In this measurement column, we will address frequently asked questions received by our customer support center.
We are presenting the answers.
The timing for acquiring data from impact tests and signals from external devices is used to acquire the data.
When importing data, you use the trigger function. Within the trigger function settings, there is a setting called hysteresis.
There is a set value, but if this value is set to a value greater than the trigger level, the data will
If the signal is not strong enough, or too weak, it triggers repeatedly, and the intended signal cannot be captured.
This can happen. This time, I will explain hysteresis.
Trigger function
Trigger level: How strong is the trigger?
Hysteresis: If the range of the hysteresis is not exceeded, the system will wait for the next trigger.
No.
Trigger position: How many points before or after the point where the trigger was applied (trigger point)?
Start sampling?
If 0, it's the beginning of the frame.
-340 would be the 340th point in one frame.
If it's +100, the 100th point after the trigger is hit will be at the beginning of frame 1.
Hysteresis and pretrigger
1. Cases where a 0% hysteresis is acceptable.
If the signal is lower than the trigger level within a single frame, for example,
In impact testing, it is necessary to capture the impact waveform and response waveform within one frame, so trigger
Position yourself towards the beginning of each frame.
After the trigger is activated, one frame's worth of signal is captured and analyzed.
After capturing one frame, it waits for the trigger, so within the time frame of one frame,
This will not trigger the event again.
2. Cases where problems arise if hysteresis is not set correctly.
If you want to analyze a signal that occurs before the trigger signal.
Correct settings;
In the figure below, the hysteresis is greater than the range of waveform fluctuation, so the initial belief
It responds only to the rising edge of the signal, allowing you to hold onto the signal you want to analyze.
Incorrect settings:
Because the hysteresis width is small, the trigger is generated by waveform fluctuations.
The data acquisition is delayed, causing you to miss the waveforms you want.
In the diagram below, the first rising edge of the time waveform used for triggering is detected, and the vibration wave prior to its occurrence is analyzed.
Ideally, we'd like to capture the shape and perform averaging, but the subsequent fluctuations in the signal trigger it again.
The data import is delayed.
Before taking the measurement, please check the time waveform on the screen and adjust the trigger level and hysteresis.
stomach.
(Excerpt from the email newsletter issued on February 19, 2020)
