JPH04335106A - Thickness measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a measuring apparatus which is hard to receive temperature change and disturbance such as radiation noises and the like from the outside and uses the radiowave at an intermediate frequency by amplifying the output of an intermediate- frequency receiver with a high-input resistance amplifier circuit which does not have a resonance point. CONSTITUTION:The output of an oscillating circuit 11 is amplified with a power amplifier circuit 12. The radiowave at an intermediate frequency is outputted from a transmitting electrode 13. The output is transmitted through a material to be measured 3 and attenuated. The radiowave at the intermediate frequency is received with a receiving electrode 14. The transmitting electrode 13, the receiving electrode 14, a high-input resistance amplifier circuit 16, which amplifies the output of the receiving electrode 14 and does not have a resonance point, and a detecting circuit 18 are placed in a detecting part 1. Therefore, the output is stabilized without the effect of temperature. The weak signal outputted from the receiving electrode is immediately inputted into the high-input resistance amplifier circuit 16. Therefore, the radiation noises from the outside are hard to receive. The pass line of the material to be measured 3 is suppressed by providing a guide plate 4 whose relative interval can be adjusted in parallel with the transmitting electrode 13 and the receiving electrode 14. Thus, the thickness can be accurately measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thickness measuring device that measures the thickness of an object using intermediate frequency radio waves, with an object to be measured interposed between a transmitter and a receiver.

0002

2. Description of the Related Art Methods for measuring the thickness of paper, rubber sheets, plastic sheets, etc. while they are in motion include methods that use ultrasonic waves or high frequencies. Japanese Unexamined Patent Publication No. 11604/1983 discloses a technique for measuring using high frequencies. FIG. 8 shows a block diagram of this device, and the sensor section 2 consists of a transmitter 201 and a receiver 202 placed opposite each other with the object to be measured 3 in between.
00, an oscillation circuit 101 that generates a high frequency, a power amplification circuit 102, a resonant circuit 103 that resonates with the output of the receiver 202 and extracts the output, a voltage amplification circuit 104 that amplifies the resonant output, and a signal from this amplified output. A detection circuit 105 that separates and extracts the components, a voltage amplification circuit 106 that amplifies this detection output, and compares this amplified output with a reference value of a reference setting circuit 107 to output the thickness of the object to be measured 3 or its increase or decrease. a display circuit 109 that displays the output of the comparison circuit 108; and an output circuit 110 that outputs the output of the comparison circuit 108 to the outside.
A coaxial cable 300 connects the controller section 100 and the sensor section 200.

0003

[Problems to be Solved by the Invention] In the above configuration, the output of the receiver 202 is connected to the resonant circuit 1 via the coaxial cable.
03, which is input to the subsequent amplifier circuit 1.
Inserted for consistency with 04. In a resonant circuit using a coil, the center frequency of resonance changes due to temperature changes, so the output is not constant. In addition, the sensor section 20
The weak received wave from the receiver 202 of 0 is sent to the coaxial cable 3.
00 to the controller unit 100, it is susceptible to radiation noise from the outside.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a thickness measuring device using intermediate frequency radio waves that is less susceptible to disturbances such as temperature changes and external radiation noise. do.

[0005]

[Means for Solving the Problems] In order to achieve the above object, an object to be measured is interposed between an intermediate frequency transmitter and an intermediate frequency receiver, and the thickness of the object to be measured and its variation are determined by the output of the intermediate frequency receiver. In this thickness measuring device, the output of an intermediate frequency receiver is amplified by a high input resistance amplifier circuit that does not have a resonance point.

