JP2005249620A - Rotation number detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation number detection system which performs stable rotation number detection for both lower rotation numbers and higher rotation numbers. <P>SOLUTION: The rotation number detection system comprises a pulse counter 12 which derives a predetermined number of continuous pulses, wherein the number depends on the rotation number of an object to be detected, a logarithmic convertor 18 to which pulse outputs derived from the pulse counter 12 are inputted and which derives a pulse number of pulse outputs, wherein the pulse number is equivalent to the logarithm of the pulse number of the pulse outputs, and a D/A convertor 19 which converts pulse outputs derived from the logarithmic convertor 18 from a digital signal to an analog signal. An output by the D/A convertor 19 is derives as a rotation number signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rotational speed detection device, and more particularly to a rotational speed detection device for a motor in various industrial plants such as water treatment, sewage treatment, sludge treatment plant, and steel, industrial, chemical, and power generation.

The rotation speed N (rpm) when the electric motor is unloaded is obtained by the following equation (1). If the number of poles is 2 and the power frequency is 60 Hz, it is 3600 rpm, and if it is 50 Hz, it is 3000 rpm.
N = 2f × 60 / P (1)
f: Power supply frequency P: Number of poles N: Number of rotations (rpm)

When a load is applied, a sliding speed is generated according to the magnitude of the load, and the rotational speed is reduced. A tachometer generator (tachometer_generator), a power pickup, an eddy current sensor, and the like are widely used for detecting the rotational speed.
In any case, the signal to be extracted is an AC voltage signal close to a sine wave synchronized with rotation (hereinafter referred to as a rotation speed signal). This is converted into an electrical signal suitable for the receiving instrument by a converter. The measuring instrument, the measuring instrument, the controller, the computer, and various other devices measure, monitor, control, and store data.

When the electric motor is used as power, it is operated at a synchronous speed or a rotational speed close to the synchronous speed. Combined with gears, gears, belts, etc., according to the mechanical equipment to be connected, the desired number of rotations is obtained.
It may be used at extremely small rotational speeds. It is often found in the control to keep the injection rate of chemicals used for the purpose of disinfection and promotion of sedimentation of suspended matter in the water treatment, sewage treatment and sludge treatment, or the control to make the injection amount constant. The concentration of the chemical is injected in units of ppm (mg / L) to g / L to%.
Electric motors are also used to drive the pumps used for these, but because the injection is necessary for regular and fixed quantity, the control is delicate and the rotation speed is 1 rpm, 0.1 rpm, when the first injection from the order to the tank May need to be completed in a short period of time or may exceed the synchronization rate.
Since an electric motor used for such a purpose is difficult to control with a commercial power supply, an inverter is often used.

In recent years, it has become possible to control and operate with small 0.1 rpm or 1 rpm order due to technological progress. At the same time, there is an increasing need for monitoring and indicating instruments that can handle 0.1 rpm and 1 rpm.
Although not limited to the number of rotations, the range ability (maximum scale: minimum scale that can be read) is usually about 100: 1, and is often limited to about 100: 0.5. It is extremely difficult to display the maximum scale with a conventional rotation speed detection device, for example, 0.1 rpm or 1 rpm with a device of 5000 rpm.
At present, two devices for low speed and high speed are installed, and the devices are dealt with by special measures.

A scale of up to 5000 rpm has a range ability of 50000: 1, with a range of 50000: 1, which is a dead zone for transducers, indicators, recorders, and other devices. It can't be read.
In addition, if the dead zone is zero, the output is disturbed by a minute signal change, so it cannot be used for monitoring and control.

  Considering display of 0.1 rpm or 1 rpm with a digital display type indicator, the rotation speed signal has a pulse interval of 600 seconds and 60 seconds. Many commercially available digital display type indicators indicate zero when no pulse is received after a certain period of time. Therefore, it is impossible to display 0.1 rpm or 1 rpm.

  The present invention intends to perform stable rotation speed detection from a small rotation speed to a large rotation speed by applying logarithmic transformation.

  A specific configuration of the logarithmic conversion circuit has been proposed (see, for example, Patent Document 1 and Patent Document 2), but there is no application to rotation speed detection.

Japanese Patent Laid-Open No. 55-16210 JP 61-255435 A

  As described above, it is difficult to display 5000 rpm and 0.1 rpm with a single instrument in the prior art.

