JPS5849825B2 - period detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a period detector that detects the period of a pulse signal.

For example, as a tachometer, a sensor is placed opposite a rotating disk, the sensor generates a pulse signal as the rotating disk rotates, and the number of rotations is detected by detecting the period of this pulse signal. However, the period detector according to the present invention is suitable for use in detecting and processing the period of a pulse signal generated by the sensor of this type of tachometer.

By the way, some tachometers detect the number of rotations and simply display the number of rotations, and in recent years, with the automation of various processes, when a predetermined number of rotations is reached, an output is output and an alarm is issued. There are also devices that are used as a type of control device, such as to emit light, or to start or stop the operation of other controlled devices.

Even if the tachometer is used as a control device as described below, it is necessary to provide a display section to display the number of rotations as necessary for maintenance and inspection or to confirm operation. It is necessary to provide a display section on the period detector connected to the output.

By the way, when the rotation speed becomes very high, the interval between pulses generated by the sensor becomes very short, and even if you try to operate the display while detecting the pulses, the output time to drive the display will become shorter. The interval becomes so short that the human eye cannot follow the displayed value, making it impossible to read the displayed value.

In such a case, in order to extend the display time, it is possible to use a flip-flop, one-shot multi circuit, etc., but it is expected that the circuit structure will become complicated, and furthermore, it is difficult to extend the display time in this way. This has the disadvantage that the input pulse detection function must be stopped unless a display-only counter or latch circuit is provided.

This invention is proposed in view of the above-mentioned circumstances, and it is possible to obtain an output with a time width sufficient to drive the display section with a simple circuit configuration, and also to prevent the detection function from stopping even when displaying. The purpose is to obtain a period detector that requires only a few seconds.

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

In FIG. 1, 11 is a basic pulse generation circuit, and the output of this basic pulse generation circuit 11 is connected to an AND gate 14.
is connected to one input of the

The output of this AND gate 14 is connected to the counting power C of the counting circuit 18.

Reference numeral 12 denotes an input terminal, to which pulses to be measured from a sensor or the like (not shown) are input.

This input terminal is connected to an AND gate 1 via a differentiating circuit 13.
5, and this AND gate 15
The output of is connected to the reset input of the counting circuit 18.

The counting circuit 18 is composed of, for example, an N-ary counter, and 1T is a setting switch for setting the N-ary of the counting circuit 18, and 19 is connected to the count output of the counting circuit 18 to display the counted value. display device, 20 is a count/
This is the up output end.

21 is a pulse processing circuit, and this pulse processing circuit 21 includes a D type flip-flop 21a1 a resistor 21
The main components are a CR time constant circuit consisting of a b1 capacitor 21c and a diode 21d.

That is, the reset output Q of the D-type flip-flop 21a is connected to the data input of the flip-flop via a CR time constant circuit, and a diode 21d is connected to the data input of the flip-flop to promote charging of the capacitor 21c of the CR time constant circuit. The reset output Q is connected to one end of the capacitor 21c, and the clock input and set output of the flip-flop 21a are used as an input end and an output end, respectively.

The input terminal of the pulse processing circuit 21 described above is connected to the differential circuit 1.
On the output side of 3, the output end is connected via a NOT circuit 16 to the gate input of the AND gate 14.15.

Note that 22 is a switch, and by turning on this switch 22, the D type flip-flop 21a is turned on.
The data input of the device is configured to be grounded.

Next, the operation will be explained with reference to the operation waveform diagrams of FIGS. 2 and 3.

First, to explain the period detection of the pulse to be set, the period of the pulse to be measured is the pulse to be measured a 1 +a2...
. . . The operation for detecting this pulse interval will be explained with reference to FIG. 3.

If the switch 22 is turned on now, the pulse processing circuit 21
Therefore, the output of the NOT circuit 16 is "H", and this output is the AND circuit 14.15.
It will always be input to one input terminal of.

Then, the pulses to be measured a1, a2, a3, a4...
. . ., the differential circuit 13 outputs b1, b2, b3, b4, . . . as shown in FIG. 3b.

Therefore, every time the output of the differentiating circuit 13 and the output of the NOT circuit 16 are simultaneously input to the AND circuit 15, f1, f2, f3, f4, etc. are input to the reset input terminal of the counting circuit 18.
The counting circuit 18 is reset by inputting the signal . By doing so, the pulse interval of the pulse to be measured can be detected (see FIG. 3h).

Also, when the pulse interval exceeds a set value, the count-up output can be taken out from 20 (see Figure 3 i).
, This output 20 can operate a controlled device (not shown).

In this way, it is possible to detect the pulse interval of the pulse to be measured, but since the interval of the pulse to be measured is short, even if the display unit 19 is connected to the output circuit of the counting circuit 18, the display unit itself Even if it displays the detected value, the human eye cannot follow it and visual confirmation is difficult.

