questions about analog out and analog in

[kristof1983]

Hello,

I have a few questions concerning my project. I'm using the 9004 RT controller with 9103 chassis and 9263 AO and 9215 AI modules.

My assignment is as follows:

I write an arbitrary wave to the memory of the FPGA, then I start sending out the wave using the 9263, the wave passes an impedance and finally it's sampled by the 9215.

To make the wave as accurate as possible I need as much samples I can store, so..

QUESTION 1: How large is the memory on the 9103 (in bytes)?

I've based my project on an example I found on the ni website: http://zone.ni.com/devzone/cda/tut/p/id/3027 

As you can notice, in the Arb_load_FPGA the samples are converted using "nominal to binary vi"

QUESTION 2: Isn't it possible to just convert the samples to FXP and store them like this (without using nom2binary vi)? Is it accurate?

To test my application I connected AO directly with AI without impedance. When I store a sine with ampl 5,3 and 9263 starts sending out I measure 5,3 on my oscilloscope but when I'm reading the samples back in there is a deviation (samples don't match)
Does this have to do with calibration? How can I solve this?

QUESTION 3: I don't really understand this nom2binary vi

for instance: what if reading calibration data times out in Arb_Load_FPGA. Calibration data is zero (LSB and offset).
If you look at nom2bin you notice that this vi divides by LSB weight (=zero) without LabVIEW complaining (I ran it several times)

If I use this code instead:

 code width = voltage range of module 9263 (=20V) / resolution (=2^16)

 binary value = (output voltage x 2^16) / 20V

 How do I take calibration data into account

[Ipshita_C]

Hi,

To answer your questions:

1. The memory is on your controller and FPGA, not on the chassis itself.

2. FXP is a format that provides economy of storage in FPGA. When you are doing data acquisition on the FPGA, by default, the samples get stored on the FPGA in FXP format. In order to view them in a readable format, you do conversion in the Real-Time interface so that the numbers make sense when you plot them on a graph. 

3. Using the 9263 module you should be getting data that is already calibrated. Therefore, you should not really need to use the Nominal to Binary VI. 

I hope this helps and please post back if you have further questions.

Ipshita C.