JPH07501138A - Time-gated ultrasonic sensor and measurement method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] name of invention Technical background of the time-gated ultrasonic sensor and measurement method invention This invention describes an ultrasonic sensor for measuring physical properties of materials within a defined space. The present invention relates to time-gated ultrasonic sensors, and in particular to time-gated ultrasonic sensors.

Many ultrasonic distance and level measurement systems are known. ing. For example, U.S. Patent No. 4 by Ellinger et al. , 815.323 discloses an “echo range (r anging)” ultrasonic transducer is taught, and this ultrasonic signal is It is reflected by the liquid surface of the fuel tank and detected.

Then, the round trip time from transmission to reception is measured, and the round trip time and stored data are The amount and density of fuel are calculated by the CPU from the data.

U.S. Patent No. 4.299 to Sllvermetz et al. In another type of ultrasonic sensor taught in the '114 specification, Ultrasonic transmission between the receiving transducers oscillates when the amount of feedback exceeds a predetermined value. form a feedback loop for the circuit. The level of liquid in the container is When raised to the position where the receiver transducer is installed, a large volume of fluid is passed through the fluid. Feedback is applied and the circuit oscillates. This type provides stable operation In order to There must be a significant difference. Moreover, undesirable fibrils passing through the sensor body back-up may impair stability. If air gets mixed into the liquid, the fi The feedback signal is attenuated, resulting in false detection. This type of sensor is usually very large. For example, 3/4 inch NPT (American National 5 standard tapered pipe thread) like a screw hole It is unsuitable for insertion into containers through small holes. With this type of sensor, Misalignment of the transducer reduces the amount of feedback passing through the liquid, leading to false positives and Become.

Ultrasonic sensors use a sensing (receiving) piezoelectric element (crystal) for self-test functionality. ) or “piggybacked” Additional piezoelectric elements can be provided. The additional piezoelectric element excites the receiving piezoelectric element. Functional testing of the receiving piezoelectric element without any material in the gap To complete the feedback loop. However, this method does not allow pressure from the sensor body. Since it does not detect that the electronic element has peeled off, it detects the substance in the gap. We have not fully tested the capabilities of the sensor. This method increases the overall size. It also adds complexity to the sensor and wiring.

U.S. Patent No. 4.299 to Silvermetz et al. No. 114 discloses another self-test structure in which an ultrasound system While the system is in test mode, the The ultrasonic waves transmitted by the device are monitored. The piezoelectric element, if the system operates Connected in the feedback loop of the oscillating oscillator. If the system The strength of the ultrasonic signal transmitted through the support member is sufficient to continue the oscillation. If it is, it is considered to be in working condition. However, in this structure, the sensor is made of plastic. support members, the plastic damping will reduce the feedback signal. It is not easy to operate properly because it is weak and difficult to maintain oscillation. do not have.

Summary of the invention This invention is a function of the velocity of an ultrasound signal traveling through a defined space (gap). A time-gated ultrasonic sensor that measures the physical properties of matter within a defined space. It is related to. For example, a sensor detects the presence of liquid within a defined space. By this, the position of the liquid level in the container can be measured.

The ultrasonic sensor is fixed to the support member and for transmitting and receiving ultrasonic signals. and at least one transducer positioned generally adjacent the defined space. ultrasonic The wave signal consists of a main waveform that propagates across a defined space and a main waveform that propagates along the supporting member. self-test waveforms. The sensor monitors the received ultrasonic signal and determines the main time Whether the main waveform appears in the received signal within the window and within the self-test time window. Detect whether a self-test waveform appears. The sensor has a main waveform within the main time window. matter in a defined space as a function of whether it appears or not (this includes various solids, suspended Detect physical properties of liquids, foam, or other process materials. The sensor detects the sensor as a function of whether the self-test waveform appears within the self-test time window. Detect the integrity of the server.

Ultrasonic signals are typically generated in a gas (which may be air or a process gas). It propagates faster in liquids, and it propagates faster in solids than in liquids. One example , the sensor detects the presence or absence of liquid within a defined space. Measure the position of the liquid level. The existence of the main waveform within the main time window is , since the transmission speed in each is different, it is difficult to determine whether ultrasonic waves are transmitted through liquid or gas. It really depends. If the main waveform appears within the main time window, the ultrasound signal It is transmitted throughout the body. If the main waveform does not appear within the main time window, the ultrasound signal , the main waveform signal is transmitted through the gas, which takes a long time to receive.

Since the propagation time of a signal through a material is related to the density of the material, the sensor is It is possible to measure the density of a substance and the density of a substance at the same time. In this example, the gap time to detect the density of the material as well as the presence or absence of the material within the sample. Windows are adjustable. If the densities of the two substances are known, the ultrasonic sensor The boundary between two materials within the cap can be measured.