  The present invention is intended to solve the above problems and to provide a rotation speed detection device that can stably detect a rotation speed from a small rotation speed to a large rotation speed.

  In the rotational speed detection device according to the present invention, the pulse output derived by the pulse output means for deriving the number of continuously generated pulses corresponding to the rotational speed of the detection target is input, and the number of pulses of the pulse output is determined. Logarithmic conversion means for deriving a pulse output of the number of pulses corresponding to the logarithm, and digital / analog conversion means for converting the pulse output derived by the logarithmic conversion means from a digital signal to an analog signal, by the digital / analog conversion means The output is derived as a rotation speed signal.

  According to the present invention, it is possible to provide a rotation speed detection device that can perform stable rotation speed detection from a small rotation speed to a large rotation speed.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a circuit configuration in the first embodiment. FIG. 2 is a perspective view showing the external configuration of the logarithmic compression scale indicator in the first embodiment and a diagram showing the input / scale characteristics of the logarithmic compression scale indicator.

  In FIG. 1, a rotation speed signal 9 generated by a rotation speed signal generator 8 is input to a waveform shaper 10 provided in the wide range rotation speed signal converter 1. The wide-range rotation speed signal converter 1 includes a clock pulse generator 11, a pulse counter 12, a logarithmic converter 18, a digital / analog converter 19, an output adjuster 20, a gain adjusting variable resistor 22, and a zero adjusting variable resistor. 23 is constituted by a rotation speed zero detection circuit 17. The output of the wide range rotation speed signal converter 1 is led to a logarithmic scale indicator 51.

The operation will be described.
In FIG. 1, a rotation speed signal generator 8 outputs a sine wave or a pulse signal synchronized with the rotation of the motor. The tachometer generator (tachometer_generator: generator for speedometer), electromagnetic pickup, eddy current sensor, etc. are used for the rotational speed detector for motors driven by a commercial power supply. But you can. In the case of an electric motor operated by an inverter, a pulse signal synchronized with the motor rotation is output from the inverter.

  The rotation speed signal generator 8 outputs a rotation speed signal 9. The waveform shaper 10 shapes the rotation speed signal 9 into a pulse signal having a voltage and a time width at which the pulse counter 12 operates reliably. The output of the waveform shaper 10 and the frequency and phase of the rotation speed signal 9 are the same. The clock pulse generator 11 generates a pulse signal having a voltage at which the pulse counter 12 operates reliably at a frequency of 10 kHz. The pulse counter 12 starts counting with the pulse signal Pn and ends counting with Pn + 1. The logarithmic converter 18 generates an analog signal proportional to the logarithm of the number of pulses M counted by the pulse counter 12. The output adjuster 21 converts the output of the logarithmic converter 18 into an instrumentation unified signal DC4 to 20 mA. A gain adjustment variable resistor 22 and a zero point adjustment variable resistor 23 are connected to a logarithmic scale indicator 51 and a gain adjustment zero point adjustment is performed.

  The rotation speed zero detection circuit 17 detects the rotation speed signal zero state at the outlet of the pulse counter 12, reports this to the digital-analog converter 19, stops the conversion operation in the digital-analog converter 19, and rotates. Instability of the conversion operation in the digital-analog converter 19 in the zero state of several signals is prevented.

The motor rotation speed N and the clock pulse number M have the relationship shown in the following equation (2).
N = fc × 60 / M (2)
Motor rotation speed: N [rpm]
Clock pulse frequency: fc [kHz]
Number of pulses counted by the counter 12: M [pieces]

When the clock pulse frequency is 10 kHz, the motor rotation speed N and the clock pulse number M have the relationship shown in the following equation (3).
N = 60 × 10 × 10 ³ / M (3)

(3) The logarithm of both sides of the equation is taken. The following equation (4) is obtained.
logN = log (600000 / M) (4)

Consider the output regulator output from 0 to 100%. If the rotation speed scale minimum 0.5 rpm is 0%, 0 rpm cannot be read. Therefore, the minimum rotation speed scale is set to the 12.5% position. The maximum rotation speed scale of 5000 rpm is the 100% position. The% indication position Y12.5-100 between the 12.5-100% scales of the indicator needle is as shown in the following equation (5).
Y12.5 ~ 100 = 87.5log (N / 0.5) / (log5000−log0.5) +12.5
＝ 21.875 × log (N / 0.5) / (log5000−log0.5) + 12.5 ……… (5)

  For the logarithmic converter 18, it is effective to use a digital-analog logarithmic conversion circuit disclosed in Japanese Patent Laid-Open No. 55-16210 presented as Patent Document 1 in the background art section. Further, the logarithmic conversion device disclosed in Japanese Patent Application Laid-Open No. 61-255435 presented as Patent Document 2 may be applied. Furthermore, logarithmic conversion can also be realized by combining a DA converter with a logarithmic arithmetic element incorporated in a calculator with a function arithmetic function that is currently commercially available in large quantities. There are many other strategies, but any one may be used.

