JPH0721506B2 - Tachometer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tachometer, and more particularly to an electronic circuit tachometer.

[Conventional technology]

As one of the means for inexpensively measuring a low rotation speed such as engine rotation, a pulse signal having a constant voltage and a constant time width is generated from a pulse generated in proportion to the rotation speed, and this pulse signal is generated. There is a so-called monostable multivibrator system in which the average voltage is obtained through a low-pass filter and the rotation speed is obtained based on this average voltage.

[Problems to be Solved by the Invention]

However, according to this method, the ripple of the input frequency is superimposed on the output voltage, which causes an error in the measurement. In order to reduce this ripple, the time constant of the low-pass filter may be increased, but this reduces the response and, for example, when measuring the engine speed from an ignition pulse, the frequency of the input pulse is reduced. Is especially problematic when is low.

The present invention has been made in consideration of the above matters, and an object thereof is to provide a tachometer which is not only inexpensive, but also has good responsiveness and high measurement accuracy. .

[Means for Solving the Problems]

In order to achieve the above object, a tachometer according to the present invention is a circuit that receives a pulse signal having a constant voltage and a constant time width as an input and integrates the pulse signal, and synchronizes the output of the integration circuit with the pulse signal. A sample holding circuit is provided and the output of the sample holding circuit is fed back to the input side of the integrating circuit.

[Action]

In the above configuration, first, the pulse signal input first is integrated by the integrating circuit, and the output of the integrating circuit is sampled and held in synchronization with the pulse signal by the sample and hold. Since the output of the sample hold circuit is fed back to the input side of the integrating circuit, the output of the integrating circuit gradually decreases. When the next pulse signal is input, the output of the integration circuit increases and the output of the sample hold circuit also increases. When this is repeated each time a pulse signal is input, the increase in the output of the integrator circuit due to the input of the pulse signal and the decrease in the output of the integrator circuit due to the feedback from the sample and hold circuit are balanced, and the output of the sample and hold circuit becomes constant. Since the value becomes the value, an output voltage proportional to the rotation speed can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of a tachometer according to the present invention. In this figure, 1 is an input terminal to which a pulse a proportional to the rotation speed is input, and 2 is a waveform of the pulse a. , A circuit for outputting a shaped pulse b, 3 is a pulse b
Based on the one-shot multivibrator as a circuit for outputting a pulse signal c having a constant voltage and a constant time width toward an addition point 8 described later, 4 integrates the pulse signal c input via the addition point 8 It is an integrating circuit that outputs an integrated output d.

Reference numeral 5 denotes a circuit for sampling and holding the integrated output d. The output is output to the output terminal 6 and the addition point 8 on the input side of the integrating circuit 4 is fed via the feedback circuit 7.
The feedback is made in the opposite polarity. A one-shot multivibrator 9 is a circuit for outputting a hold command h to the sample-hold circuit 5 based on the pulse signal c, and its input side is at a point 10 between the one-shot multivibrator 3 and the addition point 8. It is connected.

Next, the operation of the above configuration will be described with reference to FIG. 2 showing the signal waveform of each part.

First, the pulse a (see FIG. 2A) proportional to the rotational speed input through the input terminal 1 is converted into a pulse b having a predetermined waveform in the waveform shaping circuit 2 (see FIG. 2B). After being shaped, it is input to the one-shot multivibrator 3. Then, the pulse b is converted into a pulse signal c having a constant voltage and a constant time width (see FIG. 7C) in the one-shot multivibrator 3, is input to the integrating circuit 4 via the addition point 8, and the connection point 10 Is input to the one-shot multi-vibrator 9 via.

The pulse signal c input to the integrator circuit 4 is integrated, the integrated output d increases (see, for example, part p in FIG. 7E), and is generated at the trailing edge (falling side) of the pulse signal c. The hold command h (see FIG. 3D) is held by the sample hold circuit 5 (see FIG. 4F).
However, since the output e of the sample hold circuit 5 is fed back to the integrating circuit 4, the integrated output d of the integrating circuit 4 gradually decreases (see, for example, part q in FIG. 7E).

Next, when the pulse signal c is input, the integrated output d further increases and the output e of the sample hold circuit 5 also increases. When this is repeated each time the pulse signal c is input,
The increase of the integrated output d due to the input of the pulse signal c and the decrease of the integrated output d due to the feedback from the sample hold circuit 5 are balanced, and the output e of the sample hold circuit 5 becomes a constant value ((F) in the figure). See, for example, part r).

Now, assuming that the output e of the sample hold circuit 5 is vo, the voltage of the pulse signal c is vs, the pulse width is to, and the pulse period is To,
Since the output e of the sample hold circuit 5 changes until the integrated value vs.to of the pulse signal c and the integrated value vo.To of the feedback become equal, vs.to = vo.To. And equilibrate.

When the input frequency (rotation speed) is f _IN , f _IN = 1 / To ∴ vo = to · vs · f _IN , and the output voltage vo proportional to the rotation speed f _IN can be obtained.

The present invention is not limited to the above-described embodiment. For example, in order to generate a pulse signal c having a constant voltage and a constant time width based on the pulse b, instead of the one-shot multivibrator 3, a crystal oscillator and a logic circuit are used. A combination of and may be used.

〔The invention's effect〕

As described above, the tachometer according to the present invention can be obtained at low cost because it can be configured by using inexpensive parts, and the response speed is fast and there is no ripple. The number of rotations can be measured with high accuracy and in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a tachometer of the present invention, and FIG. 2 is a diagram showing signal waveforms of respective parts. 4 …… Integrator circuit, 5 …… Sample hold circuit, a ……
A pulse generated in proportion to the number of revolutions, c ... A pulse signal having a constant voltage and a constant time width, d ... Output of an integrating circuit, e ... Output of a sample hold circuit.

Claims (1)

[Claims] 1. A tachometer in which a pulse signal having a constant voltage and a constant time width is generated from a pulse generated in proportion to a rotation speed and a rotation speed is obtained from an average voltage of the pulse signal, and the pulse signal is input to the tachometer. Is provided, and a circuit for sampling and holding the output of the integrating circuit in synchronization with the pulse signal is provided, and the output of the sample and hold circuit is fed back to the input side of the integrating circuit. And a tachometer.