how to acquire time readings from 2 channels

[Garry]

hi, i am trying to get some time readings from 2 or more channels using LeCroy scope 334AM. my aim is to get the readings say from the 1st postive clock cycle of the wave in one channel to the one from another channel (different source). anyone out there with experience in this? please advice, thanks

[wha@atmel]

Hi Garry

first you should download @:

http://zone.ni.com/idnet97.nsf/9b2b33e1993d877786256436006ec498/35d38729d3cb1d88862568ab005fbcd9?OpenDocument

the instrument driver for your scope. Search inside the examples - how to communicate with your scope. Then you should readout the waveforms or take values of measurements.

regards
wha

[Garry]

Hi Wha,

i forgot to add that i have already downloaded the driver and used some its features. its only the time acquisition part that currently gives me a problem. furthermore,the driver does not give enough description in this area, or else the function that enables me to do so, is only available in other models of the LeCroy Scope. DO u have any experience in this area?

[Ben]

Hi Garry,

It has been a while since I developed anything using a LeCroy scope but I will do my best to answer based on memory.

I set the scope for single sweep of two channels and set my time to something appropriate.
After triggering the scope I was able to fetch the waveforms and proceesed the data (1-d array) to take the measurements I was after.

In your case, I would suggest setting time base so that you get only one cycle. Compare each reading (from both channels) with a threshold and then compare the index of the first reading above the threshold with the index of the first reading above the threshold of the other channel. Multiply the difference by the time of each sample and you should get the value you are looking for.

I hope this helps,

B
en

[Garry]

Hi Ben,

your answer is the just one I'm looking for. But i still have a slight problem. for the part on setting the element to the 1st reading above the threshold, i don't seems to have it right, as there are times that the value i've set, is not inside the array, so the returned value is 0 or index -1.

Is there a proper way to set the threshold? i am now using another way by using using the maximum value of the array as the element and using index 0 as start, and the index output multiple by the delta time, i assume it as the time i am looking for, but i am not very sure. please advice, thank you.

sincerely,
Garry

[Ben]

Hi Garry,

Without nowing what your data looks like, I am hard pressed to tell you how to procced.

If you can specify a value that represents should only be present durring the rising edge (i.e. about half way between max and min) you could run all of your samples through a ">" function that has the the "Value" wired to the bottom input. The resulting boolean array should have tues for any signal above the threshold. Search this boolean array for "T", the index returned can be used as previously discussed.

Let me know how it goes.

Ben