JP2007003317A - Probe type step profiler for surface shape measurement and automatic calibration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for calibration of force to be performed automatically in a short time after changing the probe for the probe type step profiler and a probe type step profiler provided with the automatic calibration function. <P>SOLUTION: The method obtains the relationship between the current flowing through the coil of the needle pressure generation device and the needle pressure of the probe, from this relationship, the fluctuation of the needle pressure of the probe is automatically calibrated. In the probe type step profiler provided with automatic calibration function is provided with a computer means for automatically calibrating the fluctuation of the needle pressure from the previously obtained relationship between the current flowing through the coil of the needle pressure generation device and the needle pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stylus profilometer for measuring the surface shape of a sample and an automatic calibration method thereof.

  In the present specification, the term “surface shape of the sample” is meant to include the concept of the step, film thickness, and surface roughness of the sample.

  An example of a stylus type step meter according to the prior art is shown in FIG. 8 of the accompanying drawings. In FIG. 8, A is attached to one end of a support C which is swingably attached to a fulcrum B by a probe, and a displacement sensor D for detecting the vertical displacement of the probe A is provided adjacent to the one end. It has been. The displacement sensor D is composed of a differential transformer that generates an electrical signal in accordance with the vertical displacement of the probe A. On the other hand, a needle pressure generator E that applies a needle pressure to the probe A is provided at the other end of the support C. The needle pressure generator E includes a coil F and a core G of a high permeability material arranged at a position shifted in the axial direction from the center of the coil F, and is generated according to the magnitude of the current flowing through the coil F. The probe A is configured to be pressed against the sample by a force that pulls the core G of the high permeability material into the center of the coil F. Then, by scanning the sample or the detection system of FIG. 8, the probe A traces the surface of the sample, and finely rotates around the fixed fulcrum B according to the surface shape. And the surface shape and level difference of the sample are measured.

  Also, the tip of the two styluses are brought into contact with both sides of the measurement sample with the measurement sample sandwiched between them, and the difference in the movement distance of the stylus from the case where the tips of the two styluses are in direct contact with each other is measured. A stylus type film thickness measurement technique for measuring a film thickness is conventionally known (see Patent Document 1).

Furthermore, a stylus body that contacts the object to be measured is provided at the end of the arm that can swing around the bearing, and the position of the arm that is generated by the contact between the stylus body and the object to be measured is detected. A shape measuring device configured to obtain a displacement amount is also known (see Patent Document 2). In addition, the arm is supported rotatably on the frame via an elastic hinge, a stylus is provided at one end of the arm, a movable plate is provided at the other end of the arm, and the movable plate can be moved between two parallel plates. In addition, a shape measuring device is also known in which a bridge electrode is formed by these plates, and the balance to the bridge is lost by the rotation of the movable arm, thereby measuring the displacement of the tip of the stylus ( (See Patent Document 3).
JP-A-9-229663 Japanese Patent No. 3401444 Special table hei 8-502357

By the way, in this type of step gauge, the force at the probe, that is, the needle pressure is measured as follows. When the current flowing through the coil of the needle pressure generator is 0, the needle is raised upward due to the weight balance of the movable part on the fulcrum and is stationary against the stopper. When an appropriate current is passed through the coil of the needle pressure generator, the probe is lowered by the generated force. The needle pressure can be obtained by measuring the time change of the needle tip displacement z at that time and obtaining the acceleration by second-order differentiation with respect to time. Relationship of the force and acceleration, in the region of, for example, several 10 mgf is measure the force F ₁ at the needle tip in the electronic balance, etc., to obtain the relationship between the coil current I ₁ and the force F ₁ at that time, the coil current I _If the acceleration α ₁ at ₁ is measured, the relationship between F ₁ and α ₁ is obtained. Since force and acceleration are in a proportional relationship, a proportionality constant is obtained, and a force value corresponding to the value can be calculated from an arbitrary acceleration value.

The needle pressure of the probe is F, the z-direction position of the probe tip is z, the moment of inertia around the fulcrum is I, the distance from the fulcrum to the tip is r, and the equation of motion around the fulcrum has a small rotation angle The following equation is obtained by transforming as

F = I / r ² d ² z / dt ²

That is, it can be regarded as the motion of the mass point of mass I / r ^{2 in} the field where the force F is applied. In other words, the proportionality constant of the aforementioned means I / r ^2.

