Having issues with using edge triggers on waveform from tektronix dpo2012b scope.

[Taa1000]

Hello.

I`m trying to use a tektronix dpo2012b scope to determine the edge times of a waveform. I am trying to use the basic level trigger detection to achieve this. It worked fine when i used a prototype where I just had a sinus signal, it created multiple triggers for both the rising and falling edges. When I added it to the example files from the drivers I only got one repeated number(for each update) in the array, the value was also not a believable one. I tried to set the hysteresis to a higher value but it did not change this number. The settings used is location mode: time, start duration format:relative. I am most likely also going to add timestamps into the mix at a later time. Btw I don`t have much experience with labview.

Thanks in advance.

[cbutcher]

Hello Taa,

The values of 'Numeric' and 'Numeric 2' in the attached VI are both 0 (the default). Have you tried using other values? These are wired to the inputs of your For loops and so they'll never execute as it is now.

Given you say you are getting one value out (for each update - what do you mean by this?) I guess that you have some other values set in your copy, but I wanted to mention it just in case.

Copying from the detailed help:

hysteresis specifies the amount above or below level through which signal in must pass before a trigger level crossing is detected. The default is 0.

Trigger hysteresis is used to prevent noise from causing a false trigger. For a rising edge trigger slope, the signal must pass below level – hysteresis before a trigger level crossing is detected. For a falling edge trigger slope, the signal must pass above level + hysteresis before a trigger level crossing is detected.

Is it possible that (since you said you tried increasing the hysteresis value to get more crossings) your hysteresis value is preventing subsequent triggers from occuring? I would suggest lowering it unless you are receiving false triggers.

With regards to values sent to the array - I'm again not sure what you're expecting in terms of a 'believable' value, but remember that your setting is currently (on the uploaded VI) set to 'Index' - not to time. Depending on how your previous sine wave was generated, it might be that the previous result (even with the same settings) was more closely tied to time than a wave with 10k points in 400us. 

[Taa1000]

Hey and thank you for your answer cbutcher.

Because of you I just found out how to store default values. I apologize for the mix up. 

I added a updated attachment where the values I have been using is set as standard. 

Given you say you are getting one value out (for each update - what do you mean by this?) I guess that you have some other values set in your copy, but I wanted to mention it just in case.

What i mean by for each update is that I am using a continuous waveform which updates my graph. 

With regards to values sent to the array - I'm again not sure what you're expecting in terms of a 'believable' value, but remember that your setting is currently (on the uploaded VI) set to 'Index' - not to time.

I will also attach a screenshot of my waveform to show what i mean by  'beliavable' value. 

Again, thank you for the reply. -Taa

[Taa1000 · Accepted solution]

This is kinda late, but found the answer in this thread. 

https://forums.ni.com/t5/LabVIEW/basic-level-trigger/m-p/456019#M221110