Setting 0.4 ms ( lower than 1 ms resolution) time delay after the trigger

[newbieeng]

Thank you Brandonj. Unfortunately, my device (NI USB X 6343) does not provide HW-Timed single point option. In the link, startdelay dawmx property node unit is set to seconds, but there are two more options which are "sample clock periods" and "ticks". According to these options, the most proper one is "ticks" option, as far as I understand. What I understand is, if thick unit is set, the counter counts the thick from the source, which can be any timer available on the device for the job. What I understood is from this link: If I choose the counter source 100 kHZ timebase (period time = 1/100000 s = 0.01 ms), to trigger the signal after 0.4 ms, tick # must be set to 39 (if first tick is counted as 0). Did I understand the vi correctly? Can I do achive my aim with my USB X 6343 device?

[brandonj]

I believe your understanding is correct. You can setup a finite analog output to occur and setting up the delay to be counted in ticks or sample clock units should both work. You may also find it worthwhile to look at "voltage - finit output.vi" example. 

[newbieeng]

Instead of using AOs for this task, I found that use of a second counter is possible to count the edges on the same device (NI USB X 6343 I use). It is explained here. I hadn't known that an external clock must be used  while counting edges for one USB device. Anyway, this method seems ok for now. I think that the same thing can be done via AO channels via generating buffered signal (as a clock), as you referred. Do I understand you correctly?

However, one thing I confused about this task. When I use Test Panels to count edges on MAX, it count edges without any setting information of external clock (the test panel does not ask about the external clock for this task). It works perfectly. How can the test panel count edges without setting of external clock? Why do I must define an external clock programming on labview? For case of using one device (6343), is there any other way without occupying a second counter (and also AO) as an external clock?

[brandonj]

newbieeng,

I am not sure I understand your first question about edge counting or how it relates to your application of delaying an output after a trigger. If your AO channels are used up by a different part of your setup, you may want to try using a digital output. 

[newbieeng]

Hi brandonj,

The aim of the counting of the edge is to catch the correct delay time, for my case it is 0.4 ms, for triggering the device. I try to explain briefly what I am trying to do. I have a combustion chamber on which pressure transducer and spark plugs are installed. After the gas filling process of the chamber, I ignite the spark plugs for pre-combustion inside the chamber to get the desired high pressure and temperature like engine operating conditions. After the ignition, for instance 0.4 ms later, I have to inject the diesel fuel immediately in to the chamber to get the complete combustion. This delay time is important to catch the desired pressure and temperature values for the complete combustion. The four AO channels on the device (NI USB-X 6343) are occupied for valve controlling necessary for gas filling process so I cannot use them for adjusting the time delay. All in all, I need to trigger the injector by sending a TTL signal after 0.4 ms ignition trigger. I am searching for doing that job only one device, 6343. If I will not able to do that, I can utilize the other one also, NI USB-X 6353. I also have Measurement Computing USB 4301 but I cannot utilize it even though I installed the proper drivers.

[brandonj]

You should not need to count edges to get your desired 0.4ms trigger delay. I see your AO are used elsewhere, but you can do what we had discussed before with a digital line. So try doing exactly what was discussed before (adding a DAQmx trigger property node after the DAQmx start trigger VI, select "sample clock periods" for start delay units, choose whatever start delay (i believe you did the math correctly before)). This time you are using a digital output instead of analog.

[brandonj]

You should be able to set the sample clock source to "onboard clock". Look at the example at Help->Find Examples...->Hardware Input and Output->DAQmx->DigitalOutput->Digital - Finite Output.vi (this example does not yet include the DAQmx Trigger property node with the delay).