KR800000139B1 - Apparatus for measuring automatically succesive sections of an elongated material - Google Patents

Abstract

This is a device to measure both thickness and ecentricity of the pressed jacket of the succesive sections of an elongated material by supersonic waves. It comprises two receivers - one is for the pulse reflected from the front surface and the other for the pulse from the other surface - detectors to distinguish between the first and second echoed pulse, on-off sign generators and control pulse generators to response the measured result.

Description

Automatic measuring device of continuous section of linear object

1 is a partial cutaway perspective view of an extrusion apparatus covering a cable core with a plastic material.

2 is an enlarged partial cross-sectional view of the water-cooled trough shown in FIG.

3 is a typical one channel schematic diagram of four channels used for ultrasonic measurement.

4 is a state diagram of the pulser-receiver circuit shown in FIG.

FIG. 5 is a detailed view of the receiver-logic circuit shown in FIG.

6 is a waveform diagram relating to the operation of the apparatus shown in FIG.

The present invention relates to an apparatus for ultrasonically measuring a continuous cross section of a linear object, and more particularly to an apparatus for ultrasonically measuring the thickness and eccentricity of a jacket extruded around a continuous cross section of a cable advancing along a certain path.

In one example of a cable for use in the telecommunications industry, one metal moisture barrier is bellowed around a cable core wire as long as it is traveling along a certain path. At this time, the overlapping ends of the moisture barrier layer are bound together to form a waterproof seal. A jacket of plastic material is then extruded over the core and moisture barrier to cover one jacket on the outside of the moisture barrier. The jacketed cable then passes through a relatively long water-cooled trough to lower the jacket's temperature.

It is desirable to continuously check the jacket thickness as well as the eccentricity of the jacket. By inspecting the jacket, it is possible to maintain a uniform thickness of the jacket and to prevent waste of plastic material by applying the minimum applicable jacket thickness.

By inspecting the eccentricity, the extrusion device can be adjusted to prevent out-of-round of the final product.

In the related art, a method of directly contacting a plastic jacket with an electrode, measuring a capacity between the electrode and the metal layer, and examining a thickness of the plastic jacket extruded onto the metal moisture barrier layer was adopted. However, these conventional capacitive methods could not be used without a metal moisture barrier surrounding the inner jacket and had to use off-line testing.

For effective control, it is recommended to check the thickness of the jacket as soon as possible after the plastic is extruded over the cable core. Conventionally, these tests were performed after the cable passed through the water cooling trough so that the electrodes did not come into contact with the cable jacket until the temperature of the cable jacket decreased. The non-contact jacket thickness measuring device, which is close to the point where the jacket extrusion inevitably occurs, is marked for use by an operator who makes the feedback control device connected to the extruder optimal or to make adjustments to check jacket eccentricity and thickness. Is optimized. By using this method, the jacket material can be saved.

Examples of conventional measuring devices include those exemplified in US Patent Nos. 3, 407, 352 and 3, 500, 185, using magnetic coils and capacitive pickup probes supplied to bridge circuits, respectively.

The technique of using ultrasonic waves to measure the thickness of a solid object is already known in the art and can be generally divided into two techniques. One is the method of using pulse echo, which transmits the pulse and uses the return echo, and the other is using resonance, which uses the principle that the peak of the feedback signal is reached when the wavelength of the ultrasonic signal reaches an integer multiple of the thickness of the object under test. Way.

Ultrasonic pulse echo technology seems ideal for measuring eccentricity and thickness. The crystal is electrically excited using a high voltage potential to produce a mechanical crystal signal. This mechanical movement is transmitted in a cable, measured in the form of pressure or sound waves, through a cooling material such as water in the cooling trough.

Depending on the acoustical mismatch between the cooling material and the object, such as the cable for inspection, some of the acoustic energy will be reflected and some will continue through the object medium under test. At each interface of the object under inspection, a similar deformation occurs. Measure the thickness of the jacket using the echo signal.

Conventionally, in the ultrasonic measurement of a linear object, such as a pipe, a crystal with one line focus is usually used to position the crystal so that it lies parallel to the longitudinal axis of the line. However, in the manufacture of the tube, the strength of the tube excludes any significant movement in the lateral direction of the continuous section of the tube. This is not the same as the lateral movement that occurs when the continuous section of the cable passes through the cooling trough. Conventional patents relating to ultrasonic measurement include US Pat. Nos. 3,423,992, 3,474,664, 3,509,752 and 3,605,504.

However, these prior arts did not provide a framework for measuring the thickness and eccentricity of the continuous section of the cable jacket immediately after extrusion, but could only measure these signals while the cable was moving forward.

In the method of the invention, one on and off signal relates to the elapsed time between the reception time of the first echo pulse from the outer surface of the jacket and the reception time of the second echo pulse from the inner surface of the object. Generated at the time duration between the on and off signals. These on and off signals are automatically generated only when the first and second echo pulses having a predetermined minimum amplitude are received by a second pulse generated a predetermined time after the first pulse is started. Measure the elapsed time between signals.

More specifically, there is provided an apparatus for setting an inspection period which is a period during which echo pulses reflected from a cable jacket on which an ultrasonic signal is projected are examined. Ultrasonic pulses are projected into the cable jacket, and then the first echo pulses reflected from one surface of the object under test and the second echo pulses reflected from the opposite side are received, at which point the reception of irrelevant low-level signals is isolated. .

The first echo pulse is checked for qualification and then the second echo pulse is checked. Qualification check Generates an on signal in response to the receipt of the first echo pulse, thereby starting the inspection of the qualification check of the first echo pulse and possibly facilitating the generation of a control pulse in response to the first echo pulse under qualification. . In response to the examination of the first echo pulse and the receipt of the qualification test associated with the second echo pulse, the characteristic test of the qualification test associated with the second echo pulse begins, while the off signal is generated. The duration between the on signal and the off signal is related to the elapsed time between the reception of the first echo pulse and the reception of the second echo pulse. The elapsed time between the on signal and the off signal is measured and the condition of the device is enabled to generate a control pulse in response to a valid second echo pulse. The measured elapsed time causes the jacket thickness to appear in response to the generation of the control pulse.

Features of the present invention will be more readily understood in the detailed description of specific embodiments described below with reference to the accompanying drawings.

Referring to FIG. 1, reference numeral 10 may be used to cover the continuous cross-section of the cable core 11 with a plastic material such as polystyrene to make a cable 12 coated with a jacket (see FIG. 2). You can see one device displayed. As can be seen in FIG. 1, this apparatus 10 is equipped with a cooling trough 16 downstream of the extruder and the two extruders indicated by the number 14. The continuous cross section of the core 11 is advanced through an extruder 14 through which the plastic material is extruded by the capstan 17. The continuous cross section of the cable 12 then passes through the cooling trough 16 and is wound on the reel 18.

