JPH0575680U - Waveform observer trigger signal generator - Google Patents

Abstract

(57) [Summary] [Purpose] In addition to the function to generate a trigger signal only by comparing the waveform levels, the trigger signal is generated only in the waveform that satisfies the change amount of the input signal (in other words, the quality of the waveform). It also has the function to A first trigger circuit that compares the waveform level of an analog input signal with a predetermined reference value and changes its output based on the comparison result, a low-pass filter, and a differentiator that receives the output of this low-pass filter and uses a low frequency And a second trigger circuit whose output changes based on the comparison result obtained by comparing the waveform level of the output of this calculus circuit with a predetermined reference value, and the analog input signal is selected for the low-pass filter. A second trigger portion consisting of a switch for receiving the signal, and an AND circuit for taking a logical product of the outputs of the first trigger circuit and the second trigger circuit and outputting this as a trigger signal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a trigger signal generating device in a waveform observing device, and more particularly, to improvement of a trigger function for generating a trigger signal based on an analog input waveform.

[0002]

[Prior Art]

 Conventionally, a waveform observer for displaying an analog input signal on a CRT screen or the like and observing the waveform of the input signal is well known. An example of a waveform observer is a digital oscilloscope that digitizes an analog input signal with an analog-to-digital converter, stores it in a waveform memory, captures it, and then reads it from the waveform memory and displays it on a display screen. In such a digital oscilloscope, a trigger signal is required to determine from which timing the digitization of the analog input signal is started. Normally, the waveform level of the analog input signal is compared with a predetermined reference value (voltage level), and a trigger signal is generated when the analog input signal waveform level exceeds the reference value.

[0003]

[Problems to be solved by the device]

 With such a digital oscilloscope, the trigger signal is generated by determining the waveform level. Therefore, regardless of the amount of change in the rising edge of the waveform (waveform quality), when a waveform with a certain voltage or more is input, the trigger signal is input. Occurs, and the input signal is converted from analog to digital, and the waveform is displayed. That is, regardless of the waveform of the analog input signal, the trigger signal is generated only by the magnitude of the amplitude. However, when observing a waveform, there are cases in which only certain waveforms, for example, only those for which the change in the rising edge of the analog input signal is within a predetermined amount of change are targeted for waveform observation. In such a case, the conventional function of only generating a trigger signal at the waveform level does not consider the rising speed of the waveform at all, and there is a problem that the purpose may not be achieved. There is also a method of extracting and displaying only the target waveform by processing the waveform data loaded in the waveform memory with software, but there is a problem that the processing takes time, etc. I can't say.

The object of the present invention is to eliminate such a drawback. In addition to the function of generating a trigger signal only by comparing the waveform levels, the change amount of the input signal (in other words, the quality of the waveform) is We are trying to realize a trigger signal generator for a waveform observing device that also has a function to generate a trigger signal only in a waveform that is satisfied so that it is possible to observe only the waveform that is closer to the observation waveform desired by the observer. It is something to do.

[0005]

[Means for Solving the Problems]

 In order to achieve such an object, the present invention compares the waveform level of an analog input signal with a predetermined reference value, and changes the output based on the comparison result, a first trigger circuit, a low-pass filter, A calculus circuit that receives the output of this low-pass filter and acts as a differentiator at a low frequency, and the output changes based on the comparison result obtained by comparing the waveform level of the output of this calculus circuit with a predetermined reference value. And a second trigger portion comprising a switch for selectively receiving the analog input signal to the low-pass filter, and the logical product of the outputs of the first trigger circuit and the second trigger circuit is obtained. It is characterized by comprising an AND circuit for outputting as a trigger signal.

[0006]

[Action]

 Like the conventional trigger circuit, the first trigger circuit compares the waveform level of the analog input signal with a reference value, and outputs a signal which becomes "H" level when it exceeds the reference value. The calculus circuit of the second trigger section works as a differentiator at low frequencies, and realizes a single-peak filter or bandpass filter by combining the lowpass filter and the highpass filter of the differentiator, and the second trigger circuit passes this filter. Similar to the first trigger circuit, only the analog input signal is compared with the reference value. The AND circuit takes the AND of the first trigger circuit and the second trigger circuit and outputs it as a trigger signal. The second trigger circuit is interlocked with the switch, and when the switch is off, the output is unconditionally set to the "H" level.

[0007]

【Example】

 The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the principle of a trigger signal generating device according to the present invention. In the figure, reference numeral 1 denotes a first trigger circuit, which is a basic trigger circuit using a comparator (not shown) as in the conventional case, and an analog input signal V IN is supplied from a certain reference value (a reference power source (not shown)). Generated voltage), and when the value (voltage value) of the input signal exceeds the reference value, it generates a trigger signal that goes to "H" level. The path a having the first trigger circuit 1 is referred to as a first trigger portion here. Reference numeral 1a denotes a second trigger circuit, which has the same configuration as the first trigger circuit 1. However, the reference values are not necessarily the same voltage. Reference numeral 2 denotes a fine integration circuit that differentiates and integrates an input signal. Reference numeral 3 is a low-pass filter for passing only the low frequency components of the input signal. An AND circuit 4 takes a logical product of two signals from the path a and the path b. Reference numeral 5 is a switch for taking the analog input signal into the path b. The path b formed by the switch 5, the low-pass filter 3, the fine integration circuit 2 and the second trigger circuit 1a is referred to as a second trigger portion here. When the switch 5 is turned off, the trigger signal is generated by discriminating only by the waveform level, as in the case of the conventional waveform observer. In this case, the output of the trigger circuit 1a on the path b side is set to the "H" level in conjunction with the switch 5.

