JP5717911B2 - Frequency measuring method, frequency measuring device, and oscillation type sensor - Google Patents

Description

  The present invention relates to a frequency measurement technique including a procedure for performing frequency conversion on a signal under measurement, and a sensing technique using the same.

  As a measuring instrument for measuring the frequency, for example, a reciprocal frequency counter (hereinafter referred to as a reciprocal counter) is used.

  FIG. 13A shows a conceptual diagram of a reciprocal counter. The reciprocal counter counts the number of clock pulses CLK per cycle T of the signal under measurement S. Since the count value represents the length of the period T, the frequency can be specified by calculating the reciprocal thereof.

  In the reciprocal counter, the higher the frequency, the lower the resolution because the number of counts decreases, and the lower the frequency, the longer the time required for one measurement. For this reason, it may be desired to limit the frequency measurement range to a certain finite interval in consideration of trade-offs.

  Here, the reciprocal counter has been described. Generally, as with other measuring instruments, a certain finite interval (hereinafter referred to as an appropriate interval) is used in order to guarantee appropriate measurement in which the measuring instrument can exhibit a desired performance. May be recommended for use within.

  As disclosed in Patent Documents 1 to 3, if a frequency outside the appropriate section is to be measured, a known frequency conversion may be performed on the signal under measurement prior to measurement. By selecting a frequency conversion so that the frequency after conversion belongs to the appropriate interval, measurement in the appropriate interval becomes possible, and the frequency can be calculated by performing the corresponding inverse conversion operation on the measured value.

JP 2014-9979 JP 2007-10593 JP 2009-5259 JP S57-52837

  In the techniques of Patent Documents 1 to 3, a configuration in which the frequency conversion is variable is essential in order to enable proper measurement of the frequency over a wider section than the appropriate section.

  Patent Document 4 discloses a concept in which a section in which a physical quantity to be measured can vary is shared by a plurality of measuring instruments. According to this idea, it is not necessary to make the frequency conversion variable. For example, when it is desired to extend the appropriate section to both sides, a measuring instrument that handles the proper section, a measuring instrument that handles a section lower than the proper section, and Three measuring instruments that handle the higher section than the appropriate section are required, and the configuration becomes larger.

  An object of the present invention is to provide a technique capable of expanding a section in which a frequency can be appropriately measured without using a variable frequency conversion while using a configuration that is difficult to increase in size.

  According to one aspect of the present invention, when considering (a) first to Nth extended sections (where N ≧ 2) different from a certain appropriate section, the i th frequency conversion is Is converted into a value within the appropriate interval, and the frequency of the j-th expansion interval (where i and j are any natural numbers from 1 to N where i ≠ j) is An intermediate signal is formed by performing known first to Nth frequency conversions such as conversion to values outside the appropriate interval on the signal under measurement, and the frequency component of the appropriate interval in the formed intermediate signal is formed. , A procedure for measuring the number of repetitions per known period, or a period or a time width depending on the period, and (b) from the first to Nth frequency conversions as frequency conversions forming the frequency components of the appropriate section A specified frequency conversion, the known signal being measured Using the calculation of inverse conversion of the frequency conversion specified using the result of measuring the number of repetitions per period, or the period or the time width depending on the period, and the measurement value obtained in the procedure (a), There is provided a frequency measurement method including a procedure for calculating the frequency of the signal under measurement.

  In this specification, the fact that a certain section is different from another section means that at least one of the sections has a section that does not overlap with the other section. However, the first to Nth extended sections do not overlap with the appropriate sections, and the extended sections do not overlap each other.

  Of the first to Nth frequency conversions, only the effect of the frequency conversion corresponding to the extended section to which the frequency of the signal under measurement belongs is used for measurement. Therefore, even if the frequency conversion is not variable, the kth (where k is 1) It can be measured after converting the frequency belonging to the extended interval of .about.N to the value in the appropriate interval by k-th frequency conversion.

  Thus, although the section in which the frequency can be properly measured can be expanded by the first to Nth extended sections, the frequency conversion that forms the frequency component of the appropriate section is specified, so the first It becomes possible to use a common measuring instrument for the measurement of the frequency of the Nth expansion section, and it is difficult to increase the size of the configuration.

Conceptual diagram of the frequency measuring device according to the embodiment, Conceptual diagram showing the gain of the bandpass filter, A graph of functions representing the first and second frequency transformations; A flowchart showing the processing procedure of the processor; A graph of functions representing the first and second frequency transformations; Conceptual diagram of a frequency measurement device according to another embodiment, A graph of functions representing the first and second frequency transformations; A graph of functions representing the first and second frequency transformations; A graph of functions representing the first to fourth frequency transformations; A flowchart showing the processing procedure of the processor; A flowchart showing the processing procedure of the processor; Further, a conceptual diagram of a frequency measuring device according to another embodiment, Conceptual diagram of a frequency counter as a measuring instrument, The conceptual diagram of the oscillation type pressure sensor by an Example.

  In FIG. 1, the conceptual diagram of the frequency measuring device by an Example is shown.

  The distributor 1 distributes the measured signal SA having the measured frequency fs to the heterodyne unit 2 and the switch 4. The distributor 1 can be composed of nodes, for example.