In order to most effectively control the thickness "d" of the jacket 13 extruded over the core 11 (see FIG. 2) and the eccentricity of the jacket, generally indicated by the number 20 (see also FIGS. 1 and 2). ) An ultrasonic and jacket measuring device is placed on the device 10. The device 20 immediately checks the thickness and eccentricity of the jacket as the continuous cross section of the jacketed core 11 enters the water cooling trough 14. This ultrasonic jacket measuring device 20 is designed to use the pulse echo measurement technique required by at least one crystal 21 (see FIG. 2). The water in the cooling trough 16 serves as a bonding medium for transmitting ultrasonic energy to the cable jacket 13.

In order to check the thickness "d" of the jacket 13, it is necessary to measure the thickness at several points around the jacket. This is also necessary to measure the eccentricity of the cable jacket 13.

As can be seen in FIG. 2, a plurality of crystals 21-21 are arranged at a distance from the circumference of the jacketed cable 12. As shown in FIG. At this time, each crystal is partially submerged in a cooling medium such as water in the cooling trough 16. These crystals 21-21 must choose one that can concentrate as much energy as possible in the micro area. The preferred crystal is one with a focus line, which crosses the cable 12. Also important to the choice of crystal 21 should be made available for cables of all expected sizes for as many different materials as possible and for the manufacturing environment.

Another important characteristic to consider is the attenuation of the crystal 21. If this attenuation rate is not very fast, it will not be possible to reliably indicate the thickness of the jacket 13. That is, the pulse echoes (Echoes I and Echo II in FIG. 6A) are intermingled and cannot be distinguished.

Several different types of crystals were tested. Testing has shown that soft zirconate crystals are the most suitable. This is because the crystal generates an amplitude signal greater than 10 MHz for the same excitation with better attenuation.

The crystals 21-21 are excited using voltage impulses that cause periodic mechanical stress. These stresses generate a high frequency pressure gradient or high frequency in the bonding medium, here the water of the cooling trough. This high frequency, whose strength changes with the attenuated sinusoidal wave, propagates to the surface of the cable jacket 13, part of which is reflected (time 6A degrees T) due to the mismatch of the acoustic impedance. This produces an external surface echo (echo I in FIG. 6a).

In addition, part of the pressure wave propagates into the cable jacket 13, and a second reflection occurs on the surface inwardly contacted with the cable jacket. This determines the second echo or the inner surface echo (echo II in FIG. 6a). Referring to the interrelationship between a surface and an object, the word "interface" in the specification and claims appended hereto will be understood that the surface is determined in the direction of the object, but need not necessarily adhere to or approach the object.

The measurement technique here is to determine the time difference (2t in 6a degrees) between the echo signals. This time difference is directly related to the thickness "d" of the cable jacket 13.

The data of thickness depend on whether or not the speed of sound is constant in polystyrene. Experimental results show that this velocity is virtually constant, so the equation 2d = Vt holds. Where d is the thickness of the polystyrene layer, V is the speed of sound, and t is the reverberation time. The reverberation time difference is measured, and the sound velocity V is known (about 0.051 cm / μs), so d is easily determined.

Each crystal 21-21 is electrically connected to the associated one of the plurality of channels 22-22 (see also FIG. 3). Each channel 22-22 has a number of objects in line with the corresponding crystal 21. A plurality of elements are provided which convert the parallax between the pulse echoes received at the inner surface into an output proportional to the thickness of the cable jacket 13.

In addition, another element is added to form one electrical circuit, indicated by the number 25, with four channels 22-22. The output of circuit 25 for thickness and eccentricity is displayed on console 26 (see FIG. 2).

Referring to FIG. 3, typical channels 22 and 22 are shown, including other elements common to the four channels. Each of the channels 22-22 contains one of the relevant ones of the crystals 21-21, which are electrically connected to the associated pulsar receivers indicated by the number 27. The pulser receiver 27 is specially designed and used to initially transmit a pulse to the associated of the crystals 21-21 in each cycle to generate a signal at natural frequency in the associated crystal. In each cycle, the pulser receiver 27 is activated to receive pulse echoes from the cable 12 under test.

This pulser receiver 27 is electrically connected to the receiver logic circuit 29 along the line 28. The receiver logic circuit 29 operates the pulser receiver 27 as soon as it receives a command from the pulse repetition frequency circuit (PRF) 30 to cause the associated transducer crystal 21 to pulse.

As can be seen in FIG. 3, the pulse repetition frequency circuit 30 is connected to the receiver logic circuit 29 along the line 31. As shown in FIG. The receiver logic circuit 29 can examine the echo pulses received from the cable 12 under test to remove these pulses independent of the measurement of the jacket 13 thickness.

As such, the receiver logic circuit 29 must not only distinguish between the first and second echo signals, but must also have unique information to distinguish between the noise spike and the valid signal.

The receiver logic circuit 29 is electrically connected to a counter 32 including a plurality of decimal counters 33-33.

This counter 32 measures the width of the output pulse from the receiver logic circuit 29. This counter 32 is pulsed by the generator 36 (see oscillator output in FIG. 6) and once a pulse received by the pulser receiver 36 is found to be valid by the receiver logic circuit 32 into a buffer memory. Store the pulse count.

The stored digital count from the count 22 is transferred to a digital-to-analog converter 37 that converts the digital count into an analog voltage.

The function of this digital-to-analog converter 36 is to provide an analog voltage that matches the digital count stored in the counter 32. This voltage is an indication of the thickness for that channel. Appropriately scaled analog voltages continue to appear on instrument 37 (see FIG. 2) of that channel 22. This marking allows the operator to continuously check the thickness "d" of the cable jacket on the part of the circumference corresponding to one channel.

Alternatively, the counter output stored in the buffer may be contacted with a digital electronic calculator (not shown) to perform data analysis and reduction.

In order to measure the eccentricity of the cable jacket 13, the eccentricity measuring circuit 38 is connected to each digital-to-analog converter 36 of the channels 22-22. This eccentricity measuring circuit 38 compares the jacket thickness at the top and bottom of the cable jacket 13, as shown in FIG. 2, and compares the jacket thickness at the top and bottom of the jacket 13 between the left and right ends. To compare the jacket thickness "d" between the left, right and right ends. Of course, it is not necessary to make these comparative measurements along the horizontal axis and the vertical axis. What is necessary is just to be symmetrical to the origin with respect to the coordinate axis of the cable jacket 13.

The eccentric rule measuring circuit 38 subtracts the bottom thickness from the top thickness of the jacket 13, as shown in FIG. 2, and multiplies this value by 100 times to create a percentage of the nominal jacket thickness.

This calculation is also performed on the thickness at the left and right portions of the cable jacket 13. These measurements are displayed on the upper and lower gauges 39 and the left and right gauges 40 respectively connected to the eccentricity measuring circuit 38.

The pulse repetition frequency circuit 30 applies a signal to the first channel contact 43 through the line 31 at a certain time, called a PRF time, to the pulsing element 48 or optical along the line 44. This signal is applied to the input 47 of the isolator (see FIG. 5). The pulsing element 48 applies one pulse to the pulser receiver 27 and controls the pulser receiver so that pressure waves are emitted from the associated transducer 21.