  In addition, there is an atomic force microscope that can measure with weak force, but the measurable range of displacement is usually as narrow as several μm, and the control system is also displaced so that the deflection of the cantilever, that is, the force becomes constant. Since the feedback is applied, the measurement and control system becomes complicated and expensive.

  In this type of level gauge, the tip is replaced when the tip of the probe is worn. However, since the weight balance of the movable portion on the fulcrum is lost, the relationship between the coil current and the force needs to be obtained again. The range of force generally required for surface shape measurement is about 0.05 mgf to 20 mgf, and it is necessary to accurately and stably produce a weak force of 0.05 mgf. That is, in the weak force region of about 0.05 mgf, it is necessary to re-determine the relationship between the coil current and the force with an error sufficiently smaller than 0.05 mgf. In addition, it is necessary to recalculate the relationship even in a wide range of about 0.05 mgf to 20 mgf. However, doing this requires a great deal of time and effort. In addition, it takes time to write the calculated relationship again in the computer program.

  The stylus profilometer to which the present invention is directed is capable of measuring displacements in the range of several hundreds of μm to several mm, and has the advantage that the sensor, measurement, and control system have a very simple structure and configuration and are inexpensive. Moreover, the displacement resolution is as high as 0.3 nm with a measurement time constant of 3 ms.

  Accordingly, the present invention provides a method for automatically and accurately performing a force calibration performed after replacing a probe in a stylus profilometer and a stylus profilometer having the automatic calibration function. It is an object.

In order to achieve the above object, according to the first aspect of the present invention, a probe is attached to one end of a support that is swingably attached to a fulcrum, and the probe is perpendicular to the one end. A magnetic core of a displacement sensor that detects displacement is attached, and a magnetic core of a needle pressure generator that applies needle pressure to the probe is attached to the other end of the support, and the surface shape of the sample captured by the probe is supported. In the automatic calibration method of the stylus type step meter that measures with a displacement sensor by the rotational movement around the fulcrum of
It is characterized in that the relationship between the current flowing through the coil of the needle pressure generator and the probe needle pressure is obtained, and the change in the probe needle pressure is automatically calibrated based on the obtained relationship.

  In the method of the present invention, the shift of the center of gravity of the movable portion including the probe on the fulcrum, the magnetic core of the displacement sensor, and the magnetic core of the needle pressure generator caused by the loss of weight balance due to the replacement of the probe is automatically performed. Can be calibrated.

In one embodiment of the method of the present invention, when the probe needle pressure y is the vertical axis, the current x flowing through the coil of the needle pressure generator is the horizontal axis, and a, b, and c are constants, the current flows through the coil. The relationship between the current x and the probe needle pressure y is expressed by the function y = ax ² + bx + c, and x = x ₀ where y = ₀ is obtained, and c is obtained from y = ax ₀ ² + bx ₀ + c = 0. The shift of the center of gravity of the movable part on the fulcrum can be automatically calibrated by shifting the function in the vertical axis direction.

 In the method of the present invention, the probe needle pressure y is determined by measuring the time variation of the probe displacement with a displacement sensor, obtaining the acceleration by second-order differentiation of the displacement with respect to time, and calculating the moment of inertia and fulcrum around the fulcrum. And the distance between the probe and the probe.

The automatic calibration of the displacement of the center of gravity of the movable part on the fulcrum is performed by a computer device, and the current x flowing through the coil is roughly varied to obtain the current x flowing through the coil where the probe needle pressure y is near 0. The current x flowing through the coil in the vicinity is finely varied to determine the relationship between the current x flowing through the coil and the probe needle pressure y, and the relationship between the current x flowing through the coil in a narrow range and the probe needle pressure y is linear. Approximate with an equation, find a linear equation that fits with the least squares method, solve for x by setting y = 0 in the obtained linear equation, set x _0, and set the point (x ₀ , 0) on the graph to the function y = ax ^It may consist of determining the value of c so that a quadratic curve represented by ² + bx + c passes and recording this value of c in a computer.