  The heterodyne device 2 includes a local oscillation signal source 21 and a mixer 22. The local signal source 21 generates a local signal having a known frequency fr. The mixer 22 multiplies the local signal and the signal to be measured SA to form an intermediate signal having a sum frequency component of frequency fs + fr and a difference frequency component of frequency | fs−fr |.

  The intermediate signal is input to a band-pass filter (hereinafter referred to as BPF) 3. The BPF 3 has a fixed pass band, but the sum frequency component fs + fr may be allowed to pass or the difference frequency component | fs−fr | may be allowed to pass depending on the value of fs.

  The switch 4 selects which of the passing signal SB that has passed through the BPF 3 and the signal to be measured SA to be input to the measuring instrument 5 according to the control from the processor 6.

  The measuring instrument 5 is composed of a reciprocal counter, and measures the period of the signal input to itself by counting the number of clock pulses per period. The count value is a measurement value of the measuring instrument 5.

  The processor 6 performs control of the switch 4 and processing for specifying the measured frequency fs by obtaining the reciprocal of the measured value of the measuring instrument 5 or the like.

  FIG. 2 schematically shows the frequency dependence of the gain of BPF3.

  As shown in FIG. 2A, the lower cutoff frequency of BPF 3 is fL, and the upper cutoff frequency is fH. The width fH-fL of the pass band P between fL and fH is equal to the frequency fr of the local oscillation signal. Therefore, when fs belongs to the section P, both the sum frequency component fs + fr and the difference frequency component | fs-fr | can be blocked by the BPF 3.

  On the other hand, the pass band P is equal to the appropriate section M in which measurement appropriate for the measuring instrument 5 can be performed. Therefore, when fs belongs to the section P (= M), if the signal to be measured SA is input to the measuring instrument 5 by the switch 4, it is possible to appropriately measure fs.

  As shown in FIG. 2 (B), even if fs is higher than the upper limit value fH of the appropriate section M, if fH + fr or less, the difference frequency component | fs-fr | passes through the BPF 3. This section H (fH <fs ≦ fH + fr) adjacent to the upper side of the appropriate section M will be referred to as an upper extended section.

  When fs belongs to the upper extended section H, fs itself is too high and cannot be properly measured by the measuring instrument 5, but can be properly measured if the difference frequency component | fs-fr |. For this purpose, the passing signal SB only needs to be input to the measuring instrument 5.

  As shown in FIG. 2C, even if fs is lower than the lower limit value fL of the appropriate section M, the sum frequency component fs + fr passes through the BPF 3 if it is equal to or greater than fL−fr. This section L (fL−fr ≦ fs <fL) adjacent to the lower side of the appropriate section M will be referred to as a lower extended section.

  When fs belongs to the lower extended section L, fs itself is too low and cannot be properly measured by the measuring instrument 5, but can be appropriately measured if the sum frequency component fs + fr. For this purpose, the passing signal SB only needs to be input to the measuring instrument 5.

  FIG. 3 shows a graph of y = fs + fr and y = | fs-fr |, that is, a dependency of the sum frequency component and the difference frequency component on the measured frequency fs, and a graph of y = fs.

  Hereinafter, the conversion of the measured frequency fs into the sum frequency component fs + fr is referred to as “upward conversion”, and the conversion into the difference frequency component | fs−fr | is referred to as “downward conversion”. The y axis shows the frequency after conversion.

  When the measured frequency fs belongs to the lower extended section L, it is converted to a value in the pass band P by upward conversion, and when it belongs to the upper extended section H, it is converted to a value in the pass band PM by downward conversion.

  Note that when the measured frequency fs belongs to the lower extended section L, it undergoes downward conversion at the same time, but the frequency after the downward conversion is out of the pass band P and blocked by the BPF 3. Further, when the measured frequency fs belongs to the upper extended section H, it undergoes upward conversion at the same time, but the frequency after the upward conversion is out of the pass band P and blocked by the BPF 3.

  Thus, only the effect of the frequency conversion corresponding to the extended section to which fs belongs is selected by the BPF 3 among the up conversion and the down conversion. Since the passing signal SB has only a single frequency component, the measuring device 5 can appropriately measure the frequency. The frequency represented by the measured value is assumed to be fB.

  However, what we want to know is the value of fs. In order to know fs from fB, it is necessary to specify which of up-conversion and down-conversion should be applied to fB. For that purpose, it suffices to specify whether fs belongs to the lower extension section L or the upper extension section H. Specifying the extended section to which fs belongs is equivalent to specifying the inverse transformation.

  The extension section is specified by measuring the signal under measurement SA. Although the frequency of the extended section cannot be measured properly, it is sufficient if it can be specified whether fs belongs to section L or H. If fs belongs to the interval L, the value is fA1 obtained by performing reverse conversion of upconversion on fB, and if it belongs to the interval H, the value is fA2 obtained by applying reverse conversion of downconversion to fB.

  FIG. 4 shows a flowchart of processing performed by the processor 6.

  First, the processor 6 controls the switch 4 so that the signal under measurement SA is input to the measuring instrument 5 (S1), and determines whether the measured value of the measuring instrument 5 represents the frequency of the appropriate section M (S2).

  When the measured value represents the frequency of the appropriate section M (S2: appropriate), the processor 6 specifies fs with the frequency (S3), outputs the specified fs value externally, and returns to S2.