  Depending on the logarithmic converter, it takes time T seconds to capture the signal into the logarithmic converter and to calculate it, but the signal reading of the logarithmic converter can be cleared by resting the capturing for time T + α seconds. Since the change in the rotational speed is not abrupt, even if T + α seconds is 5.10 seconds, the measurement is not adversely affected. During this time, the indicated value is measured and output as the previous value.

FIG. 2A is a perspective view showing an external configuration of the logarithmic compression scale indicator in the first embodiment. FIG. 2B is a characteristic diagram showing the input / scale characteristics of the logarithmic compression scale indicator.
In FIG. 2, a logarithmic scale indicator 51 receives the output of the wide range rotational speed signal converter shown in FIG. 1 and instructs the rotational speed. The relationship between input and scale is shown in FIG. The indicator of the type shown in FIG. 2 is widely used in a panel-mounted type square indicator. In addition, both vertical and horizontal types can be applied. The purpose of the bar graph display by the LED is achieved by combining it with a scale plate that satisfies the relationship between the input and the scale shown in FIG.

  The first embodiment according to the present invention has a clock pulse generator, a pulse counter, and a logarithmic converter, and outputs an electric signal proportional to the logarithm of a large number of revolutions from a small number of revolutions, for example, 0.5 to 5000 rpm. A characteristic wide-range rotational speed signal converter has been proposed.

  In Embodiment 1 according to the present invention, an electrical signal (eg, DC 4 to 20 mA) formed by the wide-range rotational speed signal converter having the configuration of the previous section is received, and a rotational speed that is two orders of magnitude smaller than before is read on a logarithmic scale. An indicator that can be used has been proposed.

  In the first embodiment according to the present invention, the wide-range rotation number signal converter counts how many clock pulses are within the time required for one rotation, obtains the logarithm of the number, converts it to an analog signal, and outputs it. It is possible to measure and display small and large rotation speeds.

  In the first embodiment according to the present invention, the rotation speed indicator is an indicator that receives a logarithmically processed analog signal, and is capable of indicating a wide range from a small rotation speed to a large rotation speed by a logarithmic scale.

  According to the first embodiment of the present invention, the pulse output means comprising the pulse counter 12 for deriving the number of continuously generated pulses corresponding to the rotational speed of the detection target, the pulse output means comprising the pulse counter 12 Derived by a logarithmic conversion means comprising a logarithmic converter 18 for receiving a pulse output derived from the above and receiving a pulse output having a pulse number corresponding to the logarithm of the pulse number of the pulse output, and a logarithmic conversion means comprising the logarithmic converter 18 A digital-to-analog converter 19 comprising a digital-to-analog converter 19 for converting the pulse output from a digital signal to an analog signal, and the output from the digital-to-analog converter comprising the digital-to-analog converter 19 is derived as a rotation speed signal Therefore, stable rotation speed detection is performed from a small rotation speed to a large rotation speed. It is possible to provide a speed detecting device that.

  Further, according to Embodiment 1 of the present invention, in the configuration of the preceding paragraph, an indicator comprising a logarithmic compression scale indicator 51 into which an output from the digital-analog converter means comprising the digital-analog converter 19 is input as a rotation speed signal. Alternatively, since a meter such as a recorder is provided, it is possible to provide a rotational speed detection device having a meter that can stably detect the rotational speed from a small rotational speed to a large rotational speed.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram showing a circuit configuration in the second embodiment. FIG. 4A is a perspective view showing an external configuration of the double scale indicator in the second embodiment. FIG. 4B is a characteristic diagram showing the input / scale characteristics of the double scale indicator.
In the second embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configuration in the first embodiment described above, and exhibits the same operation. In the drawings, the same reference numerals indicate the same or corresponding parts.

