JP2008139100A - Position measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position measuring system which reduces operation errors and can carry out a measurement precisely and speedily. <P>SOLUTION: The system is equipped with a moving-iron type transformer 001 including a moving iron, an excitation winding L0 for exciting the moving iron and an output winding L1, and a measuring device 500 including: an oscillator 002 for generating an excitation signal which excites the excitation winding of the moving-iron type transformer; an A/D converter 003 for applying an A/D conversion to the excitation signal; a Fourier-transform section 005 for applying a Fourier transform to an output of the A/D converter; an amplitude calculating section 007 for calculating an amplitude of the Fourier transformed excitation signal; an A/D converter 004 for applying an A/D conversion to an output signal generated in the output winding; a Fourier-transform section 006 for applying a Fourier transform to an output of the A/D converter; an amplitude calculating section 008 for calculating an amplitude of the Fourier transformed output signal; a dividing section 009 for calculating a ratio of an output of the amplitude calculating section which calculates the amplitude of the Fourier-transformed excitation signal, to an output of the amplitude calculating section which calculates the amplitude of the Fourier-transformed output signal; and a position computing section 010 for computing a position of the moving iron, based on an output of the dividing section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position measurement system, and more particularly to a position measurement system that measures a position using a movable iron piece transformer.

  In power plants and the like, movable iron transformers (LVDT: linear differential transformers, resolvers, etc.) that are excellent in earthquake resistance and high temperature resistance environment are widely used as sensors for detecting valve positions and the like.

  Sensors used under adverse conditions such as power plants do not exist as a substitute for moving iron transformers due to environmental resistance problems as described above, and have conventionally been used as indispensable devices in power plants. ing.

  Since the movable iron transformer detects the transition of the movable iron piece by directly converting the mechanical displacement of the movable iron piece into an electrical signal, the position measuring unit connected to the movable iron piece transformer is an analog signal from the movable iron piece transformer. It consists of an analog circuit that directly handles However, the position measuring unit configured with an analog circuit increases errors due to aging of electronic components that configure the circuit.

By the way, in recent years, A / D converters have been increased in speed and DSP (Digital Signal Processor) technology has been developed, so that digital signals can be sequentially calculated. For this reason, it has become possible to solve the above-mentioned various limitations due to analog control by using digital signal processing technology. In addition, in a position measuring device connected to a movable iron piece transformer, a highly accurate, high speed, and highly reliable position measuring device to which a digital signal processing technique is applied is required. An example of such a measuring device is shown in Patent Document 1, for example.
JP 2001-41703 A

  The movable iron piece transformer is a transformer that excites with an AC voltage having a constant amplitude and frequency and outputs an AC voltage with an amplitude corresponding to the displacement of the target object. The problems of the measuring device using this transformer are listed as follows.

(1) [Response speed] The control of the movable iron piece transformer is a method in which the output AC voltage of the transformer is AC / DC converted by a rectifier and a smoothing circuit, and position information is derived from the DC voltage value which is the conversion result. It is used. On the other hand, the control cycle in the plant control tends to be shortened, and when the above-described AC / DC conversion by the analog circuit is adopted, the response speed is lowered because several cycles are required for the smoothing.

(2) [Cost] In plant control, a method of preparing a plurality of movable iron piece transformers and forming a multiplex system is often used. In such a case, controlling each of the plurality of movable iron piece transformers using a dedicated measuring device is disadvantageous in terms of cost. For this reason, it is desired to control a plurality of movable iron piece transformers with a single measuring device.

(3) [Frequency] When a plurality of movable iron transformers are arranged in the plant and controlled, if each movable iron transformer is excited at the same frequency, resonance or resonance occurs, resulting in an error in the measurement result. . For this reason, it is desirable that the movable iron piece transformers are excited at different frequencies. For this purpose, it is desirable that the excitation frequency of the movable iron piece transformer can be made variable.

