help to new user

[drtbrl]

I am a very new user of Labview. My application consists of acquiring
high-speed voltage data on several channels. I intend to use triggering to
initiate the acquisition. I am using PCI-MIO-16E-1 card for this. I am
having following problems, please advice

A. Is there a ready-made VI available in Labview which I can use? (I am
still learning Labview programming)

B. As output I want two things-
1. A data file containing two columns of acquired data showing time
and voltage and
2. An XY graph with actual time on X-axis (so that I can compute delta t
between two measurements) and voltage data on Y-axis. I want to see time on
X axis with time=0 when the acquisition started. I also want to be able to
set X-min and X-max explicitly
. For this what should be used - a XY chart or
XY graph? When I select real time on X format (with Xo=0) I do not get
desired results. Moreover I am unable to set X-min and X-max at all (like I
can do it in Excel) .

C. My inputs are single ended for sure. But are they NRSE or RSE ? I am
still not very clear.

D. While testing my card I used test panel. I connected ACH0 pin of
PCI-MIO-16E-1 to 1MHz sine wave input( taken from my pulse generator) .
However the test panel was not able to reproduce the sine wave exactly. When
I reduced the input frequency to 100KHz it was able to reproduce the wave
shape to a certain extant. What is wrong?

E. In several VI's a buffer is used to store the incoming data? Is it the on
card buffer or some software buffer?

F. Will the total performance of the system depend upon the processor
(computer in which DAQ card is installed) used? For example is it preferable
to use a PIII instead a PII computer.

I shall be grateful if any one can explain i
n detail.

[Melissa Niesen]

"drtbrl" wrote:
>I am a very new user of Labview.

I'm not as experienced as many of the people in this group, but I'll try
to help a little...

>My application consists of acquiring
>high-speed voltage data on several channels. I intend to use triggering
to
>initiate the acquisition. I am using PCI-MIO-16E-1 card for this. I am
>having following problems, please advice
>
>A. Is there a ready-made VI available in Labview which I can use?

The LabVIEW solution wizard has a high-speed data acquisition wizard, but
I can't tell you much about this since I never use the wizard. I don't think
that solution can be triggered (besides by you clicking the mouse.)

If you want to get up and running quickly, it looks like Functions>>Data
Acquisition>>Analog Input>>Analog Input Utilities>>AI Waveform Scan.vi might
work for you. It looks like that VI can be triggered.

>B. As output I want two things-
> 1. A data file containing two columns of acquired data showing
time
>and voltage and

Functions>>File I/O>>Write to Spreadsheet File.vi is a fast and easy way
to do this.

>2. An XY graph with actual time on X-axis (so that I can compute delta t
>between two measurements) and voltage data on Y-axis. I want to see time
on
>X axis with time=0 when the acquisition started. I also want to be able
to
>set X-min and X-max explicitly. For this what should be used - a XY chart
or
>XY graph? When I select real time on X format (with Xo=0) I do not get
>desired results. Moreover I am unable to set X-min and X-max at all (like
I
>can do it in Excel).

First of all, there are basically two ways to get data: 1) by taking single
points in a loop -- this sounds like it would be way to slow and unreliable
for you, or 2) letting the DAQ system buffer the data for you. Using the
second method will let you take high speed data at fixed time intervals (so
you don't have to calculate actual time delta t's for each point). Any of
VIs that ask for a scan rate and number of points will give you back data
that has been buffered. (anyone correct me if I'm wrong!) If you want to
make an array of times, you can build it up, e.g. using a for loop.

For this the display of arrays of data, if you already have a time array,
you probably want to use the XY graph, that way you don't need to mess with
Xo and delta X. You can use the text tool on the numbers on the graph scales
to change the min and max scale values. Also, once you get deeper into LabVIEW,
you can set those in the program using attribute nodes.

>
>C. My inputs are single ended for sure. But are they NRSE or RSE ? I
am
>still not very clear.

I can't help much here. If they are grounded, I think they are referenced.
If they are battery operated, probably non-referenced. This is something
specific to whatever you are using to take the measurements.
>
>D. While testing my card I used test panel. I connected ACH0 pin of
>PCI-MIO-16E-1 to 1MHz sine wave input( taken from my pulse generator)

[Melissa Niesen]

I guess that other message was too long, so here is the rest:

>D. While testing my card I used test panel. I connected ACH0 pin of
>PCI-MIO-16E-1 to 1MHz sine wave input( taken from my pulse generator)

[Melissa Niesen]

One last try to post the second half. If this doesn't work, I'll mail it.
(something is weird with the NI newsgroup form)...

>D. While testing my card I used test panel. I connected ACH0 pin of
>PCI-MIO-16E-1 to 1MHz sine wave input. However the test panel was not able
to reproduce the sine wave exactly. When
>I reduced the input frequency to 100KHz it was able to reproduce the wave
>shape to a certain extant. What is wrong?
>
According to the LabVIEW manuals, the PCI-MIO-16E-1 can sample at rates up
to 1MSamples/s, therefore, you will not be able to get any meaningful information
if your input is a 1MHz sine wave. You need to sample at at least twice
the frequency of the input wave, and if you want it to actually look like
a sine wave, you need to sa
mple even faster than that (it might be good to
read about the Nyquist theorem and the Nyquist frequency.)

Remember also, that if you sample more than one channel, your maximum sample
rate will go down, i.e. your max sample rate is 1MS/s (where S stands for
Samples) NOT necessarily 1MHz.

>E. In several VI's a buffer is used to store the incoming data? Is it the
on
>card buffer or some software buffer?

I don't know exactly where it is stored.

>
>F. Will the total performance of the system depend upon the processor
>(computer in which DAQ card is installed) used? For example is it preferable
>to use a PIII instead a PII computer.

If you use one-shot buffered DAQ (not a circular buffer) either computer
should be fine. The scan rate is timed on the board itself, not on the computer.

Hope this helps,
Melissa