  On the other hand, when the measured value represents a frequency exceeding the upper end point fH of the appropriate section M (S2: over), the processor 6 controls the switch 4 so that the passing signal SB is input to the measuring instrument 5 (S4). It is determined whether the value represents the frequency of the appropriate section M (S5).

  When the measured value represents the frequency of the appropriate section M (S5: appropriate), the processor 6 is a value obtained by performing inverse conversion of downward conversion (hereinafter referred to as reverse downward conversion), that is, an operation of adding fr to the frequency. fs is specified (S6), the value of the specified fs is externally output, and the process returns to S5.

  Here, the reverse descending conversion is performed because the measurement result of S2 is used. That is, since the result of “over” was obtained in S2 when the switch control was performed in S4, it became definite that fs belongs to the upper extended section H by obtaining the “appropriate” measurement result in S5. This is because it can be seen that fs belonging to the upper extended section H is properly measured by the measuring instrument 5 after undergoing downward conversion.

  In S5, when the frequency represented by the measured value reaches the lower end point fL of the appropriate section M (S5: under), the processor 6 returns to the start to input the signal to be measured SA to the measuring instrument 5 again. In this case, fs may return from the upper extended section H to the appropriate section M.

  When the frequency represented by the measured value reaches the upper end point fH of the appropriate section M in S5 (S5: over), the processor 6 outputs an error (S7) and returns to the start. In this case, fs may even exceed the upper extended section H.

  On the other hand, when the measured value represents a frequency lower than the lower end point fL of the appropriate section M in S2 (S2: under), the processor 6 inputs the passing signal SB to the measuring instrument 5 (S8), and the measured value is appropriate. It is determined whether the frequency of the section M is represented (S9).

  When the measured value represents the frequency of the appropriate section M (S9: appropriate), the processor 6 uses the value obtained by performing the inverse conversion of the upward conversion (hereinafter referred to as the reverse upward conversion), that is, the operation of subtracting fr to the frequency. Is identified (S10), the identified value of fs is externally output, and the process returns to S9.

  Here, the reverse ascent conversion is performed because the measurement result of S2 is used. That is, when the switch control is performed in S8, the result of “under” is obtained in S2, so that the measurement result of “appropriate” is obtained in S9, so that fs belongs to the lower extended section L. This is because it can be seen that fs belonging to the lower extended section L has been subjected to the upward conversion and measured by the measuring instrument 5.

  In S9, when the frequency represented by the measured value reaches the upper end point fH of the appropriate section M (S9: over), the processor 6 returns to the start to input the signal under measurement SA to the measuring instrument 5 again. In this case, fs may return from the lower extended section L to the appropriate section M.

  In S9, when the frequency represented by the measured value reaches the lower end point fL of the appropriate section M (S9: under), the processor 6 outputs an error (S11) and returns to the start. In this case, there is a possibility that fs does not satisfy the lower extended section L.

  According to the above example, when the passing signal SB is used for measurement, in order to specify whether the signal SB is formed by the up-conversion or the down-conversion, it is common to the measurement of the frequencies in the extended sections L and H. A measuring instrument 5 can be used. Further, since the switch 4 is used to switch between a state in which the signal under measurement SA is used for measurement and a state in which the passage signal SB is used for measurement, the common measuring instrument 5 can be used for measuring the signal under measurement SA. As a result, one measuring instrument 5 is sufficient.

  Hereinafter, a modified example of the determination of S2 in FIG. 4 will be described.

  When the frequency of the signal input to the measuring instrument 5 is out of the appropriate section M, the measuring instrument 5 is located on the upper or lower side of the appropriate section M without showing a specific measurement value. It is only necessary to show a measurement result having an information amount that can identify the

  For example, the measuring instrument 5 may output a signal indicating that the frequency has deviated from the appropriate interval M to the upper side, or a signal indicating that the frequency has deviated to the lower side. The processor 6 can determine whether S2 is “over” or “under” based on the signal. Examples of such a signal include a borrow signal and an overflow signal of a counter that constitutes the measuring instrument 5.

  Next, with reference to FIG. 5, a modified example of ascending conversion and descending conversion will be described.

  In FIG. 5, the section ML located at the lower end of the appropriate section M is referred to as the lower end section, and the section MH located at the higher end of the appropriate section M is referred to as the upper end section. To.

  In this example, the up conversion further plays a role of converting the frequency of the lower end section ML into the value of the upper end section MH, and the down conversion plays a role of converting the frequency of the upper end section MH into a value of the lower end section ML. Fulfill further. This can be realized by, for example, fH−fL> fr.

  In this example, the flow shown in FIG. 4 is applied as follows.

  In S2, when the frequency represented by the measurement value belongs to the upper end section MH, that is, when it is equal to or higher than the lower end point of the upper end section MH, it is judged as “over”, and when it belongs to the lower end section ML, “Under” is determined when it is equal to or lower than the end point on the high frequency side of the lower end section ML, and “appropriate” is determined when it belongs to the central section MM excluding the sections ML and MH of the appropriate section M.

  As a result, when fs continuously shifts from the appropriate section M to the extended section L or H, fs does not deviate from the proper section M and the switch 4 is switched afterwards, but fs changes from the proper section M. Since the switch 4 can be switched before deviating, proper measurement can be prevented from being interrupted at the boundary between the appropriate section M and the extended sections L and H.