In one embodiment, the ultrasonic sensor transmits a transducer separated by a gap. the support member includes one or more support members between the transmitting transducer and the receiving transducer. It has a stem (handle or shaft member). In other embodiments, the support member includes a gap. includes a container or tube having an inner diameter and a circumferential wall defining a pipe. Transmit converter and receive The transducer allows the ultrasound signal to pass across the gap from the transmitting transducer to the receiving transducer. It is attached to the wall of the container so that the

In yet other embodiments, the ultrasonic sensor both transmits and receives ultrasonic signals. one transducer that performs. In this example, the ultrasound signal is sent from the transducer. signal, travels across the gap to the reflective surface, and then returns to the transducer. , the support member is positioned across the gap to face the transducer. Including reflective surfaces. The reflective surface focuses the reflected signal across the gap toward the transducer. It may also be a concave surface with a curvature selected so as to The support member is a container or tube. In some embodiments, one transducer is attached to the wall of the container and transmits ultrasound waves. The signal is transmitted from the transducer in the inner diameter direction toward the wall facing the transducer, and is reflected. Return to the converter.

The time gated configuration of the present invention utilizes a self-test waveform to transmit through the support member. Also provides an accurate and reliable method to test the integrity of ultrasonic sensors do. Ultrasonic signals generally propagate faster in solids than in gases or liquids. , the first waveform received is the self-waveform transmitted along the solid support member. This is a test waveform. The second waveform received is the main waveform that propagates across the gap. It is a waveform. A self-test waveform should always be present with each transmitted signal.

The sensor is configured to detect the presence of the self-test waveform within the self-test time window. , monitor the received ultrasound signals within a predetermined self-test time window. . The presence or absence of the self-test waveform is indicative of sensor integrity. This te The detection method is based on the functionality of the individual transducers and the Test the capabilities of multiple transducers. If the receiving transducer separates from the supporting member This fault is detected because the self-test waveform no longer passes through the support member. Will. Additional piggyback transducer even with process material in the gap Continuous self-test to test transmit and receive transducers respectively without is feasible.

This reduces the overall size and complexity of the sensor.

Brief description of the drawing FIG. 1 is a cross-sectional view of a time-gated ultrasonic sensor according to the invention.

FIG. 2 shows a cross-section of a time-gated ultrasonic sensor attached to a tube in accordance with the present invention. It is a front view.

FIG. 3 shows the main waveforms and waveforms received by the ultrasonic sensors shown in FIGS. 1 and 2. FIG. 3 is a diagram showing a self-test waveform.

FIG. 4 is a circuit diagram of an ultrasonic sensor circuit according to the present invention.

FIG. 5 is a diagram showing various signals appearing in the ultrasonic sensor circuit shown in FIG. 4.

Figure 6 shows the main waveform detection pulse and self-test that appear in the ultrasonic sensor circuit shown in Figure 4. FIG. 3 is a waveform diagram showing a waveform detection pulse.

FIG. 7 is a cross-sectional view of a single piezoelectric element ultrasonic sensor according to the present invention.

Detailed description of the preferred embodiment The present invention consists of a main waveform passing through the sensor gap and a self-testing waveform passing through the sensor body. the receiving piezoelectric element within a specific time period or “window” for detecting the waveform. Detect physical properties of matter within a defined space to gate the received ultrasound signal. It is a time-gated ultrasonic sensor. The presence or absence of the main waveform within the main window is , indicates the presence or absence of material in the gap, and also provides a self-test time window. The presence of a self-test waveform within indicates that the sensor is functioning.

FIG. 1 is a cross-sectional view of a time-gated ultrasonic sensor according to the invention. The sensor 10 is Holding member 12, ultrasonic transmitting transducer (piezoelectric element) 14, ultrasonic receiving transducer (piezoelectric element) ) contains 16. Support member 12 includes a stem 18 and a gap 20.

Stem 18 is also known as a bridge member. Transducers 14 and 16 are They cross the gap 20 and transmit and receive ultrasound signals along the stem 18. It is mounted on the support member 12 so as to. The support member 12 is made of metal or plastic. It can be made from various materials such as sticks. A typical production example is Transducers 14 and 16 are a pair of halves of member 12 that are secured to stem 18. Mounted in a resonant box.

Stem 18 is made of solid metal or plastic with a groove for passing lead wire 36. formed by The entire sensor 10 is then sealed.

Transmitting transducer 14 is connected to transmitter 30 by lead 32. transmitter 30 periodically provides electrical transmission pulses to lead 32 of transducer 14. Sending When the transmitter 30 provides a transmit pulse to the transmit transducer 14, the pulse energizes the transducer ( or excitation) to cause the transducer to resonate at its natural frequency.

Transducer 14 emits an ultrasonic signal 22 that transmits through gap 20 and stem 18. Ru. The ultrasonic signal passing through the gap 20 becomes the main waveform, while the ultrasonic signal passing through the stem 18 The signal that passes through is the self-test waveform.