The pulser receiver 27 is a triggering circuit in which a pulse is applied from the pulsing sour 48 to apply a high voltage current pulse to the control electrode 53 of the first SCR 54 so that the first SCR 54 is turned on. 51) (FIG. 4).

The SCR 54 is a commercially available element and is a two-state semiconductor element having an operation characteristic such as a cycle. Normally, the SCR 54, which is in a non-conductive state, has a cathode 56 and an anode 57, the anode 57 being forward biased by an external means such as a constant voltage source 58. The control electrode 53 acts when properly excited by the bias voltage to bring the SCR 54 into a conductive state.

As can be seen in FIG. 4, the positive electrode 57 of the first SCR 54 is connected in series with the negative electrode 62 of the second SCR 63 via the contact 59 and the contact 61. The contact 61 is connected to the gate 64 of the second SCR 63. The anode 66 of the SCR 63 is connected to the cathode 69 of the SCR 71 via the contacts 67 and 68. The contact 68 is connected to the control electrode 72 of the SCR 71.

Finally, the anode 73 of the SCR 71 is connected to the cathode 77 of the SCR 78 via the contacts 74 and 76, and the contact 76 is connected to the gate 79 of the SCR. .

The anode 81 of the SCR 78 is connected to the ground 83 via the contact 82. The SCRs 54, 63, 71 and 78 have resistors 84, 86, 87 and 88 connected in parallel, respectively. The contact 82 is connected to a contact 91 connected to the series ends of the resistors 84, 86-88 along a line 89 and then to the contact 93 via a capacitor 92. This contact 93 is connected to the cathode 94 of the diode 96 and the anode is connected to the associated one of the transducers 21-21 via the contact 98. The diode 96 serves to block a noise signal having a small amplitude. If this diode 96 is not present, a small noise signal from all of the rooms of the circuit is moved to line 98 via contact 93 to reduce the echo signal from associated transducer 21. In response to these low level noise signals, diode 96 acts as an open circuit for positive or negative excursions. This breaking diode 96 is connected via contact 98 along line 101 and via resistor 102 to contact 103 and to input 104 of wide area image amplifier 106. In order to avoid the large negative voltage occurring at the input terminal 104 of the amplifier 106, a diode 107 is inserted into the line 108 connected to the contact 103.

A wide area, low noise, image amplifier 106 receives, amplifies, and transmits a feedback echo signal from the cable 12. The low level current feedback signal should be amplified to about 1-3V. The wide area image amplifier 106 should select that the semiconductor device used has low noise characteristics. In this way, the signal received and amplified for transmission to the receiver logic circuit 29 is stronger than the signal due to noise and thus enables the detection of a meaningful signal.

Installing a device in the pulser receiver circuit 27 to reduce the noise level while the echo pulse is received by the circuit 25 for inspection is particularly important when using the device 20 to measure the thickness of the inner jacket. Do. The pulse echo received from the inner jacket is smaller in amplitude than that received from the outer jacket. This is due to the more nonuniform surface of the polystyrene of the inner jacket. Peaks and valleys in the inner jacket reduce the target area of the cable, thus reducing the amplitude of the front end of the echo signal. This phase difference can be increased by a phase having a low amplitude. These peaks and valleys also generate phase differences in some of the electrical reflection signals. Echo signal strength varies between the inner and outer jackets and also depends on the size of the cable, but fixed gain devices can be used for all types of polystyrene cables.

The inner jacket shrinks around the cable core 11 and results in a slightly uneven outward surface. In contrast, the outer jacket is extruded onto a tubular metal shield that makes the outer surface of the outer jacket more uniform. This should inevitably result in a setting for low threshold pickup and inevitably increase the chance of picking up a noise signal.

A diode 96 connected to the pulse generator portion of the circuit comprising the SCRs 54, 63, 71, 78 and the wideband image amplifier 106 of the pulser receiver 27 is provided during the time that the receiver 27 listens for echo. It increases the impedance level. This enables better operation of the wide area image amplifier in terms of noise related to the operation of the device 20.

The diode 96 is located on the line 89 connecting the pulse forming portion or pulse generator of the circuit 27 to the wide image amplifier 106, opening the circuit in the first direction. In another direction, as shown in FIG. 14, on the left side, a passage of negative current is formed by the diode 96 to pulse one of the transducers 21-21.

The detection device is adapted to the characteristics of the expected signal. For example, since the distance between the transducer 21 and the cable 12 and the propagation speed of sound waves in the water medium can be known, the time interval at which the pulse echo signal is expected is generally known. Therefore, the ultrasonic apparatus 20 is designed to accept the pulse echo signal only for two time intervals.

The polyacoustic properties of foretylene, ie the propagation speed and acoustic impedance, are particularly important. These depend on the temperature of the porietirene and therefore require extensive on-line inspection.

The velocity equation of the longitudinal wave in the medium (shear stress wave is not required here) is

Where V ₁ = longitudinal velocity.

μ = number of steps

ρ = density

Kc = volume elastic modulus

The acoustic impedance of polystyrene is very important. Because this affects the magnitude of the echo signal. The acoustic impedance equation is as follows.

Z = ρV ₁

The amount of reflection at the two media interfaces increases as the difference in acoustic impedance increases. This amount of impedance mismatch determines the echo amplitude. The interface between the water and the polystyrene determines the first echo, and the interface between the polystyrene and the air, steel, aluminum or frudding compound determines the second echo.

Experiments have shown that the acoustic impedance for porietirene decreases with high temperatures. In particular, the first echo is much smaller in amplitude than the second echo. This is because larger acoustic mismatch occurs at the surface of the second polystyrene. The second reflection signal has a longer period than the first direction signal. These signal characteristics are advantageously used for the "information" design of the receiver logic circuit 29. "Information" is particularly beneficial in the measurement of the inner jacket, in which the magnitude of the signal varies considerably due to surface irregularities. If the amplitude or duration of the echo drops momentarily below the minimum value, no inaccurate measurements will be made. Instead, the final good measurement remains in the Ridgestar buffering counter 32 to maintain the correct thickness output.

The receiver logic circuit 29 is designed to check the expected signal characteristics as follows. That is, (1) whether echoes occur in a signal within a certain time limit (called window width) after pulse transmission, (2) whether the initial polarity of each echo is negative, or (3) the first echo pulse is the second echo pulse. Whether the duration is shorter than that of the echo pulse, (4) there is at least 200 ns between the first and second echoes, and (5) the minimum value of the first echo pulse for which the amplitude of the second echo pulse is required. (6) Check whether the second echo pulse lasts for a duration of at least 0.700 ms. If these characteristics are satisfied for the characteristic sequence of the first and second echo pulses, a command of the read pulse type is transmitted from the receiver logic circuit 29 to the counter 32 and recorded for the time 2t (see also 6h). Store the count as valid data.

In FIG. 5, the contact 43 is connected to the input terminal 111 of the monostable multivibrator 112. The far vibrator 112 generates a delay pulse applied from the output terminal 115 to the second monostable multivibrator 114 along the line 113. One output terminal 116 of the multivibrator 114 is connected to the input terminal 119 of the constant voltage threshold detector or comparator 120 and the input terminal 121 of the negative voltage comparator 122 through the contact 118 along the line 117. Is connected.