  In addition, since a reciprocal counter is used for the measuring instrument 5, the resolution of the measurement value in the section MH can be increased by down-converting and measuring the frequency belonging to the upper end section MH, and belongs to the lower end section ML. By performing the up-conversion measurement, the time required for one measurement of the frequency belonging to the section ML can be shortened.

  In S5, when the frequency represented by the measurement value falls below the high-frequency end point of the lower end section ML, it is determined as “under”. In S9, the frequency represented by the measurement value is determined as the low-end end point of the upper end section MH. It is judged as “over” when exceeding. Thereby, even when fs returns from the extended section to the appropriate section, it is possible to prevent proper measurement from being interrupted at the boundary between the expanded section and the appropriate section.

  Although one modification has been described above, more generally, in S2, when the frequency represented by the measurement value of the measuring instrument 5 approaches the upper end point fH within the appropriate section M, “over” is indicated. Judgment is made, and when the lower end point fL is approached, it can be judged as “under”.

  Here, “approaching the end point” is, for example, repeated measurement as shown by the loop process of S 2 → S 3 → S 2 in FIG. 4, and the frequency represented by the measured value is higher than the frequency represented by the previous measured value. , Indicates that the frequency is close to the end point, and includes that the frequency reaches the end point.

  Whether or not the frequency approaches the end point can be determined by whether or not the frequency represented by the measurement value belongs to an end section from a certain boundary point to the end point as in the above example, for example, the measurement value represents Regardless of the frequency itself, it can also be determined by whether or not the amount of change from the frequency represented by the previous measurement value exceeds a certain reference value.

  That is, when the frequency represented by the measurement value changes greatly toward the end point, the frequency represented by the next measurement value is likely to exceed the appropriate section. Therefore, by performing switching control of the switch 4 in advance, it is possible to prevent proper measurement from being interrupted.

  Similarly, in S5, when the frequency represented by the measured value approaches the lower end point fL of the appropriate section M, it is determined as “under”, and in S9, the frequency represented by the measured value approaches the upper end point fH of the appropriate section M. It can be determined that it is “over”.

  Hereinafter, another modified example of the determination of S5 and S9 in FIG. 4 will be described.

  In S5 and S9, the determination of “over” or “under” can be made even when the amplitude of the passing signal SB becomes zero. This is because when fs returns to the appropriate interval M, the passing signal SB becomes zero (see FIG. 2A), when the sum frequency component falls below the appropriate interval, and the difference frequency component exceeds the appropriate interval. This is because sometimes the passing signal SB becomes zero.

  For example, in S5, “under” is also determined when the passing signal SB becomes zero while the difference frequency component approaches fL, and in S9, the passing signal SB becomes zero while the sum frequency component approaches fH. It is possible to determine that it is “over”. The fact that the passage signal SB has become zero can be detected by the processor 6 through the measurement result of the measuring instrument 5, for example.

  Thus, in a state where fs belongs to the extended section adjacent to the appropriate section, not only when fs approaches the end point on the proper section side of the extended section, but also when the end point deviates to the proper section side. The switch 4 can be controlled so that the signal under measurement SA is input to the measuring instrument 5.

  Similarly, in S5, when the passing signal SB becomes zero while the difference frequency component approaches fH, it is determined as “over”. In S9, the passing signal SB approaches zero while the sum frequency component approaches fL. When it becomes, it can be determined as “under”.

  Next, another embodiment will be described with reference to FIGS.

  FIG. 6 shows an example in which frequency conversion is realized by frequency division and multiplication. The signal under measurement SA is distributed to the frequency divider 7. The frequency divider 7 includes a distributor 71, a multiplier 72, a frequency divider 73, and an adder 74. The distributor 71 distributes the signal under measurement SA to the multiplier 72 and the frequency divider 73. The distributor 71 can be composed of nodes, for example.

  The multiplier 72 multiplies fs by n, and the frequency divider 73 multiplies fs by 1 / m. The adder 74 adds the multiplied signal and the divided signal to form an intermediate signal having a frequency-multiplied wave component of n · fs and a frequency-divided component of frequency fs / m. Here, n and m are natural numbers of 2 or more, and in this example, n = m = 2.

  FIG. 7 shows a graph of y = 2 · fs and y = fs / 2, that is, a dependency of the multiplied wave component and the divided frequency component on the measured frequency fs, and a graph of y = fs.

  Hereinafter, the conversion of the measured frequency fs into the multiplied wave component 2 · fs is referred to as multiplication conversion, and the conversion into the divided frequency component fs / 2 is referred to as frequency division conversion. The y axis shows the frequency after conversion.

  In the multiplication conversion, the frequency in the lower extension section L is converted into a value in the appropriate section M, and the frequency in the upper extension section H is converted into a value outside the proper section M. In the frequency division conversion, the frequency in the upper extended section H is converted into a value in the appropriate section M, and the frequency in the lower extended section L is converted into a value outside the proper section M.

  In this example, the width of the lower extended section L is (fH−fL) / n, and the width of the upper expanded section H is m · (fH−fL).

  In this example as well, the flow of FIG. 4 is read as “inverse increase conversion” in FIG. 4 as an inverse conversion of multiplication conversion, that is, an operation of multiplying by 1 / n, and “inverse decrease conversion” is converted into an inverse conversion of frequency division conversion. That is, it can be read and applied to the operation of multiplying by m.

  Next, a modified example of the arrangement position of the extended section will be described with reference to FIG.