Receive transducer 16 is connected to receiver 34 by lead 36. receiving converter 16 converts the ultrasonic signal 22 into an electrical signal and outputs it to the lead wire 36.

The attenuation (absorption) of an ultrasound signal across the gap 20 depends on the density of the material in the gap. be inversely proportional. Therefore, if the gap 20 is not filled with liquid, the gap 20 The attenuation of the main waveform is much greater than if liquid were present in the waveform. Attenuation (absorption) ) is especially large at high frequencies above a few kilohertz.

When gap 20 is empty, there is virtually no signal passing through the gap. gap When 20 is filled with liquid, the main waveform is received by transducer 16. . The main waveform causes transducer 16 to resonate and generate an electrical signal on lead 36. result As such, the presence or absence of the main waveform at the receive transducer 16 is determined by the gap 20 This will indicate the presence or absence of liquid within the liquid.

The ultrasonic signal 22 (self-test waveform) passing through the stem 18 is constantly It should exist in . This signal can be used for self-test functions. Gya Continuous self-testing can be performed regardless of whether substances are present in the step 20. It is. Details of the self-test function will be described later.

Sensor 10 can be used to measure physical properties of materials in the gap. example For example, by detecting the presence or absence of liquid in the gap 20, It is possible to measure the height of the liquid level. Sensor 10 is a standard NPT 3/4 inch Flange fittings such as inch fittings can be fixed to the fitting. can. The fitting is further fixed to the wall of the container containing the substance to be measured. Ru. As discussed in more detail below, the sensor of the present invention is well suited for a variety of applications. They can be made to fit into very small fittings for use. Wear.

The time gating technique of the present invention can be applied to transmit and receive converters as shown in FIG. need not be coupled by a conventional sensor "stem". The two converters are , each separately if joined by some member that conducts the self-test waveform. It can be configured as follows. This means that the transmit and receive converters are shown in FIG. Made of any material, with any wall thickness, as long as they are mounted opposite each other so that It can be installed in any constructed tube or container.

FIG. 2 is a cross-sectional view of an ultrasonic sensor attached to a tube according to the invention . The transmit transducer 40 and the receive transducer 42 are connected to the tube 4 such that they face each other. 4 wall 43. The tube 44 has an inner diameter 46 defining a gap 1. I have it. The main waveform 48 has an inner diameter from the transmitting transducer 40 to the receiving transducer 42. 46. Self-test waveform 50 is transmitted along circular wall 43. from the converter 40 to the receiving converter 42. The wall 43 is connected to the stem 18 shown in FIG. It acts as a similar pointing member. Wall 43 is therefore a substitute for stem 18.

FIG. 3 is received by receiving transducers 16 and 42 shown in FIGS. 1 and 2. FIG. 7 is a diagram showing the main waveform and self-test waveform, respectively, as a function of time; The amplitude of the ultrasonic signal is shown. Ultrasonic signals are stronger in liquids than in gases. It also propagates faster in solids than in liquids. Therefore, passing through gap 20 The velocity of the ultrasonic signal 22 depends on the presence or absence of liquid in the gap (i.e., the height of the liquid level). ) is a function of Ultrasonic signals travel faster in solids than in liquids, so they are difficult to receive. The first signal transmitted is a self-test signal 60 that transmits the stem (or support wall). It is. The second signal received is the main waveform 62 that conveys the liquid in the gap. be. The amplitude of the self-test signal 60 is the peak amplitude D0 when the signal first arrives. After , it approaches zero. The main waveform 62 is generated after multiple reflections across the gap. with subsequent waveforms 64a-64f.

The waveform 66 indicated by the dotted line is transmitted through air (when there is no liquid in the gap). Shows the received signal. Waveform 66 is the waveform 62 and 64 transmitted through the liquid. It arrives significantly slower and with a significantly weaker amplitude than a-64f.

In the oscillator type ultrasonic sensor used in the conventional example, the transmission and and the receiving transducer are connected in a feedback loop, which It will not oscillate if there is no process material in the pump. This is “dry” called a state. When material enters the gap, the circuit goes into oscillation. child This state is called the "wet" state. Oscillator tie not included in this invention There are many problems inherent in the design of First, the wet/dry signal ratio is low. not large enough for regular operation. This is because an excessive signal is passing through the system, or the attenuation due to the air is greater than the attenuation due to the process material. Being only slightly larger can be the cause. Second, the concentration of process materials temperature can affect sensor performance. If the material contains a high concentration of bubbles, The circuit will not oscillate.