According to a second aspect of the present invention, the probe is movable in a direction perpendicular to the surface of the sample to be measured and is relatively movable along the surface of the sample to be measured;
A stylus pressure generator that applies stylus pressure in a direction perpendicular to the surface of the sample to be measured to the probe;
A displacement sensor for detecting the vertical displacement of the probe;
A control means for obtaining a relationship between a current passed through the coil of the needle pressure generator and the probe needle pressure, and automatically calibrating a change in the probe needle pressure based on the obtained relationship;
A stylus profilometer for measuring a surface shape of a sample is provided.

The control means uses the probe needle pressure y as the vertical axis, the current x flowing through the coil of the needle pressure generator as the horizontal axis, and a, b, and c as constants. The relationship with the needle pressure y is expressed by the function y = ax ² + bx + c. When measuring the surface shape, after setting the probe needle pressure y ₁ , the measurement is started and the value of c is automatically read. the x = x ₁ comprising ₁ determined from the function, may be configured to control the current flowing to output x ₁ to the coil of the needle pressure generator.

  As described above, according to the method of the first aspect of the present invention, the relationship between the current flowing through the coil of the needle pressure generator and the needle pressure of the probe is obtained, and the needle pressure of the probe is obtained based on the obtained relationship. Since the change of the needle is automatically calibrated, the effect of changing the needle can be considered as a constant change of force, and it is not necessary to reexamine the relationship between the coil current and the force over a wide range. It is possible to accurately calibrate the probe needle pressure with respect to the accompanying loss of weight balance in a short time.

  In the method of the first invention of the present invention, the relational expression in the weak force area where high accuracy is required is derived by deriving the relational expression between the coil current and the force from the measurement result in the small force area. As a result, the needle pressure can be calibrated with high accuracy.

 In the stylus profilometer according to the second aspect of the present invention, the relationship between the current flowing through the coil of the needle pressure generator and the needle pressure of the probe is obtained, and the needle pressure of the probe is calculated based on the obtained relationship. By providing a control means for automatically calibrating the changes, the use of the calibration results in the calibration and surface profile measurement is made automatically by the computer device, thus saving time and effort.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows an embodiment of a stylus step meter to which the present invention is applied. Reference numeral 1 denotes a fixed support base, on which a swing support bar 3 is provided via a fulcrum 2, and this swing support is shown. A probe 4 is attached to one end of the rod 3 downward. The tip of the probe 4 is made of diamond, and the radius of the tip is generally 2.5 μm, but it may be larger or smaller. The other end of the swinging support bar 3 is provided with a needle pressure generating device 5 that generates a force that applies a vertically downward force to the probe 4, that is, a force that applies a needle pressure. This needle pressure generating device 5 is composed of an actuator 5a composed of a magnetic core extending upward from the other end of the swing support rod 3 and a coil 5b having a hole for receiving the actuator 5a. A displacement sensor 6 for detecting the displacement of the probe 4 in the vertical direction is provided on the fulcrum 2 side of the probe 4 at one end of the swing support rod 3. The displacement sensor 6 has one end fixed to the swing support rod 3. It is composed of a differential transformer including a measuring element 6a formed of a magnetic core and a coil 6b that receives the other end of the measuring element 6a, that is, a free end.

  In FIG. 1, reference numeral 7 denotes a sample holder, on which a scanning stage 8 is provided so as to be movable at a predetermined operation speed with respect to the probe 4, and a sample 9 to be measured is attached on the scanning stage 8. obtain.

  The displacement sensor 6 for detecting the vertical displacement of the needle pressure generating device 5 and the probe 4 is connected to the control means 10, which controls the operation of the needle pressure generating device 5 based on the output signal from the detection means 6. Configured to control. In the apparatus shown in FIG. 1, the sample 9 can be fixed and the probe side can be scanned.

  FIG. 2 shows an example of the configuration of the control means 10 shown in FIG. In FIG. 2, reference numeral 11 denotes a computer apparatus. This computer apparatus 11 is connected to a needle pressure generator power source 13 connected to a coil 5 b in the needle pressure generator 5 and a drive device for the scanning stage 8 via an analog input / output board 12. 14 respectively. Further, the computer device 11 is connected to a detection circuit 16 having a digital lock-in amplifier and an oscillator via a general-purpose interface board 15, and the detection circuit 16 is a primary coil and a secondary coil of a differential transformer constituting the displacement sensor 6. It is connected to the.

