JPS62263483A - Ultrasonic scaler - Google Patents

Abstract

PURPOSE:To measure a distance in a wide distance range stably and accurately, by the ultrasonic transducer fixed to one end of a pipe having a slit cut therein in the axial direction and an ultrasonic transducer movable in a state guided by the shift. CONSTITUTION:The ultrasonic wave from a transmitting ultrasonic transducer T is received by the distance calibrating ultrasonic transducer R0 provided to a position at a known distance L0 in order to calibrate a distance and an output signal (r) is converted to a rectangular wave signal (s) through an amplifying circuit A and a circuit RW forming a reference wave into a rectangular wave. The phase difference of the rectangular wave signal (s) and the output signal of an oscillation circuit OSC is detected by a phase difference detector PHD and converted to a voltage signal by a phase/voltage converter P/V to be held to a sample holding circuit S/H for a predetermined time. A distance L obtained by calibrating the phase difference of ultrasonic waves on the basis of the distance L0 is displayed on a display part DISP. The end of a pipe is allowed to correspond to the position of one point among two points having to measure a distance and a transducer R movable to the position of the other point is allowed to correspond to the guide element B of a slit S to be allowed to correspond to the distance between both transducers and an accurate distance can be measured.

Description

[Detailed description of the invention] a. Industrial application field The present invention relates to an ultrasonic scaler.

b. Prior Art There is a magnet scale, which arranges small magnets in a line and counts the number of north and south poles.

There is also an ultrasonic scaler that electromagnetically generates ultrasonic waves in a metal rod and measures distance from the propagation time.

C0 Problems to be Solved by the Invention In a magnet scale in which magnets are arranged, the measurement accuracy is limited by the dimensions of the unit magnet, and there is a limit to the distance resolution.

What is measured from the ultrasonic propagation time in a metal rod is noise,
It is weak against external induction, and the sound attenuation inside the metal rod is large, so it can only measure short distances.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic scaler that can perform measurements with high resolution and precision without being affected by noise or external guidance, and has a small ultrasonic attenuation rate.

Means for solving the d0 problem The above problem involves an ultrasonic transducer fixed to one end of a tube with a slit in the axial direction, and an ultrasonic transducer that is movable guided by the slit. and an ultrasonic wave generator equipped with a time difference detection circuit for determining the time difference or phase difference between the rising time on the receiving side of a specific carrier wave among the carrier waves constituting the ultrasonic burst propagated in the pipe and the rising time on the transmitting side of the ultrasonic burst. The above problems have been solved by a sonic scaler.

More specifically, the professional 7 shown in FIG. an ultrasonic transducer R that is movable while being guided by a voltage-controlled oscillation circuit (surin) S, a voltage-controlled oscillation circuit, a frequency control circuit that controls the oscillation frequency of the voltage-controlled oscillation circuit, and a carrier that is the output of the voltage-controlled oscillation circuit 5. A transmitter circuit 1 includes a burst wave forming circuit that generates burst waves by intermittent control of waves and excites one of the ultrasonic transducers, and an amplifier circuit that amplifies the signal received by the other ultrasonic transducer. 2, a burst wave comparison circuit 3 that generates a signal when the envelope signal of the received burst wave exceeds a predetermined level, and a burst wave comparison circuit 3 that generates a signal when the envelope signal of the received burst wave exceeds a predetermined level; a gate circuit 4 that opens the gate only for a period;
゛A rectangular wave conversion circuit 6 that converts the carrier wave output from the amplifier circuit into a rectangular wave, a frequency multiplier circuit 7 that converts the oscillation frequency of the voltage controlled oscillation circuit to a high frequency, and a rise or rise of the burst wave of the transmitter circuit. A counting circuit 7 that counts the output of the frequency multiplication circuit with the falling signal as a start signal and the output signal of the rectangular wave converting circuit that has passed through the gate as an end signal, and a recurrent sound wave based on the output of the counting circuit. The problem was solved by an ultrasonic scaler characterized in that it is equipped with a display circuit 8 that displays the distance between transducers.

e. After a predetermined period of time has passed since the envelope signal of the ultrasonic burst on the receiving side exceeds a predetermined value, the rise point of a specific carrier wave is detected using a gate circuit that opens for a predetermined short period of time. do. The time difference between the rising time of the ultrasonic burst on the transmitting side and the rising time of the specific carrier wave on the receiving side is determined by a counting circuit. In order to improve measurement accuracy, a counting circuit counts signals having a frequency obtained by multiplying the oscillation frequency of an oscillation circuit for ultrasonic excitation using a PLL circuit or the like.

To calibrate the distance, ultrasound is detected with a reference ultrasound transducer located at a known distance, and the phase difference of the ultrasound is made to correspond to the distance.

f. Embodiment FIG. 1 is a block diagram of a preferred embodiment of the ultrasonic scaler according to the present invention, and FIG. 2 shows signal waveforms at main points of the first block diagram.

