unstable output

[sperelat]

I'm making pulses with NI-6733 board

I generate analog square pulse with "pulse" block in "signal
processing".

(labview 8.0)

I make multi channel output with Pulse block,waveform builder,and
daqmx write block.

Update rate is from 1,000 to 1000,000

It works,but output is very unstable.

The pulse must have two output value,but it often shows intermediate
value .

It even make pulse that oscillate between maximum and middle value and
never falls to 0.

Is it a hardware problem, or something that happens with labview
daqmx pulse often?

I will atttach screen capture soon

[Matthew_Kelton]

What voltage level are you pulsing at?  Have you considered using the timer/counter on the board instead?

[sperelat]

screen capture  of code is included

Output is 1~3 V

I need to output 3 pulses to 3 channels. counter pin  was not considered

for that reason

메시지가 12-06-2007 12:46 AM에 sperelat에 의해 편집되었음

[altenbach]

Is your output wiring properly terminated?

[Matthew_W]

 Hi sperelat,

 Is there any change in the performance when you slow the sampling rate way down?
 
 Have you looked at the waveforms to see what will be generated?
 You can just create a indicator on the doubles and wire it to a waveform chart.

 Are certain update rates more stable than others? This would be the result of the sample
 clock being a integer division of 20Mhz.
 
 Do you see this behaviour with a resistive load? What is on the output of the 6733?

 Have a great evening.
 
 Best regards,
 
 MatthewW
 Applications Engineer
 National Instruments



 
 

[sperelat]

I tried to change pulse width and delay with given sampling rate.

Output became unstable if delay+width exceeds 7.

( sampling   100,000  or 1000,000)

It was also affected by increas of output from other channel.

Did anyone tried the code I posted with your own daq board?

I don't know if it's problem of NI 6733 board or problem of code.

[Matthew_Kelton]

You didn't post any code, just an image of your block diagram.

[sperelat]

When I  wrote the word "code", it was block diagram..because labview doesn't have seperate code

for the block diagrams ^^;

[Matthew_Kelton]

But they do have VIs which you can post.

[F._Schubert]

You should place an DAQmx-WaitUntilFinished between Start Task and Clear Task.

Felix