In the present invention, when the liquid level is measured, the amplitude of the main signal is within the main time window. The signals from the stem are separated in time (delay time passing through the stem) before or after the main time window) so it does not give any disturbance. self test to provide a long ultrasound path to delay the start signal until after the main waveform. The stem should be shaped like a “U”, coiled or other longer shape than straight. It can be made into a state. On the other hand, when measuring density, the parameter being measured is not amplitude but time. The amplitude is not used to maintain oscillation as in the conventional example. Not used. “The values corresponding to the wet/dry ratio are consistently significantly higher. stomach. This greatly improves quality and reliability. equivalent ratio ratio) W 1/Di is the “wet” ratio that has passed through the process material in the gap. The amplitude W1 of the "start" signal 62 and the sensor's step at the time when the "start" signal 62 is received. is the ratio of the amplitude D1 of the "dry" signal 60 passed through the system. This time is much later than the first arrival of the signal passing through the stem of the sensor, its amplitude D1 is It is considerably smaller than the peak amplitude DO. If the maximum value received through the gap is If the initial signal is too close to the peak amplitude DO, a larger equivalent “wet/do” A slower reflected signal can be used to obtain the lie ratio.Oscillator type ultrasound The wet/dry ratio of the sensor is Wl/Do, which is less than Wl/D1 .

FIG. 4 is a circuit diagram of a time-gated ultrasonic sensor circuit according to the present invention. The circuit is sensor 10, transmitter 30, receiver 34, time gate section 70, main waveform detection/comparison section 7 2. Self-test waveform detection/comparison section 74, main waveform integration section 76, and self-test wave It consists of a shaped integral part 78. The time gate section 70 has integration sections 76 and 78 connected to the receiver 3. 4 to open a window to detect the main and self-test waveforms received by the predetermined an enable signal that “gates” detection/comparison sections 72 and 74 at a time of generate a number. Integrating sections 76 and 78 are integrated with the main components within their corresponding time windows. and output signals 80 and 82 indicating the presence or absence of the self-test waveform. do. The presence or absence of the main waveform indicates the fluid in the gap 20 of the sensor 10. Indicates the presence or absence of a body. The presence or absence of a self-test waveform The integrity of sensor 10 is shown. The amplitude of the self-test waveform is a measure of sensor degradation. It can be used for

Sensor 10 includes a transmit transducer 14 and a receive transducer 16. The transmitter 30 is It is connected between the transmit converter 14 and the time gate section 70. Transmitter 30 is typically includes an oscillation circuit that operates at a repetition frequency of 10Hz to 5kHz, and the oscillator According to each cycle of the transmitter 30, the transmitter 30 is Excite transmit transducer 14 with a 25 volt transmit pulse lasting 1/2 time. send The pulse resonates transmit transducer 14 and passes through gap 20 and stem 18 An ultrasound signal 22 (also shown in FIG. 1) is generated. The ultrasonic signal 22 is transmitted to the receiving transducer 1 received by 6. The receiving transducer 16 transmits an electrical signal representing the ultrasound signal 22 at a high frequency. It is supplied to a filter 84. A high-pass filter 84 increases the filtered signal. It is supplied to the width gauge 86. The filtered signal is amplified and output to amplifier output 88. .

The time gate window is defined by the rising edge 9 of the transmit pulse generated by the transmitter 30. 8 (FIG. 4), generated by time gate section 70. Time gate section 7 0 is capacitor C1, C2 and C3, resistor R1, R2 and R3, inverter 11, including Work 2, Work 3, and Work 4. Capacitor C1 is connected to transmitter 30. It is connected between the vertices 1 and 1.

Resistor R1 is connected between ground 90 and the connection point of capacitor C1 and inverter 11. It is. Resistor R1 is connected to the connection point between capacitor C1 and inverter E1. This is a variable resistor with a center tap 92. Inverter 11 outputs Generates the main waveform enable signal.

Capacitor C2 is connected between transmitter 30 and inverter I2. Resistance R2 is connected between ground 90 and the connection point of capacitor C2 and inverter I2 . Resistor R2 is a sensor connected to the connection point of capacitor C2 and inverter I2. This is a variable resistor with a power tap 94. Inverter 12 has a transmit pulse at its output. Generates a disable signal.

Capacitor C3 is connected between transmitter 30 and inverter I3. Resistor R3 is connected between ground 90 and the connection point of capacitor C3 and inverter I3 . Resistor R3 is a sensor connected to the connection point between capacitor C3 and inverter 13. This is a variable resistor with a power tap 96. Inverter I4 is the output of inverter I3. connected to power. Inverter I4 has a self-test waveform enable signal at its output. Occur.

The rising edge 98 of each transmitted pulse is divided into three points within the time gate generator 70. Differentiated by RC time constant. Capacitor C1 and resistor R1 are the main waveform enable signal forms a first time constant that controls the length of time that is active (logic high). . Capacitor C2 and resistor R2 are connected to the time when the transmit pulse disable signal becomes active. Form a second time constant that controls the length of time that controls the length of time that the signal is active. form a third time constant. These enable/disable signals are illustrated in Figure 5. Ru.

