How to do Analog to Digital Conversion with DAQ-700?

[Violette]

Hi, I have a DAQ-700 card and I'm recieving analog input from a video camera. I am trying to render this input digitally for viewing in LabView. Do I need a certain codec? Please tell me how I can view input from the video camera.

[Conseils]

Are you referring to this hardware.
100 kS/s, 12-Bit, 16 Analog Inputs -- for PCMCIA
http://sine.ni.com/nips/cds/view/p/lang/en/nid/5503

This is a general purpose analogue input card.
Surely a suitble frame grabbing card would be better?

[Violette]

I was under the impression that my card had an ADC built in. Surely there is some way to convert the video signals to digital and render them in LabView?

[Conseils]

In answer to your basic question - I don't believe that there is a 'driver' that will produce video or a video image on the screen.

Have you thougt about the maths involved i.e. sampling rates?

Basically I think you will find that the sampling rate is just a bit low!

A baseband video signal has a bandwith typically around 12MHz, that implies a sampling rate at least a couple of orders of magnitude higher than this card is capable of.

Video ADC's are specified in Megasamples per second not Kilosamples per second.

The way a capture card works is to reduce the processing overhead by presenting complete frames in a frame buffer to the host device. The mechanisim for placing data into the frame buffer is normally done by a hardware device i.e. a high speed video ADC with some form of high speed memory access. I beleive also that NI say this will dii the job as well (NI PCI-5911100 MHz, 100 MS/s, 8 to 21-Bit Digitizer) there are probably others but I wanted to point out an example.

Perhaps you could identify more clearly the basis of your project?

[Violette]

We are moving bubbles off a heating element with pulsed ultrasound in microgravity. It's an experiment for NASA, but we are all undergraduate students and this is our first time doing this sort of thing. We are using the video camera to capture the movement of bubbles off of the heating element, so we can measure the velocities of the bubbles under varying conditions (such as increased amplitude of the sound wave). Obviously we should sync the video feed with Labview (which we are using to control a function generator, turn the heating element on and off, among other things) so we can know exactly what test conditions correspond to the video image (when we turned the element on and off, etc.) since these events will vary from microsecond to microsecond. The only data acquisition or ADC capability we possess at this time is the DAQ-700.

Here's our website, I'm the kid with purple hair.

http://www.seattlecentral.edu/learn/microgravity/

[Conseils]

Well I always wanted to consult on a NASA project and I guess through your efforts I got the chance.

We had better be sure we get it right! I am reasonably sure that that data aquisition card won't hack it (one could knock up a frame store or something but I don't think you have either the time or expertise OR SHOULD).

Not only do you need some video capture but I think you need some fairly competent image processing software as well to track / measure the bubbles in the medium. Carefull control of Lighting will help and you will need to be sure that ambient lighting changes don't cause miss counts or miss measurements.

I belelieve that what you should do is continue to capitalise on your project teams strenghs and focus heavily on your basic skills sets. As chief communicator you have, I hope, quickly identified a weak area in your teams knowledge base. Which you can now capitalise on by leveraging your communication skills. I thus make the following recomendation: -

National Instruments do some fantastic software for processing images and I would strongly suggest that you consider formally approaching them for both technical and hardware assistance for such an exciting piece of work. I would imagine a number of other techniques are possible for tracking movement of the bubbles through the medium and I know that this type of work is related to fluid dynamics so this is an area that you could use as the basis for researching how others might have gone about similar tasks.

It transpires that I will be in Seattle (WA) in a couple of weeks perhaps it would be possible to meet up with you guys?

[Violette]

National Instruments is certainly the vendor to be interested in for this kind of project. Almost all of the academic websites I've visited on the topic agree. This message board was a great start, and based on your reply I will contact an NI representative. I would be glad to meet with you, and I'm sure the team would too. My email address is syntheticka@gmail.com. Do you do any programming in G?

[Conseils]

I have done quite a bit of Labview G work over all Labview versions released on the P.C. platform but mailnly under DOS / Windows platforms.

Well that's enough of my C.V.

I will send an email and try to make some arrangements.