[0006] In addition, in a thickness measuring device that interposes an object to be measured between an intermediate frequency transmitter and an intermediate frequency receiver and measures the thickness of the object to be measured and its variation from the output of the intermediate frequency receiver, the intermediate frequency transmitter The transmitter side consists of a transmitting circuit, a power amplifier circuit that amplifies the output of this transmitting circuit, and a transmitting electrode that transmits intermediate frequency radio waves from the output of this power amplifier circuit, and the intermediate frequency receiver side consists of an intermediate frequency radio wave. It consists of a receiving electrode that receives the signal, a high-input resistance amplification circuit with no resonance point that amplifies the output of this receiving electrode, and a detection circuit that voltage-amplifies and detects the output of this high-input resistance amplification circuit. Consists of a detection section that integrates an intermediate frequency transmission side and an intermediate frequency reception side, and a controller section that compares the output of this detection section with a reference value to detect the thickness of the object to be measured or a change in the thickness. This is what I did.

[0007] Further, a measuring object guide plate is provided around the transmitting electrode and the receiving electrode in parallel to each electrode surface and whose relative spacing can be adjusted.

Furthermore, two guide rods are arranged on the transmitting electrode side and the receiving electrode side of the object to be measured, respectively, parallel to the object to be measured and perpendicular to the direction of movement of the object, with both electrodes in between. However, the distance between the guide rod on the transmitting electrode side and the guide rod on the receiving electrode side can be adjusted.

[0009] Furthermore, the transmitting electrode and the receiving electrode are housed in a transmitting casing or a receiving casing each having a convex curved surface on the side of the object to be measured, and the convex curved surfaces of the transmitting casing and the receiving casing are faced and a covered surface is placed between them. The transmitter case and the receiver case can be placed diagonally with respect to the object to be measured by sandwiching the object to be measured.

0010

[Operation] By inputting the output of the intermediate frequency receiver to a high input resistance amplifier circuit having no resonance point and amplifying it, a stable output that does not change with temperature can be obtained.

[0011] Furthermore, since a high input resistance amplifier circuit and a detection circuit having no resonance points are included in the detection section to amplify the outputs of the transmitting electrode, receiving electrode, and receiving electrode, the output is stable regardless of temperature, and Since the weak signal output from the receiving electrode is immediately input to the high input resistance amplifier circuit, the structure is not easily affected by external radiation noise.

By providing two guide plates parallel to the transmitting electrode and the receiving electrode, the relative spacing of which can be adjusted, variations in the path line of the object to be measured can be suppressed to enable accurate thickness measurement. Furthermore, since the relative spacing can be adjusted, it becomes easy to set the object to be measured. Further, the same effect can be obtained by using two rods instead of one guide plate.

The transmitter electrode and the receiver electrode are housed in a transmitter housing and a receiver housing, respectively, each having a convex curved surface on the side to be measured. By sandwiching the transmitter and receiver housings so that they can be placed diagonally with respect to the object to be measured, the convex curved surfaces of both casings suppress the path line fluctuations of the object to be measured, making it easier to use guide plates, etc. It becomes unnecessary.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. The present embodiment is roughly composed of a detecting section 1 and a controller section 2. A measured object 3 is inserted into the detecting section 1, and its thickness and thickness variations are measured. Further, the detection unit 1 is provided with a guide plate 4 for suppressing path line fluctuations of the object to be measured 3.

The detection section 1 is composed of the following circuits. 11
12 is an oscillation circuit that oscillates a sine wave or a rectangular wave having a constant frequency and amplitude, 12 is a power amplification circuit that amplifies the output of this oscillation circuit 11, and 13 is a power amplification circuit that amplifies the output of this oscillation circuit 11.
This is a transmitting electrode that transmits intermediate frequency radio waves to the object to be measured 3 using the output of the . Here, the intermediate frequency is 300 KHz
This refers to 3MHz FM waves. In the example, 500 KH
Around z was used. 14 is a receiving electrode that receives intermediate frequency radio waves from the transmitting electrode 13 via the object to be measured 3;
The transmitting electrode 13 and the receiving electrode 14 have a flat plate shape and are disposed facing each other with a predetermined interval. The receiving electrode 14 is connected to a load resistor 15 and a high input resistance amplifier circuit 16, and the wiring between them is kept as short as possible (for example, about several cm), and the value of the load resistor 15 is set to a high value (several 10 to 100 cm).
(about kiloohms). The high input resistance amplifier circuit 16 is a circuit having high input impedance and low output impedance, and is composed of an operational amplifier or the like.

