JP2537901Y2 - Tuning frequency measuring instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" This invention relates to a tuning frequency measuring instrument used for adjusting the frequency of the sound of a musical instrument to a regular frequency.

[Prior Art] Conventionally, various tuning frequency measuring devices have been used.

FIG. 7 shows a schematic configuration of a conventional tuning frequency measuring device.

In the figure, reference numeral 10 denotes a phase lock loop. The phase-locked loop 10 compares a frequency of a musical instrument sound with a reference frequency with a voltage-controlled oscillator (hereinafter referred to as a VCO) operating as a reference frequency generating means 11 and calculates a deviation amount between the frequency of the musical instrument sound and the reference frequency. , A phase comparator that operates as measuring means 13 for measuring the frequency, a loop filter 14, a frequency divider 12, an analog adder 15, and the like.

The measuring means 13 is provided with the frequency of the reference signal output from the reference frequency generating means 11 divided by 1 / N by the frequency divider 12, and the musical instrument to be tuned from the musical instrument sound-electric signal converter 30. Input the electric signal of the sound of. That is, the musical instrument sound-electric converter 30 includes the microphone 31 and the amplifier 32.

The reference frequency generating means 11 is supplied with a reference voltage V _REF generated by the resistance ladder circuit 20, and oscillates at the reference frequency assigned to each pitch name by the reference voltage V _REF .

When a musical instrument sound is input from the reference frequency generating means 11 while oscillating at the reference frequency of each note name, the measuring means 13 measures the amount of deviation between the frequency of the musical instrument sound and the reference frequency. The corresponding phase detection output signal is
Given to.

The loop filter 14 smoothes the phase detection output signal, inputs the phase detection output signal to the analog adder 15, adds a voltage corresponding to a deviation from the reference frequency to a voltage for generating the reference frequency, and generates a reference frequency. Means 11 is drawn to the frequency of the instrument sound.

At this time, by giving the output voltage of the loop filter 14 to the indicator 40, it is possible to instruct the indicator 40 to indicate an amount corresponding to the amount of deviation between the frequency of the musical instrument sound and the reference frequency.

“Problem to be solved by the invention” The indicator 40 is configured by an ammeter. As is well known, the relationship between the current given by the characteristics of a spring or the like that elastically supports the pointer and the indicated position varies among the ammeters.

For this reason, an indicator whose relationship between the current and the indicated position is within a predetermined linearity range is selected and used. However, in this case, the yield is poor and the cost is increased. In addition, there is a disadvantage that the pointing accuracy is poor.

"Means for Solving the Problem" In the present invention, duty conversion means for measuring the amount of deviation between the reference frequency given to each note name and the frequency of the instrumental sound, and converting the measurement result into a pulse duty; The present invention is characterized in that a plurality of duty conversion tables for changing the conversion characteristics of the duty conversion means, and a selection means for selecting the duty conversion table in accordance with an instruction error of the ammeter are provided.

According to the configuration of the present invention, the indication error can be reduced as much as possible by selecting the duty conversion table according to the indication error of the ammeter.

Accordingly, since an ammeter having an indication error can be put to practical use, the yield can be improved.

In addition, since the duty conversion table is selected according to the indication error of the ammeter, display accuracy can be improved by selecting an appropriate duty conversion table.

FIG. 1 shows an embodiment of the present invention. In this embodiment, a controller 50 is provided instead of the resistance ladder circuit shown in FIG. The controller 50 gives a voltage signal that defines the reference frequency to the phase lock loop 10 and calculates the amount of deviation from the reference frequency by taking in the controller 50 the result of comparison with the reference frequency in the phase lock loop 10. An example is shown below.

The controller 50 can be constituted by a microcomputer. As is well known, the microcomputer includes a central processing unit 51 (hereinafter, referred to as a CPU), a read-only memory 52 (hereinafter, referred to as a ROM), a random access memory 53 (hereinafter, referred to as a RAM), which is freely readable, and an input port 54. ,
It can be configured by the output port 55.

In addition to the ROM 52, a program for operating the CPU 51 in a predetermined order is written, and reference frequency data and tone data that are used in place of the resistance ladder circuit 20 (FIG. 7) described above are written. It is.

The input port 54 is connected to an input operation device 60 and an input line 19 of a signal output from the phase lock loop 10.

Input operation unit 60 and the plurality of input lines 61 H logic is applied by the pull-up resistor P _R in this example, to one of the input lines 61 by selectively connecting the input line 61 to the common potential line 62 L
It can be constituted by an operation switch group 63 for inputting logic. Various functions are assigned to the switches of the operation switch group 63, and by selectively turning on the switches of the assigned functions, mode switching, octave switching, note name switching, and the like are performed.

The phase lock loop 10 includes a reference frequency generation unit 11 and
It is composed of a frequency divider 12 for dividing the frequency of the oscillation signal of the reference frequency generating means 11, a phase comparator 13, and a low-pass filter 14 for smoothing the comparison output of the phase comparator 13.

In this example, an analog adder 15 is provided on the input side of the reference frequency generating means 11, and the analog adder 15 converts the smoothed output V _LOW of the low-pass filter 14 and the reference frequency data read from the ROM 52 by the controller 50 into a DA converter. A case is shown in which the reference voltage signal V _REF that has been DA-converted in 56 is added to the analog, and the addition result is applied to the voltage control input terminal of the reference frequency generating means 11.

