Problem: 2 ai tasks with different sample rate and voltage range

[Souza]

Hello,

I have to read 12 sensors with ai channels. minVolt=0,maxVolt=5. Sample rate=10kHz.

Besides the 12 sensors, I need to read 2 temperatures with an LM35. 10 miliVolts is 1 Degree Celsius. I do not want to sample at same rate as the sensors, this is much too high for measuring temperatures. Neither do i have to measure the voltages in the same range as with the sensors. The range for the temperature is, minVolt= -0.5 maxVolt = 1.5.

I have created two tasks in my application. A mytaskTemp and a myTaskSensor on the same device.

When i run my application it generates an error: "Specified source is reserved".

Can anyone please help me with this problem. How can i make this work.

Hardware = PCI 6220

Software = Visual Studio 2003

Thanks in advance,

Souza

[WM_John_Weeks]

You have two choices:

Get a second board for the temperature measurements, or over-sample the temperature and then reduce the sampling by some means.

To reduce the sampling, you can either throw away extra measurements (easy) or average them down (harder, but you get better measurements). Carefully choosing the samples to average also allows you to filter out certain sorts of noise, the most common problem being 60 Hz noise (50 Hz if you're in certain parts of the world).

With NI-DAQmx (or Traditional with most boards) the different voltage ranges aren't a problem.

[Souza]

Thanks John,

for your very quick response to my question. I think I am giving your second option a try, filtering the samples. You are right about the voltages, these can be changed for each channel. Again thanks very much.

Souza