High input resistance amplifier circuit 1 with voltage amplifier circuit 17
6 is amplified, a detection circuit 18 separates the attenuated signal due to the object under test 3 inputted at the receiving electrode 14, and a low-pass filter circuit 19 removes high frequency components.

The controller section 2 includes a comparison circuit 21 that compares the output of the low-pass filter circuit 19 with a reference voltage, and a display circuit 22 that displays the results of the comparison circuit 21.
It is composed of an output circuit 23 that outputs a processing instruction based on the output result of the comparison circuit 21 to the outside.

Next, the operation will be explained. Oscillation circuit 11
The output is amplified by the power amplifying circuit 12, an intermediate frequency radio wave is output from the transmitting electrode 13, and the intermediate frequency radio wave transmitted through the object to be measured 3 and attenuated is received by the receiving electrode 14. By setting the distance between the receiving electrode 14 and the high input resistance amplifier circuit 16 to be about several cm, and using a high value for the load resistor 15, a high S/N ratio can be obtained and a high output voltage can be obtained. The load resistor 15 is provided to match the high input resistance amplifier circuit 16 having high input impedance and low output impedance, and enables efficient voltage transmission. Further, since the wiring between the receiving electrode 14, the load resistor 15, and the high input resistance amplifier circuit 16 is short, disturbances are less mixed in, and the S/N ratio is improved. In addition, since the high input resistance amplifier circuit 16 is composed of an operational amplifier or the like, if a matching circuit using a coil or the like is used in this part, when the ambient temperature changes, the inductance of the coil will change and the resonance point will change. Although the output voltage changes due to the deviation, since the high input resistance amplifier circuit 16 does not utilize resonance, the output voltage is stable against temperature changes.

The object to be measured 3 has a transmitting electrode 13 and a receiving electrode 14.
A portion of the intermediate frequency radio waves transmitted from the transmitting electrode 13 is absorbed by moisture etc. in the object to be measured 3, and the remainder reaches the receiving electrode 14. As the thickness of the object to be measured 3 increases (the number of objects increases), the amount of radio waves absorbed by the object to be measured 3 increases, so the radio waves reaching the receiving electrode 14 become weaker and the output voltage of the high input resistance amplifier circuit 16 decreases. (amplitude decreases).

The output of the high input resistance amplifier circuit 16 is input to the controller section 2 as an analog signal through a voltage amplifier circuit 17, a detection circuit 18, and a low-pass filter circuit 19. By arranging the detection section 1 up to the low-pass filter circuit 19 in an integrated housing, even if the controller section 2 is placed at a remote location, compared to a method in which the output of the receiving electrode 14 is directly input to the controller section 2. Since the voltage level can be increased and transmission can be performed with low impedance, it is less susceptible to external induced noise.

The output from the low-pass filter circuit 19 is input to a comparison circuit 21. The comparison circuit 21 uses the input voltage when the number of objects 3 to be measured is normal as a reference, and detects changes in the input voltage when the number of objects 3 to be measured increases or decreases.
The display circuit 22 and output circuit 23 connected to the output side are driven. The display circuit 22 informs the operator of an increase or decrease in the number of objects 3 to be measured, and the output circuit 23 provides a contact output necessary for stopping the device processing the objects 3 when the number of objects 3 increases or decreases.

