JPS639869A - Time width measuring circuit - Google Patents

Abstract

PURPOSE:To permit automatic instrumentation with real-time for pulse generating duration of undefined pulse width and pulse separation and to display said pulse immediately by connecting the output of two one shot circuits to a logical operation circuit and counting clock pulse. CONSTITUTION:A one shot circuit 1 capable of retrigger which is triggered by the pulse to be measured and a one shot circuit 2 which has the same output pulse width as that of the circuit 1 and is triggered by the building-up output in the circuit 1 are provided. The clock pulse is countered by a counter 4 through a gate 3 which is opened by AND of the output of the circuit 1 and inversion output of the circuit 2. The duration of high level output (b) in the circuit 1 is additional time of generating duration time T of pulse to be measured and output pulse width (tw) of the circuit 2. The duration of a signal (d) which is AND of the output of the circuit 1 and NOT output of the circuit 2, is equal to the time T which is the difference obtained by subtraction of time (tw) from the time width of output (b) in the circuit 1. The gate 3 is opened by this signal (d) so that the clock pulse counting value is expressed numerically for the time T.

Description

[Detailed Description of the Invention] A. Industrial Application The present invention is a method for generating unstable pulses used when automatically measuring switching time, chattering time, bouncing time, etc., which are one of the switch characteristics. This relates to a period measurement circuit.

When a conventional technology switch is opened or closed, irregular pulses are generated due to chattering or bouncing (rebound of the contact), which can cause circuit malfunction. It is necessary to avoid responding to opening/closing. In this case, if the non-response period is set long, reliability of circuit operation can be obtained, but the operation speed becomes slower. Therefore, the period during which chattering or the like occurs during switch operation is one of the important characteristics of the switch, and it is highly necessary to measure the period from the standpoint of circuit design and quality control in switch manufacturing.

Conventionally, a method of observing the waveform with a storage oscilloscope or the like has been used to measure the period during which unstable pulses such as chattering occur during switch operation.

C. Problems to be Solved by the Invention In the method using the storage oscilloscope described above, the waveform on the cathode ray tube is visually observed and the length of the unstable period when the switch is opened/closed is measured on a scale. However, it is not suitable for product inspection in factories.

Therefore, an object of the present invention is to provide an apparatus that can automatically measure in real time the duration of the occurrence of asynchronously occurring pulses with unspecified pulse widths and pulse intervals, such as switch chattering, and immediately display the same.

2. Means for Solving Problems As shown in FIG. 1, a re-triggerable first one-shot circuit 1 which is triggered by a test pulse whose generation duration is to be measured and outputs a pulse with an appropriate time width; A second one-shot circuit 2 is triggered by the rising edge of the output pulse of this one-shot circuit and outputs a pulse having the same width as the output pulse of the one-shot circuit, and a second one-shot circuit 2 is connected to the output of the first one-shot circuit and the second one-shot circuit. A counter 4 that counts clock pulses inputted through a gate 3 measures the duration of generation of the pulse to be tested.

Although the irregular pulses generated by the chattering of the operating switch have an indefinite pulse width and period, there is actually a certain upper limit, which can be known empirically. The width of the output pulse of the one-shot circuit 1゜2 in Fig. 1 is set to be somewhat longer than the upper limit of both this period and the pulse width. Fig. 2 a shows the pulse to be measured. The figure shows the output of the first one-shot circuit. It is triggered by the first pulse to be measured, and the next pulse to be measured comes before the output pulse width ends, so the output of the first one-shot circuit ends up being high. The level continues to be delayed by the time width tw of the output pulse of the one-shot circuit compared to the last one of the pulses to be measured, and then returns to the low level. That is, the duration of the high-level output of the first one-shot circuit is The output pulse width tw of the one-shot circuit is added to the generation duration T of the measurement pulse. Fig. 2C shows the output of the second one-shot circuit, and Fig. 2d shows the output of the first one-shot circuit. It shows the AND of the output of the shot circuit and the negation of the second one-shot circuit, and the duration of this signal is the time width of the output of the first one-shot circuit minus tw, which is This is nothing but the generation duration T of the pulse to be measured.
The gate 3 (7) is opened by the signal shown in FIG.