Figure 5 shows the transmission in the time-gated ultrasonic sensor shown in Figure 1 with a short stem. 3 is a timing diagram illustrating various signals during one period of the signal device 30. FIG. The figure is time represents the signal amplitude as a function of the Amplifier output 88 is shown at the top of the diagram. There is. The first waveform to arrive is the transmit pulse waveform 100.

This waveform is generated by transmit transducer 14 when it begins to oscillate.

Because ultrasound signals travel faster through solids than through gases or liquids, we arrive at the second The arriving waveform is the self-test waveform 102 that has passed through the stem of the sensor. thirdly The waveform that arrives is the main waveform 104 that passes through the liquid in the gap 20 of the sensor.

The fourth waveform to arrive is an echo of the main waveform 104 due to reflection within the gap 20. - It is a signal.

Waveform 108 shows the self-test waveform enable signal. Startup at time gate generation section 70 When edge 98 (Figure 4) is reached, the self-test waveform enable signal goes high first. Become a state. After a third time constant determined by capacitor C3 and resistor R3, the automatic The self-test waveform enable signal goes low.

Waveform 110 shows the transmit pulse override signal. The transmit pulse invalidation signal is the transmit pulse goes low at the rising edge of 98 and is connected by capacitor C2 and resistor R2. The frontage state is maintained for a second time constant determined by the second time constant. After the second time constant, the transmit pulse The invalidation signal goes high. The second time constant detects the transmission pulse waveform 100. is selected to temporarily disable detection/comparison sections 72 and 74 to prevent ing.

The transmit pulse disable signal 110 and self-test waveform enable signal 108 are A logic operation is performed by the D gate 114 (FIG. 4) and the self-test time gate window 116 ( Figure 5) is generated.

The self-test time gate window 116 includes: The self-test waveform detection/comparison unit 74 can detect the presence of the self-test waveform 102. The sea urchin has been selected.

The presence of a self-test waveform within the self-test time gate window 116 indicates that the sensor is It shows that it is working. Self-test within self-test time gate window 116 The absence of a strike waveform indicates that the sensor is not functioning.

Waveform 112 shows the main waveform enable signal. Rising edge of transmission pulse 98 , the main waveform enable signal 112 goes low and capacitor C1 and resistor The frontage-state is maintained for a first time constant determined by resistance R1. After the first time constant , the main waveform enable signal 112 goes high. Main waveform enable signal 112 and The signal pulse invalidation signal 110 is logically operated by the NAND game) 11g (Fig. 4). to generate the main waveform time gate window 120 (FIG. 5). Main waveform time gate window 12 0 enables the main waveform detection/comparison section 72 only during the period of the main waveform time gate window. The presence or absence of the waveform 104 can be detected. If the main waveform 104 exists within the main waveform time gate window 120, the ultrasonic signal has passed through the liquid. Ru. If the main waveform 104 does not exist within the main waveform time gate window 120, the ultrasound The wave signal is passing through the gas.

This is because it takes a very long time to receive the main waveform signal. Change In air, the main waveform 104 is the signal received by the receiving transducer 16. is attenuated to the extent that there is virtually no signal. The main waveform time gate window 120 is the transmitter Closed at the end of each of the 30 cycles. However, the time gate generator 70 Easily change the main waveform time gate window to close before the end of the cycle. Can be done.

The main waveform detection/comparison section 72 is connected between the amplifier 86 and the main waveform integration section 76. and includes resistor R4, comparator 122 and NAND gate 118. Resistance R 4 is connected between power supply terminal V+ and ground 90. Resistor R4 is comparator 12 It is a variable resistor with a center tap 124 connected to the non-inverting input terminal of 2. . The inverting input terminal of comparator 122 is connected to the output 88 of the amplifier. Comparator 1 The output of 22 is connected to NAND gate 118. NAND gate 118 Generates the main waveform detector output 126.

Center tap 124 supplies the main waveform threshold voltage to the non-inverting input terminal of comparator 122 do. Comparator 122 compares the amplitude of amplifier output 88 and the main waveform threshold voltage. main The waveform threshold voltage is set by the adjusting center tap 124 of resistor R4.

The threshold is the prediction of the main waveform 104 (FIG. 5) arriving within the period of the main waveform time gate window 120. is adjusted to indicate the expected amplitude.

This value depends on the type of transducer used, the excitation frequency, the dimensions of the sensor, the objects in the gap, etc. depends largely on the physical characteristics of the quality and the gain of the amplifier 86. Output of comparator 122 is NANDed with the main waveform enable signal 112 and the transmit pulse disable signal 110. Since the main waveform 104 is connected to the gate 118, the main waveform 104 is connected to the main waveform time gate window 120. Detected only between

The self-test waveform detection/comparison section 74 is located between the amplifier 86 and the self-test waveform integrator 78. block 74 is connected to resistor R5, comparator 128 and NAND gate. 114. Resistor R5 is connected between power supply terminal V+ and ground 90. ing. Resistor R5 is a center tap connected to the non-inverting input terminal of comparator 128. It is a variable resistor with 130 mm. Amplifier output 88 is the inverting input of comparator 128 Connected to child. The output of comparator 128 is connected to NAND gate 114. There is. NAND gate 118 generates a self-waveform detector output 132.

