LOTOOscilloscope statistical curves and fault analysis pass/fail tests
Virtual Oscilloscopes can be applied in industrial automation inspection. In addition to conventional inspection waveforms and measured value parameters, statistical curves and failure analysis (pass/fail) functions customized and validated by customers from multiple industries also bring great convenience to industrial automation inspection.
(i) Basis for failure analysis (pass/fail): statistical curve function
In the automated measurement of signal detection, most of the time you are concerned about the trend of a certain measurement value over time, such as how the peak-to-peak value of the waveform changes after the power-on test. The statistical curve function of the virtual oscilloscope can plot the trend curve of certain measurement values you are concerned about, as shown in the figure below, the maximum value of the signal tested by the oscilloscope changes with time, gradually getting higher from the lowest 0.49V until 4.73V, and then lowering to the lowest, followed by a slow rise and oscillation:
With such statistical curves, we can see the course and trend of the monitored measurement values, thus providing the basis for later fault analysis.
The entry point of the statistical curve function is "Statistics/Fault Judgment" in "Non-standard Functions", as shown in the figure below:
(ii) Which measurements can be observed by the statistical curve function:
Theoretically, all measurement values, such as "maximum value, minimum value, peak-to-peak value, RMS value, average value, frequency, period, duty cycle, positive and negative pulse widths, rise time, fall time", etc., can be plotted as statistical curves to monitor their trends. However, the standard version of the Virtual Oscilloscope software does not open the statistical curve function for all of these measurements. Depending on the model and customization, only some of the measurements are open for the statistical curve function. These can be seen in the Statistical Curve configuration page. Some oscilloscope models support statistical curves for multiple channels of multiple devices in a cascade:
You can see the corresponding curves in the statistical curve plotting area with different colors for the checked measurements. And the plotting area will show the maximum and minimum values of the corresponding curves in the upper and lower margins with the corresponding colors, as shown in the following figure:
(iii) Control and reality of statistical curves
The statistics curve only starts counting the measured values when the "Start Statistics" button is clicked, and this button becomes "Stop Statistics", which stops the plotting of the statistics curve when "Stop Statistics" is clicked. When "Stop Statistics" is clicked, the drawing of the statistics curve stops.
In order to facilitate industrial automation testing, this Start Statistics or Stop Statistics button can also be realized not by mouse clicks, but by keyboard shortcuts or the IO port of the oscilloscope.
The corresponding keyboard shortcut is "shift" + "z", and the corresponding IO port is IO2 of the GPIO function, which is pin 4 of the DE2 expansion port. Note that if you want IO2 to control this statistic start-stop button, you need to check the corresponding option, as shown in the following figure:
When "IO2" is checked to start, the GPIO on pin IO2 will be automatically set as an input, and this input signal follows the logic of 3.3V TTL digital signal, and when it jumps from low level to high level, it will be recognized as clicking the "Start Counting" button. On the other hand, when this input signal changes from high to low, it is recognized as a click on the "Stop Counting" button.
When "Start Statistics" is clicked or triggered, the previous statistics curve waveform and related data will be cleared, as well as the fault information if the fault pass/fail test is enabled.
(iv) Failure analysis pass/fail tests
On the basis of the above statistical curve, we can set the upper and lower limits of the curve for each statistical curve corresponding to the measured value. Changes in the statistical curve within the upper and lower limits are considered normal, i.e., pass, and once the upper and lower limits are exceeded, it is considered that there is a failure, i.e., fail.
Failure analysis is set at the following position:
The results of the pass/fail test are indicated by color blocks and text at the bottom of the statistical curve plotting area, as shown below:
The exact measurement or measurements that caused the fault can also be seen in the information column below, which displays the fault information in the form of "Channel number: Measurement".
In order to facilitate customers in the industrial automation of signal detection, more convenient automated processing fault analysis, such as the use of physical alarm lights, or speakers, or and PLC linkage to achieve certain actions, after the fault occurs, in addition to the display on the oscilloscope's host computer software, you can also use the IO port output. We can check the IO3 alarm in the position shown in the figure below, and it will automatically set the IO3 of the GPIO function of the oscilloscope, that is, pin 10 of the expansion port DE2, as an output, and IO3 also follows the 3.3V TTL digital logic.
By default, IO3 outputs low if it is in PASS state and high if it is in FAIL state. If the opposite logic is required, then the "IO3 Alarm Logic Reverse" option can be checked in the Fail Setup page:
(v) Status clearance
Historical data and waveforms of the statistic curve, as well as the results of the fault analysis can be cleared by clicking the button "Clear". Waveforms and data will be cleared to zero after clearing, and the output status of IO3 will be cleared if IO3 alarm is selected. In addition to manually clicking "Clear", when you click "Start Statistics" after "Stop Statistics", the statistics and fault information will also be cleared automatically, and if "IO2 Start" is checked, then the I/O status from stop to start will be cleared automatically. If "IO2 Start" is checked, the statistics and fault information will also be cleared automatically when switching the IO state from "Stop Statistics" to "Start Statistics".
(vi) Setting memory/saving and importing
The above settings for statistical curves and fault analysis can be memorized and saved as a configuration file, which can be imported back manually. This will be more convenient for industrial automation testing. We will describe this part of the content in other parts of the special description.
For more information on the use of statistical curves and fault analysis, you can refer to the following video demonstration:
Demonstration of Oscilloscope Software Functions - Measured Value Statistical Curve Demonstration and Application Examples of Automated Inspection/video/BV1RJ411C73h/
Oscilloscope-Statistical Curve 2-Fault Linkage-Automated Detection Automated Integration Signal Monitoring Judgment Pass/Fail Testing
/video/BV1h5411u7zP/?vd_source=c0bedc6c664e75d3c19935cbda8abe19
Oscilloscope Statistical Curves Fault Detection PASS/Fail Function Optimization 3 Industrial Automation Line Inspection Automated Inspection
/video/BV1Hx4y1b73n/?vd_source=c0bedc6c664e75d3c19935cbda8abe19
Oscilloscope_Multi-cascade Configuration Memory+Statistical Failure Analysis Configuration Memory Function(1)
/video/BV1QcvXe1EG6/?vd_source=c0bedc6c664e75d3c19935cbda8abe19
Oscilloscope_Multiple Cascade Configuration Memory + Statistical Failure Analysis Configuration Memory Function (2)
/video/BV1iDvQeWEYk/?vd_source=c0bedc6c664e75d3c19935cbda8abe19
Oscilloscope Update: Pass/Fail Test_Statistical Curve Function(3) GPIO Control Automation Inspection Industrial Inspection
/video/BV1pqvQeAEvk/?vd_source=c0bedc6c664e75d3c19935cbda8abe19