  In the following, when arbitrary first and second extension sections L and H are considered, frequency conversion for converting the frequency of the first extension section L into a value in the appropriate section M is referred to as first frequency conversion. The frequency conversion for converting the frequency of the second extension section H into a value in the appropriate section M will be referred to as a second frequency conversion.

  In order to use only the effect of the frequency conversion corresponding to the extended section to which fs belongs, the first frequency conversion converts the frequency of the second extended section H to a value outside the appropriate section M, and the second frequency. For the conversion, it is necessary to convert the frequency of the first extension section L to a value outside the appropriate section M.

  Up to now, as the first frequency conversion, conversion for increasing the frequency, that is, ascending conversion or multiplication conversion is used, and as the second frequency conversion, conversion for decreasing the frequency, that is, decreasing conversion or frequency dividing conversion is used. Thereby, the 1st expansion section L was arranged in the low region from the appropriate section M, and the 2nd expansion section H was arranged in the high region from the proper section M.

  As shown in FIG. 8A, both the first and second frequency conversions are conversions that increase the frequency (in the figure, α and β are natural numbers of 2 or more). Both of H can be arranged in a lower range than the appropriate section M.

  As shown in FIG. 8B, both the first and second frequency conversions are conversions that reduce the frequency (in the figure, γ and δ are natural numbers of 2 or more), so that the extended section L And H can be arranged higher than the appropriate section M.

  Next, a modified example of the number of extended sections will be described with reference to FIG.

  In FIG. 9, by adding the third frequency transformation y = ξ · fs, as indicated by the one-dot chain line, the third extension section L2 is added, and the fourth frequency transformation y = (1 / η) · By adding fs, the fourth extended section H2 is added (in the figure, ξ and η are natural numbers of 2 or more).

  This is because an adder for adding a signal of frequency ξ · fs multiplied by ξ and an adder for adding a signal of frequency (1 / η) · fs divided by η are added to the subsequent stage of the adder 74 in FIG. It can be realized by adding. Thus, it will be understood by those skilled in the art that a desired number of extended intervals can be constructed by repeatedly using addition.

  FIG. 10 is an example of a flowchart using the configuration of FIG.

  Hereinafter, with reference to FIG. 10, a process that can be applied when fs can continuously vary from the initial value in the appropriate section M will be described. In FIG. 10, it is assumed that the repetition of measurement by the measuring instrument 5 is sufficiently fast with respect to fs fluctuation.

  First, the processor 6 inputs the signal to be measured SA to the measuring instrument 5 (S21), and determines whether the measured value represents the frequency of the appropriate section M (S22). When the measured value represents the frequency of the appropriate section M (S22: appropriate), fs is specified with the frequency (S23), and the process returns to S22.

  On the other hand, when the measurement result of the measuring instrument 5 indicates that fs has deviated from the appropriate section M (S22: under), the processor 6 inputs the passing signal SB to the measuring instrument 5 (S24), and the measurement is performed. It is determined whether the value represents the frequency of the appropriate section M (S25).

  When the measured value represents the frequency of the appropriate section M (S25: appropriate), the processor 6 specifies whether fs belongs to the extended section L1 or L2 (S27), and when it belongs to the section L1 (S27: L1), The fs is specified by the value obtained by performing the inverse transformation of the n multiplication conversion on the frequency represented by the measurement value (S28), and when belonging to the section L2 (S27: L2), the fs is identified by the value obtained by performing the inverse transformation of the ξ multiplication transformation (S29), the process returns to S25.

  In S25, if the measurement result of the measuring instrument 5 indicates that fs exceeds or approaches the upper limit value of the section L1 (S25: over), the processor 6 returns to the start. In this case, fs may return from the section L1 to the appropriate section M.

  In S25, when the measurement result of the measuring instrument 5 indicates that fs is less than or near the lower limit value of the section L2 (S25: under), the processor 6 outputs an error (S26). Return to the start. In this case, there is a possibility that fs is even lower than the section L2.

  On the other hand, when the measurement result of the measuring instrument 5 indicates that fs has deviated from the appropriate section M in S22 (S22: over), the same processing as S24 to 29 is performed (S30 to 35).

  Hereinafter, a method for specifying an extended section will be described by taking the determination of S27 as a specific example.

  At the first round of the loop processing of S25 → S27 → S28 or S29, that is, when it is first determined “appropriate” in S25, it is determined as “L1” in S27. This is because fs continuously fluctuates from the initial value in the appropriate section M. Therefore, if the measurement result “under” in S22 when the switch control is performed in S24, the measurement result in S25 is “appropriate”. , Fs to which the extended section is specified as L1.

  In the second and subsequent rounds of the loop processing, the extension section to which fs belongs is specified by the change in the measurement value of the measuring instrument 5. This point will be described with reference back to FIG.

  As shown in FIG. 9, when fs shifts from the section L1 to L2, the frequency represented by the measurement value changes discontinuously from a value near fL to a value near fH at the boundary between L1 and L2. The transition to the section L2 can be detected by this discontinuous change. Similarly, when fs returns from the interval L2 to L1, the frequency represented by the measurement value changes discontinuously from the value near fH to the value near fL at the boundary between L2 and L2. Can be detected.

  Thus, using the fact that the first reference section is L1, that is, the measurement result of S22 is “under”, the extended section to which the current fs belongs can be specified by the relative displacement therefrom. After that, in S25, it is determined whether it is “over” or “under”, and those skilled in the art will understand that S31 and S33 can be similarly performed.