The oscillation circuit OSC, which is a voltage controlled oscillation circuit, has a frequency of approximately 40KHz.
oscillates. The output a of the oscillation circuit O3C is frequency-divided by the first counting circuit CNTl, and the output a of the first counting circuit CNTl is used as a trigger signal to drive the monostable flip-flop circuit MO.
NO1 outputs the output C for a certain period of time to the first circuit consisting of an AND circuit.
1 input terminal of gate G1. First gate circuit G
The output signal a of the oscillation circuit OSC is sent to the other input terminal of the oscillation circuit OSC. The output d of the first gate G1 is a burst wave that lasts for a time determined by the output of the monostable flip-flop circuit MONOI (see FIG. 2).

The output signal of the first gate) Gl is sent to a transmitting ultrasonic transducer T, which emits an ultrasonic burst into the tube. The ultrasonic waves propagated inside the tube can be transmitted to a transducer installed in the tube at a point far away from the transmitting ultrasonic transducer, or in a slit or near the slit with the ultrasonic receiving surface facing inward. It is received by the receiving ultrasonic transducer R. The receiving ultrasonic 1 lance ducer R is the guide B in the slit S.
exercise with.

As shown in FIG. 2, the waveform of the received ultrasonic signal e is distorted at the rising edge. For this reason, it is necessary to avoid the rising portion of the ultrasonic burst and detect the rising point of a specific carrier wave with a clear rising edge.

After the ultrasonic signal e is amplified by the first amplifier circuit A1, the ultrasonic signal e is amplified by the detection circuit DB? The wave is detected by A part of the output f of the detection circuit DET is passed through the automatic gain control feedback circuit AGC to the first
It is fed back to the amplifier circuit A1. As a result, the level of the output f of the upper string detection circuit DBT is kept almost constant.

- The output f of the detection circuit DET is amplified by a second amplifier circuit A2, and the amplitude of the output g of the amplifier circuit A2 is set in advance.
The comparator circuit CGMP compares the output f with the threshold value V, and generates an output signal when the output f exceeds the threshold value Va.

On the other hand, the delay time setting circuit t/V generates a voltage signal i corresponding to the set delay time, and the voltage signal i is converted into a frequency signal j by the voltage/frequency conversion circuit V/F. The output j of the voltage/frequency conversion circuit V/F is output from the third counting circuit C.
At NT3, the signal from the comparison circuit COMP is counted as a start signal. The third counting circuit CNT3 is
After counting a preset number of pulses (for example, 10), the output signal k is sent to the second monostable flip-flop circuit M.
Send to ONO2. The monostable flip-flop circuit MON
O2 uses the signal k as a trigger signal to send a pulse l with a preset short time width to the second gate G2 to open the gate, that is, to open the output g of the second amplifier circuit A2, that is, the envelope of the signal e. After a predetermined time set by the delay time setting circuit has passed since the signal exceeded a predetermined threshold value V, the second monostable flip-flop circuit MO
The second gate is opened for a predetermined time interval determined by NO2. During this time period, the rising portion of the waveform of the received wave burst ends, and the amplitude of the received wave becomes stable.

Therefore, each carrier wave forming a received wave burst can be reliably converted into a rectangular wave m using the rectangular wave converting circuit RWI consisting of a comparison circuit and the like. The rectangular carrier wave m is sent to the second gate G2. The game)G
2 is open for a predetermined short period at a given time, as described above, and the time and period are chosen to correspond to the rising time of a particular carrier wave. That is, the output of the second gate circuit G2 corresponds to the rising point of a specific carrier wave.

On the other hand, a part of the output of the oscillation circuit OSC is transmitted to a frequency multiplier circuit FMUL consisting of a phase linear loop (PLL) or the like.
The high frequency signal n is converted to a high frequency by the second
It is counted by the counting circuit CNT2.

The counting start signal is the rising time of the first counting circuit CNTl, that is, the rising signal P on the burst wave transmitting side.
The counting end signal is the signal q from the second gate circuit G2. As a result, the second counting circuit CNT2
The count corresponds to the time difference between the rise time of the burst wave on the transmitting side and the rise time of a specific carrier wave in the burst on the receiver side, except for a constant difference. Therefore, by performing appropriate conversion, the distance between the recurrence sonic transducers can be determined from the above-mentioned time difference and ultrasonic sound velocity, and the distance is displayed on the display means Rikaya sp.

In the embodiment of FIG. 1, in order to calibrate the distance, a distance calibration ultrasonic transducer R0 is provided at a known distance ML from the transmitting ultrasonic transducer T.
receives an ultrasonic wave, its output signal r is amplified by a distance calibration amplifier circuit A, and the output signal is converted to a reference wave rectangular wave circuit R-
Convert it to a rectangular wave 3 with
The phase difference between the output signals of is detected by the phase difference detection circuit PHD.The output of the phase difference detection circuit PHD is converted into a voltage signal by the phase/voltage conversion circuit P/V, and is further converted for a predetermined time by the sample hold circuit S/H. (for example, a period separated by the rising edge of each burst). Above oscillation circuit OS
C is constituted by a voltage controlled oscillation circuit, and the frequency changes so that the value held by the sample hold circuit S/H remains constant, that is, so that the output t of the phase difference detection circuit PHD remains constant. As a result, the phase difference of the ultrasonic waves is the known distance ML,
Calibrated by That is, the distance calibrated by the distance to is displayed on the display means DISP.

