This seems like it should be such a simple measurement. I attempted to use :MEAS:TVAL? 1.5,1,CHANNEL2 in order to measure the time it takes from the scope trigger (chan1) to when chan2 wave exceeds 1.5V for the first time. This gives me an error -1073807339 (timeout).
How can I read the time that chan2 goes high vs. the trigger on chan1?
Still not having much luck. Got rid of the timeout by actually triggering the scope very quickly before doing the readback. When this command is sent, it clears the previous trigger and is actually waiting for a new one before it can be read back. Is there a way to read what is on the screen already without retriggering?
Struggling through this. I have discovered that doing a VISA Write of ":MEAS:TVAL? 1,1,CHANNEL2", then creating the trigger event to the scope and doing the VISA Read of the number of bytes written, I get the expected data result. By the way, I'm using LabView 2013 and looping this Write/Trigger/Read process 20 times and will eventually need to do this process 200 times for my statistical analysis.
Now, however, I am struggling with the VISA Read occasionally timing out. Most of the time, the read task works and takes approximately 1 second. But I am seeing it start to back up (I'm using USB communications to control this scope) and when this happens, the VISA read takes 1 second, then 2 seconds, then 3 seconds. When it hits the 3 second time, that is when I get a timeout. Any suggestions, or should I go to National Instruments forum? It does not seem like it should take 3 seconds to do a VISA Read.
My favorite tool for separating code problems from instrument/command problems is the IO Libraries Suite Interactive IO. It allows me to test the commands I am sending.
You mentioned you were sending Write/Trigger/Read. If the screen has no waveform on it, that Write will have nothing to analyze and return +99e+36 at the read after the trigger.
Fungible,
The Interactive IO you show does the write then read. That is exactly what I was doing. And I do have waveform data displayed but each time I send this command, the screen clears and I get the timeout. Wonder why my scope is not behaving the way yours is? Here is my code snip-it.
When I was using that method, I always get a VISA read timeout. However, if I place the Write and Read in-line with my app that triggers my UUT test then it works. Here is a snip-it of what works.
I would like to know why using that TVAL command is clearing my scope forcing it to wait for a trigger. I would much rather trigger my UUT, see the waveform and simply read the data and log it with LabView.
So I have figured out that if I set the scope to do a single trigger, the waveform is left on the screen and then I can to the TVAL command. Here is my code change
But programmatically this works when my time scale = 5ms/div. I get no errors. But when I change the time scale to 50ms/div and call this same function, the VISA read times out or reads " " blank. With the 50ms/div setting, I can enter these commands in my instrument control panel manually and it works each time. Is the scope taking to long to produce a result? This is pretty frustrating.
Keep in mind, as the sweep speed goes down, it will take longer for the scope to acquire the data. At 50ms/div and 10 divs that is half a second.
Thanks but the VISA read has no delay time input. It will simply do the operation and pass the results.
Anyway, I figured out the root of the issue. My UUT was actually causing the failure. Even though I was telling it to send data, it did not send 100% of the time. So I figured out a way to read the trigger status of the scope and don't move on until it has triggered. All of the timeouts were because the scope did not actually trigger. This issue is now resolved. Thanks for taking the time to assist. 
I am starting to understand what your overall objective is (beyond the scope commands). And it triggered a couple of thoughts.
It appears you are sending the :SING command to the scope followed by the GSIF to the UUT. And that the GSIF should cause a signal from the UUT that triggers the scope. Depending on the sweep speed, there could be a timing issue. Once the scope receives the :SING command, it starts acquiring pre-trigger data. The scope does not arm the trigger until all the pre-trigger time has passed. If the GSIF causes the desired signal to occur before the pre-trigger data has been gathered and the trigger is armed, the event will be missed.
I see a need for two loops. One loop after the :SING command. It would monitor bit5 of :OPER:COND?. The program stays in the loop until bit 5 is set. That indicates the pre-trigger data is captured and the trigger is armed. Then the GSIF signal can go to the UUT. After the GSIF signal goes the second loop monitors bit 3 of :OPER:COND?. The program stays in the loop until bit 3 goes low. That indicates the scope has triggered, the post-trigger data is captured and the scope has stopped the acquisition. At that point, it is safe to send the TVAL? command.
Thanks but the VISA read has no delay time input. It will simply do the operation and pass the results.
Anyway, I figured out the root of the issue. My UUT was actually causing the failure. Even though I was telling it to send data, it did not send 100% of the time. So I figured out a way to read the trigger status of the scope and don't move on until it has triggered. All of the timeouts were because the scope did not actually trigger. This issue is now resolved. Thanks for taking the time to assist.