  FIG. 11 shows another example of a flowchart using the configuration of FIG.

  First, the processor 6 inputs the signal under measurement SA to the measuring instrument 5 (S51), and determines which section of the frequency the measured value represents (S52).

  When the measured value represents the frequency of the appropriate section M (S52: appropriate), fs is specified with the frequency (S53), and the process returns to S52. When the frequency represented by the measured value does not belong to the appropriate section M or any of the extended sections L1, L2, H1, and H2 (S52: outside extended section), an error is output (S54), and the process returns to S52.

  On the other hand, when the frequency represented by the measurement value belongs to any one of the extended sections L1, L2, H1, and H2 (S52: extended section), the processor 6 inputs the passage signal SB to the measuring instrument 5 (S55). At this time, the processor 6 specifies which of the extended sections L1, L2, H1, and H2 fs belongs to.

  Next, the processor 6 determines whether or not the measured value represents the frequency of the appropriate section M (S56). When the measured value represents the frequency of the appropriate section M (S56: appropriate), the frequency corresponds to the extended section specified in S52. The inverse conversion is performed to calculate fs (S57).

  Next, the processor 6 determines whether or not a predetermined time has elapsed since the switch control was performed in S55 (S58), and if it has elapsed (S58: YES), returns to the start, and if it has not yet elapsed. (S58: NO), the process returns to S56. In S56, when the measurement result of the measuring instrument 5 indicates that the frequency is outside the proper section M (S56: outside the proper section), the process returns to the start.

  According to the above flow, since the section to which fs belongs is confirmed at regular intervals, it is positively determined whether fs has returned from the extended section to the appropriate section M in the state where the passing signal SB is being used for measurement. There is no need to do it.

  By the way, in S52, the frequency of the extended section is also measured through the signal under measurement SA. Since the frequency of the extended section L1 or L2 is low, a long time is required for measurement. However, since the determination of S52 is made only at regular intervals, the time resolution of repeated measurement by the measuring instrument 5 is not significantly impaired.

  In addition, since the frequency of the extended section H1 or H2 is high, measurement with high accuracy cannot be performed. However, it is sufficient if it is possible to specify whether fs belongs to H1 or H2. For this purpose, in S52, the frequency of the clock CLK may be increased as necessary.

  FIG. 12 is a conceptual diagram of a frequency measuring device according to another embodiment. The frequency converter 8 includes the heterodyne unit 2 in FIG. 1 or the frequency divider 7 in FIG.

  The pre-converter 9 performs variable known frequency conversion (hereinafter referred to as pre-conversion) on the input signal S0. For the pre-conversion, the heterodyne method, frequency division, multiplication, etc. are used. The signal subjected to the pre-conversion is the signal under measurement SA.

  The processor 6 calculates the frequency of the input signal S0 by performing a reverse conversion operation on the value of fs specified in the flow of FIG. 4 and the like, and performs the preconversion based on the calculated frequency. Control.

  For example, the frequency of switching the switch 4 can be reduced by controlling the pre-conversion so that fs follows the median value of the appropriate section M. In addition, the section in which the frequency can be measured appropriately can be further expanded.

  Even when the frequency of the input signal S0 changes suddenly, the switch 4 can be switched more quickly than the control of the pre-converter 9. Even if fs suddenly deviates from the appropriate section, if it belongs to the extended section L or H, it can be appropriately measured in real time by switching the switch 4.

  The embodiment of the frequency measuring device has been described above. For example, the following modifications are possible.

  In each of the above examples, (a) measurement of the signal to be measured SA → (b) measurement of the passing signal SB → (c) identification of inverse transformation → (d) calculation of fs (FIGS. 4 and 10) Or (a) → (c) → (b) → (d) (figure 11), for example, (b) → (a) → (c) → (d) Processing may be performed. That is, immediately after obtaining the measurement value of the appropriate section by using the passing signal SB for measurement, the measurement may be switched to the measurement of the signal SA to be measured and the inverse transformation to be applied to the measurement value may be specified.

  In each of the above examples, the switch 4 is used. However, this may be omitted, and a first measuring instrument that measures the signal under measurement SA and a second measuring instrument that measures the passing signal SB may be provided. Even in this case, the second measuring instrument can be used in common for the measurement of each extended section, and the increase in size of the configuration can be suppressed.

  In each of the above examples, the appropriate section, the extended section, and the adjacent expanded sections are adjacent to each other, but there may be a gap between them. In this specification, “adjacent” means that two sections have a common end point at the boundary between them. Since these sections have no overlap, their end points are included in only one section. “Adjacent” means to allow a gap between them.

  In each of the above examples, the appropriate section coincides with the pass band of BPF 3, but this need not be the case. For example, the appropriate section may be included in the pass band of the BPF 3, or may be included from the lower zero cross frequency to the upper zero cross frequency of the BPF 3.

  In each of the above examples, the frequency converter is always operated. However, the frequency converter is activated only when fs approaches the end point of the appropriate section while the frequency converter is paused. In this case, the processor may perform control in preparation for switching of the switch 4.

  In each of the above examples, the reciprocal counter constituting the measuring instrument 5 measures the period of the signal under measurement. However, a time width depending on the period, such as an integral multiple of the period or a half period, may be measured.