Note that it is also possible to use the output of the comparison circuit COMP as the counting end signal of the second counting circuit CNT2 without using the output signal of the second gate, but the measurement accuracy will be slightly lowered.

g. By making the tube end correspond to one of the two points at which the effective distance is to be measured, and making the other point correspond to the guide B that guides the movable ultrasonic transducer along the slit, The distance is made to correspond to the distance between the recurrence sound wave transducers, and the distance is measured. Therefore, distance can be stably and accurately measured over a wide distance range without being affected by noise, disturbance, external induction, sound speed, etc.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an ultrasonic scaler according to a preferred embodiment of the present invention, Fig. 2 is a signal waveform at the main points of the block diagram of Fig. 1, and Fig. 3 is a basic diagram of an ultrasonic scaler according to the present invention. This is a block diagram. 1... Transmission circuit, 2... Amplification circuit,
3... Burst wave comparison circuit, 4... Gate circuit,
5... Rectangular wave conversion circuit, 6... Frequency multiplication circuit, 7... Counting circuit, 8... Display circuit, A... Distance calibration amplifier circuit, AI, A2...
Amplifier circuit, AGC...feedback circuit for automatic gain control, CN
T1. CNT2. CNT3... Counting circuit, COMP.
...Comparison circuit, DISP...Display means, D
ET...detection circuit, FMUL...frequency multiplier circuit,
G1. G2...Gate, MONOI, MON
O2...monostable flip-flop circuit, OSC...
Voltage controlled oscillation circuit, POD...Phase difference detection circuit, P/D...Phase/voltage conversion circuit, R...Ultrasonic transducer for reception, Ro...Ultrasonic transducer for distance calibration , R-... Reference wave rectangular wave converting circuit, R&41... Rectangular wave converting circuit, S/H・
...sample hold circuit, T...transmission ultrasonic transducer, t/V...
Delay time setting circuit, ■...Threshold value, V/F...
Voltage/frequency conversion circuit, L...known distance, L...unknown distance, P...tube, S...slit, B...guide. Patent applicant: Tokyo Keiki Co., Ltd. (and 2 others) Figure 2 (p) □

Claims (3)

[Claims] (1) An ultrasonic transducer fixed to one end of a tube with a slit in the axial direction, an ultrasonic transducer that is movable while being guided by the slit, a voltage-controlled oscillation circuit, and oscillation of the voltage-controlled oscillation circuit. a transmitting circuit comprising a frequency control circuit that controls the frequency, a burst wave forming circuit that generates a burst wave by intermittently controlling the carrier wave that is the output of the voltage controlled oscillation circuit, and excites one of the ultrasonic transducers; an amplifier circuit that amplifies the signal received by the ultrasonic transducer; a burst wave comparison circuit that generates a signal when the envelope signal of the received burst wave exceeds a predetermined level; and a burst wave comparison circuit that generates a signal when the envelope signal of the received burst wave exceeds a specified level; a gate circuit that opens the gate for a predetermined short time when the time has elapsed; a rectangular wave converting circuit that converts the carrier wave output from the amplifier circuit into a rectangular wave; and a voltage controlled oscillation circuit that increases the oscillation frequency of the voltage controlled oscillation circuit. Count the output of the frequency multiplier circuit, with the rising or falling signal of the burst wave of the frequency multiplier circuit to be converted and the transmitting circuit as a start signal, and the output signal of the rectangular wave converting circuit that has passed through the gate as the end signal. An ultrasonic scaler comprising: a counting circuit; and a display circuit that displays distance based on the output of the counting circuit. (2) The transmitting circuit calculates the difference between the phase of the signal obtained by the distance calibration ultrasonic transducer whose distance from the transmitting ultrasonic transducer is known and the phase of the signal obtained by the ultrasonic transducer and the voltage controlled oscillation circuit. It is characterized by comprising a phase difference detection circuit that detects the phase difference and a sample hold circuit that holds a signal corresponding to the phase difference, and the oscillation frequency of the voltage controlled oscillation circuit is controlled so that the phase difference becomes a constant value. An ultrasonic scaler according to claim (1). (3) The gate circuit includes a delay time setting circuit that sets a delay time, a conversion circuit that converts the output signal of the delay time setting circuit into a frequency signal, and generates an output signal when the frequency signal is counted a predetermined number of times. Claim 1 is characterized in that it consists of a predetermined number counting circuit, a monostable flip-flop circuit using the output of the predetermined number counting circuit as a trigger pulse, and a gate controlled by the output of the flip-flop circuit. Ultrasonic scaler described in ).