how to read the time from waveform

[henryfgfg]

i want to read the time between two different probes from TDS3014, or the time between ch4 at start up and ch2 at max volt point. just as you know ,we can read the time directly from hp scope, but for tek scope,we cann't do the same,anybody know ?pls help which will be kindly appreciated. the attached file for you referrence

[Dennis_Knutson]

This could all be done on the pc and not with the scope itself. I'm assuming that you've got the driver for the scope and are able to transfer the waveforms to the pc. I believe you will get a waveform array for each channel and an x increment value. It's a matter of finding the index of the desired point of each of the two different waveforms, subtracting the indexes, and multiplying by the x increment to get time. I'm not sure of your definitions of 'start up' and 'max volt point'.

[henryfgfg]

Dennis, Tks,yes ,you are right,i have transfered the waveform from scope to pc, i know what you mean,and i want to measure the time just as attached, but i don't know how to find the index of each waveform,could you help me? "start up" means the begining ponit of the rising edge of channel 4, and the "max volt point" means the end point of the rising edge of channel 2,just the time between two cursors of the attached. Besides,i want to save the waveform ,so i must move and position the two cursors in scope.

[Dennis_Knutson]

There's a couple of ways that you can do it. There is the Basic Trigger Level Detection and the Treshold 1D Array. You could even wire the array in a while or for loop and use a simple Greater Than Equal function in the loop and then return the 'i' of the loop when the condition is met. The Threshold 1D will interpolate the result but that may not matter. The Basic Trigger Level Detection can be set to return the index of the point that first exceeds the trigger level or if you create a waveform data type, it can return the time of the trigger event.

[henryfgfg]

yes,the trigger time i can get,but the other cursor position i cann't get ,would you pls give some advice?i try to position the cursor ,but it's difficult to realize.

[Dennis_Knutson]

I don't understand what you are doing. Are you trying to position the cursors on the scope or in LabVIEW? My suggestion doesn't require curosrs at all and is done entirely on the waveforms in LabVIEW. Take the waveform for one channel and wire it into the Basic Trigger Detection. Take the waveform from the other channel and wire it into another Basic Trigger Detection. Subtract the two index results and multiply by the dt of the scope.

[henryfgfg]

of course on scope

[Dennis_Knutson]

Sorry. I thought you wanted to know how to make the measurement in LabVIEW since you had posted to the LabVIEW board.

I don't have the manual and don't think I want to download it right now so I'll have to speculate. If there is no built in function for channel to channel time interval measurements, then I think you will still have to do a lot of the processing in LabVIEW. If you can get a trigger location in LabVIEW, you should be able to translate that into cursor locations and place two separate cursors. The Configure Vertical Cursors function allows you to place cursors based on time. The function Read Cursors will return the delta. I have no idea if the delta is displayed on the scope itself.

[henryfgfg]

anyway,thank you very much