topic CLAD DAQ question in Multifunction DAQ

CLAD DAQ question

mayur95 — Thu, 18 Jan 2018 12:13:24 GMT

Hello everyone.

Please explain what is actually asked in the question especially what is 'buffer underrun'.

Thanks .

Re: CLAD DAQ question

Kevin_Price — Thu, 18 Jan 2018 14:55:38 GMT

Ok, it sounds like you just want clarification on the question so I won't reveal the answer.

"Buffer underrun" can happen on an output task when the board is ready to generate the next sample, but the application software hasn't delivered it yet. (The analogous "buffer overrun" happens when an input task is ready to add a sample into a buffer, but the application software hasn't retrieved prior samples to make room for it yet.)

It's significant that regeneration is set to 'none'. If regeneration were allowed, the aforementioned "buffer underrun" wouldn't happen, the task wouldn't be trying to *avoid* generating the same data a 2nd time, it would happily regenerate the buffer over and over forever.

In short, all tasks shown do not allow regeneration, so all are *eligible* for a buffer underrun. So now see if you can work out which code will lead to one.

-Kevin P

Re: CLAD DAQ question

mayur95 — Thu, 18 Jan 2018 18:49:28 GMT

In other words , does buffer under run mean that the application is not writing data quickly enough?

Re: CLAD DAQ question

Kevin_Price — Thu, 18 Jan 2018 18:53:58 GMT

Yep, that's right. Typically solved by some combination of writing larger chunks and/or more often. Or, when appropriate, allowing regeneration.

-Kevin P

Re: CLAD DAQ question

mayur95 — Fri, 19 Jan 2018 12:41:02 GMT

In option D , there is a boolean conditon under autoindexed tunnel.

Can you tell me what is it exactly?

How to use it in labview?

Re: CLAD DAQ question

crossrulz — Fri, 19 Jan 2018 13:22:55 GMT

Right-click on the output tunnel and there will be an option for the conditional input. When false, that value is not added to the output array. So it is a way to filter an output array.

Re: CLAD DAQ question

mayur95 — Fri, 19 Jan 2018 13:29:41 GMT

Sir, I right clicked the output tunnel but there is no option for the conditional input.

Is there any other way?

Thanks.

Re: CLAD DAQ question

Kevin_Price — Fri, 19 Jan 2018 13:50:04 GMT

It's in a sub-menu under "Tunnel Mode->". The first set of options (indexing, last value, concatenating) are exclusive and only 1 can (and must) be selected. The conditional option can then be optionally applied as a separate decision.

-Kevin P

Re: CLAD DAQ question

mayur95 — Fri, 19 Jan 2018 13:53:12 GMT

I tried , but still can't find it.

Does it have anything to do with labview version?

Re: CLAD DAQ question

mayur95 — Fri, 19 Jan 2018 17:09:41 GMT

I think I have figured out the correct answer.

It should be option D.

As mentioned in one of the responses , conditional tunnel is used to filter out an array.

In option D any value outside the range mentioned should be filtered out.

So 'write function' won't get samples as per the rate it is working.

Hence we will get buffer underrun error.

Am I correct?

Re: CLAD DAQ question

Kevin_Price — Fri, 19 Jan 2018 20:04:39 GMT

You got it! Right answer and more importantly, right reasoning.

-Kevin P

Re: CLAD DAQ question

mayur95 — Sun, 21 Jan 2018 05:36:03 GMT

Thank you Sir.

Re: CLAD DAQ question

blink247 — Fri, 25 Jan 2019 06:34:34 GMT

look closely letter D is the answer.