In the present invention, the relationship between the needle pressure y of the probe 4 and the coil current x flowing through the coil 5b in the needle pressure generator 5 can be expressed as y = ax ² + bx + c (a, b, and c are constants), The calibration of the weight imbalance caused by the probe replacement results in recalculating the constant c. For this purpose, the value x ₀ of x at which y = 0 is obtained, and then c is obtained and stored in the recording device of the computer device 11. This calibration operation is automatically performed by the computer device 11.

The calibration operation will be described in detail below. As described above, the relationship between the needle pressure y of the probe 4 and the coil current x flowing through the coil 5b in the needle pressure generator 5 can be expressed by a quadratic function of y = ax ² + bx + c. In FIG. 3, the circles are measured data, the solid line is a fitted quadratic equation, and the downward force is expressed as negative. The constants a, b and c are in this example −2058.3, 14.924 and 0.23332, respectively, so the quadratic expression is y = −2058.3x ² + 14.924x + 0.233332. The correlation coefficient indicating the degree of coincidence between the measurement data and the fitting function is as high as 0.99997, which indicates a very good fit.

The influence of the replacement of the probe is that the position of the center of gravity of the movable portion on the fulcrum 2, that is, the probe 4, the measuring element 6 a of the displacement sensor 6, and the operating element 5 a of the needle pressure generator 5 changes. The movement of the center of gravity in the z direction from the structure of the movable part has little influence on the relationship between the current x and the force y flowing through the coil 5b of the needle pressure generator 5. A difference between the x component of the fulcrum 2 and the center of gravity is a problem. The difference determines the force (the direction in which the needle is raised) when the coil current is zero. In other words, the influence of the deviation of the center of gravity position is an increase or decrease of a constant force, and is to change the value of c in the above-described function y = ax ² + bx + c. Therefore, the value of c may be obtained accurately.

In particular, since accuracy is required in a small force region, the coil current x ₀ flowing through the coil 5b of the needle pressure generator 5 where the force y is _zero is obtained, and y = ax ₀ ² + bx ₀ + c = 0 to c You can ask for. Coil current x ₀ flowing through the coil 5b of the needle pressure generator 5 is automatically obtained as follows by programming the computer unit 11.
1. The coil current x flowing through the coil 5b of the needle pressure generator 5 is roughly swung from a small value to obtain x where the force y changes from positive to negative.
2. Finely shake x in a narrow range near x to obtain the relationship between x and y.
3. Its relationship to a narrow range can be approximated by a linear equation to determine the coil current x ₀ flowing from the expression to the coil 5b of the needle pressure generator 5.
The value of c thus obtained is stored in the recording device of the computer device 11.

Hereinafter, the procedure of force calibration will be described with reference to FIG.
Measuring displacement at intervals of 10 μs to 1 ms using a data memory of a measuring instrument or a buffer of an analog voltage input board for a personal computer, and performing a moving average process for every 10 points, etc., actually displacement measurement with noise Acceleration and force can be obtained with high accuracy even from values.

Such measurement is performed with various coil currents, and for example, the relationship between the coil current and the force as shown in FIG. 3 is obtained. The relationship between the coil current x and the force y can be fitted by a quadratic expression y = ax ² + bx + c. That is, a, b, and c are obtained so as to fit. These values are stored in the computer device 11.

When measuring the surface shape with a stylus profilometer without replacing the probe 4, the value and relational expression are used to calculate the coil current x for obtaining it from the specified force y. Output. That is, the computer device 11 reads the constant c in the relationship y = ax ² + bx + c between the coil current x and the force y flowing in the coil 5b of the needle pressure generator 5 stored in the file of the computer device 11 from the file and designates it. A coil current x flowing through the coil 5b of the needle pressure generator 5 is calculated from the force y. Based on the calculated coil current x, the computer device 11 outputs a control signal to the needle pressure generator power source 13 via the analog input / output board 12. As a result, a current set in the coil 5b of the needle pressure generating device 5 is supplied from the power source 13 for the needle pressure generating device, the coil 5b is excited, the needle pressure is applied to the probe 4, and the surface shape is measured.

