DAQmx - one chassis two modules synchronous readings

[lmd2]

I have a chassis with two 9205 modules, and a 9211 temperature module. I can continuously read voltages on any combination of channels on the two 9205 modules, but when I try to also read the 9211, either in the same while loop or a parallel while loop I get an error on the 9205 that the resource is reserved. I have the 9205 set for reading 10K/sec, in blocks of 2K (i.e. the loop reads 5X a second) so I configure the 9211 to read 2 samples at 10Hz (also 5X a second). The error I get -50103: The specified resource is reserved - I am not sure what resource is in conflict, the clock or some bus allocation?? can I read the three modules (at different clock rates) simultaneously?
thanks
lmd2

[Nick_F1]

Hi Lawrence,

Since all three modules are analog input modules, you will have to have them all in the same task.  There is only one timing machine for analog inputs on the cDAQ chassis, so any analog input on the cDAQ chassis will have to be in the same task and use the same timing.  One thing you can do is to run the analog input task at the faster rate and then only grab the samples you need from the channels that you want to acquire at a slower rate. 

Hopefully this will get you on your way with your application.

[lmd2]

Thanks Nick
my confusion here is that the 9211 has a max sampling rate of 14Hz, the other sensors need to be read faster (typically 50Hz but up to 200Hz) if I set the clock to 50Hz will the 9211 error (over-clock error or something)? do you know of an example using a 9205 and a 9211 together?
Thanks for your time and help,
lmd2

[Nick_F1]

Hi Lawrence,

What happens is that the slower module will repeate samples until it can acquire another sample.  Both of the channels will acquire the same number of points, but the thermocouple module will store multiple instances of the same value until a new value is read in by DAQmx.

Here is what it looks like to have multiple channels setup for a single task:



Message Edited by Nick F on 04-29-2008 02:18 PM

[lmd2]

thanks Nick, looks like this will work fine for us. Again thanx for your help
lmd2