Which DAQ do I want?

[Bill_Connelly]

I'm sure you get this question a lot. I have looked through the very large list of DAQ devices, but I am over whelmed, and I hope someone can help me.

What I want to do, is when a TTL pulse comes into the DAQ, it triggers lab view to send an analog out pulse. It would be awesome if there were up to 8 digital ins, and so if the TTL pulse came in on one channel, it would sent out one analog out, but if it came in on another channel, it would send out a different amplitude of analog out. A stand alone box with BNCs would be ideal, but I can deal with any plug format. Finally, it needs to be able to run at atleast 10kHz. Price is a big factor here. The cheaper the better.

TL;DR I need a DAQ that sends an analog signal out in response to a digital signal in at 10kHz.

[TrottM]

Hi Bill

If price is a big factor then i would recomend one of the USB based DAQ devices offer. One such device that would acheive everything you want would be the NI USB-6008. This has 8 analog inputs, 2 analog outputs,12 digital I/O and a 32-bit counter.

Hope this helps

Matt T

[Bill_Connelly]

Am I right in reading it's description? It can only output at 150Hz?, i.e. the briefest pulse it could put out is  6.6ms ?

[John_P1]

You probably don't want the 6008.

The problem with your application is that you need to output a variable voltage based on which channel your digital pulse occurs on.  Unless you choose a device with a user-accessible FPGA (expensive), the logic to determine what voltage to output will have to be implemented in software.

The software implementation of this will not be able to keep up with 10 kHz on a regular Windows-based PC.  You might possibly be able to keep up on RT, but again this would be expensive.

You will have to make some compromises.  If you don't need the voltage to change, and merely need to generate an analog output pulse based on an external trigger signal, you can do this with a USB 6211.  Generate a retriggerable counter output pulse train of two samples to use as the sample clock, the period of this pulse train would be the width of your AO pulse.  Write a given voltage to the AO as your first sample, and 0V as your 2nd sample.  Then, whenever you receive a trigger, the AO will pulse for the desired time at the desired voltage.  Note that the output is pre-buffered, and so cannot change values deterministically.  The 6211 does not support change detection, so you can only trigger off of a single line.

Best Regards,

[Henrik_Volkers]

If you want it cheap a µC is the solution, might only be beaten by an 555, 8bit latch, one OP and some caps and resistors 😉 (If the voltages are fixes, otherwise it would need trimpots and the µC will end up cheaper.

UUps, it's a Multifunction DAQ forum here isn't it? 😉

Have a nice weekend

Edit: If the TTL trigger pulse length equals the analog out pulse lenght its only about 10 resistors and one OP 😉

[TrottM]

Hey Bill

Just as a bit of follow up. Have you thought about phoning one of National Instruments Sales Engineers where you are? They may be able to advise you better for what you need and further what you are working on.

Thanks

Matt