  In the wide-range rotation speed signal converter 1 according to the first embodiment, the output is only a logarithmically compressed signal. The indicator is logarithmic and the scale markings are not evenly spaced, making it difficult to read. Even if the scale is finely cut like a calculation scale, it is often read from a point about 0.5 to 1.5 m away, and it may be difficult to read. Considering that the reading error and the variation among reading people increase, the linear proportional scale of the prior art is practically advantageous above a certain number of rotations.

FIG. 3 is a circuit configuration diagram showing the second embodiment. In the wide-range rotational speed signal converter 2 in the second embodiment, in addition to the rotational speed signal from the wide-range rotational speed signal converter 1 in the first embodiment, a linear proportional signal according to the prior art can be output.
In FIG. 3, an analog switch 13 selected by a scale selection switch 61 is provided, and a one-shot generator 14, an integrator 15, a used scale display lamp power supply circuit 16, an output adjustment circuit 25, and a linear proportional signal gain adjustment. A resistor 32 and a linear proportional signal zero adjustment resistor 33 are provided. The output of the output adjustment circuit 25 is supplied to the double scale indicator 52. Other components are the same as those in the first embodiment.

The operation will be described.
In FIG. 3, a one-shot generator 14, an integrator 15, a linear proportional signal gain adjustment resistor 32, and a linear proportional signal zero adjustment resistor 33 are general components for obtaining a linear proportional signal according to the prior art. The relationship between input and scale is a straight line.
The analog switch 13 receives the mode selected by the manually operated scale selection switch 61 and sends either a linear proportional output or a logarithmic scale signal to the indicator via the output adjustment circuit. The scale used in the lamp display output circuit 16 is lit on the indicator lamp on the indicator scale plate.
If linear proportional output is selected in a large rotational speed range, the output signal in the large rotational speed range of the wide-range rotational speed signal converter 2 can be easily identified, and reading errors can be reduced and readability can be improved. By selecting the logarithmic scale output at a small rotation speed, it is possible to read a small rotation speed that cannot be read on a linear proportional scale.

  FIG. 4A is a configuration diagram showing the appearance of the double scale indicator in the second embodiment. In FIG. 4A, a double scale indicator 52 having both a logarithmic scale and a linear proportional scale indicates the rotational speed at the output of the wide range rotational speed signal converter 2 shown in FIG. The LED-type indicator lamp 53 is lit when reading on a linear proportional scale. The LED indicator lamp 54 is turned on when reading on a logarithmic scale. FIG. 4B shows the input / scale characteristics of the double scale indicator.

  In the second embodiment according to the present invention, the rotational speed signal converter enables output of both the linear scale signal obtained by the conventional rotational speed signal converter and the logarithmic scale signal described in the first embodiment. It takes advantage of the linear scale to make it easier to read.

  In the second embodiment according to the present invention, the rotation speed indicator has two signals, a linear scale signal and a logarithmic scale signal formed by the wide-range rotation speed signal converter according to the invention described in the previous section. The meter can read both the linear scale and logarithmic scale.

  According to the second embodiment of the present invention, in the configuration of the first embodiment, there is provided selection means including a scale selection switch 61 for selecting a linear proportional scale signal and a logarithmic scale signal obtained by the logarithmic conversion means. Therefore, it is possible to provide a rotational speed detection device that can perform stable rotational speed detection from a small rotational speed to a large rotational speed, and can select either a linear scale signal or a logarithmic scale signal and easily identify an output signal. .

  Further, according to the second embodiment of the present invention, in the configuration in the preceding paragraph, a double indicator such as an indicator or a recorder that receives the linear proportional scale signal or logarithmic scale signal selected by the selection means as the rotation speed signal. Since a scale meter is provided, it is possible to detect a stable speed from a small number of revolutions to a large number of revolutions, and to select either a linear scale signal or a logarithmic scale signal. A number detection device can be provided.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a block diagram showing a circuit configuration in the third embodiment. FIG. 6A is a perspective view showing an external configuration of a two-zone scale indicator in the third embodiment. FIG. 6B is a characteristic diagram showing the input / scale characteristics of the 2-zone scale indicator.
In the third embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configurations in the first and second embodiments described above and exhibits the same operation. It is. In the drawings, the same reference numerals indicate the same or corresponding parts.