FIG. 2 is a diagram showing output waveforms of each circuit in FIG. 1. The symbols a to g on the left side of FIG. 2 indicate the positions of a to g on the output side of each circuit in FIG. A is the output waveform of the oscillation circuit 11 and is a rectangular oscillation wave, and b is a power amplified waveform of a and has the same waveform. c is the output waveform of the high input resistance amplifier circuit 16. In the waveform, the left side shows the case where there is no object to be measured 3, the center part shows the case where there is one object to be measured 3 and this is taken as the reference number, and the right side shows the case where there are two objects to be measured. d is a waveform obtained by voltage amplifying c, and e is an output of the detection circuit 18. f indicates a waveform obtained by removing high frequency components from e using a low-pass filter. This makes it possible to grasp the state in which the number of objects 3 to be measured changes from zero to one to two. g is a signal indicating that one sheet is normal and zero or two sheets are abnormal; when abnormal, an ON signal is output to the display circuit 22 and output circuit 23, and when normal, no signal is output.

FIG. 3 is a diagram showing the relationship between the number of objects to be measured 3 and the output voltage of the low-pass filter circuit 19 (corresponding to f in FIG. 2). As shown in the figure, as the number of objects 3 to be measured increases, the output voltage decreases. As the number of objects 3 to be measured increases, the voltage increase/decrease per object becomes smaller. Further, if a conductive object is inserted as the object to be measured 3, the output becomes 0.

Next, a guide plate for guiding the object to be measured 3 to a predetermined position between the transmitting electrode 13 and the receiving electrode 14 will be explained. The object to be measured 3 is a continuous strip of paper, plastic sheet, rubber sheet, etc. that runs continuously between the transmitting and receiving electrodes 13 and 14. In such a case, the object to be measured 3
If the voltage runs undulating between the electrodes 13 and 14, the output voltage of the receiving electrode 14 may fluctuate even if there is no change in the thickness of the object to be measured 3, making the operation unstable. Errors also occur, so a guide plate is provided to suppress this waviness.

FIG. 4 is a diagram showing changes in the output voltage of the detection section 1 when the object to be measured 3 undergoes wave fluctuation (path line fluctuation). In (a), the horizontal axis shows the transmitting electrode 13 and the receiving electrode 1.
4, and the output voltage of the low-pass filter (f in FIG. 2) is plotted on the vertical axis, and (b) is an explanatory diagram of x. As shown in (a), when the object to be measured 3 is located at the center of both electrodes, the output voltage is minimum, and increases as the object deviates from the electrodes.

FIG. 5 is a diagram showing the guide plate, with (a) showing the external appearance and (b) showing a sectional view. The guide plate 4 consists of two plates, each of which has a movement mechanism in a direction perpendicular to the surface of the object 3 to be measured. This moving mechanism narrows the interval to the extent that movement of the object 3 in the plane cannot be prevented, and restricts movement of the object 3 in the direction perpendicular to the plane. Note that holes are made in the guide plate 4 at positions facing the transmitting electrodes 13 and receiving electrodes 14 so as not to impede the passage of radio waves.

Note that instead of the guide plate 4, four guide rods 5 are arranged parallel to the surface of the object to be measured 3 and perpendicular to the direction of movement of the object to be measured 3, and two guide rods are placed in the direction of the object to be measured 3. Two electrodes are provided on the upper side and before and after the transmitting electrode 13 (or receiving electrode 14), and two are provided below the object to be measured 3 and before and after the receiving electrode 14 (or transmitting electrode 13), so that the distance between the upper and lower sides can be adjusted. You may also do so. Figure 6 shows this state, with the four guide rods 5 (b)
Place it as shown.

FIG. 7 shows a diagram in which casings of the detecting section 1 are provided separately on the transmitting electrode side and the receiving electrode side, and these two casings are used to suppress wave fluctuations in the object 3 to be measured. (a) shows the external appearance, and (b) shows a cross-sectional view. Transmitting electrode 13, receiving electrode 1
4 are placed in semi-cylindrical transmitting electrode housings 6 and receiving electrode housings 7, respectively, and are placed with their semi-cylindrical surfaces facing each other and spaced apart at a constant interval. Next, as shown in FIG. 7, when each of the casings 6 and 7 is tilted at a certain angle, each semi-cylindrical surface prevents the object to be measured 3 from undulating and functions similarly to a guide plate.

