
The signal is output from the O port of the AGC operation circuit 3 as an AC voltage signal having a constant amplitude.

The AC voltage signal output from the O port is input to the FB port as a signal attenuated at a constant attenuation ratio by the resistors 18 and 19, and at the same time, the AC amplifier 4
And is supplied to the oscillation circuit 20. The AC voltage signal amplified by the AC amplifier 4 is used as a drive signal of the transmitter 1 via the buffer 8, and is subjected to half-wave rectification by the rectifier 10 for level detection to detect the level. Then, when the level-detected DC signal is input to the DC amplifier 11, the difference from a predetermined voltage V ₀ is amplified and fed back to the GAIN port of the AGC operation circuit 3.

On the other hand, among the AC signals output from the receiver 2, those input to the AC amplifier 12 are amplified by the AC amplifier and then detected in level by the rectifier 13, ie, rectified. The rectified DC signal 13b, that is, the DC output voltage value P is a signal output from the monitor terminal 14. Thereafter, the output voltage value P is compared with the threshold voltage P ₀ set by the resistor 16 by the comparator 15, and the relay 17 is opened and closed by the comparison output. Further, since the DC signal 13b is proportional to the amount of attenuation of the ultrasonic wave attenuated by the sludge of the liquid between the transmitter 1 and the receiver 2, by measuring the signal output from the monitor terminal 14, the liquid signal of the liquid is measured. The concentration can be taken out and displayed.

FIG. 5 is a graph showing the relationship between the output voltage value P of the monitor terminal 14 and the temperature t. Generally, the output voltage value P
Has a temperature dependency, and shows a lower value as the temperature is lower, and a higher value as the temperature is higher. If the graph of water without sludge is G1 in the figure, the detection signal is attenuated if there is sludge, and the graph of water with sludge to be measured is G2 in the figure.
Is located below G1.

Assume that the threshold value of the output voltage value at which the sludge is detected is P ₀ . In this case, at a certain temperature t _0, the measured output voltage value P ₁ is assumed to be P ₁ <P _0, the measurement target can be determined to a large sludge concentration. If the measured output voltage value P ₂ is P ₂ > P ₀ at the same temperature t ₀ , it can be determined that the measurement target has a low sludge concentration.

[0041] Incidentally, in the graph G1 of no sludge water, the ultrasonic output voltage value temperature t ₁ comprised between P _0, the output voltage value in the graph of the measurement object G2 is the temperature t ₂ which is a P ₀ distinguishable temperature range of the sensor control circuit can be defined as a t ₂ from the temperature t _1. In this, if the actual temperature is lower than t ₁ will not be able to identify the density difference between the measured and no sludge water, because the temperature can not be identified similarly density difference be higher than t ₂ is there.

Ideally, the output voltage value of the monitor terminal 14 does not depend on the temperature, and it is desirable that the slope of the graph of FIG. 5 is a horizontal straight line with zero slope. However, the configuration of the ultrasonic sensor control circuit of FIG. Elements (rectifiers, amplifiers, transmitters, receivers, and the like) have a certain degree of temperature dependence, and therefore, in reality, a graph having a slope as shown in FIG. 5 is obtained. Here, considering the rate of change of the output voltage value P per 1 ° C., it can be said that the smaller this rate is, the smaller the slope of the graph is, and the more sludge can be detected in a wide temperature range.

Now, when the distance between the transmitter 1 and the receiver 2 is 250 mm, the resonance frequency of the transmitter 1 is 3.8 MHz, and the measuring object is water having a sludge concentration of 0%, the conventional circuit shown in FIG. Is used, the rate of change of the output voltage value P becomes
0.588 [% / ° C] in the range of 5 ° C to 60 ° C
On the other hand, when the circuit of FIG. 1 of the present invention is used, the rate of change of the output voltage value P is
It was 0.134 [% / ° C] in the range of ° C. From this result, in the ultrasonic sensor control circuit of the present invention, the rate of change of the output voltage value P with respect to the temperature change is small.
It can be seen that even a low concentration of sludge can be detected in a wider temperature range.

Further, when it is actually determined that water having a sludge concentration of 0% and water having a sludge concentration of 0.3% are used, the conventional circuit shown in FIG. However, in the case of using the ultrasonic sensor control circuit of FIG. 1 according to the present invention, the temperature was in the range of −15 ° C. to 60 ° C.
It was possible to discriminate both in the range of. That is, by using the ultrasonic sensor control circuit of the present invention, the measurable temperature range could be improved by 5 ° C. or more. Furthermore, when an experiment was conducted also on low-concentration sludge water, it was possible to discriminate between water having a sludge concentration of 0.2% and water having a sludge concentration of 0% in a temperature range of -15 ° C to 60 ° C.

Next, an embodiment in which the output signal 13b output from the rectifier 13 is digitally processed and the ultrasonic sensor control circuit of the present invention is used for sludge concentration management or control will be described. Here, instead of the comparator 15 having the configuration shown in FIG. 1, an arithmetic unit or the like for performing digital processing is provided.