  In the wide range rotation speed signal converter 1 according to the first embodiment, the output is only a logarithmic scale signal. In logarithmic scales, the scale markings are not evenly spaced, so it is confusing for a moment. It is easier for the operator to use the linear proportional scale if possible. In the combination of the wide-range rotation speed signal converter 2 and the double scale indicator 52 according to the second embodiment, a cable for the wide-range rotation speed signal converter and a used scale lamp display cable are required from the place where the scale selection switch is installed. Expense increases.

  FIG. 5 is a circuit configuration diagram showing the third embodiment. The wide-range rotation speed signal converter 3 according to the third embodiment is provided with a comparator 41, an analog switch 42, a linear proportional signal gain adjustment resistor 32, and a linear proportional signal zero adjustment resistor 33. The output of the output adjustment circuit 25 is supplied to a two-zone scale indicator 53. Other components are the same as those in the first embodiment.

The operation will be described.
In FIG. 5, the comparator 41 determines whether the rotational speed is less than or exceeds the rotational speed set for discriminating the rotational speed of the zone section. The analog switch 42 sends a logarithmic scale signal to the output regulator when the rotational speed is equal to or lower than the rotational speed set by the output of the comparator 41. When the set speed is exceeded, a linear scale signal is sent to the output adjuster. For example, assuming that the zone rotation speed is 10 rpm, a logarithmic scale signal is output when the speed is 10 rpm or less, and a linear proportional scale is output when the speed is 10 rpm or more.

  FIG. 6A is a perspective view showing an external configuration of a two-zone scale indicator in the third embodiment. 6A, the two-zone scale indicator 53 has a logarithmic compression scale and a linear proportional scale. In the double scale indicator shown in the second embodiment, an indicator lamp indicating which scale is to be read is necessary. However, since the two-zone scale indicator according to the third embodiment has one scale, the scale used is displayed. No indicator light is required. FIG. 6B shows the input / scale characteristics of the 2-zone scale indicator.

  In the third embodiment according to the present invention, the wide-range rotation speed signal converter 3 can output a logarithmic scale signal in an area smaller than an arbitrary rotation speed and a linear proportional signal in a larger area. As a result, the output signal in the large rotational speed range of the wide-range rotational speed signal converter 3 can be easily identified, and the reading error can be reduced and the readability can be improved.

  In the third embodiment according to the present invention, the two-zone scale indicator receives the output of the rotational speed signal converter according to the invention of the preceding paragraph, and is a logarithmic scale in a region smaller than an arbitrary rotational speed and a linear proportional scale in a large region. It is possible to read.

  According to the third embodiment of the present invention, in the configuration of the first embodiment, a linear proportional scale signal as a rotational speed signal and a logarithmic scale as a rotational speed signal obtained by a logarithmic conversion means comprising the logarithmic converter 18. Since the selection means including the analog switch 42 for selecting the signal according to the rotation speed is provided, the rotation speed can be stably detected from a small rotation speed to a large rotation speed, and either a linear scale signal or a logarithmic scale signal can be detected. Can be selected according to the number of rotations, and the rotation number detection device in which the output signal can be easily identified can be provided.

  Further, according to Embodiment 3 of the present invention, in the configuration of the preceding paragraph, the indication comprising the two-zone scale indicator 53 to which the linear proportional scale signal or the logarithmic scale signal selected by the selection means is inputted as the rotation speed signal. Since a two-zone scale instrument such as a meter or recorder is provided, it is possible to detect a stable rotational speed from a small rotational speed to a large rotational speed, and either a linear scale signal or a logarithmic scale signal is selected according to the rotational speed. Thus, it is possible to provide a rotation speed detection device having a two-zone scale meter that is easy to read.

  The rangeability (maximum scale: minimum scale that can be read) of the conventional rotational speed detection device is about 100: 1, but the rotational speed detection device and the indicator in the first to third embodiments according to the present invention. 10000: 1 can be realized in this combination. It becomes possible to read values as small as the previous 1/100.

  If the linear proportional output is selected in a large rotational speed range by combining the wide range rotational speed signal converter and the double scale indicator in the second embodiment of the present invention, reading error can be reduced and readability can be improved. By selecting the logarithmic scale output at a small rotation speed, it is possible to read a small rotation speed that cannot be read on a linear proportional scale. The advantages of the linear proportional scale and the logarithmic scale signal can be arbitrarily switched and used.