Threshold detectors 120 and 122 are included in comparator portion 123 of receiver logic circuit 29. As shown in Figure 5, this comparator portion 123 of the circuit 28 has an RF input stage 124, which is connected to a wide area image amplifier 106. The input 124 is a threshold detector. Are applied to input terminals 126 and 127 of 120 and 122, respectively.

Detectors 120 and 122 show negative advance forces when the threshold is exceeded. As shown in FIG. 5, the output 128 of the threshold detector 120 is applied to the input 129 of the NOR gate 131 with negative logic. When the NOR gate has a low level or a low level applied to the input 129 or another input 133, the output level 134 shows a positive level or a high level. The output 132 of the detector 122 is applied to the other input terminal 133 of the NOR gate 131.

The output l34 of the NOR gate 131 is applied to the inverter 138 which changes the polarity of the input signal via the contacts 136 and 137, and is then transferred to the flip-flop 141 along the line 139. Set the flip flop.

The flip-flop 141 has a crare or reset input 142 connected to the pulse repetition frequency circuit 30 and is connected to the input 146 of the hold-off pulse generator via the contact 144. It has an output terminal 143. The hold-off pulse generator 147 is a kind of monostable multivibrator, and is connected to the effective pulse generator 149 via a line 148. This effective pulse generator 149 is also a monostable multivibrator.

The output 151 of the multivibrator 149 is connected to the input 153 of the NAND gate 154 defined along the line 152. As also shown in FIG. 5, contact 166 is connected to another input 157 of NAND gate 154 along line 156. As shown in FIG. When a positive signal is simultaneously applied to the inputs 153 and 157 of the NAND gate 154, an output of low or low level appears at the output 158.

신호에 의해 리셋트 된다. 이것은 밀티바이브레이터(112)의 출력(115)으로부터의 지연펄스의 후단부에 의해 플립-플롭의 입력(163)에 리셋트 신호를 인가하는 것에 기인한다.The output 158 of the NAND gate 154 is connected along the line 159 to the set input 162 of the flip-flop 162. Flip-flop 162 is delayed

Reset by signal. This is due to applying a reset signal to the input 163 of the flip-flop by the trailing end of the delay pulse from the output 115 of the millivibrator 112.

The output 164 of the flip-flop 162 is connected via the contact 167 along the line 166 to the input 168 indicated as the "D" input of the flip-flop 169. Clock input 171 of flip-flop 169, denoted as "C" input, is applied from output 172 of multivibrator 149 along line 173.

)에 의해 크레어된 플립-플롭(169)은 출력(174)에서 한신호를 발생하고 이 신호는 선(176)을 따라 정 NAND 게이트(178)의 한입력(177)에 전송된다. 접점(137)은 선(179)를 따라 접점(181)을 거쳐 NAND게이트(178)의 제2입력(182)에 접속된다. NAND게이트(178)의 출력(183)은 선(184)를 따라 플립-플롭(187)의 입력(186)에 접속된다.Pulse repetition frequency signal applied to input 170 (

Flip-flop 169, which is generated by the < RTI ID = 0.0 > 1, < / RTI > The contact 137 is connected to the second input 182 of the NAND gate 178 via the contact 181 along the line 179. Output 183 of NAND gate 178 is connected to input 186 of flip-flop 187 along line 184.

The flip-flop 187 has a reset input 188 coming from the pulse repetition frequency circuit 30, which is delayed at the trailing end of the pulse generated by the multivibrator 112. Output 189 of flip-flop 187 is connected to input 192 of positive NAND gate 193 along line 191. The contact 144 is also connected to the other input 196 of the NAND gate 193 along a line 194. This NAND gate generates a split or low output pulse as shown in FIG.

Another output 197 of flip-flop 187 is connected to input 199 of monostable multivibrator 201 along line 198. The mill tea vibrator 201 acts as a hold-off pulse generator for examining the characteristics of the second pulse echo. The output 202 is connected to the input 207 of the second echo effective pulse generator 208 via a contact 204 and a line 206 along a line 203. This generator 208 is also a monostable multivibrator.

The output 209 of this multivibrator 208 is connected along line 211 to one input 212 of positive NAND gate 213, and the other input 214 of this NAND gate connects line 216. Accordingly connected to contact 181. NAND gate 213 generates a negative signal at output 217 to set flip-flop 219 along line 218 via input 21l.

Flip-flop 219 is a so-called ringing flip-flop and has a reset input 222 from the pulse repetition frequency circuit 30. The flip-flop 219 generates a signal at the output 223 and is transmitted along the line 224 to the input 226 of the positive NAND gate 227. The NAND gate 227 generates a negative or low signal as soon as a positive or high signal is applied to the input 226 and the input 228 connected to the contact 167 along the line 229, and the signal is connected to the line 231. Is transmitted to the input of the pulse generator 232, which is a monostable multivibrator 233, to operate the multivibrator.

The contact 204 is connected along the line 236 to the input 237 of the amplitude comparator 238 in the detector circuit 123. The output 239 of this comparator 238 is connected to flip-flop 242 along line 241. This flip-flop 242 also has a reset input 240 from the pulse repetition frequency circuit 30. The output 243 from this flip-flop 242 is connected to the input 246 of the multivibrator 233 along a line 244. Another input 247 of this multivibrator 233 is connected to the output 249 of the multivibrator 114 along line 248.

The multivibrator 233 is configured to generate a read pulse for storing the count in a storage device (not shown) as soon as the command falls at the end of the window width.

In order to facilitate the operation of the device 20, it should be noted that there is about 3.8 to 7.6 cm of water above the top of the cable 12. Also, the lower end of each of the crystal transducers 21-21 must also be wetted with water. It is a bit difficult to meet these requirements in existing installations.

Another method is to install the cylindrical device in engagement with the cable 12 on the best of the transducers. At this time, vacuum is applied to the user to draw water into the inside so that the lower part of the crystal inside the water is wetted.

As used herein, the term "inspect" or "measure" is interpreted as comparing a measurement quantity to a reference value. For example, threshold detectors 120 and 122 check whether the echo pulse is at least greater than the threshold amplitude. On the other hand, the comparator 238 compares whether the peak amplitude of the second echo pulse is greater than a predetermined value. Of course, the device 20 may be more complicated to show the actual duration and actual amplitude.

Depending on the error rate allowed during the inspection process, the device 20 may be configured not to be more complicated. For example, channel 22 may allow the peak amplitude of the second echo pulse after a period of time as a test of any recorded second pulse to automatically check the threshold of the dufils. Of course this is under the assumption that the first echo pulse with the required threshold is a valid pulse. Optionally, the apparatus 20 checks if the threshold of the two pulses is greater than a certain value, if the peak amplitude of the second echo pulse is greater than a certain value, and if the duration of the first echo pulse is greater than a certain value. It can be configured to check if it is short.