The tone-electric converter 30 is composed of a microphone 31 and an amplifier 32, converts a musical instrument sound into an electric signal, and inputs the musical instrument signal to the phase comparator 13 of the phase lock loop 10.

The voltage input from the DA converter 56 to the analog adder 15 is such that the reference frequency generating means 11 oscillates a frequency -50 cents below the reference frequency of each pitch. The value of -50 cents is because the display range of the display 40 is zero at the center as shown in FIG. 2, and the display range is +50 cents and -50 cents for positive and negative.

That is, when the reference voltage V _REF is given, the reference frequency generating means 11 oscillates at a frequency lower by -50 cents than the reference frequency specified for each pitch. Therefore, the pointer 41 of the display 40 is the second
As shown in the figure, the position where the position of -50 cents is designated is maintained.

Here, the tone signal from the tone-electrical converter 30 is converted to a phase comparator.
When input to 13, the VCO 11 is pulled down to the fundamental frequency of the input tone signal. When the frequency of the tone signal matches the regular frequency, that is, the reference frequency specified for each note name, the controller 50 outputs a pulse having a duty of 50% shown in FIG. Indicates a center zero, indicating that it is tuned correctly.

If the frequency of the tone signal is shifted by 50 cents lower than the reference frequency, the controller 50 outputs a pulse having a duty of 0% shown in FIG. 3A. Thus, the display 40 indicates -50 cents.

If the frequency of the tone signal is shifted by 50 cents higher than the reference frequency, the controller 50 outputs a pulse with a duty of 100% shown in FIG. 3C. Thus, the display 40 indicates +50 cents.

In this embodiment, a case is shown in which signals of three frequencies are supplied to the phase comparator 13 so that a tone having a frequency different by three octaves can be tuned in one tone name selection state.

That is, the frequency divider 12 outputs signals A ₂ , A ₄ , and A ₈ obtained by dividing the oscillation frequency of the reference frequency generating means 11 into 1/2, 1/4, and _1/8, and outputs the signals A ₂ , A ₄ It gives a ₈ to the phase comparator 13. Therefore, the phase comparator can perform phase comparison of three frequencies.

The octave is switched by an input signal from the input operation device 60, and the resistance switching circuit 16 for changing the oscillation time constant of the reference frequency generating means 11 and the time constant circuit for changing the cutoff frequency of the loop filter 14 are switched. This switching control is performed by control signals CS and DS output from output port 55 of controller 50.

The display 40 is driven by the pulse width modulation signal output from the controller 10. Controller 50 is a phase lock loop
Frequency divided output signal A ₂ of the divider 12, A _4, uptake from the input port 54 for example most frequency high signal A ₂ in A ₈ constituting 10 to measure the period. The result of the cycle measurement is stored in the RAM 53.

The cycle measurement result taken into the RAM 53 is converted into a pulse duty, and is supplied from the output port 55 to the display 40 through the low-pass filter 42.

In this invention, when converting the period measurement result into the pulse duty, a plurality of conversion tables having different conversion characteristics are provided. This conversion table can be stored in the ROM 52, for example.

4 to 6 show examples of the conversion characteristics. FIG. 4 shows a case where the conversion characteristic between the cycle measurement value T and the duty D is a straight line. That is, it is a conversion table used when the indicating characteristic of the ammeter incorporated as the display 40 is a straight line.

The conversion tables shown in FIGS. 5 and 6 are conversion tables used when the indicated characteristic of the ammeter is non-linear.

In addition to the characteristics shown in FIGS. 4 to 6, conversion tables are prepared for various characteristics, that is, typical characteristics of indicating characteristics of an ammeter.

This conversion table is selected by the selection means connected to the input port 54.
Selected by 70. This selection is made at the time of adjustment,
Once set, the setting does not change.

"Effects of the Invention" As described above, according to the present invention, when the period measurement value is converted into the duty in accordance with the indicated characteristic of the ammeter incorporated as the display 40, the conversion characteristic is, for example, shown in FIGS. By configuring such that the various characteristics shown in FIG. 6 can be selected, the non-linearity of the indicated characteristics of the ammeter can be linearized and displayed. Therefore, an ammeter which has been rejected in the past can be put to practical use, and the yield can be improved and the cost can be reduced accordingly. In addition, an improvement in display accuracy can be expected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a front view showing an example of a display, FIG. 3 is a waveform diagram for explaining drive signals applied to the display, and FIGS. FIG. 6 is a graph for explaining an example of a conversion table as a main part of the present invention, and FIG. 7 is a block diagram for explaining a conventional technique. 10: Phase lock loop, 11: Reference frequency generation means, 1
3: Measuring means, 30: Tone-to-electric converter, 40: Display, 50: Controller, 60: Input controller.

Claims (1)

(57) [Scope of request for utility model registration] 1. A reference frequency generating means for generating a reference frequency of a note name; and B. a reference frequency generated by the reference frequency generating means is compared with a frequency of a sound of a musical instrument to be tuned. Measuring means for measuring the amount of deviation between the frequency of the reference frequency and the reference frequency; C. duty converting means for converting the result measured by the measuring means into a pulse duty; and D. pulse converted to a duty by the duty converting means. An indicator which is provided with a signal and indicates a deviation amount between the reference frequency and the frequency of the sound of the musical instrument; E. a duty conversion table provided in the duty conversion means for changing a duty conversion characteristic; Selecting means for selecting the duty conversion table according to an instruction error of the tuning device.