Resistor R5 generates a self-test waveform threshold voltage at center tap 130. self-te The self-test waveform threshold voltage within the self-test waveform time gate window 116 Adjust center tap 1 of resistor R5 to indicate the expected amplitude of waveform 102. Set by 30. Comparator 128 connects amplifier output 88 and self-test threshold voltage. Compare with. The output of comparator 128 is the self-test waveform enable signal 108 and is connected to a NAND gate 114 along with a transmit pulse disable signal 110. , the self-test waveform 102 is detected only within the self-test waveform time gate window 116. It will be done.

Main waveform detector output 126 and self-test on sensors with short stems The output 132 of the waveform detector is illustrated in FIG. FIG. 6 shows the detector waveform 126 and and 132 as a function of time. with a longer stem , the self-test waveform may follow the main waveform.

The main waveform detector output 126 is a series of pulses 1 corresponding to the main waveform 104 (FIG. 5). 34 and a series of pulses 136 corresponding to the echo waveform 106. Self The output 132 of the self-test waveform detector is one that corresponds to the self-test waveform 102 (FIG. 5). a series of pulses 138 . A group of pulses 134 is present at the output 126 of the main waveform detector That is, the main waveform 104 existed within the main waveform time gate window 120. It shows. Similarly, a group of pulses 138 appears at the output 132 of the self-test waveform detector. The presence of a self-test waveform within the self-test waveform time gate window 116 102 was present.

The output 126 of the main waveform detector is integrated by the main waveform integrator 76 . self test The output 132 of the test waveform detector is integrated by a self-test waveform integrator 78.

The block 76 includes the inverter 15, the main waveform counter, the hold circuit 140, and the main waveform counter. It includes a waveform relay driver 142. Inverter 15 is NAND gate 11 8 and the main waveform counter/hold circuit 140. Main waveform counter The control/hold circuit 140 is connected between the inverter I5 and the main waveform relay driver 142. It is connected. The main waveform counter/hold circuit 140 controls the oscillation within the transmitter 30. Count the number of pulses received from the NAND gate 118 during each cycle of the device. do. The number of pulses counted during a -cycle of oscillation is a given number (e.g. 3) Once exceeded, the counter indicates that the main waveform 104 was present within the main waveform time gate window 120. A signal is generated at output 146 indicative of .

Signal 146 is provided to relay driver 142 which generates main waveform output signal 80. . The main waveform counter/hold circuit 140 has a reset input connected to the transmitter 30. It has a power of 148. At the beginning of each transmission cycle of transmitter 30, transmitter 3 0 provides a reset pulse to reset the counter/hold circuit 140 do. By counting the number of pulses during one cycle, the circuit 140 calculates the main waveform. 104 false positives.

As previously mentioned, the second group of pulses 136 shown in FIG. The echo waveform 106 (FIG. 5) within the tap is shown. The main waveform threshold voltage increases The echo waveform 106 included in the output 88 of the width converter is sent to the main waveform counter/hold circuit 1. The output 126 to 40 can be adjusted so as not to generate pulse groups. However, This is not necessary, since the counter will count for the given number.

Similarly, the output 132 of the self-test waveform detector is output by the self-test waveform integrator 78. It is integrated. The pro-tsuku78 is equipped with an inputter I6 and a self-test waveform counter/hoter. field circuit 150, and a self-test waveform relay driver 152.

Inverter ■6 is a NAND gate 114 and a self-test waveform counter/hold The circuit 150 is connected between the circuits 150 and 150. Circuit 150 includes inverter I6 and self test wave The type relay is connected between the rhino 152. Self-test waveform counter/home The field circuit 150 outputs the output 1 of the self-test waveform detector during the transmit cycle. Count the number of pulses received from 32.

If the number of pulses counted exceeds a given number (e.g. 3), circuit 150 self-activates. An output signal 154 is sent to the test waveform relay circuit 152. self test The self-test waveform relay node 152 has a self-test waveform within the time gate window 116. The self-test waveform output 82 indicates the presence or absence of the self-test waveform 102. Occur. A self-test waveform counter/hold circuit 150 is connected to the transmitter 30. It is equipped with a reset manual power 156. At the beginning of each transmit cycle, the circuit 150 is reset by a reset pulse from transmitter 30.

The main waveform output signal 80 indicates the presence or absence of liquid inside the gear 20 of the sensor 10. It shows the presence. The time-gated ultrasonic sensor of this invention detects the level of liquid in a tank. can be used to detect that the object has risen to a specific position. The sensor 10 is placed in a specific position. When the liquid level rises and the gap 20 is filled with liquid, As the speed of the ultrasound signal passing through the gap increases, the main waveform time gate window 12 0, the main waveform reaches the receiving transducer 16. The main waveform output signal 80 is It shows that liquid is in the gap 20.

The time required for an ultrasound signal to pass through a material is related to the density of that material, so The top configuration allows the height and density of the liquid level to be fixed at the same time. Density nj is based on the speed of the signal passing through the material and measures the propagation time, which reflects the density of the material. It is done by doing. Typically, when measuring density, AGC (automatic (gain control) is used to control the amplitude of the main waveform. If the densities of two substances are known, If so, the sensor detects the boundary between the two materials in the gap based on the change in signal velocity. can detect the field.

Self-test output 82 indicates the integrity of sensor 10.

If the sensor 10 is functional, a self-test wave passes through the stem 18 of the sensor. A shape should always be present with each transmitted pulse. This has several advantages Exists. Even if process material is present in the gap, test each transducer individually. Continuous self-test without the need for additional piezoelectric elements to can be done. Therefore, in order to apply it to a wider range of applications, the sensor 10 The overall size of can be reduced.

Furthermore, this configuration allows you to test the entire sensor functionality rather than many sensors individually. to The sensor body uses a thicker stem for greater mechanical integrity. It can be manufactured using Like conventional oscillator type sensors, There is no limit to the signal strength that can pass through. The signal passing through the stem has a large amplitude. If present, this improves rather than detracts from performance.

Since there is no crosstalk between each sensor, the detection point can be They can be placed closer together. The amplitude of the ultrasound signal is approximately 1 millisecond or less. internally reduced to a meaningless level. The number of wires required per point is smaller, Additionally, the stem can be made mechanically stronger, allowing for more detection points. can be provided. Fewer wires required for additional piezo elements for self-testing This is because the child is no longer needed.

The same performance can be achieved using just one transducer. this In an embodiment, the ultrasonic signal to be measured is on the opposite surface of the gap from the transducer. It is a reflected wave from For example, FIG. 7 is a cross-sectional view of a single transducer sensor according to the present invention. It is. The sensor 160 includes a main body 162, a bridge member 164, a reflector 166, and a variable 168 and a gap 170. Transducer 168 includes reflector 166 An incident wave 172 passing through a gap 170 is transmitted toward the . The reflected wave 174 is From reflector 166 it passes through gap 170 and returns to transducer 168. reflector 166 is a reflected wave 17 whose surface in contact with the gap 170 returns to the piezoelectric element 168. It is configured to focus 4. In the embodiment shown in FIG. 7, the surface is A precision curve is machined to focus the reflected wave 174 back onto the piezoelectric element 168. The rate is concave. However, reflector 166 may also be a substantially flat surface.

The embodiment shown in FIG. 2 also uses a single transmitter for transmitting and receiving ultrasound waves. It can be configured to have an element.

In this embodiment, the main waveform 48 is transmitted from the transducer 40 along the inner diameter 46; It is reflected from the wall 43 toward the converter 40. Self-test waveform 50 is placed on wall 43 along the tube or container 44 and back to the transducer 40.

The time gate configuration of the present invention allows for It can be used to separate the reception of the main waveform from the noise waveform. if, If the signal generated within the stem of the sensor is not used for self-test functions, the The signal in the system becomes a noise waveform. The noise waveform is generally generated by the transmitter and receive converter. This is considered to be crosstalk between converters. The main waveform enable signal is compared to the amplitude of the main waveform signal. In all cases, the main waveform is activated only during the main waveform time gate window period when the amplitude of the noise waveform is sufficiently small. Allows waveform detection. This means that the main waveform threshold voltage for removing noise waveforms is gives a large margin in the settings. Therefore, the noise waveform is the main waveform do not interfere with

The time-gated ultrasonic sensor of the present invention substantially depends on the physics of matter within a defined space. It can be used in any application that measures physical properties. The present invention relates to a preferred embodiment. However, those skilled in the art will be able to change the shape and details without changing the technical idea of the present invention. You can see that the parts can be changed. For example, amplifier output 88 (Figure 4) and threshold voltage The comparison with the pressure is done by the microprocessor which establishes the time gate window. You can also do this. To make a similar comparison, we Software programs can also be used. DSP (digital signal processing) integrated circuits It can be used in place of the circuit shown.

