JPH02247571A - Waveform measuring instrument - Google Patents

Abstract

PURPOSE:To observe a disappearing signal without using any external trigger signal by setting preset data every time a trigger signal is outputted and outputting a data fetch inhibition signal to a memory when a counter enters a full-count state. CONSTITUTION:A trigger circuit 3 outputs the trigger signal TG to a presettable counter 5 every time a measurement signal A falls. The counter 5 outputs a carry CRY to the memory 4 when the signal TG is not inputted even a constant time after the circuit 3 outputs the signal TG last and the counted value CD becomes a full-count value. Consequently, the memory 4 quits fetching the output data D1 of an A/D converter 2. Consequently, when the data length of the memory 4 is sufficiently long as compared with the number of data inputted within the constant time, the waveform data D2 of a signal A almost at the point of time when the circuit 3 outputs the signal TG last is left in the memory 4. This data D2 is read out by a read circuit to observe the waveform state of the signal almost at the point of time when the signal A is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a waveform measuring device using digital processing technology, such as a digital oscilloscope, and specifically relates to improvement of a trigger function.

<Prior art> For example, as shown in Fig. 4, the duty ratio of the pulse signal when turning off the power of a switching power supply or motor driven by a pulse width modulation signal (PWM) increases as time passes. It will eventually disappear.

Conventionally, the state of waveform change of such a pulse signal is expressed as l12.
11, for example, a power-off signal is used as a trigger signal, and data within a desired time period after the trigger signal is detected is collected.

<Problems to be Solved by the Invention> However, according to such a method, it is necessary to provide an external trigger signal circuit that uses the power off signal as a trigger signal, which increases the number of circuits in the entire device.

Furthermore, if the pulse signal is known, it is possible to set appropriate conditions for acquiring the desired data, but in the case of an unknown pulse signal, it is necessary to find the optimal condition settings through trial and error. Measurement cannot be performed.

Furthermore, failures other than power off may result in the pulse signal disappearing, but it is impossible to measure the state of this change using the power off signal as a trigger signal, so a separate measuring device must be prepared. There must be.

The present invention has focused on such a point, and an object thereof is to provide a waveform measuring device that can observe the waveform of an extinction signal without using an external trigger signal.

Means for Solving the Problems〉 The waveform measuring device of the present invention has the following features: A that samples a measurement signal and converts it into a digital signal.
A/D converter, a first-in/first-out memory that stores the output data of this A/D converter, a trigger circuit that detects the change point of the measurement signal and outputs a trigger signal, and from this trigger circuit. The present invention is characterized by providing a presettable counter in which preset data is set every time a trigger signal is outputted, and a carry signal is outputted to the memory as a data acquisition prohibition signal when a full count is reached.

Function> The presettable counter of the present invention generates a carry signal when no trigger signal is applied for a certain period after a trigger signal is applied from the trigger circuit, and this carry signal is applied to the memory as a data acquisition prohibition signal.

As a result, the waveform data of the measurement signal near the time when the trigger signal was last output from the trigger circuit remains in the memory.

<Example> Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention.
In the figure, input terminal 1 to which measurement signal A is input is A/
It is connected to the D converter 2 and the trigger circuit 3. A/
The D converter 2 samples the measurement signal A, converts it into a digital signal, and adds the output data D to a first-in first-out (FIFO) memory 4.

This memory 4 stores data D added from the A/D converter 2.
, are stored sequentially, but when the data exceeds the storage capacity, the old data is sequentially erased and updated. Output. A clock pulse CLK is inputted to the presettable counter 5 from a tarlock generator 6, and preset data SET inputted to an input terminal 7 is inputted via a latch 8. The carry signal CRY of this presettable counter 5
is added to the memory 4 as a data import prohibition signal.

FIG. 2 is a timing chart showing an example of the operation of FIG. Indicates the clock CLK input to 5,
(c) is the trigger signal 1゛G output from the trigger circuit 3.
, (d) shows the count ICD of the presettable counter 5, and (e) shows the carry output CRY of the presettable counter 5.

Note that the presettable counter 5 has a count value CD of “
When m″′ is reached, it becomes full count and carry CRY
is output, and the preset data SET is “n (
It is assumed that n(m) is input and the period of the clock CLK is t.

The trigger circuit 3 outputs a trigger signal 1'G to the presettable counter 5 every time it detects a falling edge of the measurement signal A. The presettable counter 5 reads the preset data SET (in this embodiment, "nN") inputted via the latch 8 when the trigger signal TG is applied, and from then on, this preset data S E 'f' is used as the starting count. The value is incremented by one count in response to the tarokk CLK.

That is, in the part (■) in FIG. 2, the carry CRY is not output because the trigger signal TG is applied before the count value CD of the presetter pull counter 5 reaches the full count.

On the other hand, in the part (■) of FIG. 2, the trigger circuit 3
& After that, a new trigger signal TG is not input even after (m-n) hours have elapsed since the output of the trigger signal TG, and the count value CD of the presettable counter 5 reaches the full count "m" and the carry CRY is stored in the memory. Output to 4.

The memory 4 stops taking in the output data D1 of the A/D converter 2 in accordance with the carry CRY added from the presettable counter 5. As a result, assuming that the data length of the memory 4 is (m-n)· which is sufficiently long compared to the number of data input in a time, the trigger circuit 3 finally sends the trigger signal 'G' in the memory 4. This means that the waveform data D2 of the measurement signal A before and after the output point remains.

Therefore, by reading out the waveform data D2 remaining in the memory 4 to the display circuit using a data reading circuit (not shown), it is possible to observe the state of the waveform of the measurement signal A before and after the measurement signal A stops.

With this configuration, it is possible to observe the transition state of the PWM signal that disappears over time as shown in Fig. 4 without using a conventional external trigger circuit, which simplifies the device. This allows for rapid measurement.

In addition, even if the measurement signal A disappears due to a failure other than power-on, its transition can be reliably observed without any loss of control, which is suitable for analyzing the cause of a failure that is difficult to reproduce.

Note that the waveform measuring device configured in this manner is also effective for observing the attenuation transition of the attenuation waveform as shown in FIG.

<Effects of the Invention> As explained above, according to the present invention, it is possible to realize a waveform measuring device that can observe the waveform of a annihilation signal with a relatively simple configuration without using an external trigger signal, and the practical effects are big.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is a timing chart explaining the operation of FIG. 1, and FIGS. 3 and 4 are waveform diagrams showing specific examples of measurement signals. . 1... Measurement signal input terminal, 2... A/D converter, 3
...Trigger circuit, 4...Memory, 5...Presettable counter, 6...Clock generator, 7...Preset Figure 3

Claims (1)

[Claims] A for sampling a measurement signal and converting it into a digital signal
A/D converter, a first-in/first-out memory that stores the output data of this A/D converter, a trigger circuit that detects the change point of the measurement signal and outputs a trigger signal, and from this trigger circuit. A waveform measuring device comprising: a presettable counter in which preset data is set every time a trigger signal is output, and a carry signal is output as a data import prohibition signal to the memory when a full count is reached.