(4) [Maintenance] The measuring device that controls the movable iron transformer absorbs the inherent characteristics of the movable iron transformer by adjusting the combination of the movable iron transformer and the measuring device. Can be implemented. When analog measurement is used as a basis, it is necessary to directly adjust components and the like in the measurement device, and resetting is required when the measurement device is replaced. It should be noted that the movable iron piece transformer and the measuring device can be adjusted in combination only when the plant is stopped during periodic inspection or the like. That is, the replacement of the measuring device cannot be performed when the plant is operating, and the reliability of the entire plant is reduced.

(5) [Aging and temperature change] The excitation output accuracy (0-point drift, amplitude) of the excitation output of the measuring device changes due to aging or temperature change. For this reason, an error occurs in the position information as compared with the initial state when the measuring apparatus is installed, and the reliability is impaired. In addition, when the plant is shut down during periodic inspections and the like, it is necessary to readjust the deteriorated part due to secular change and the like, and maintainability is lacking.

(6) [Calculation error] When the excitation frequency is variable as shown in the above (3), the frequency of the excitation signal of the variable movable iron transformer and the fundamental frequency of Fourier calculation are inconsistent, and the calculation error peculiar to the Fourier transform is appear.

  The present invention has been made in view of these problems, and provides a position measurement system that can reduce calculation errors and perform measurement with high accuracy and high speed.

  In order to solve the above problems, the present invention employs the following means.

  Movable iron piece, movable iron piece transformer having an excitation winding and an output winding for exciting the movable iron piece, an oscillator for generating an excitation signal for exciting the excitation winding of the movable iron piece transformer, and the excitation signal as A / D An A / D converter for conversion, a Fourier transform unit for Fourier transforming the output of the A / D converter, an amplitude value calculation unit for calculating the amplitude of the Fourier-transformed excitation signal, and an output signal generated in the output winding as A / D An A / D converter for D conversion, a Fourier transform unit for Fourier transforming the output of the A / D converter, an amplitude value calculation unit for calculating the amplitude of the Fourier-transformed output signal, and calculating the amplitude of the Fourier-transformed excitation signal A division unit that calculates a ratio between an amplitude value calculation unit output and an amplitude value calculation unit that calculates the amplitude of the Fourier-transformed output signal; and a position calculation unit that calculates the position of the movable iron piece according to the division unit output Equipped with a measuring device.

  Since the present invention has the above-described configuration, it is possible to provide a position measurement system capable of reducing calculation errors and measuring with high accuracy and high speed.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a diagram for explaining a position measurement system using a three-wire LVDT (linear differential transformer) as a movable iron piece transformer. The movable iron piece transformer 001 includes an excitation winding L0 and an output winding L1. An output signal 011 of the oscillator 800 that excites the excitation winding L0 is supplied to the excitation winding L0 of the movable iron piece transformer 001 and the A / D converter 003 in the measuring device 500. That is, the excitation signal is fed back into the measuring device 500.

  Further, the output signal 012 of the movable iron piece transformer 001 is supplied to the A / D converter 004 in the measuring device. The output signal 012 of the movable iron piece transformer 001 is a position signal of the movable iron piece transformer, and is an AC voltage having an amplitude corresponding to the position.

  The A / D converters 003 and 004 in the measuring apparatus 500 A / D convert the excitation signal 011 supplied to the movable iron piece transformer 001 and the output signal 012 from the movable iron piece transformer 001, respectively. At this time, synchronous sampling is performed according to the frequency of the commonly used oscillator 002.

  The oscillator 002 is used in common for the excitation of the movable iron transformer 001 and the excitation of the Fourier transform unit, and the frequency (f1) of the excitation signal of the movable iron transformer and the Fourier calculation basic frequency (f2) of the Fourier transform unit are complete. (F1 = f2). Further, the sampling frequency of the A / D converter is set to f1 × N (based on the sampling theorem) when calculating one period of the excitation signal with N pieces of data.

  The excitation signal data 013 and the output signal data 014 synchronously sampled by the A / D converters 003 and 004 are subjected to Fourier calculation for each period of data of the excitation signal 011 in the Fourier transform units 005 and 006, respectively.