  FIG. 13B shows a direct frequency counter (hereinafter referred to as a direct counter) as another example of the measuring instrument 5. The direct counter counts the number of repetitions of the signal under measurement S per known gate period G, for example, per second. The frequency of the signal to be measured S can be specified by the count value.

  With a direct counter, for example, if the frequency to be measured is too low, the number of counts is small and sufficient resolution cannot be obtained. If the frequency to be measured is too high, the count value is saturated and sufficient accuracy cannot be obtained. For this reason, the appropriate section is determined.

  FIGS. 13A and 13B show the measured signal S having a rectangular wave, but the measured signal SA in FIGS. 1, 6, and 12 and the input signal S0 in FIG. Or non-sinusoidal waves, such as a rectangular wave, may be sufficient. The measuring instrument 5 includes a shaping device such as a Schmitt trigger for shaping a signal given to itself into a rectangular wave as necessary. The measuring instrument 5 may be an analog type.

  FIG. 14 is a conceptual diagram of an oscillation type pressure sensor according to an embodiment.

  Hereinafter, for the sake of convenience, the symbols Cs and Ri (where i = 1 to 3) are used not only for the meanings of the reference numerals of the drawings but also for the variables representing the capacitance and the resistance.

  The oscillation circuit 10 includes an operational amplifier, a resistor R1 placed between the non-inverting input terminal of the operational amplifier and the ground, a resistor R2 placed on a feedback path from the operational amplifier output terminal to the non-inverting input terminal, and the operational amplifier. It comprises an astable multivibrator comprising a resistor R3 placed in a feedback path from the output terminal to the inverting input terminal, and a capacitor Cs placed between the inverting input terminal and the ground, and the oscillation frequency is 1 / An oscillation signal represented by {2.R3.Cs.log ((R1 + R2) / R1)} is output.

  The capacitor Cs has a structure in which the distance between the electrode plates changes and the capacitance Cs changes when pressure is applied. Since the capacitance Cs determines the oscillation frequency as in the above equation, the oscillation circuit 10 outputs an oscillation signal having an oscillation frequency corresponding to the pressure value.

  An oscillation signal is input to the frequency measuring device 11. The frequency measuring device 11 includes the device shown in FIG. 1, FIG. 6, or FIG. 12, and the processor obtains a pressure value from the oscillation frequency specified in the flow of FIG. 4 and the like, and displays the pressure. In order to obtain the pressure, a memory for storing a relational expression for associating the oscillation frequency with the pressure or a correspondence table may be further provided.

  In this example, a capacitor is used as the sensing element. However, the resistance whose resistance value changes due to the influence of heat, the inductor whose inductance changes due to the displacement of the core, and the resonance frequency that is affected by humidity and gas concentration. A changing crystal unit or the like can also be used. Further, the oscillation circuit can be configured by various harmonic oscillation circuits in addition to a relaxation oscillation circuit such as a multivibrator.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

  The frequency measuring device of the present invention is not limited to the measurement of a physical quantity in a transmission type sensor. For example, the frequency measuring apparatus measures all frequencies such as measurement of transmission / reception frequency in communication, monitoring of frequency in power supply, testing of integrated circuits, inspection of electronic equipment It can be used for applications.

1 ... distributor,
2 ... Heterodyne device (frequency converter),
21 ... Local signal source,
22 ... Mixer,
3 ... Band pass filter (filter),
4 ... switch,
5 ... Measuring instrument,
6 ... Processor (calculation control means),
7. Frequency divider / multiplier (frequency converter),
71 ... distributor
72 ... multiplier,
73 ... frequency divider,
74 ... adder,
8 ... Frequency converter,
9 ... pre-converter,
10: Astable multivibrator (oscillation circuit),
11 ... Frequency measuring device,
SA: Signal to be measured,
SB ... Pass signal,
P ... pass band,
M ... appropriate section,
ML ... lower end section,
MH ... upper end section,
L, L1 ... lower extended section (first extended section),
H, H1 ... upper extended section (second extended section),
L2 ... third extended section,
H2 ... Fourth extended section,
R1, R2, R3 ... resistance,
Cs: Capacitor (sensing element).

Claims (8)