That is, in the ultrasonic type densitometer of the present invention, a signal rectified by the rectifying unit of the ultrasonic sensor control circuit is taken in at predetermined time intervals, a calculating unit for performing a predetermined calculation, and a result of the calculation is output. And an output unit. Further, the arithmetic unit obtains an average value, a minimum value, a maximum value, and a median value of the captured signals, and obtains predetermined density information. Further, an input unit for inputting setting information including the predetermined time interval and a density determination reference value, the arithmetic unit includes:
The average value of the fetched signal is compared with the input density determination reference value, and density information corresponding to the comparison result is obtained and provided to an output unit. The output unit may include a display unit that displays the density information, a signal generation unit that generates a DC voltage or a DC current corresponding to the density information, or a switching unit that switches an operation of an external device.

FIG. 7 shows an embodiment of a configuration diagram in which a peripheral device such as an arithmetic unit is connected to the ultrasonic sensor control circuit of the present invention. The arithmetic unit 51 of FIG. 7 includes a CPU, a RAM, a ROM, an I / O interface, an A
A digital signal processing unit, which includes an analog signal output from the rectifier 13, digitally processes the output signal 13b, and calculates density information based on a control program stored in a ROM or the like in advance. is there. Memory 53
Is an R which stores the setting information, control program and the like input by the input device 52 as a result of the calculation by the calculation device 51.
It is composed of an AM, a hard disk, a ROM and the like.

The input device 52 includes a keyboard, a switch,
A time interval (sampling time) for capturing the output signal 13b from the rectifier 13 into the arithmetic unit 51, a density determination reference value, the highest density value and the lowest density value of the density to be measured, and other necessary operations or display. The user inputs various setting information. Here, the concentration determination reference value refers to a numerical value to be a reference for determining the presence or absence of sludge. For example, when a value of 0.3 (%) is set as the density determination reference value, the arithmetic unit determines that there is no sludge when the result of the predetermined calculation is a value of 0.2. If the value is 0.5, it is determined that sludge is present.

The display device 55, the relay 54, and the signal generating device 56 shown in FIG. 7 constitute an output section 59 for outputting the calculation result in various forms. The display device 55 includes an LED, a CRT,
This is for visually displaying necessary density information such as an LCD (liquid crystal display). For example, various setting information, a comparison result by the arithmetic unit 51, a minimum value, a maximum value, an average value, a median value, and the like of the taken-in signals are displayed. Relay 5
Reference numeral 4 denotes a so-called switching means for switching an external device connected thereto, for example, for driving / opening / closing an external device such as a water injection pump, a drainage pump, or a drainage electromagnetic valve.

The signal generating device 56 corresponds to the concentration information and the like calculated by the calculating device 51 to a remote control panel or various actuators of a monitoring center far from the place where the ultrasonic sensor control circuit of the present invention is installed. To generate a signal. The signals generated here include a DC voltage signal 57, a DC current signal 58, and other digital signals used for communication with the remote control panel.

For example, DC voltage signal 57 is output as a signal of 1 V to 5 V, and DC current signal 58 is 4 mA.
Is output as a signal of 20 mA and sent to a control device such as a programmable controller (sequencer). The programmable controller uses the DC voltage signal 57 or the DC current signal 58 to output a signal for controlling the inverter device or the servo driver from the analog output unit of the programmable controller, and operates the servo motor and the like. The output unit 59 is not limited to this, and may be provided with a printing device or a sound notification device.

The arithmetic unit 51 mainly performs the following processing. 1) The output signal 13b, which is analog information, is A / D converted at a predetermined sampling time interval, is captured, and is stored as digital information in the memory 53. 2) The setting information input from the input device 52 is stored in the memory 5
Store it in 3. 3) A minimum value, a maximum value, an average value, and a median value are obtained by using a plurality of pieces of digital information stored in the memory 53 for a predetermined set time. 4) The average value is converted into density information (measured density value), the density information is compared with a set density determination reference value, and the comparison result is stored in the memory 53. 5) The comparison result is displayed on the display device 55. 6) The density information corresponding to the comparison result is displayed on the display device 55, and a signal (voltage 57, current 5
An instruction is given to the signal generation unit 56 to generate 8). 7) A switching signal is given to the relay 54 based on the comparison result.

Further, when calculating the sludge concentration and controlling the external equipment, specifically, for example, the following processing is performed. However, it is not limited to this.
From the input device 52, the range of the concentration of the sludge to be measured is set to a maximum value of 0.5 (%), a minimum value of 0 (%), and a concentration judgment reference value of 0.
3 (%), the capture interval (sampling time) of the output signal 13b from the rectifier 13 is 1 second, and the measurement time is 10 seconds. The arithmetic unit 51 fetches ten output signals 13b at one-second intervals based on the setting information, and calculates an average value thereof. Further, a measured density value corresponding to the average value is obtained and compared with the set density determination reference value.

As a result of this comparison, when the measured density value is 0.2%, which is smaller than the density determination reference value of 0.3%, it can be determined that no sludge is generated. An indication that no occurrence has occurred or the current measured density value is displayed on the display device 55, and the signal generation device 56 is caused to generate a predetermined output voltage 57.