Embodiment FIG. 3 shows an embodiment of the present invention. When inspecting the switch, it is necessary to inspect both the switch 08 and OFF states. FIG. 4 shows an example of the waveform of the signal to be measured, in which a shows the state when the switch is 08 and b shows the state when the switch is off. Since the explanation of the song order is only an explanation of the principle, the explanation is based on the measurement when the switch is 08. Considering the time when the switch is OFF, the first
The output of the first one-shot circuit in the figure rises at the first pulse after the switch is turned off, so it rises at point P in Figure 4,
The time width of Δt will not be measured.

In the embodiment shown in FIG. 3, in order to be able to measure both the ON and OFF states of the switch, the first one-shot circuit is a one-shot circuit IA that is triggered by the rising edge of the signal under test.
and one-shot circuit IB which is triggered by the falling edge of the signal under test are used, and the Q outputs of both are inputted to the second one-shot circuit 2 via the OR circuit 5. Also, the Q output is used instead of the negative signal of the Q output of the second one-shot circuit, and the AND circuit 6 combines the output of the OR circuit 5 with the second one-shot circuit.
The gate 3 is opened by obtaining the logical product of the Q outputs of the one-shot circuit 2. 7 is a Glock pulse oscillation circuit, the output pulses of which are input to a counter 4 via a gate 3 and counted. The count data of the counter 4 is output to and displayed on the display device 8 by the output command command E from the control circuit 10, and is also compared with the inspection standard value in the digital comparator 9, and a pass/fail determination signal is output. Further, the counter 4 is reset by a reset signal R from the control circuit 10, and is prepared for the next measurement.

One-shot circuit IA, OR circuit5. The operation of the one-shot circuit 2 system is the same as described in the section of operation. The basic operation of the one-shot circuit IB and OR circuit 5° one-shot circuit 2 systems is the same. Figure 4C explains the operation of this system.Since the one-shot circuit IB is triggered by the falling edge of the test pulse, the Q output of IB is already at the beginning of the test switch output signal. It rises at the falling edge, and the error of Δt appearing in the one-shot circuit IA system is eliminated. In addition, in the IB system, the last trigger is performed at one point at switch 08 (Figure 4a), and the last trigger of LA is performed at three points, so the Q output of IA is longer than the Q output of IB, Since time measurement is performed based on the longer Q output of both IA and IB, IB does not interfere with measurement when the switch is ON. Similarly, IA is also switched off.
It does not interfere with measurement at F.

G. Effects Although the above explanation was made for switch testing, the present invention is applicable to general measurement of the duration of generation of irregular asynchronous pulses.

According to the present invention, unlike drawing a pulse waveform with an oscilloscope and measuring time with a scale, the duration of pulse generation is measured completely automatically, and moreover, it is possible to measure the duration of pulse generation almost at the same time as the end of pulse generation (tw. Since measurement results are obtained quickly (with a slight delay), inspections and measurements can be carried out efficiently, and measurements can be made with higher precision than when determining time from a waveform drawn by an oscilloscope.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the principle of the present invention, Fig. 2 is a time chart for explaining the principle, Fig. 3 is a circuit diagram of an embodiment of the invention, and Fig. 4 is an explanation of the operation of the embodiment. This is a time chart for 1, IA, IB...first one-shot circuit, 2...
- Second one-shot circuit, 4... counter. Agent Hiroshi Agata, Patent Attorney Figure 1, Figure 2, Figure 3! Figure 4 Sui Nochi ON

Claims (1)

[Claims] a retriggerable first trigger triggered by the pulse to be measured;
a one-shot circuit, a second one-shot circuit that has the same output pulse width as this one-shot circuit and is triggered by the rising edge of the output of the first one-shot circuit, and an output of the first one-shot circuit. and the inverted output of the second one-shot circuit.