Error-200284

[chasan_2k]

Dear All,

i get the error-200284 in the attached AC Test loop vi

the objective of this vi is acquire and control the pressure(top loop) and once the preesure is stabilised switch on the valve and measure the coil current(in the second loop)

the switching is done by a external powers supply and for synchronisation of switching and current read an external trigger from power supply is used(second loop)

i get error in first loop only that too,it happens occasionally (probability of 1/40)

i have gone through all the knowledge base and forum articles and tried those but still getting thesame error

pls suggest me by seeing the vi,whether i should change anything in the code

Note:may be the chroma vi wil not open in the main vi (since you may not have the driver)so you can leave it and see the code and let me know a suggetion

Thanks in advance

Chandru 

[Neal M]

Hello Chandru,

I cannot see anything in your first loop that obviously would cause the timeout error you are seeing.  The error you specify is a timeout error, which means that you are not recieving samples from your acquisition.  The steps that I would use to figure out exactly what is going on are:

1. Use Highlight Execution to determine exactly where the error is being thrown (it should be the DAQmx Read.vi, but just to make sure)
2. Use Test Panels in Measurement and Automation Explorer (MAX) to see if you can reproduce the problem there.  If you can, then it most likely is a hardware issue.
3. Use an Example Program under Help»Find Examples... to try and recreate the problem. This will tell us the issue is somewhere in the code.

The only major thing I can see in the program is that you are configuring the task in the second loop every time.  You should either do this before the loop, or clear your task each time (the first is a better option than the second).  The fact that it only happens once out of 40 times suggests that it could be a dataflow problem (something is executing before another that once, causing the problem) but I could not see anything that obviously would cause this.

Let me know what the results of the above testing, and we can narrow down why you are seeing this timeout.

[chasan_2k]

Hello Neal,

Thanks for the reply

I tested the the same code for DC valves,it doesnt give any error and running smoothly for long time

the only difference in the code between AC and DC system is the valve is actuated by a LabVIEW Counter in DC and by an external power supply in AC

in AC we use the power supply trigger as to start the valve actuation and coil current read in synchronised way.

The DAQmx read (-200284) occurs only in AC system vi  which i posted earlier

was it due to the trigger which we use in the second loop?

but the second loop runs only once and stops

pls seethe attached code which i used for DC and this does not give any DAQmx read problem(it uses the same structure except the valve actuation)

Thanks

Chandru

[Neal M]

Hello again Chandru,

It looks like you are correct, it could be the triggering in the second loop.  It does not matter that the loop only runs once, if it does not get its trigger in the 10 second timout of the DAQmx Read, then it will throw that error.  The trigger is from your power supply, right?  Are we sure that we are starting the task before the trigger is being sent?  If it is close, then that 1/40 it does not work could be because of this.

Are you sure that the error is coming from the top loop? (That is where the arrow in your first vi is)?  I cannot see any reason that the top loop should give a timeout error (unless you are sampling at a slow rate which does not appear to be the case).  Any way you could use highlight execution and take a screenshot when the error occurs, just to make sure?

[chasan_2k]

Hello Neal,

i have done some intensive testing to identify the location of the error,theerror -200284 occurs in second loop where i used a external trigger to synchronise the coil activation and coil current measurement.This trigger we get from the chroma power supply and i see that the chroma trigger is existing but even then it produce the DAQmx read error -200284.

it happens rarely and that affects our whole measurement calculation

we tried detecting the trigger using a PFI line using a trigger detection vi but it seems it doesnot work

Do you have any suggestion to over ride the error or let me understand what might be the other causes for this error

is there any mehod to detect the trigger and arm the start task

Thanks in advance

Regards

Chandru

[Neal M]

Hello again Chandru,

In order for the trigger to work, it needs to be within TTL specifications.  If the rise time or something is not in this spec, it may or may not be recognized by the hardware as a trigger.  Is there a chance that 1/40 times the trigger is not within this spec?  That is by far the most common reason for missed triggers.  If there was a way you could scope the trigger and get an image or some measurements on on that is missed, that would be of great interest to me.

If you don't really care about the missed trigger and just want to clear it so your program stops, I would recommend using a case structure (get the code out of the error wire and wire that into the selector) and using the Clear Errors VI like so:



This will let you see other errors, but clear the error when the trigger is missed.  Another option you have is to extend the timeout on the read to longer so that a second trigger comes along.

Let me know if this works for you or if you have any other questions.


Message Edited by Neal M on 06-19-2008 10:42 AM

[chasan_2k]

hello Neal,

As discussed in the previous posts,i went for analog trigger instead of digital trigger to avoid the missing trigger(occasionally occured)

Now i am facing another probelm, when i run the Stand_alone_AC _switch program alone the program recogonise the anolo trigger and acquire the data,but when i use the stand-alone_AC_test_loop program it does not detect the trigger and outputs the same error -200284

my objective  "stand-alone_AC_test_loop program" is to continuously maintain the pressure in the loop1 and after  15 sec,the second loop has to switch the valve and acquire the valve voltage,when it detects the trigger.

but it is not happening,when i remove that start trigger analog edge vi and run the code,it is working,i do not understand where i am going wrong.

as mentioned when i run the "stand-alone_AC_test_loop program " alone it is detecting the trigger perfectly,the same functionality only i used as a second loop in "stand-alone_AC_test_loop program .

please go through it and let me guive a thought about where i go wrong

hope to hear some remedy

Thnaks

Chandru

[dansch]

Hi Chandru,

Just to make sure I understand the problem correctly, it sounds like you are unable to get “Stand-alone AC test loop PID.vi” to run correctly using the analog start trigger, but that you are able to get “Stand-alone AC Switch.vi” to run correctly when using the trigger. The -200284 error is occurring at the DAQmx Read in the bottom loop, where you are configuring the analog input channel to use the analog start trigger? Does this error occur every time you run the VI or only sometimes? It looks like there may be a possibility that the trigger is occurring before you actually start your task, and thus you are missing the trigger. Looking at your code, this could be possible since you are calling the “chr616xx Output Switch.vi” independently of the DAQmx functions, and thus there is no guarantee of when the trigger occurs in relation to the DAQmx Start function. One thing you may want to try is to route the error out from the DAQmx Start function to the error in of the chr616xx output switch, and then wire the error out of this to the error in of the DAQmx Read. This will force the DAQmx task to start before the trigger is sent. I hope this helps,