On the other hand, when the measured density value is 0.4% and is higher than the density determination reference value 0.3%, it is determined that sludge is generated. A predetermined output current 58 is generated, and an indication that sludge is generated or a current measured concentration value is displayed on the display device 55. Here, by switching the relay 54, one of the external devices connected to the relay 54 is switched.
One of the drain pumps is driven to perform a process for reducing sludge.

As described above, by taking the output signal 13b output from the rectifier 13 into the arithmetic unit and performing a series of processing such as calculation, display, signal generation, switching, etc., it is possible to improve the performance of density detection, the density determination, and the like. This makes it possible to automate and facilitate the control of external devices and improve the function of the ultrasonic densitometer.

[0057]

According to the present invention, since the output signal output from the receiver is input to the AGC operation circuit, a stable ultrasonic wave can be transmitted without being affected by a temperature change. Therefore, since a detection signal with a small temperature change can be output from the rectification unit that rectifies the output signal output from the receiver, the measurable temperature range can be expanded, and further, low-concentration sludge is detected. be able to.

Further, the ultrasonic densitometer of the present invention is provided with an arithmetic unit and an output unit for performing so-called digital processing, and takes in an output signal output from the rectifier at a predetermined time interval to obtain a predetermined value such as an average value. Since the result of the calculation is output, the inconvenience due to the dispersion of the measurement is suppressed.
Stable sludge detection is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of an ultrasonic sensor control circuit of the present invention.

FIG. 2 is a sectional view of an ultrasonic transmitter and a receiver according to the present invention.

FIG. 3 is an AG used in the ultrasonic sensor control circuit of the present invention.
It is a block diagram of a schematic structure of a C operation circuit.

FIG. 4 is a circuit diagram of one embodiment of the rectifier shown in FIG. 1 of the present invention.

FIG. 5 is a graph showing a relationship between an output voltage value of a monitor terminal and a temperature in the present invention.

FIG. 6 is a schematic configuration diagram of a conventional ultrasonic sensor control circuit.

FIG. 7 is an embodiment of a configuration diagram in which peripheral devices are connected to the ultrasonic sensor control circuit of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitter 2 receiver 3 AGC operation circuit 4 AC amplifier 5 resistor 6 inductor 7 capacitor 8 buffer 9 changeover switch 10 rectifier for level detection 11 DC amplifier 12 AC amplifier 13 rectifier 14 monitor terminal 15 comparator 16 threshold setting Resistor 17 Relay 18 Resistor 19 Resistor 20 Oscillation circuit 21 Vibration plate 22 Piezoelectric element 23 Case 24 Ground lead 25 Positive lead 26 Sound absorption damper 30 Ultrasonic wave

Claims (10)

[Claims] 1. An ultrasonic sensor unit in which a transmitter for transmitting an ultrasonic wave and a receiver for receiving an ultrasonic wave are arranged opposite to each other, an oscillating unit for generating a high-frequency signal to be applied to the transmitter, and an output signal from the receiver. A feedback control unit that receives the output signal as input, generates an AC voltage signal having a constant amplitude by feeding back an AC voltage signal for driving the oscillation unit, and a rectifier that rectifies the output signal output from the receiver. An ultrasonic sensor control circuit, comprising: 2. The method according to claim 1, wherein the feedback control unit rectifies a fed-back AC voltage signal to detect a DC voltage, and multiplies the detected DC voltage by an output signal output from the receiving unit. 2. The ultrasonic sensor control circuit according to claim 1, further comprising: a gain controller configured to generate an AC voltage signal having a constant amplitude. 3. The rectifier according to claim 1, wherein the rectifier includes two NPN transistors, and the bases of the NPN transistors have the same potential.
The described ultrasonic sensor control circuit. 4. The device according to claim 2, wherein the detection unit includes two NPN transistors, and the bases of the NPN transistors have the same potential.
The described ultrasonic sensor control circuit. 5. The ultrasonic sensor control circuit according to claim 1, wherein said gain control section is an AGC operation circuit. 6. An ultrasonic densitometer comprising the ultrasonic sensor control circuit according to any one of claims 1 to 5. 7. The ultrasonic sensor control circuit according to claim 1, further comprising: a calculation unit that takes in the signal rectified by the rectification unit at a predetermined time interval and performs a predetermined calculation; and an output unit that outputs the calculation result. 7. The ultrasonic densitometer according to claim 6, wherein: 8. The ultrasonic densitometer according to claim 7, wherein said arithmetic unit obtains an average value, a minimum value, a maximum value, and a median value of the fetched signal to obtain predetermined density information. 9. An input unit for inputting setting information including the predetermined time interval and a density determination reference value, wherein the arithmetic unit calculates an average value of the captured signal and the input density determination reference value. 9. The ultrasonic densitometer according to claim 8, wherein the comparison is performed, and density information corresponding to the comparison result is obtained and provided to an output unit. 10. The output unit includes a display unit that displays the density information, a signal generation unit that generates a DC voltage or a DC current corresponding to the density information, or a switching unit that switches an operation of an external device. The ultrasonic densitometer according to claim 9, wherein: