Incorrect analog values from NI 9205 in multichannel mode

[Socki]

Hy José

The example "Set Convert Clock.vi" mentioned earlier shows you how to set the sampling rate (see point 2 in the vi).

The difference of convert clock rate and sampling rate is as follows:

- The sampling rate defines, how many samples from each value you will get per second.

- The convert clock rate defines the rate, with which the signals at the measuring module are scanned.

Example:

10 voltages to acquire, Sampling rate = 10, convert clock rate = 200:

Every 5ms (1s/200), a single voltage signal is scanned (one after each other) by the module.

Every 100ms (1s/10), all 10 voltage signals are acquired by the software.

Regards Socki

[KTM Enthusiast]

I am having a similar issue with the 9205 module and was hoping to get some help.  I am using channels 0-7 to read 0-10VDC differential signals but have found that Im getting crosstalk between channels.  I believe by reducing the clock rate I can fix this problem but am having some trouble doing that with the Set Convert Clock vi.

I modified the Set Convert Clock vi and called it Set Convert Clock - Entire Module.  When I run this vi, I get the following error:

Then when I instead set physical channels only to 0 through 7, I get the following error:

Can anyone help me in the right direction?  If I set physical channels to 0:31 I get the first message which doesnt like that all channels are configured as differential.  If I set physical channels to 0:7 I get a message because I can only change the convert clock for the entire module.

Thanks,
Justin

[Socki]

Hey Justin

You have two problems:

1) You cannot configure the channels as differential, if you choose other channels than 0-15. In differential mode, the channel number of the NI9205 is halved (16 instead of 32). So if you want to make differential measurements, only choose channels 0-15. I would only define channels 0:7 if you do not need the others.

2) The convert clock can only be changed for the entire module. In the property node where you change the clock rate, you also need to define the "ActiveDevs" input, which is the name of your NI9205 ("....Chassis1Mod6"). You find this option in the path "More => AI Convert => Active Devices".

As an example, I attach you a VI which I use to acquire temperatures and voltages. Hope you can open and understand it because there are some globals and typedefs which will be missing.

Please feel free to ask, if you have more questions.

Cheers

Socki

[KTM Enthusiast]

Socki,

Thanks for the help, that makes sense.

With the DAQ Assistant that I was previously using, I had scales set up to translate the voltage into pressure.  Is there an easy way to use those same scales with the DAQ-mx code?

Thanks,

Justin