In one embodiment described herein, if the first and second echo pulses are valid, the time count between these echo pulses is recorded. The first pulse is valid if its amplitude is greater than a certain threshold and its duration is shorter than a certain value. The second pulse is effective when its peak amplitude exceeds a certain value and its duration is larger than a certain value. The effective sequence of the first and first echo pulses should appear in the window width.

The present invention may reveal the actual pulse amplitude value and duration, and may also reveal the frequency content of the echo pulse for comparison with those associated with the particular material of the jacket under test.

Since the device is for measuring the cable jacket thickness dynamically during advancing of the cable 12, a complicated structure is inevitable. Thus, unlike in the measurement of pipe wall thickness, the measurement process must take into account the lateral movement of the cable and the deformation of the jacket 13. In conventional devices, manual changes were required when the cable size or other parameters changed. However, the device of the present invention is automatically adjusted for these changes.

The logic circuit must have unique information in view of the relatively more incomplete state in the cable jacket than has been experienced in conventional vacuum tubes.

The logic elements used here, that is, the NAND gate, the NOR gate, and the bistable element, i.e., flip-flop, the monostable element, i.e., the single-ended multivibrator, have a high level or a constant level voltage of "1" and a low level or zero level voltage. The operation of the positive logic circuit showing "0" is explained. In general, in the overall signal generation method, inputs and outputs of various devices are described in terms of high level or low level.

In a positive NAND gate, a low level output is generated only when a high level input is applied to the entire input terminal. And for any other input combination, the output is always high.

In the negative NOR gate, if a low level signal is applied to any of the input terminals, a high level output is always generated. The low level output is generated only when there is no low level input.

Flip-flop means a bias table multivibrator with two steady states. The flip-flop may include a plurality of inputs for applying one input to its input stage and switching from one state to another. Typically, flip-flops have two output stages, but only one of them is used. The high level or "1" output produces a low output voltage level and the "0" output produces a high output voltage level when the flip-flop is in the first reset or crease state. The output voltage level is reversed when this flip-flop is set to the second state.

A single-ended multivibrator is a type of monostable multivibrator in which a single output pulse of level "1" appears with a selected duration on an input going from "0" to "1" as soon as this input is applied to "1". The delay loop refers to a multivibrator in which a delay of a certain period occurs after "1" is applied to the input terminal by an output pulse of "1" having a constant duration.

The inverter refers to a circuit that generates an output of "0" when "1" is applied to the input and conversely generates an output of "1" when "0" is applied to the input.

It should be noted that applying this signal to the reset or crere input of a conventional flip-flop will reset this flip-flop. Resetting the flip-flop causes a low level to appear at its output terminal, which first shows a high level. This reset causes the low level input to change to a high level.

The operation method of the ultrasonic measuring apparatus 20 in accordance with the principles of the present invention will be described with reference to FIGS. 4 and 5. The pulse repetition frequency circuit 30 applies a pulse to the contact 43 along the line 41 and then to the pulsing device 48 along the line 44. The optical isolator 48 then applies a triggering pulse to the triggering circuit 51.

In the triggering circuit 51, a constant voltage is applied to the control electrode 53 to operate the first SCR 54, and the first SCR 54 operates the second SCR 63 by applying an excessive anode to the cathode potential. Similarly, both SCRs 71 and 78 are operated.

The four SCRs 54, 63, 71, 78 can sustain the applied potential divided evenly by the resistors 84, 86-88. However, when the first SCR 54 is given conductive, the remaining three SCRs do not support the applied potential and are damaged as described later.

In this way, the four capacitors 92, 63, 71, and 78 connected in series are continuously operated to discharge the capacitor 92, and one voltage pulse is applied to the associated converter 21. The pulse applied to the converter 21 is a negative pulse of 200-250V in magnitude and about 60ns in duration. This pulse is applied to ground along line 98 via diode 96. By applying this pulse to the transducer 21, the pressure wave which cooperates with the cross section of the cable 21 jacketed by the transducer 21 is generated.

Immediately after the SCRs 54, 63, 71, 78 are operated, the potential of the contact 91 is low and substantially zero, while the potential of the contact 93 is about 200 to 250V. By this voltage, the capacitor 92 discharges. Capacitor 92 is selected not to discharge immediately. The capacitor 92 discharges from the diode 107 through the contact 98 and the diode 96 after a certain time. The capacitor discharges through the SCR while the capacitor has a zero potential.

Current then flows from power source 109 to recharge capacitor 92 to its original state. Current in the SCR is applied in a direction from the SCR 78 to the SCR 54. This current also falls below the current level at which the SCR is blocked at peak currents of several amperes. Note that this occurs after the trigger pulse passes and before the next trigger pulse occurs.

The receiver logic circuit 29 of FIG. 5 is adapted to generate one forward pulse when the echo pulse received by the pulser receiver 27 is within a constant amplitude range. The receiver logic circuit 29 is provided with a logic circuit for determining the outer band and the inner band with respect to the unidirectional pulse. If the amplitude of the echo pulse received by the pulser receiver 27 is greater than a certain value, this circuit will record a negative or outer band pulse.

One set of effective echo pulses received by the pulsar receiver 27 is isolated by time 2t relative to the first unidirectional pulse I as shown in FIG. 6 and occurs for about 40 to 120 microseconds after the onset of echo. The first echo pulse is generated when the pulse emitted from the associated signal converter crystal 21 touches the outward surface of the jacket 13. The second directional pulse II is generated when the non-reflective portion of the pulse emitted from the transducer crystal touches the inward surface of the jacket 13.

The amplitude of echo pulse I is a function of the acoustic impedance mismatch between the heated polystyrene jacket and the water in cooling trough 14. The amplitude of the echo pulse II is a function of the acoustic impedance mismatch between the heated polystyrene jacket and the core 11. In addition, the first echo pulse has a smaller amplitude and duration than the second echo pulse.

During the " window-width " (see also FIG. 6 (b), about 90-120 Hz), a hold-off pulse (see also FIG. 6 (d)) is generated as soon as the receiver logic circuit 29 receives the first echo pulse. do. The valid pulse (see also the sixth (e)) starts immediately after the first hold-off pulse ends. This first effective pulse is preferably generated after the amplitude of the first echo pulse has attenuated. If the receiver logic circuit 29 directs the positive output 158, then a valid first pulse is generated. Thus, at the beginning of the second echo pulse, a second hold-off pulse is generated, and the second valid pulse starts at the end of the second hold-off pulse. Unlike the first valid pulse, the second valid pulse is necessarily generated during the decay period of the second echo pulse. As a result, the portion of the circuit associated with the second valid pulse exhibits a sub-output 217 indicating that the second echo pulse is outside a certain limit of the threshold band.

When the receiver logic circuit 29 receives the negative output from the first echo signal, the receiver logic circuit does not find the second echo and therefore does not generate a read pulse during the first period.

The effective pulse also avoids fraudulent pickup of noise signals due to bubbles and the like in the water medium of the cooling trough 16. If the noise signal precedes the first echo pulse, this circuit picks up this noise signal as the first echo pulse signal and then attempts to validate the true first echo signal as the second echo signal. In this case, the receiver logic circuit 29, which has not received the expected government signal, does not generate a read pulse.