On the other hand, when the probe 4 is replaced and the surface shape is measured with a stylus profilometer, the constant c changed in the above relational expression is obtained again. In order to re-determine the constant c, the coil current x = x ₀ that flows through the coil 5b of the needle pressure generator 5 where the force y becomes ₀ is precisely obtained in the region where the force y is small. That is, c is obtained from y = ax ₀ ² + bx ₀ + c = 0. The coil current x ₀ flowing through the coil 5b of the needle pressure generator 5 is automatically obtained as described above by programming the computer device 11, and c is obtained from y = ax ₀ ² + bx ₀ + c = 0. . The constant c obtained in this way is rewritten in the file of the computer device 11, and calibration suitable for the replaced probe is automatically performed. In this state, when measuring the surface shape, if the force y ₁ is specified on the monitor of the computer device 11, the value of c is read and the coil voltage x ₁ satisfying y ₁ = ax ₁ ² + bx ₁ + c is calculated. Then, a control signal is output from the computer device 11 to the power source 13 for the needle pressure generator via the analog input / output board 12. As a result, a current set in the coil 5b of the needle pressure generating device 5 is supplied from the power source 13 for the needle pressure generating device, the coil 5b is excited, an appropriate needle pressure is applied to the probe 4, and the surface shape is measured. Is called.

Examples of the present invention will be illustrated below.
In FIG. 5, the example which measured the time change of the displacement of the probe tip of the probe 4 is shown. This is a time change of the needle tip displacement z after the coil current flowing through the coil 5b of the needle pressure generating device 5 at time 0 is changed from 0 to 2.36 × 10 ⁻² A. There is a lower limit stopper at z = −1.3 mm. After the tip of the probe 4 reaches the lower limit stopper, it bounces and repeats vibration.

  In FIG. 6, since the range of z used in the displacement sensor 6 is -0.15 to +0.15 mm, the speed v = dz / dt during that time (time is 400 to 450 ms) is shown. Note that the time origin in FIG. 5 has no meaning, and z = + 0.15 mm at the left end of the horizontal axis and z = −0.15 mm at the right end. The acceleration α = dv / dt is obtained from the slope of this graph. From this acceleration α, the force at the tip of the probe 4, that is, the needle pressure, is calculated using the known moment of inertia and the distance between the fulcrum and the probe as described above. In this example, the force is about 0.27. mgf.

After the probe 4 is replaced, the constants a and b do not change and c changes in the relational expression y = ax ² + bx + c, so only this c is obtained again. For this purpose, the coil current x ₀ at which the force y becomes 0 is obtained as described above. This in order to find the values _{x 0,} while increasing the coil current x for example, 0.4 × ^{10 -2} A distance from 0A, continue to measure the force y. Then you can find x ₁ whose force changes from positive to negative.

In order to give high accuracy values _{x 0,} waving x at around, for example, 0.4 × ^{10 -3} A distance x _1, to measure the force y. An example of the result is indicated by a circle in FIG. The stylus pressure generator power supply 13 uses a voltage noise of less than 0.01 V, indicating that a weak force of 0.05 mgf can be accurately measured and output. A solid line in FIG. 7 is obtained by fitting these measurement data with a linear equation using the least square method. The primary formula is x ₀ to x across the x-axis. Error of corresponding force from 7 it can be seen that determined is sufficiently small x ₀ than 0.05Mgf.

C is obtained by solving at the ^{_{y = ax 0 2 + bx 0}} + c = 0 with the _{x 0.} The constant c thus obtained is rewritten and saved in the file in which the value is written in the hard disk of the computer 11. When measuring the surface shape, if the force y ₁ is specified on the monitor of the computer apparatus 11, the value of c is read from the file, and the coil voltage x ₁ satisfying y ₁ = ax ₁ ² + bx1 + c is calculated and output.

  By the way, in the above-described embodiment, the current is controlled by the current, but it can also be controlled by the voltage instead. In this case, the resistance value of the coil is about 50Ω. I want. In the present invention, it is not necessary to be a function of current.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic partial cross-sectional view of a configuration of a stylus profilometer embodying the present invention. The block diagram which shows an example of a structure of the control means in FIG. The graph which illustrates the relationship between the coil current which flows into the coil of a needle pressure generator, and force. The flow diagram which shows the procedure of the calibration of the force by a computer apparatus. The graph which illustrates the time change of the probe tip displacement of a probe. The graph which illustrates the time change of the probe tip speed of a probe. The graph which shows the example of a measurement of force in the vicinity of force 0. Schematic which shows the prior art example of a probe type level difference meter.