(A) When considering the first to Nth (N ≧ 2) extended sections different from a certain appropriate section, the i-th frequency conversion converts the frequency of the i-th extended section to the appropriate section. The value in the interval is converted, and the frequency of the jth (where i and j are any natural numbers from 1 to N where i ≠ j) is converted to a value outside the appropriate interval. The known first to Nth frequency conversions are applied to the signal under measurement to form an intermediate signal, and the number of repetitions of the frequency component of the appropriate section in the formed intermediate signal per known period, Or a procedure for measuring a period or a time width dependent on the period;
(B) Frequency conversion specified from the first to Nth frequency conversions as frequency conversions forming the frequency components of the appropriate section, and the number of repetitions or period of the measured signal per known period Alternatively, the frequency of the signal to be measured is calculated using the inverse conversion of the frequency conversion specified using the result of measuring the time width depending on the period, and the measurement value obtained in the procedure (a). A frequency measurement method including a procedure to perform.   The frequency measuring method according to claim 1, wherein a common measuring instrument is used for measuring the frequency component of the appropriate section in the intermediate signal and measuring the signal under measurement. When considering the first to Nth (N ≧ 2) extended sections different from a certain appropriate section, the i-th frequency conversion converts the frequency of the i-th extended section within the appropriate section. The frequency of the extended section of the jth (where i and j are any natural numbers from 1 to N where i ≠ j) is converted to a value, and is known to be converted to a value outside the appropriate section. A frequency converter that forms an intermediate signal by subjecting the signal under measurement to the first to Nth frequency conversions of:
A filter that receives the intermediate signal, passes the frequency in the appropriate section, and cuts off the frequency converted to a value outside the proper section by the frequency converter;
The passing signal that has passed through the filter or the signal to be measured that is input to the frequency converter is input, and the number of repetitions of the signal input to itself per known period, or a period or period-dependent time A measuring instrument to measure the width;
A switch for selecting which of the passing signal and the signal under measurement is input to the measuring instrument according to an external control;
Computation control means for controlling the switch, wherein (A) the frequency of the signal under measurement is obtained using the measurement result of the measuring instrument in a state where the signal under measurement is input to the measuring instrument by the switch. Is the function of specifying which of the first to Nth extended sections, and (B) the measured value of the measuring instrument is in the state in which the passing signal is input to the measuring instrument by the switch. In the case of representing the frequency in the appropriate section, the inverse conversion operation of the frequency conversion for converting the frequency in the extended section specified by the function (A) into the value in the appropriate section among the first to Nth frequency conversions. And a calculation control means having a function of calculating the frequency of the signal under measurement using the measured value representing the frequency of the appropriate section.   The arithmetic control means further (C) when the measured value of the measuring instrument represents the frequency of the appropriate section in a state where the signal to be measured is input to the measuring instrument by the switch. A function of specifying the frequency of the signal under measurement by (D), and (D) in a state where the signal under measurement is input to the measuring instrument by the switch, the measurement result of the measuring instrument is the frequency of the signal under measurement The passing signal is input to the measuring instrument when it indicates that it is out of the proper section or the frequency represented by the measurement value of the measuring instrument approaches the end point of the proper section within the range of the proper section. The function of (A) is used to specify the extended section using the measurement result of the measuring instrument at the time of switching the switch. The wave number measurement device. One of the first to Nth extension sections is a lower extension section disposed adjacent to the appropriate section at a lower frequency side than the appropriate section, and the first to Nth frequency conversions are performed. Among them, the frequency conversion for converting the frequency of the lower extended section into the value in the appropriate section is the frequency of the lower end section located at the lower end in the appropriate section, and the lower end in the appropriate section. Converted to values in intervals other than sub-intervals,
When the calculation control means has the frequency represented by the measurement value of the measuring instrument as the function (D) in the state where the signal to be measured is input to the measuring instrument by the switch. The frequency measurement device according to claim 4, further comprising a function of switching the switch so that the passing signal is input to the measuring instrument. One of the first to Nth extended sections is an upper extended section arranged adjacent to the appropriate section on a higher frequency side than the appropriate section. Of the first to Nth frequency conversions, , The frequency conversion for converting the frequency of the upper extended section into the value in the appropriate section, the frequency of the upper end section located at the end on the high frequency side in the appropriate section is changed to the upper end section in the appropriate section. Converted to a value in the interval other than
When the calculation control means, as the function (D), inputs the signal under measurement to the measuring instrument by the switch, and the frequency represented by the measurement value of the measuring instrument belongs to the upper end section The frequency measuring device according to claim 4, further comprising a function of switching the switch so that the passing signal is input to the measuring instrument.   A program for causing a computer to function as the calculation control means in the frequency measuring device according to any one of claims 3 to 6. By including a sensing element whose characteristic changes under the influence of the physical quantity to be sensed in a manner in which the characteristic determines the oscillation frequency, an oscillation signal having an oscillation frequency corresponding to the value of the physical quantity is generated. An output oscillation circuit;
When considering the first to Nth (N ≧ 2) extended sections different from a certain appropriate section, the i-th frequency conversion converts the frequency of the i-th extended section within the appropriate section. The frequency of the extended section of the jth (where i and j are any natural numbers from 1 to N where i ≠ j) is converted to a value, and is known to be converted to a value outside the appropriate section. A frequency converter that forms an intermediate signal by subjecting the oscillation signal to first to Nth frequency conversions of:
A filter that receives the intermediate signal, passes the frequency in the appropriate section, and cuts off the frequency converted to a value outside the proper section by the frequency converter;
The passing signal that has passed through the filter or the oscillation signal that is input to the frequency converter is input, and the number of repetitions per known period of the signal that is input to itself, or the period or time width depending on the period A measuring instrument that measures
A switch for selecting which of the passing signal and the oscillation signal is input to the measuring instrument according to an external control;
Computation control means for controlling the switch, wherein (I) the oscillation frequency is calculated by using the measurement result of the measuring instrument when the oscillation signal is input to the measuring instrument by the switch. 1 to the Nth extended section, and (II) the measurement signal of the measuring instrument is the frequency of the appropriate section in a state where the passing signal is input to the measuring instrument by the switch. Of the first to Nth frequency conversions, the inverse conversion of the frequency conversion for converting the frequency of the extended section specified by the function (I) into the value in the appropriate section, and the appropriate conversion An oscillation type sensor comprising: an arithmetic control unit having a function of calculating the value of the physical quantity using the measured value representing the frequency of the section.