The pulse repetition frequency circuit 30 also controls the operation and interaction of the channels 22-22. To this end, the pulse repetition frequency circuit 30 generates four pulse repetition rate signals, one for each of the channels 22-22, having a period of about 1 ms. These four pulses are staggered up to about 250 Hz (see also the sixth (j)), whereby staggering of the operation sequence of the four channels occurs. As such, starting in the upper channel 22 and then down and into the left and right channels, all valid operation in the upper channel occurs within the first 250 Hz before the transition pulse associated with the lower channel occurs. .

회로에서 나온 부펄스로서 정의된

펄스가 플립-플롭(141, 169, 219, 242)각각의 고레벨 또는 "1"의 입력(142. 170, 222, 240)에인가되어, 이들 출력을 저레벨 또는 "0"레벨로 리셋트 한다.

펄스의 인가는 검사주기의 시작으로 간주된다. 또한

회로(30)는 윈도우-폭(제6(b)도 참조)인 일정시간 동안만 관련 변환기(21)의 반향 펄스를 받아들이도록 회로(29)를 제어한다. PRF회로(30)에서 나온 펄스는 멀티바이브레이터(112)의 입력(111)에 인가된다.The PRF circuit 30 regulates the circuit 29 during each cycle.

Defined as a negative pulse from the circuit

A pulse is applied to the high level or " 1 " inputs 142. 170, 222, 240 of flip-flops 141, 169, 219, 242, respectively, to reset these outputs to a low level or " 0 " level.

The application of the pulse is considered the start of the inspection cycle. Also

The circuit 30 controls the circuit 29 to receive echo pulses of the associated transducer 21 only for a period of time, which is the window-width (see also sixth (b)). The pulse from the PRF circuit 30 is applied to the input 111 of the multivibrator 112.

The multivibrator 112 causes a window delay (see also sixth (b)) for a period of time, which is applied to the reset input 165 of the flip-flop 162 to output its " 0 " 164 indicates a high level. In addition, this delay pulse is applied to the reset input 188 of the flip-flop 187 so that the high level output 197 indicates a low level and the low level output 189 indicates a high level.

The delay applied to line 113 causes the window-width pulse (see FIG. 6) in the multivibrator 114 by the trailing end of the pulse. Sow in Window Pulses "Window-Width" means the time it takes to receive an effective pulse echo from a pulse radiated onto the cable 12 by the transducers 21-21 in channel 22 and thus avoid scattering pulses. do. The end of the window pulse is considered to be the end of the test cycle. At this time, the receiver logic circuit 29 determines whether a pulse is generated to further control the measurement process according to the reception of the echo pulse.

The window pulse is transmitted at output 116 and applied to contact 118 to enable detectors 120 and 122. The detector circuit 123 has a facility for detecting the positive or negative echo pulse applied by the amplifier 106 to the input terminal 124. Note that the pair of critical amplitude detectors 120 and 122 operate only when the window signal appears at the contact 118.

The threshold amplitude detector 120 is adapted to apply a negative signal to the input 129 of the NOR gate 131 in response to applying an effective forward pulse to the input terminal 124 of the threshold detection circuit 123. On the other hand, the threshold amplitude detector 122 also applies a sub-signal to the input 133 of the NOR gate 131 in response to the effective negative echo pulse.

The threshold detection circuit 123 applies a signal to the NOR gate 131 only when the first echo pulse is at least a predetermined threshold amplitude. An echo pulse with a predetermined minimum amplitude is called the outer band and causes one of the amplitude detectors 120 or 122 to generate a negative signal. If this amplitude is smaller than the predetermined threshold amplitude, this amplitude is called the inner band, and no sub-signal appears.

When the foretylene jacket 13 is cooled, the amplitude of the echo pulses coming out of this jacket increases. The apparatus of the present invention is designed to measure the thickness and eccentricity of the jacket as close to the extruder as possible. Thus, the measurements herein are for the porietyrene material in the heated state. Detectors 120 and 122 are optionally adjusted to detect only pulses with a predetermined minimum amplitude that matches what is expected at the outward surface of the polythiene jacket 13.

The receiver logic circuit 29 then checks the first echo pulse to see if the duration of the first echo pulse is greater than a certain value. According to the experiment, the first pulse expected at the interface between the outward surface and the water of the foretylene jacket was very short in duration, for example, about 1/2 [mu] s. In comparison, the second echo pulse from the interface between the inward surface of the polythiene jacket and the core or shield layer had a duration of 1-2 ms. This is due to the polythiene properties to remove the high frequency energy and the greater reflection in the second interface. Any valid signal must be able to meet the criteria established in terms of duration and amplitude.

When the amplitude of the first echo pulse is greater than a predetermined value, the threshold detector 120 or 122 applies a signal to each input terminal 129 or 133 of the NOR gate 131. The gate 131 is then applied to the inverter 138 via a contact 136, 137 with a positive or high voltage level signal. A negative signal is then applied to flip-flop 141 via line 139 in inverter 138. As a result, the output 143 of the flip-flop 141 is set to a high level voltage, and a high level signal appears at the contact 144.

신호를 인가하므로서만이 크레어된다.Flip-flop 141 is next to the next measurement cycle

Only by applying a signal is it creased.

펄스는 출력(189)를 고레벨에 리셋트하고, 이에 의해 NAND게이트(193)의 입력(192)에 정 신호가 나타난다. 이에 의해 NAND게이트(193)에서 측정 싸이클의 시각을 의미하는 부출력펄스를 발생하고 카운터(32)에서 카운팅을 시각한다.The high voltage level signal at the contact 144 is applied as an input to the input terminal 196 of the NAND gate 193. As shown in FIG. 5, the delay applied to the input 188 of the flip-flop 187.

The pulse resets the output 189 to a high level, whereby a positive signal appears at the input 192 of the NAND gate 193. As a result, the NAND gate 193 generates a negative output pulse that represents the time of the measurement cycle, and counts the counter 32.

펄스를 인가하는 이유는 설명할 가치가 있다. 만약 플립-플롭(141)의 출력(143)이 고레벨이며, 플립-플롭(187)의 입력(188)과 플립-플롭(141)의 입력(142)에

펄스가 인가되면, 플립-플롭(187)은 플립-플롭(141) 보다 더 빨리 응답할 것이다. 이때 NAND게이트(193)의 두 입력(196, 192)에는 정신호가 나타난다. 이에의해 NAND게이트(193)에는 지속시간이 짧은 출력의 부펄스가 나타날 것이다. 그러나 플립-플롭(141)이 리셋트될때는, 출력(143)은 출력(196)에 저레벨을 나타내는 저레벨이며, 이에 의해 NAND게이트(193)의 펄스 출력이 중단되고 발진기 펄스 카운트가 중단된다.Delay on input 188

The reason for applying the pulse is worth explaining. If the output 143 of the flip-flop 141 is at a high level, the input 188 of the flip-flop 187 and the input 142 of the flip-flop 141 are high.