Explanation of symbols

1: Fixed support base 2: Supporting point 3: Swing support rod 4: Probe 5: Needle pressure generator 6: Displacement sensor 7: Sample holder 8: Scan stage 9: Sample to be measured 10: Control means 11: Computer device 12 : Analog I / O board 13: Power supply for needle pressure generator 14: Drive device 15: General-purpose interface board 16: Detection circuit

Claims (8)

A probe is attached to one end of a support that is swingably attached to a fulcrum, a magnetic core of a displacement sensor that detects the vertical displacement of the probe is attached adjacent to this end, and the other end of the support is attached to the other end of the support. A magnetic core of a needle pressure generator that applies needle pressure to the probe is attached, and automatic calibration of a stylus profilometer that measures the surface shape of the sample captured by the probe with a displacement sensor by rotational movement around the support point In the method
A stylus profilometer that obtains the relationship between the current flowing through the coil of the needle pressure generator and the probe needle pressure, and automatically calibrates the change in the probe needle pressure based on the obtained relationship. Automatic calibration method.   It is characterized by automatically calibrating the deviation of the center of gravity of the movable part including the probe on the fulcrum caused by the loss of weight balance due to the replacement of the probe, the magnetic core of the displacement sensor, and the magnetic core of the needle pressure generator. The method for automatically calibrating a stylus profilometer according to claim 1. When the probe needle pressure y is the vertical axis, the current x flowing through the coil of the needle pressure generator is the horizontal axis, and a, b, and c are constants, the current x flowing through the coil and the probe needle pressure y Is expressed by a function y = ax ² + bx + c, and x = x ₀ where y = ₀ is obtained, c is obtained from y = ax ₀ ² + bx ₀ + c = 0, and the function is shifted in the vertical axis direction. The automatic calibration method of the stylus type step meter according to claim 1 or 2, wherein the displacement of the center of gravity of the movable part on the fulcrum is automatically calibrated.  The probe needle pressure y is measured by measuring the time variation of the probe displacement with a displacement sensor, and the displacement is second-order differentiated with respect to time to obtain the acceleration. The moment of inertia around the fulcrum and the distance between the fulcrum and the probe The method for automatically calibrating a stylus step meter according to claim 1, wherein the method is obtained using a distance.   2. The method of automatically calibrating a stylus profilometer according to claim 1, wherein automatic calibration of the shift of the center of gravity of the movable portion on the fulcrum is performed by a computer device. The current x flowing through the coil is roughly varied to obtain the current x flowing through the coil at which the probe needle pressure y is near 0, and the current x flowing through the coil is finely varied in the vicinity of the current x flowing through the coil. The relationship between the needle pressure y and the current x flowing through the coil in a narrow range and the probe needle pressure y are approximated by a linear equation, and a linear equation that is suitable for the least squares method is obtained. X is solved by setting y = 0 to x _0, and the value of c is obtained so that a quadratic curve represented by the function y = ax ² + bx + c passes through the point (x ₀ , 0) on the graph. 5. A method for automatically calibrating a stylus profilometer according to claim 4, comprising recording the value of c in a computer device. A probe that is movable in a direction perpendicular to the surface of the sample to be measured and is relatively movable along the surface of the sample to be measured;
A stylus pressure generator that applies a stylus pressure in a direction perpendicular to the surface of the sample to be measured to the probe;
A displacement sensor for detecting the vertical displacement of the probe;
A control means for obtaining a relationship between a current flowing through the coil of the needle pressure generator and the probe needle pressure and automatically calibrating a change in the probe needle pressure based on the obtained relationship;
A stylus profilometer for measuring the surface shape of a sample, characterized by comprising: The control means uses the probe needle pressure y as the vertical axis, the current x flowing through the coil of the needle pressure generator as the horizontal axis, and a, b, and c as constants. The relationship with the needle pressure y is expressed by the function y = ax ² + bx + c. When measuring the surface shape, after setting the probe needle pressure y ₁ , the measurement is started and the value of c is automatically read. the x = x ₁ comprising ₁ determined from the function, stylus according to claim 7, characterized in that it is configured to control the current flowing to output x ₁ to the coil of the needle pressure generator Type step gauge.

Images