If the amplitude of the self-test signal is too strong and causes disturbances in the main time window, Alternatively, the stem may be fabricated to include a discontinuity. The discontinuity is the bottom section. of stems separated by annular grooves whose faces may be square, round, or triangular It may also be formed as a plurality of overhanging ribs provided around the periphery. multiple tensions The stem acts as a resonant element, absorbing signals traveling along the stem. multiple thicknesses The discontinuities are preferably each spaced a quarter wavelength apart and It extends about half a wavelength from TEM. In order to cover a wavelength band consisting of multiple wavelengths, Multiple overhangs on the same stem can each have different dimensions. I can do it. The stem should be placed along the center axis of the sensor rather than on the side of the sensor. It may be arranged as follows.

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Claims (10)

[Claims] 1. having a conversion means attached to a support member generally adjacent the defined space; The steps of preparing an ultrasonic sensor and preparing an ultrasonic signal having a main waveform inside a defined space. applying a pulse to the conversion means to generate the signal and the space in which the signal is defined; receiving the ultrasonic signal by a converting means after passing through the ultrasonic signal; received within the main time window to detect whether the main waveform exists within the main time window. as a function of the presence of the dominant waveform within the dominant time window. , generating an output representative of the presence of matter within the defined space. A method of detecting whether or not a substance exists inside a space. 2. a support member; is fixed to a support member and transmits and receives an ultrasonic signal containing a main waveform across the gap. transducer means disposed adjacent to the gap as believed; is connected to a transducer means to determine whether a main waveform is present in the received ultrasound signal. In order to detect a monitoring means that is connected to the monitoring means and that determines whether or not the main waveform exists within the main time window; and a means for detecting physical properties of the material within the gap. Ultrasonic sensor for measuring physical properties of materials within a defined gap. 3. connected to the transducer means for exciting the transducer means and generating a main waveform in the transducer means; The ultrasonic device according to claim 2, further comprising an oscillator that periodically generates a transmission pulse that causes wave sensor. 4. The monitoring means a threshold generator for generating a main waveform threshold level; a threshold generator and a received ultrasound signal; a ratio representing the comparison between the amplitude of the received ultrasound signal and the main waveform threshold level. generates a comparison output each time the amplitude of the received signal exceeds the main waveform threshold level. A comparator that outputs a pulse to the power and a comparison output that is connected to the comparison output and compares within the main time window. Count the number of pulses being output and calculate the number of pulses within the main time window as a function of the number of pulses counted. a counter that generates a main waveform output signal indicating the presence of a main waveform to be detected; Connected between the oscillator and the counter and resets the counter based on the input of each transmitted pulse. The ultrasonic sensor according to claim 3, further comprising a reset circuit for setting the ultrasonic sensor. 5. connected between the oscillator and the monitoring means to receive the transmitted pulses and to select the main time window. means for monitoring, in order to monitor the ultrasound signals only within selected time windows; The claimed invention further includes time gate generation means for generating an enabling signal to enable the The ultrasonic sensor according to claim 3. 6. The time gating means is arranged at a first preselected time following reception of the transmit pulse. The main waveform enable signal is active after the main time window and is active during the main time window. and the main waveform enable signal is active during the main time window. only when the received ultrasonic signal is connected to a monitoring means, The ultrasonic sensor according to claim 5. 7. The time gating means generates a main waveform enable signal as a function of the first RC time constant. 7. The ultrasonic sensor according to claim 6, comprising a first RC circuit that generates. 8. The transducing means transmits and transmits an ultrasonic signal with a self-test waveform that passes through the support member. The sensor also monitors the received ultrasound signals to generate a self-test waveform. is within the self-test time window; means for monitoring the gate waveform are connected between the converter means and the time gate generation means; Additionally, the ultrasonic sensor according to claim 5. 9. The means for monitoring the self-test waveform generates a self-test waveform threshold level. a threshold generator and a self-test waveform threshold level between the amplitude of the received ultrasound signal and the self-test waveform threshold level. a threshold generator and the received ultrasound to generate a comparison output representative of the comparison results; wave signal, and whenever the amplitude of the received signal exceeds the self-test waveform threshold level a comparator that outputs a pulse to the comparison output; Connected to the comparison output and counts the number of pulses in the comparison output within the self-test time window and the test waveform within the self-test time window as a function of the number of pulses counted. a counter that generates a test waveform output signal indicating the presence of the , is connected between the oscillator and the counter, and based on the reception of each transmitted pulse the counter The ultrasonic sensor according to claim 8, further comprising a reset circuit for resetting the ultrasonic sensor. 10. Includes a main waveform passing through the gap and a self-test waveform passing through the support member. applying a pulse to the transmitting transducer means for generating an ultrasonic signal and self-test waveforms pass through the gap and support member, respectively. receiving the ultrasound signal by means; A predetermined self-test waveform is used to detect the presence of a self-test waveform within a time window. monitoring the received waveform within the test time window; The completeness of the sensor as a function of the presence of the self-test waveform within the self-test time window. generating a self-test output representative of the Ultrasound with transducer means fixed to a support member generally adjacent a defined gap How to test the integrity of a wave sensor.