  At this time, as the SIN / COS table 900 used for the Fourier calculation, sine / cosine values when 360 degrees are equally divided into N are used, and the movement of the table pointer is synchronized with the sampling period. The Fourier transform units 005 and 006 and the amplitude value calculation units 007 and 008 can calculate the amplitude values 019 and 020 of the excitation signal 011 and the output signal 012.

  The amplitude values 019 and 020 of the excitation signal 011 and the output signal 012 calculated by the Fourier transform units 005 and 006 and the amplitude value calculation units 007 and 008 are divided by the division unit 009. The position calculation unit 010 calculates the position of the movable iron piece based on the division result.

  In the Fourier calculation, the amplitude calculation excluding the influence of the direct current component is possible in principle. For this reason, the influence of the zero point drift change of an excitation signal or an output signal can be excluded. Further, when an aging change or the like occurs in the amplitude value (peak value) of the excitation signal 011 of the oscillator 002, the influence can be suppressed. That is, since the output signal 012 of the movable iron piece transformer changes at the same ratio as the excitation signal 011, the influence can be compensated by performing division using the divider 009.

[Second Embodiment]
FIG. 2 is a diagram illustrating an example in which a variable frequency oscillator is used as the oscillator. Similarly to the first embodiment, the output signal 011 of the oscillator 002 for exciting the movable iron transformer 001 is supplied to the movable iron transformer 001 and the A / D converter 003 in the measuring device 500. The oscillator 002 for exciting the movable iron piece transformer 001 and the clock CLK800 in the arithmetic unit for determining the sampling frequency of the A / D converter and the fundamental frequency of the Fourier calculation are independent oscillators and oscillate at different frequencies. can do.

  When the frequency f1 of the excitation signal 011 by the oscillator 002 coincides with the fundamental frequency f2 of the Fourier transform, that is, when f1 = f2, this is equivalent to the first embodiment.

  When the frequency f1 of the excitation signal 011 and the fundamental frequency f2 of the Fourier transform do not match, the calculation result of the Fourier transform units 005 and 006 and the calculation result of the amplitude value calculation units 007 and 008 indicate the excitation frequency due to the characteristics of the Fourier calculation. An arithmetic error that fluctuates at twice the frequency occurs.

  In an actual apparatus, it is difficult to accurately match the frequency f1 of the excitation signal 011 and the fundamental frequency f2 of the Fourier transform. For this reason, the calculation error caused by the frequency mismatch between the fundamental frequency of the Fourier calculation and the frequency of the excitation signal and the output signal which are Fourier calculation targets is necessarily included.

  For example, in an apparatus that forms a multiplex system in a plant, it is often advantageous in terms of availability to make the excitation frequency variable in order to avoid the influence of resonance between movable iron transformers. In such a case, there is a demand for a technique that can perform highly accurate calculation by changing only the excitation frequency without changing the fundamental frequency of Fourier calculation.

  In the present embodiment, as a method of removing a calculation error caused by a mismatch between the fundamental frequency of the Fourier calculation and the excitation frequency, the Fourier calculation result (amplitude value) of the excitation signal 011 of the movable iron transformer and the output signal 012 of the movable iron transformer is used. (Calculation result) A method of dividing 019,020 by 009 is adopted. That is, since the frequency of the excitation signal 011 of the movable iron piece transformer and the frequency of the output signal 012 are the same, and the amplitude results 019 and 020 have the same relative error, the relative error is canceled by performing the division. Is possible. Thereby, it is possible to obtain highly accurate position information that does not include a relative error due to Fourier calculation.

[Third Embodiment]
3, 4, and 5 are diagrams for explaining processing when there is a phase difference between the excitation signal 011 and the output signal 012 of the movable iron piece transformer 001.

  A phase difference occurs between the excitation signal 011 and the output signal 012 of the movable iron transformer 001 due to the influence of the characteristics of the movable iron transformer or the cable laying conditions.