  In the combination of the wide-range rotational speed signal converter and the two-zone scale indicator in the third embodiment according to the present invention, the small rotational speed is a logarithmic scale and in the large rotational speed range without the scale selection as in the second embodiment. Can be read with a linear scale. Since the 2-zone scale indicator has one scale, no indicator lamp for use scale is required.

  In the first to third embodiments according to the present invention, the rotation speed display is a notation limited to an indicator, but may be a recorder. In the case of a recorder, the scale is written on the recording paper, but the same effect as in the case of the indicator can be obtained by writing a logarithmic scale on the recording paper. When applied to a recorder with a double scale method corresponding to the second embodiment, both logarithmic scale signals or linear proportional scale signals may be recorded.

  By providing a comparator at the output of the wide-range rotation speed signal converter in the first to third embodiments according to the present invention, even if a logarithmic scale signal is used, the contact closes at a set value or more as in the case of a linear proportional scale signal. It is also possible to output a signal or the like. Not only contact type but also transistor open collector output can be installed without problems.

  In the first to third embodiments according to the present invention, the rotation speed scale is set to 0.5 to 5000 rpm. However, typical numerical values for facilitating calculation, explanation, and understanding are listed. It is not limited to. It can be applied to specifications required by various mechanical systems.

  In the third embodiment according to the present invention, the thorn division set point is set to 10 rpm, but any number can be dealt with. The linear proportional scale zone becomes narrower as the thorn segment set point becomes larger, but the thorn segment set point can be used without any problem in practice by considering the operating conditions of the machine.

It is a block diagram which shows the circuit structure in Embodiment 1 by this invention. It is a perspective view which shows the external appearance structure of the indicator in Embodiment 1 by this invention, and a characteristic line figure which shows an input and scale characteristic. It is a block diagram which shows the circuit structure in Embodiment 2 by this invention. It is a perspective view which shows the external appearance structure of the indicator in Embodiment 2 by this invention, and a characteristic line figure which shows an input and a scale characteristic. It is a block diagram which shows the circuit structure in Embodiment 3 by this invention. It is a perspective view which shows the external appearance structure of the indicator in Embodiment 3 by this invention, and a characteristic diagram which shows an input and scale characteristic.

Explanation of symbols

1, 2, 3 Wide range rotation speed signal converter, 8 rotation speed signal generator, 9 rotation speed signal, 10 waveform shaper, 11 clock pulse generator, 12 pulse counter, 13 analog switch, 14 one shot generator, 15 integrator, 16 scale display lamp power supply circuit, 17 rotation speed zero detection circuit, 18 logarithmic converter, 19 digital-analog converter, 21 output regulator, 22 gain adjustment variable resistor, 23 zero adjustment variable Resistor, 25 Output adjustment circuit, 32 Linear proportional signal gain adjustment resistor, 33 Linear proportional signal zero adjustment resistor, 41 Comparator, 42 Analog switch, 51 Logarithmic compression scale indicator, 52 Double scale indicator, 53 2 Zone scale indicator, 61 scale selection switch.

Claims (6)

  Pulse output means for deriving a number of continuously generated pulses corresponding to the number of rotations of the detection target, and a pulse corresponding to the logarithm of the pulse number of the pulse output that is input with the pulse output derived by the pulse output means Logarithmic conversion means for deriving a pulse output of a number, and digital-analog conversion means for converting the pulse output derived by the logarithmic conversion means from a digital signal to an analog signal, and the output from the digital-analog conversion means is derived as a rotation speed signal A rotational speed detection device characterized by:   The rotation speed detection apparatus according to claim 1, further comprising a meter for inputting an output from the digital / analog conversion means as a rotation speed signal.   2. The rotation speed detection device according to claim 1, further comprising selection means for selecting a linear proportional scale signal and a logarithmic scale signal obtained by the logarithmic conversion means.   The rotational speed detection apparatus according to claim 3, further comprising a double scale meter into which the linear proportional scale signal or the logarithmic scale signal selected by the selection means is input as a rotational speed signal.   2. A selection means for selecting a linear proportional scale signal as a rotational speed signal and a logarithmic scale signal as a rotational speed signal obtained by the logarithmic conversion means according to the rotational speed. Rotational speed detection device. 6. The rotational speed detection device according to claim 5, further comprising a two-zone scale meter to which the linear proportional scale signal or the logarithmic scale signal selected by the selection means is input as a rotational speed signal.

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