If a pulse is applied, the flip-flop 187 will respond faster than the flip-flop 141. At this time, a positive signal appears at two inputs 196 and 192 of the NAND gate 193. As a result, the NAND gate 193 will show a negative pulse of a short duration output. However, when flip-flop 141 is reset, output 143 is a low level indicating a low level at output 196, thereby stopping the pulse output of NAND gate 193 and stopping the oscillator pulse count.

펄스를 플립-플롭(187)의 입력(188)에 인가한다. 이에 의해 출력(189)의 리셋트부가 고레벨로 지연되어, 플립-플롭(141)의 출력(143)이 최소한 부분적으로 유효한 임계 펄스I에 의해 리셋트될 때까지 NAND게이트(193)의 입력(192)에 고레벨이 인가된다.To avoid this, delay

A pulse is applied to the input 188 of the flip-flop 187. As a result, the reset portion of the output 189 is delayed to a high level so that the input 192 of the NAND gate 193 until the output 143 of the flip-flop 141 is reset by at least partially valid threshold pulse I. High level is applied.

The high level appearing at contact 114 indicates a first echo signal that is at least partially valid. To prove this assumption, a kind of check is started to determine if the duration is about 50ns and a time interval or gap occurs even when there is no signal. To this end, the high level signal is applied to the input 146 of the first hold-off pulse multivibrator 147 by the high level at the contact 144. The signal at the contact 144 indicates the presence of an effective echo pulse as long as its amplitude maintains the relationship determined by either of the threshold detectors 120 or 122.

Applying a signal to the contact 144 causes a delay or holdoff pulse (see also sixth (d)) in the hold-off multivibrator 147 to cause the first pulse to have a valid duration (eg For example, 1/2 있는) qualified as an effective first echo pulse) is determined. The holdoff pulse multivibrator 147 is for generating a holdoff pulse having a duration of 1/2 ms. After 1/2 ms, a pulse of about 500 ns (see also sixth (e)) is generated by the effective pulse multivibrator 149 by the rear end of the hold-off pulse.

During this time, a high level appears at the input 153 of the NAND gate 154 by this pulse, enabling the NAND gate to operate. If the duration of the echo pulse is longer than the hold off pulse, a high level is applied to the input 157 of the NAND gate 154 via the line 156 at the contact 136. As a result, a positive signal is applied to two inputs of the NAND gate, and a low level signal is displayed at the output 158.

If an echo pulse still appears indicating that no valid echo pulse I has been received because of excessive duration, measuring the signal is stopped unless this signal is stored.

펄스에 의해 고레벨로 리셋트 또는 크레어된다. 만일 NAND게이트가 작동하여 반향 펄스의 지속 기간이 500ns 이상인 저레벨이 출력(158)에 나타난다면, 플립-플롭(162)는 셋트되어 그 출력(164)에 저레벨이 나타난다. 출력(164)에서의 저레벨은 접점(167)에도 나타나고 플립-플롭(169)의 소위 "D"입력(168)에도 나타난다.The output 164 of the flip-flop 162 is delayed as applied to the input 163.

It is reset or cleared to a high level by a pulse. If the NAND gate is activated and a low level with an echo pulse duration of at least 500 ns appears at output 158, flip-flop 162 is set and a low level appears at its output 164. The low level at output 164 also appears at contact 167 and also at the so-called “D” input 168 of flip-flop 169.

When the clock input or " C " input 171 occurs at the leading end of the effective pulse generated by the multivibrator 149, if the " d " input of the flip-flop 169 is low level, the output 174 has a low level. Appears. This is consistent with the absence of a gap, ie the first echo pulse is invalid. If output 174 indicates a low level, NAND gate 178 is not operational and output 174 remains at a low level. The flip-flop 169 is then about to be reset by the PRF pulse. However, because the output 174 is already low level, the output remains low level.

On the other hand, if the echo pulse disappears after the hold off pulse (representing a valid first echo pulse), no high level appears at the input 157 of the NAND gate 154. NAND gate 154 is not activated and does not set flip-flop 162, and a high level at output 164 appears at the "D" input of flip-flop 169. Since the "D" input is at a high level when clock "C" appears at the input 171, the output 174 is at a high level, and a high level appears at the input 177 of the gate 178 to operate this gate. When the pulse resets flip-flop 169 and causes the low level to appear at the output, output 174 remains high until the next operating cycle.

If a high level appears at the output 177 of the gate 178, the first echo pulse is valid for time and duration. This causes circuit 29 to find the second echo pulse.

The high level appearing at contact 167 causes the high level to appear at input 228 of NAND gate 227 to operate this gate. The operation of the NAND gate 227 operates the gate to generate a read pulse at the NAND gate when the received second pulse is valid, so that the count is stored in the counter 32.

When the second echo pulse is received by the input 124 of the circuit 29, one of the threshold detectors 120 or 122 operates as described above to cause the NAND gate to generate a high level signal at its output 134. do. As a result, a high level signal is applied to the input 182 of the NAND gate 178 which is already operated via the contact 181 via the line 139 to operate the NAND gate.

This flip-flop is set so that the low level at the output 183 due in part to the operation of the NAND gate 178 (partly due to the reception of the second echo pulse) appears at the input 186 of the flip-flop 187. This is the condition that allows the receiver logic circuit 29 to see the second echo pulse, which also means the end of the counting cycle (see Figure 6). The low level signal, i.e., the sub-signal at 189, appears at the input 192 of the NAND gate 193, which puts the NAND gate in an inactive state and stops the production of the low signal at the output. The count of the oscillator output by 6 (h) is also stopped.

In the remaining cycles, the validity of the second echo signal, in which the count is transferred to a buffer (not shown), is determined. The validity determination procedure is used for the second echo pulse similarly to the one used for the first echo pulse. Note that the duration of the second echo pulse is 1 / 2-2 ms. Examining the Second Pulse This portion of the receiver logic circuit 29 is configured to add a 1 ms delay. Once the pulse has been checked, and yet there is still a critical amplitude, the pulse is stored.

The setting of flip-flop 187 makes the low level signal at output 197 high and applies along line 198. The pulse rising end from flip-flop 187 causes exclusion 2 hold off pulse generator 201 to generate one pulse having a duration of approximately 1.0 ms.

When a holdoff delay pulse is generated in the multivibrator 201, a signal is sent from the contact 204 via line 236 to the input 237 of the threshold detector 238 to activate the detector. The positive amplitude of the second pulse is checked by the threshold detector 238 to check if the amplitude of the second echo pulse exceeds a predetermined value that is much larger than the initial threshold. As shown in FIG. 5, the exit detector 238 only checks the forward signal. However, according to the present invention, another threshold detector for checking the negative signal may be included in the circuit 123.

If the maximum threshold amplitude is exceeded, detector 238 applies a low level signal to input of flip-flop 242 along line 241 to set this flip-flop and cause the high level signal to appear at output 243. . The high level at the output 243 is applied along the line 244 to the input 246 of the multivibrator 233 to operate this multivibrator.