[0029]

As is clear from the above description, the present invention prevents measurement errors due to temperature changes by amplifying the output of the receiving electrode with a high input resistance amplifier circuit that does not have a resonance point. By connecting the high input resistance amplifier circuit and the high input resistance amplifier circuit with short wiring and storing them in an integrated housing, measurement errors due to external disturbances are prevented. In addition, a guide plate or the like is provided to prevent the object to be measured from waving.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing output waveforms of each circuit shown in FIG. 1;

FIG. 3 is a diagram showing the relationship between the number of objects to be measured and the output voltage of the detection section.

FIG. 4 is a diagram showing changes in output voltage when the object to be measured moves in the direction of the transmitting and receiving electrodes.

FIG. 5 is a diagram showing a configuration in which a guide plate is attached.

FIG. 6 is a diagram showing a configuration in which a guide rod is attached.

FIG. 7 is a diagram illustrating a configuration in which the receiving and transmitting electrode storage housing prevents wavering of the object to be measured.

FIG. 8 is a block diagram showing the configuration of a conventional high frequency thickness measuring device.

[Explanation of symbols]

1 Detection part 2 Controller part 3 Object to be measured 4 Guide plate 5 Guide rod 6 Transmission electrode housing 7 Receiving electrode housing 11 Oscillation circuit 12 Power amplifier circuit 13 Transmitting electrode 14 Receiving electrode 15 Load resistance 16 High input resistance amplifier circuit 17 Voltage amplification circuit 18 Detection circuit 19 Low pass filter 21 Comparison circuit 22 Display circuit 23 Output circuit

Claims (5)

[Claims] Claim 1: In a thickness measuring device that measures the thickness of the object to be measured and its fluctuations from the output of the intermediate frequency receiver by interposing the object to be measured between the intermediate frequency transmitter and the intermediate frequency receiver, the intermediate frequency receiver A thickness measuring device characterized in that the output of the device is amplified by a high input resistance amplifier circuit having no resonance point. 2. In a thickness measuring device that interposes an object to be measured between an intermediate frequency transmitter and an intermediate frequency receiver and measures the thickness of the object to be measured and its variation from the output of the intermediate frequency receiver, the intermediate frequency transmitter The transmitter side consists of a transmitting circuit, a power amplifier circuit that amplifies the output of this transmitting circuit, and a transmitting electrode that transmits intermediate frequency radio waves from the output of this power amplifier circuit, and the intermediate frequency receiver side consists of a transmitting circuit that transmits intermediate frequency radio waves. It consists of a receiver electrode that receives data, a high input resistance amplifier circuit that has no resonance point that amplifies the output of this receiving electrode, and a detection circuit that voltage amplifies and detects the output of this high input resistance amplifier circuit. a detection unit that integrally constitutes an intermediate frequency transmitting side and an intermediate frequency receiving side;
A thickness measuring device comprising a controller section that compares the output of the detection section with a reference value to detect the thickness of the object to be measured or a change in the thickness. 3. The thickness measuring device according to claim 2, further comprising a measuring object guide plate provided around the transmitting electrode and the receiving electrode in parallel with each electrode surface and whose relative spacing can be adjusted. . 4. Two guide rods are arranged on the transmitting electrode side and the receiving electrode side of the object to be measured, respectively, parallel to the object to be measured and perpendicular to its traveling direction, with both electrodes in between. 3. The thickness measuring device according to claim 2, wherein the distance between the guide rod on the transmitting electrode side and the guide rod on the receiving electrode side is adjustable. 5. The transmitting electrode and the receiving electrode are housed in a transmitting casing or a receiving casing each having a convex curved surface on the side of the object to be measured, and the convex curved surfaces of the transmitting casing and the receiving casing face each other, and the convex curved surface of the receiving casing is placed between them. 3. The thickness measuring device according to claim 2, wherein the transmitting casing and the receiving casing can be placed diagonally with respect to the object to be measured.