The fine integration circuit 2 is a circuit using an operational amplifier as shown in FIG. 2, for example. That is, the inverting input terminal of the operational amplifier 21 is connected to the series connection circuit of the capacitor 22 and the resistor 23, and the feedback path is connected to the parallel connection circuit of the capacitor 24 and the resistor 25. The non-inverting terminal is connected to the common line via the resistor 26. This calculus circuit 2 acts here as a differentiator at low frequencies. The low-pass filter 3 is a filter including a resistor 31 and a capacitor 32 as shown in FIG. 3, for example, and has a frequency characteristic corresponding to the frequency characteristic of the calculus circuit 2. That is, the cutoff frequency is adjusted to be substantially equal to or significantly higher than the cutoff frequency of the fine integration circuit 2. By doing so, a single-peak filter or band-pass filter can be realized by combining the low-pass filter 3 and the high-pass filter of the differentiator. By passing through such a filter, it is possible to handle only signals in which the amount of change (ΔV / Δt) in rising of the analog input signal is within a predetermined range. The portion for displaying the waveform using the trigger signal is the same as the conventional one, and since it is not directly related to the present invention, its explanation is omitted.

The operation of such a configuration will be described below. First, when the switch 5 is off, the trigger generation operation is the same as the conventional one as described above. That is, the trigger circuit 1 of the path a compares the analog input waveform with a preset reference voltage, and outputs a signal which becomes "H" level when the reference voltage is exceeded. If it does not exceed, it is at "L" level. In this case, since the trigger circuit 1 on the path b outputs the "H" level in conjunction with the switch 5, the signal from the trigger circuit 1 on the path a passes from the AND circuit 4 and serves as a trigger signal. Is output. That is, the circuit in this case has a function of generating a trigger signal by comparing only the voltage levels.

Next, the operation when the switch 5 is turned on will be described. The path a generates a signal by the same operation as described above. In the path b, the analog input signal that has passed through the low-pass filter 3 and differentiated by the fine integration circuit 2 is input to the trigger circuit 1a. Focusing on the magnitude (voltage) of the analog signal input to the trigger circuit 1a, the rise of the analog input signal VIN is not cut off due to the frequency characteristics of the low-pass filter 3 and the fine integration circuit 2. The signal is large in the vicinity of t (t is time), and in the case of other variation amounts, that is, the ratio becomes smaller as the distance is farther from ΔV / Δt. The second trigger circuit 1a compares such a signal with a reference value, and outputs a signal which becomes "H" level when the signal exceeds the reference value. The amount of change in the rising edge of the analog input signal that triggers is determined by the reference value of the trigger circuit 1a. The reference value is preferably adjustable.

The AND circuit 4 outputs a trigger signal which becomes “H” level when the outputs of the respective trigger circuits of the path a and the path b become “H” level. As is clear from the above operation, when the switch 5 is turned on, the trigger signal is output only when the voltage level of the input signal and the change amount of the rising edge of the input signal both reach the predetermined values. It If the analog input signal has a very slow rising edge, or if the rising edge is too fast, or if high frequency noise is superimposed on the input signal, the voltage level of the analog input signal may be The trigger signal is not generated even if it becomes higher than the predetermined reference value. Therefore, it is possible to trigger only the waveform of the target rising speed, that is, the waveform quality is limited.

[0012]

[Effect of the device]

 As described above, according to the present invention, it is possible to easily realize the function of generating a trigger signal based on the quality of a waveform, in addition to the function of generating a trigger signal by comparing voltage levels as in the conventional case. As a result, the trigger signal can be generated only for the target quality waveform, which is practically useful for waveform observation.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a trigger signal generator of a waveform observer according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a fine integration circuit.

FIG. 3 is a configuration diagram showing an embodiment of a low-pass filter.

[Explanation of symbols]

 1 Trigger circuit 1a Trigger circuit 2 Calculus circuit 3 Low pass filter 4 AND circuit 5 Switch

Claims (1)

[Scope of utility model registration request] 1. A first trigger portion having a first trigger circuit for comparing a waveform level of an analog input signal with a predetermined reference value and changing an output based on the comparison result, a low pass filter, and this low pass filter. And a second trigger circuit that operates as a differentiator at a low frequency and that changes the output based on the comparison result obtained by comparing the waveform level of the output of this fine integration circuit with a predetermined reference value, A second trigger portion formed of a switch for selectively receiving the analog input signal in a low pass filter, and a logical product of two outputs of the first trigger portion and the second trigger portion are used as a trigger signal. AND to output
A comparison level at the time of generating a trigger signal, when the switch is turned off, only the voltage level of the analog input signal is targeted, and when the switch is turned on,
A trigger signal generator for a waveform observing device, characterized in that a change amount of a signal is also targeted together with a voltage level of an analog input signal.