  FIG. 13 is a diagram illustrating a Fourier calculation result (amplitude value calculation result) of the excitation signal 011 and the output signal 012, and FIG. 13A is an example in the case where a phase difference exists between the excitation signal 011 and the output signal 012. FIG. 13B is a diagram showing an example where there is no phase difference between the excitation signal 011 and the output signal 012.

  As shown in the figure, a phase difference corresponding to the phase difference between the excitation signal 011 and the output signal 012 occurs in the Fourier calculation results 019 and 020 of the excitation signal 011 and the output signal 012. Therefore, an error component corresponding to the phase difference remains in the division result of the Fourier calculation results 019 and 020 of the excitation signal 011 and the output signal 012. In this embodiment, a method for removing this error component will be described.

  FIG. 3 is a diagram illustrating an example in which a phase difference detection unit 0999 that detects a phase difference between the Fourier calculation result 019 of the excitation signal 011 and the Fourier calculation result 020 of the output signal 012 is provided.

  As shown in the figure, the phase difference detection unit 0999 calculates the phase difference of each signal from the Fourier calculation result of the excitation signal 011 of the movable iron piece transformer 001 and the Fourier calculation result of the output signal 012, and according to the calculation result, For example, the phase correction is performed by feedback 888 to the phase correction unit φ that delays the excitation signal 011. By this phase correction, the phases of the excitation signal 011 and the output signal 012 of the movable iron piece transformer 001 can be matched. Thus, the error component included in the amplitude calculation results 019 and 020 can be canceled by the division unit 009.

  Thus, after performing phase correction, an accurate position calculation result can be obtained by performing division processing on the Fourier calculation result of the excitation signal and output signal of the movable iron piece transformer. Note that the configuration of the phase correction unit is not limited to the illustrated example. For example, a method of correcting SIN / COSTABLE 900, a method of correcting after Fourier calculation, or the like can be employed.

  FIG. 4 is a diagram for explaining an example in which a filter 123 is provided after the Fourier transform unit. As described above, the error component included in the calculation result of the division unit 009 has a periodicity corresponding to the phase difference between the excitation signal 011 and the output signal 012 of the movable iron piece transformer. For this reason, accurate position information can be obtained by inserting an IIR or FIR filter (smooth filter) such as a moving average filter after the division unit 009. The filter can be inserted before or after the amplitude value calculation unit. That is, the position of the filter may be any position as long as it is after the Fourier calculation.

  FIG. 5 is a diagram illustrating an example including both the phase difference detection unit 0999 illustrated in FIG. 3 and the filter 123 illustrated in FIG.

[Fourth Embodiment]
6, 7 and 8 are diagrams for explaining a position measurement system using a 4-wire LVDT (linear differential transformer). As shown in the figure, the 4-wire LVDT includes an excitation winding L0, a first output winding L1, and a second output winding L2. Here, the output of the output winding L1 and the output of the output winding L2 can be regarded as equivalent to the excitation signal 011 due to its characteristics. For this reason, the excitation signal 011 of the movable iron piece transformer fed back into the measuring device 500 is used only for monitoring, and the output signal 102 of the output winding L1 and the output signal 012 of the output winding L2 are used for actual position calculation. use. 6, 7, and 8, the phase difference detection unit 0999 performs Fourier transform on the output signal generated in the second output winding and the Fourier transform unit 005 that performs Fourier transform on the output signal of the first output winding. The moving direction of the movable iron piece of the movable iron piece transformer is determined based on the output of the Fourier transform unit 006, and the polarity of the position calculation unit output signal is determined according to the determination result. Since the processing in the 4-wire LVDT is the same as the processing in the 3-wire LVDT, the description thereof is omitted.

[Fifth Embodiment]
9, 10, and 11 are diagrams illustrating an example in which a plurality of movable iron piece transformers are connected to one measuring device. Here, a configuration in which the movable iron piece transformers 001 and 101 are processed by one arithmetic unit 600 will be described as an example.