To visually check this pulse interval, switch 22
This can be done by turning off the switch, and its operation will be explained below.

Now, when the switch 22 is turned off, the output of the pulse processing circuit 21 is transmitted to the NOT circuit.

As a result, the measured pulses al, a2, a3, a4
...(Figure 2 a) is the differential output b from the differentiating circuit 13.
1, b2, b3, b4... (Figure 2 b
), and the differential outputs b1, b2, b3, b4 are
The signal is input to the pulse processing circuit 21 and also to one input terminal of the AND circuit 15 .

To explain the operation of this pulse processing circuit 21 in detail, the above-mentioned differential outputs b1, b2, b3, b4, . Then, the reset output Q becomes “L”
However, since the CR time constant circuit is composed of a resistor 21b and a capacitor 21c, the output of this CR time constant circuit falls slowly as shown in FIG. 2C.

At this time, if the output of the CR time constant circuit is higher than the threshold voltage of the data input D of the D type flip-flop 21a, the data output D is still "H".
Since the input is being applied, even if the clock power T changes, the output at the output terminal Q remains at "H"' and does not change.

The output of the CR time constant circuit is output after a predetermined time (time t3 in Figure 2).
When the data falls below the threshold voltage of the D terminal, the D-type flip-flop 21. The data input of a becomes “L”.

Therefore, when the next pulse to be measured is input, the D type flip-flop is inverted, and the reset output Q becomes "H".
The set output Q becomes "L", and this is inverted by the NOT circuit 16 (see FIG. 3d).

The output d2 of this NOT circuit 16 is the AND circuit 14, 15
is input to one input terminal of.

Therefore, the output of the AND circuit 15 is the output of the NOT circuit 16.
Since the output d1 of the differential circuit 13 and the differential output b3 of the differential circuit 13 are subjected to an AND operation, as shown in FIG.

This output f1 is input to the reset input terminal R of the counting circuit 18.

Then, while the above-mentioned signal d2 is occurring, the interval between the pulses to be measured a3 and a4 is detected.

Then, the signal d2 is input when the next differential output b4 is input. However, due to this, the output of the NOT circuit 16 becomes “L”.
'', the AND circuits 14 and 15 do not satisfy the AND condition, and no signal is input to the counting circuit 18, and the output h of the counting circuit continues to output the detected value when the signal d2 is present. The detected value will be displayed on the display section 19.

According to the period detector of the present invention, the first and second gate circuits are provided between the output of the basic pulse generation circuit and the input of the counting circuit, and between the input end of the pulse to be measured and the input of the counting circuit, respectively. The clock input and set output of the D-type flip-flop are used as input and output terminals, respectively, and the reset output of the D-type flip-flop is connected to the data input via a CR time constant circuit. , and a diode that enables charging of the capacitor of the CR time constant circuit is connected to the CR time constant circuit to form a pulse processing circuit, and the input terminal of the pulse processing circuit is connected to the input terminal of the pulse to be measured. The output end of the processing circuit is connected to the gate inputs of the first and second gate circuits, and the first and second gate circuits are opened at each period determined by the CR time constant circuit to display the period of the pulse to be measured. So,
Even if the interval between pulses to be measured is short, the displayed value can be visually checked.

In the above embodiment, the pulse processing circuit can be arbitrarily connected to the period detector using a switch. However, this is not necessarily the case, and the pulse processing circuit is It is also possible to configure the circuit so that it is always connected so that the display can be visually checked at all times.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are waveform diagrams for explaining the operation of FIG. 1. 11: Basic pulse generation circuit, 13: Differential circuit, 14,1
5: AND circuit (gate circuit), 16: NOT circuit, 1
8: Counting circuit, 19: Display section, 21: Pulse processing circuit,
21a: D type flip-flop, 21b: resistor, 2
1c: capacitor, 21a: diode.

Claims (1)

[Claims] 1. The basic pulse generated from the basic pulse generation circuit and the pulse to be measured are input to the counting circuit, and the period of the pulse to be measured is detected while comparing and counting the basic pulse and the pulse to be measured. In a period detector equipped with a display unit that displays the period of First and second gate circuits are inserted and connected, and the clock input and set output of the D-type flip-flop are used as input and output terminals, respectively, and the reset output of the D-type flip-flop is connected to the CR. The CR time constant circuit is connected to the data input via the time constant circuit, and a diode for promoting charging of the capacitor of the CR time constant circuit is connected to the CR time constant circuit.
R time constant circuit to form a pulse processing circuit, the input terminal of the pulse processing circuit is connected to the input terminal of the pulse to be measured, and the output terminal of the pulse processing circuit is connected to the first and second pulse processing circuits. A period detector characterized in that it is connected to a gate input of a gate circuit.