JPS6356506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to improvements in methods for measuring time intervals in signal waveforms, particularly delay times.

(b) Background of the Technology Conventionally, methods using oscilloscopes or counters have been widely used as a means of observing the waveforms of analog or digital signals, or measuring time intervals between multiple signals or signal change points, or signal delay times.

(c) Prior art and problems Oscilloscopes usually use a cathode ray tube (CRT) to apply an input signal voltage to one deflection means to make the bright spot swing in the Y direction, and at the same time deflect the input signal in the X direction to synchronize it. The waveform of the input signal voltage is observed by sweeping the input signal voltage.

For this reason, the oscilloscope is an amplifier of the input signal,
It has a built-in time axis generator, various adjustment circuits, etc., and is widely used as a means of observing signals ranging from DC to several GHZ. In addition to multi-phenomenon observation means that simultaneously measure multiple signals using a CRT having multiple sets of input signal deflection means or means for extracting instantaneous values using narrow sampling pulses synchronized with input signals, Since the device is equipped with a means for starting the sweep when triggered by It is also possible to measure the delay time of a circuit. However, in this case, the preceding signal that serves as the trigger is not necessarily a sharp rising or falling pulse, which is the ideal condition for triggering, so the reference point may float due to fluctuations in the trigger level, or depending on the value of the delay time. Particularly when the delay time is large, there is a problem in that sufficient measurement accuracy cannot be obtained due to the reading accuracy. Another counter method uses a counter gate to start counting the reference clock with a preceding input signal or change point, and clocks by closing the gate with a subsequent input signal or change point, usually using a digital counter. Not only can it be easily read on a display, etc., but it is also possible to perform precise time measurements by using a high-precision, high-resolution pulse as a reference clock, but since the gate trigger of the counter is usually based on the signal level, For signals with changes or complex changes, it is inferior to visual observation using an oscilloscope in that there is no guarantee that the desired change point can be accurately captured.

(d) Purpose of the Invention The purpose of the present invention is to eliminate the disadvantages of conventional time measurement using an oscilloscope, and to provide a means for measuring delay time that is highly accurate and easy to handle, taking advantage of the advantages of visual observation and counters in the oscilloscope. This is what we are trying to provide.

(e) Structure of the Invention The objects are: a variable period oscillator that generates a pulse waveform with an arbitrary repetition period; a period measuring device for measuring the period length of the pulse waveform; A counting circuit that outputs double the long-period pulse, delays the long-period pulse and doubles it.
A delay circuit for obtaining the next pulse and a timing observation means using an oscilloscope are provided, and while changing the repetition period of the variable period oscillator, the rising edge of the secondary pulse is made to coincide with the rising edge of the primary pulse using a period measuring device and observation means. Measure the first period length τ ₁ and then apply a secondary pulse to the circuit under test. At the rising edge of the pulse under test, a variable period oscillator generates a primary pulse whose rise or fall coincides. Seshimeko pulse period length τ ₂
This can be achieved by a delay time measuring method characterized in that the delay time of the circuit under test is measured from the difference time between the first period length τ ₁ and the second period length τ ₂ . I can do it.

(f) Embodiment of the invention An embodiment of the invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a delay time measuring method according to an embodiment of the present invention, and FIG. 2 is a time chart thereof.

In the figure, 1 is a variable period oscillator, 2 is a counting circuit, 3 is a delay circuit, 4 is an oscilloscope, 5 is a period measuring device, and 6 is a circuit under test (DUT).

The variable period oscillator 1 continuously generates the primary pulse Pa of any repetition period to be set, or if necessary (not shown in the figure), the counting circuit 2
Send to. It is assumed that the period is set to be shorter than the expected value of the delay time T, which will be described later. A counting circuit 2 having an n-ary counting function converts the long-period pulse Pb into a long-period pulse Pb having a period length n times the period length of the primary pulse Pa, for example, eight times the period length in this case, and sends it to the delay circuit. to is the delay time of the counting circuit 2. This n may be any value and does not necessarily have to be in the form of ^2K , but it should be selected to be a sufficiently large value in consideration of the expected delay time T so as not to interfere with measurement. Here, the delay circuit 3 that has received the long-period pulse Pb gives an arbitrary delay time and outputs the secondary pulse Pc.
The variable period oscillator 1 is adjusted so that the rising edge of the primary pulse Pa, which was previously used as the reference for the long-period pulse Pb, matches the secondary pulse Pc, and observed on the screen of the oscilloscope 4. At the same time, the first period τ ₁ is obtained by the period measuring device 5.

Next, apply the secondary pulse Pc to the circuit under test DUT6 and extract the pulse under test Pb to be measured.
Furthermore, the pulse to be measured Pd and the primary pulse Pa are applied to the oscilloscope 4, and while observing the rising edge of the secondary pulse Pc as a trigger, the primary pulse Pa is changed at the rising edge of the pulse to be measured Pd to obtain a changed primary pulse Paa ( or Paa') after one cycle or after multiple cycles, and the period measuring device 5
The second period length τ ₂ or τ ₃ is obtained. Here, if we obtain the difference between the first period length τ ₁ and the second period length τ ₂ or mτ ₃ , the delay time T is determined by T=τ ₁ to τ ₂ or T= τ ₁ to _{τ 3.} The delay time of DUT6 can be easily measured with high accuracy.

(g) Effects of the Invention As explained above, according to the present invention, the pulse generated by the pulse generation means is lengthened to a long period, and the pulse is transformed into a measurement pulse convenient for observation by the delay means and applied to the circuit under test DUT. The coincidence of the waveform rises can be achieved by a waveform observation means that is easy to confirm, and the delay time can be obtained by a pulse generation means that is not affected by the slowing characteristic of the delayed pulse and has a pulse with little change in the rise characteristic. Errors due to threshold ambiguity can be removed. In addition, since the applied measurement pulse has a long period length, it is possible to easily avoid the influence of reflected waves caused by impedance mismatch in high-speed rising pulses, and the delay time can be easily applied to a wide range of delay times without sacrificing accuracy. A method for measuring this can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a delay time measuring method according to an embodiment of the present invention, and FIG. 2 is a time chart thereof. In the figure, 1 is a variable period oscillator, 2 is a counting circuit, 3 is a delay circuit, 4 is an oscilloscope, 5 is a circuit under test, and 6 is a period measuring device.

Claims (1)

[Claims] 1. A variable period oscillator that generates a pulse waveform with an arbitrary repetition period, a period measuring device for measuring the period length of the pulse waveform, and applying a primary pulse from the pulse generating means to output an n times longer period pulse. A counting circuit, a delay circuit for delaying the long-period pulse to obtain a secondary pulse, and a timing observation means using an oscilloscope are provided, and while changing the repetition period of the variable period oscillator, the rising edge of the secondary pulse is detected by a period measuring device and an observation means. , the first period length τ ₁ is measured by matching the rising edge of the primary pulse, and the rising or falling edge coincides with the rising edge of the pulse to be measured obtained by applying the secondary pulse to the circuit under test. A variable period oscillator generates _a primary pulse that changes _as shown in FIG _. A method for measuring delay time characterized by measuring.