Using Two DAQ, is it possible?

[DFGray]

Support of DAQ boards in SignalExpress is done using the same DAQ Assistant available from the LabVIEW palettes.  The DAQ Assistant offers custom scales and I believe it offers pressure options.  You should be able to succeed using either platform.

I would encourage you to download the 30 day trials and check out both.  Use the one that works best for you.

[carlosdga]

Thanks for the time taken to help me with the problem. I´ll check DAQ Assistant in the SE I installed

I found SE while I was looking for some videos that I could use to understand about Labview on youtube. I noticed how easy it is to take measures and register data with it. But my University doesn´t have any license that I could use to get the program.

If you see my first post, all I need is to measure temperature and pressure in real time and register it so I can analyze it and make some heat transfer calculations. Judging by everything I have watched, SE would fit for this objective, right?

But what about controlling (starting/ turning off) some parts of the system (Compressor, fans..if you can see the picture i attached in the first post you will see), I was checking the SE i have downloaded it and I couldn´t find that option, I guess I can´t, can I? in that case, what would you recommend to do to make this possible?

Best regards

[NIquist]

That's what I was saying.  Signal Express is a simple way to do data-logging with some advanced analysis functionality built in.  It's NOT capable of ANY true programming tasks.

TBH, if SE was <$200, I would highly recommend it, but at its current price I think most people would be better off saving up for LabVIEW.  F. Shubert is correct however, in saying that the LV base version is very limited compared to the Full and Pro versions.  Once you start adding modules the costs can really add up.  Ask your Professors about a student licence though, you may get off cheap!

[carlosdga]

It´s something i got to analyze. Tomorrow I´ll be talking with my project tutor so we can define the situation in order to select the program that fits in a better way for the project.

Last night I was checking NI USB-9008 specifications and i noticed it said:

Simultaneous sampling: NO

What does it means? Because I need to continuously take values from several points from the test bank. Is is related with that?

For last, a stupid question that i couldn´t find in the whole page from the NI USB-6008. It comes with it´s USB cable right?

Best Regards

[NIquist]

Most of the multi-function DAQ cards can't do simultaneous sampling.  If you have a 16 channel DAQ card, what it does is multiplex the channels into one DAC chip.  They can multiplex very quickly so in most applications the microseconds between consecutive samples on each channel doesn't matter.  Keep in mind, that means you lose sampling rate when you increase the channel count.  i.e: If you buy a DAQ that can do 1MHz sampling speed, that's for ONE channel.  When you scan multiple channels your sampling rate gets divided up between the channels.  Two channels limits the rate to 500Khz, five channels gets you only 200Khz/channel, etc.  Max sample rate on each channel = overall DAQ sampling rate / # of channels.  In your case a multiplexed DAQ should be more than adequate but, of course that depends on your particular needs.

Every USB product I've ever bought from NI came with cables and driver disks.

[carlosdga]

For example, I´m buying two NI USB-6008. I need 10 analog inputs. NI USB-6008 has a 12 kS/S sample rate. According to the idea i got from your last message, it means I should connect 5 channels on one DAQ and 5 on the another one? How will be the perfomance of each DAQ on my case? Because now i´m worry

[DFGray]

With five channels on each and a 12kHz sample rate of the digitizer, the maximum sample rate you will get is 2.4kHz (12kHz/5).  If this is not enough, you should look at other solutions.  If you need to do this, give us your complete requirements (e.g. sample rate, bandwidth, range, number of channels=10, maximum cost, etc.) and we can probably give suggestions.

[NIquist]

Actually, the USB-6008 has a top sampling rate of 10KHz aggregate (total of all channels used).  That means 5 channels running on a 6008 will sample at 20KHz max for each channel.  Now 20 KHz is pretty fast if you're measuring real world signals like temperature so you're probably alright.  Once you determine what your input signals will be, you'll know if the 6008 will be adequate. 

If you need to accurately measure faster signals you need a faster DAC in your DAQ card.  The Nyquist theorem states that you must sample a signal at (at least) TWICE its maximum frequency.  Anything less and you will experience aliasing .

One more point (worry?):  The output speed of the 600X series is very slow (12-bit @ 150S/s).  150 Hertz is OK for near DC stuff but you won't be able to generate a high speed waveform with it.  I don't know if you need to but it's something to keep in mind.

[carlosdga]

I´ll be measuring temperature and pressure (5 analog inputs for each one). I have to focus to get values from those points continuously (in some cases, because the test bank will let the students to do many experiments). But I need to visualize how those values change continuously, and I want to know how fast I`ll be watching thoses changes in my case.

The range for temperature will be from -10ºC up to 150ºC. I built with a LM35 (Temperature sensor) a circuit that I just tested and gives an outcoming voltage from -550mV (at -55ºC) until 1500mV (150ºC). With the USB NI-6008, can I work with this sensor?  Because I´m on a tight budget so I have to reduces the total cost of the bank (that´s why I´m considering the DAQ 6008)

[DFGray]

The LM35 has a relatively slow response, so sampling at anything over about 5Hz (200ms sample period) is probably overkill.  The 6008 should work well for you.  What is the time response of your pressure sensor?