  The excitation frequencies of the oscillator 002 and the oscillator 102 are set to different frequencies to avoid the influence of mutual resonance. That is, the movable iron piece transformers 001 and 101 are excited at different frequencies.

  One clock 800 is used as the sampling frequency of the A / D converters 003, 004, 103, 104 and the calculation timing of the Fourier transform units 005, 006, 105, 106, and the position calculation is performed by synchronizing them. . That is, after data is sampled by the A / D converter, the amplitude value is calculated by the Fourier transform unit and the amplitude value calculation unit, and the position signal is sequentially calculated by the position calculation unit.

  The sampling frequency of the A / D converter is synchronized with the clock 800 in all of the A / D converters 003, 004, 103, 104 in the measurement apparatus. The frequency at which the excitation signal or the output signal of the movable iron transformer 001, 101 is sampled may be at least twice the highest frequency among the excitation frequencies to at least a plurality of movable iron transformers. Is optional. The reason for taking more than twice the highest frequency is due to the sampling theorem. Since the process up to the position calculation of each movable iron piece transformer 001, 101 is the same as the process in the 3-wire LVDT, its description is omitted.

[Sixth Embodiment]
9 and 12 are diagrams illustrating a position measurement system including a communication device 1000 connected to the external storage device 700. FIG.

  As shown in the figure, the measuring device 500 has a communication device 1000 to which an external storage device 700 is connected. When the system is used, an adjustment operation for obtaining the characteristics of the individual movable iron transformers 001 and 101 is performed before the position measurement by the individual movable iron transformers 001 and 101 is started.

  FIG. 12 is a diagram illustrating an example of adjusting the characteristics of the movable iron piece transformer. As shown in FIG. 12, the standard characteristic H of the position and output (division result) according to the type of the movable iron transformer is written in the nonvolatile memory of the position calculation unit 010 in advance.

  The characteristic of the movable iron piece transformer 001 that is actually used is a characteristic (individual characteristic K) different from the standard characteristic in accordance with manufacturing variations or cable laying conditions. The individual characteristic K is written in the memory of the position calculation phase determination unit 010 as the respective outputs A, B, C at a fixed position of the movable iron piece of the movable iron transformer 001 at 0, 50, 100%. Next, an interpolation operation is performed based on the output (A / Aref, B / Bref, C / Cref) and standard characteristics H at these three points (movable iron piece position is 0, 50, 100%), and an individual for each position is calculated. The characteristic K is obtained. The obtained individual characteristics are stored in the nonvolatile memory of the position calculation unit 010.

  With the parameters (A / Aref, B / Bref, C / Cref) or individual characteristics 1100, 1200 obtained through the above adjustment work as “data obtained by quantifying the individual characteristics of the movable iron piece transformer”, the communication apparatus 1000 is And stored in the external storage device 700. The position calculation unit of the movable iron piece transformers 001 and 101 measures the position with reference to the individual characteristic K at the time of position calculation.

  When the measuring device 500 is replaced with a new one or the like, the “data obtained by quantifying the individual characteristics of the movable iron piece transformer” stored in the external storage device is taken into the newly replaced measuring device via the communication device 1000. . The newly replaced measuring device starts position measurement using the movable iron transformer 001, 002 based on the written “data obtained by quantifying the individual characteristics of the movable iron transformer”.

  Conventionally, when performing position measurement using a movable iron piece transformer, it is necessary to perform adjustment work to absorb individual differences in the characteristics of the movable iron piece transformer before starting the measurement. However, in the present embodiment, it is possible to take in “measured data obtained by digitizing the characteristics of the movable iron piece transformer” into the measuring device and perform position calculation based on the data. That is, readjustment work for absorbing individual differences in the characteristics of each movable iron piece transformer becomes unnecessary. In this way, readjustment to absorb the individual differences in the characteristics of the movable iron transformer is not necessary, so that it is possible to replace the measuring device without stopping the plant, thereby improving the maintenance and reliability of the device. It is out.