The rear end of the pulse generated by the multivibrator 201 appears in the multivibrator 208, and the second pulse effective multivibrator 208 generates about 500 ns of effective pulses (see also the sixth (g)). At the output 209 of the second effective pulse multivibrator 208, a high level signal is applied to the input 212 of the NAND gate 213 along the line 211.

In addition, as shown in FIG. 5, when the positive or negative threshold is exceeded during the duration of the effective pulse, a signal is applied from the contact 137 to the contact 181 along the line 139 and the next line. Along 216 is applied to the input 214 of the NAND gate 213 as a high level signal. Threshold checking of the second echo pulse is necessary to check for virtual defects.

The high level signal is applied to the input 214 from one of the threshold detectors 120 or 122 indicating the presence of the second echo pulse, and from the multivibrator 208 to the input 212, then to the low level at the output 217. A signal appears to set flip-flop 219. The setting of flip-flop 219 causes a high level signal to appear at input 226 of NAND gate 227 which is already operable via line 224.

The low-level signal is applied to the one-end multivibrator 233 that operates the NAND gate 227 and then generates a lead pulse and is already operable by amplitude effective via the line 231.

The generation of the low level pulse applied to the multivibrator 233 by the NAND gate 227 indicates that the duration of the first pulse is shorter than 1 ms, which is a gap appearing in the second echo pulse and the second echo pulse. It indicates that the duration of is 1 / 2-2㎲.

As soon as the window pulse is interrupted, a decision is made whether to generate a read pulse. The interruption of the window pulse is instructed by a signal applied by the one-ended monostable multivibrator to the input 247 of the multivibrator 233 via the line 248. The multivibrator 233 already operable by the input 246 from the multivibrator 242 has an input applied to it from the NAND gate 227. The multivibrator 233 is activated to instruct the counter 32 to record the pulse width from the NAND gate 193 upon receipt of the trailing end of the window pulse at the input 247.

The oscillator 34 generates a pulse. These pulses are counted by the counter 32, which starts at the initial point of the first hold-off pulse and ends at the initial point of the second echo pulse, the difference between which is the measurement of the time interval between the echo pulses. This counter 32 includes three decimal counters, namely 100, 10 and one counters with four bit storage associated with each decimal counter. If a suitable pulse is generated for echo pulses I and II in positive-negative order, one read pulse is generated at the end of the "window-width" of the window-pulse. The count stored in the register of the counter 32 thereby transitions from the counting portion of the counter to the memory portion of the counter. The count from this memory is then applied to a digital-to-analog converter 36 to provide a continuous voltage output that indicates the jacket thickness at this digital-to-analog converter.

Note that the count already stored in the buffer does not change until the next valid read pulse is generated to transition the associated count to this buffer. The circuit 25 holds the preceding count in the buffer until the next valid count is received, and discards this count when the invalid count is received.

The digital-to-analog converter also includes a luminous body that is driven for about 800 ms between successive read pulses. Four of these emitters are associated with the device 20. If acceptable measurements have been made, the emitters will remain on for about 80-90% of the time. On the other hand, when this signal is lost, there is no light emission indicating the position of the crystal 21 or the defect of the channel.

The light emitter for each channel 22-22 is used as a warning to warn the operator when an abnormality occurs in the operation of the apparatus. This light emitter remains on when the lead pulse stream continues to generate. Under such conditions, an 80% basic cycle signal drives this illuminant. When the cable oscillates towards the crystal, the light emitter tends to flicker as if excitation does not appear when the crystal does not see the cable.

The device 20 is characterized by recording the thickness of the jacket 13 under inspection. In general, a jacket 13-13 of at least 20 mils thick is no problem at all. However, problems arise when the jacket thickness is smaller than this. The receiver logic circuit 29 is adapted to adjust 20 mils per second for the first holdoff pulse generation and the effective portion.

For example, the holdoff pulse multivibrator 147 must generate a holdoff pulse for a time that at least matches the decay time of the associated crystal 21. Crystals with a low decay time of 0.5µs can be selected.

The effective pulse generator 149 must then generate one pulse for at least one cycle of the associated crystal 21 signal. The crystal 21 generates signals in five cycles, and this pulse width is lowered to about 200 ns.

Once these two durations are determined, the continuous operation of the device 20 depends on the second echo pulse that is not received until the end of the first hold off and validity determination process for the first echo. These requirements are not met if the device 20 is used to measure a jacket of 20 mils thick or less.

Of course, when using the plastic insulating material commonly used for thin-walled jackets, the time between the echo pulses is longer because the speed of the ultrasonic pressure waves in this particular material is relatively slow. In heated polystyrene, the expected rate is 20 mils / dl. Therefore, making a jacket of 20 mils or less from polyetherene causes the problem of overlapping echo pulses. However, for the same thickness of heated polyvinylchloride, the overlapping problem of echoes can be avoided even if the length of time between echoes I and II is thinner.

Of course, it is also within the scope of the present invention to measure the thickness between the first surface and a second surface opposite to the first surface and isolated from each other with several different layers of material therebetween. In addition, instead of measuring cable jacket thickness, the apparatus of the present invention may be used to measure the thickness of the continuous cross section of a curved layer surrounding the continuous cross section of a solid core or a hollow core, such as in a tube.

In some cable constructions, the inner jacket is engaged with a core shell or other material in which the second echo pulse in each of the associated directional pulses extends. However, it will be remembered that the generation of the off signal by the NAND gate 193 occurs immediately upon receipt of the initial fraction of the second echo pulse for thickness measurement. Again, of course, the pig amplitude and duration characteristics of the second echo pulse will be satisfied. On the other hand, when the core shell is isolated on the inward surface of the jacket, the air acts as an open switch without transmission. In addition, inspecting and using the second echo pulse in the thickness measurement does no harm.

What has been described above is merely to illustrate the principles of the present invention, and those skilled in the art may make modifications within the principles or scope of the present invention.

Claims (1)

As described in the text and illustrated in the figures, for transmitting ultrasonic pulses to an object, receiving a first echo pulse reflected from one surface of the object and then receiving an associated second echo pulse from the opposite surface of the object. A device comprising an apparatus and devices for limiting a first direction pulse based on amplitude and a second direction pulse associated therewith (120, 122 in FIG. 5), in response to receiving a calibration first echo pulse. A device (29, FIG. 3, 238, 187, 193, 147 of FIG. 3, FIG. 3) that initiates a test that generates an on signal and confirms the test characteristics of the first echo pulse; An apparatus (178, 227 of FIG. 5) initiating a test to verify test characteristics of said associated calibration second echo pulse in response to receipt of the calibration second echo pulse, and the first echo pulse on one side of the object. When received, A device (187, 201, 238, 208) for generating an off signal at a time interval between an on-signal and an off-signal in relation to the elapsed time between receiving an associated second echo pulse on the opposite side of the object; A device 169 that is conditionally configured to generate a control pulse in response to the first echo pulse, and a condition of the device in response to confirmation of the associated second echo pulse to generate a control pulse. A device for ultrasonically measuring a continuous cross section of a linear object characterized by devices (227, 233).

Images