  In addition, here, as a parameter to be stored, the explanation has been given by taking “data obtained by quantifying the characteristics of the movable iron piece transformer” representing the position of the movable iron piece transformer (movable iron piece position) as an example. It is not limited to the information regarding the position of the iron piece transformer.

  As described above, according to the embodiment of the present invention, the movable iron piece transformer is excited using an oscillator, and the AC voltage value of the excitation signal and the output signal of the movable iron piece transformer is converted to DC without DC conversion. / D-converted to capture as a digital signal and calculate position. For this reason, the response delay accompanying DC conversion can be suppressed. Moreover, position calculation can be performed for each transformer using a plurality of movable iron piece transformers.

  Moreover, the AC voltage value which is an output signal of a movable iron piece transformer is directly digitized, and the amplitude value (crest value) of the AC voltage value is calculated by Fourier calculation. At this time, the Fourier calculation is performed on the output signal of the movable iron transformer and the excitation signal of the movable iron transformer is fed back. At this time, the amplitude value calculation unit calculates the amplitude of the excitation signal subjected to Fourier transform and the amplitude of the output signal subjected to Fourier transform, and performs a division process on these amplitude values to eliminate errors caused in the computation of Fourier transform. Can be removed.

  Further, by performing a division operation using the excitation signal and the output signal of the movable iron piece transformer, it is possible to suppress an error due to a secular change or a temperature change of the excitation signal. Moreover, a plurality of movable iron piece transformers can be arranged in the plant, and each movable iron piece transformer can be excited at a different frequency.

  In addition, even when a phase difference is generated between the excitation signal and the output signal of the movable iron piece transformer, it is possible to suppress calculation errors and to realize calculation with high accuracy and excellent high-speed response.

  In addition, by preliminarily measuring and accumulating “data obtained by digitizing the characteristics of the movable iron transformer” from the external storage device as a calculation parameter, the device is maintained without stopping the plant. And reliability can be improved.

It is a figure explaining the position measurement system using 3 wire type LVDT as a movable iron piece transformer. It is a figure explaining the example using a variable frequency oscillator as an oscillator. It is a figure explaining a process in case a phase difference exists between the excitation signal and output signal of a movable iron piece transformer. It is a figure explaining the example which provides a filter in the back | latter stage of a Fourier-transform part. It is a figure which shows the example provided with both the phase correction | amendment part and the filter. It is a figure explaining the position measurement system using 4-wire type LVDT. It is a figure explaining the position measurement system using 4-wire type LVDT. It is a figure explaining the position measurement system using 4-wire type LVDT. It is a figure explaining the position measurement system provided with the communication apparatus connected with an external storage device. It is a figure explaining the example which connects a some movable iron piece transformer to one measuring device. . It is a figure explaining the example which connects a some movable iron piece transformer to one measuring device. It is a figure explaining the adjustment example of the characteristic of a movable iron piece transformer. It is a figure which shows the Fourier calculation result (amplitude value calculation result) of an excitation signal and an output signal.

Explanation of symbols

001, 101 Movable iron transformer 002, 102 Oscillator 003, 004, 103, 104 A / D converter 005, 006, 105, 106 Fourier transform unit 007, 008, 107, 108 Amplitude value calculation unit 009, 109 Division unit 010 , 110 Position calculation phase determination unit 500 Measuring device 600 Calculator 700 External storage device 800 Clock (CLK)
900 SIN / COS table 0999 Phase difference detector 1000 Communication device 1100, 1200 Movable iron transformer parameter

Claims (9)

A movable iron piece, a movable iron piece transformer having an excitation winding and an output winding for exciting the movable iron piece;
An oscillator for generating an excitation signal for exciting the excitation winding of the movable iron piece transformer,
An A / D converter for A / D converting the excitation signal, a Fourier transform unit for Fourier transforming the output of the A / D converter, an amplitude value calculating unit for calculating the amplitude of the Fourier-transformed excitation signal,
An A / D converter for A / D converting the output signal generated in the output winding, a Fourier transform unit for Fourier transforming the A / D converter output, and an amplitude value calculating unit for calculating the amplitude of the Fourier transformed output signal ,
A division unit that calculates a ratio of an amplitude value calculation unit output that calculates the amplitude of the Fourier-transformed excitation signal and an amplitude value calculation unit that calculates the amplitude of the Fourier-transformed output signal;
And a position measuring system having a position calculating unit that calculates the position of the movable iron piece according to the output of the dividing unit. The position measuring device according to claim 1,
A position measurement system comprising a plurality of movable iron piece transformers and measurement devices, wherein the oscillation frequencies of the oscillators constituting each measurement device are different from each other. The position measurement system according to claim 1,
The position measurement system according to claim 1, wherein the oscillation frequency of the oscillator is different from a clock that determines a fundamental frequency of the Fourier calculation. The position measurement system according to claim 1,
A phase difference detection unit for detecting a phase difference between the phase of the Fourier-transformed excitation signal and a Fourier-transformed output signal, and phase correction for matching the phases of the excitation signal and the output signal in accordance with the detection output of the detection unit A position measurement system characterized by comprising a section. The position measurement system according to claim 1,
A position measurement system comprising a filter for smoothing the division unit output. The position measurement system according to claim 1,
A position measuring system, wherein a Fourier transform unit for Fourier transforming the excitation signal and a Fourier transform unit for Fourier transforming an output signal generated in the output winding each include a filter for smoothing the output of the Fourier transform unit. A movable iron piece transformer having a movable iron piece, an excitation winding for exciting the movable iron piece, and first and second output windings;
An oscillator for generating an excitation signal for exciting the excitation winding of the movable iron piece transformer,
An A / D converter for A / D converting the output signal of the first output winding, a Fourier transform unit for Fourier transforming the output of the A / D converter, and an amplitude value calculation for calculating the amplitude of the Fourier-transformed excitation signal Part,
An A / D converter for A / D converting the output signal generated in the second output winding, a Fourier transform unit for Fourier transforming the A / D converter output, and an amplitude for calculating the amplitude of the Fourier transformed output signal Value calculator,
A division unit for calculating a ratio between an amplitude value calculation unit output for calculating the amplitude of the first output signal subjected to Fourier transform and an amplitude value calculation unit for calculating the amplitude of the second output signal subjected to Fourier transform;
And a position measuring system having a position calculating unit that calculates the position of the movable iron piece according to the output of the dividing unit. A movable iron piece, a movable iron piece transformer provided with an excitation winding and an output winding for exciting the movable iron piece;
An oscillator for generating an excitation signal for exciting the excitation winding of the movable iron piece transformer,
An A / D converter for A / D converting the excitation signal, a Fourier transform unit for Fourier transforming the output of the A / D converter, an amplitude value calculating unit for calculating the amplitude of the Fourier-transformed excitation signal,
An A / D converter for A / D converting the output signal generated in the output winding, a Fourier transform unit for Fourier transforming the A / D converter output, and an amplitude value calculating unit for calculating the amplitude of the Fourier transformed output signal ,
A division unit that calculates a ratio of an amplitude value calculation unit output that calculates the amplitude of the Fourier-transformed excitation signal and an amplitude value calculation unit that calculates the amplitude of the Fourier-transformed output signal;
And a measuring device having a position calculation unit that calculates the position of the movable iron piece according to the output of the division unit,
The position calculation unit includes an internal storage unit that stores characteristic data representing a relationship between a position of the movable iron piece in the movable iron piece transformer and an output corresponding to the position, and an external storage device that stores the characteristic data, and the measurement A position measurement system for transferring characteristic data stored in an external storage device to an internal storage unit when the device is replaced. The position measurement system according to claim 7,
The movable iron piece of the movable iron transformer based on the output of the Fourier transform unit that Fourier transforms the output signal of the first output winding and the Fourier transform unit that Fourier-transforms the output signal generated in the second output winding A position measurement system comprising: a phase difference detection unit that determines a moving direction of the position calculation unit, and determining a polarity of the position calculation unit output signal according to a detection output of the phase difference detection unit.

Images