Selection of a subset of channels to read with DAQmx

Hello

I use a 32 channel NI9205 analog input module, connected with the chassis OR cDAQ-9174 and LABVIEW 2011.

I created a task in the measurement and Automation Explorer who has 16 analog input of virtual channels (each of them with her has an entry configuration, scale, calibration, etc...). Inside LABVIEW, I opened this task to acquire some data, but I just want to read some of the 16 channels (defined by the user), not all, so before the "time DAQmx", I put a 'DAQmx reading node' and I put the ChannelsToRead with the names of the channels that I want to read. It seems to work, but when I put the acquisition rate it's error.

The acquire module supports a rate of 250 kHz (divided by each channel). So if I put 5 channels to read, for example, it should work with a rate of up to 50 kHz. But whenever I try to use an acquisition rate higher than 15 625 kHz (which is 250 kHz/16) I get an error that says that the maximum rate is 15, 625kHz. As if I was using 16 channels of the task, but I'm not...

Here the screenshot of channels read and sync configuration.

Thank you
Alexander

Hello Alexander, and welcome to the forums,

As odessy27 says that you do not reach the correct sample rate because the task is to be set up to read 16 channels; in spite of you more later by specifying which channels are to read.

To preserve the configuration settings of your created able task and Automation Explorer (MAX), I recommend creating global chains of these. A Global channel will store your configuration for each physical channel and can be accessed from multiple tasks

Creating a Global channel by the physical channels in your task of MAX right-clicking and then selecting create Global Channel. .

You can drag these through to your block diagram and wire in the task/channels in the terminal of a function of mx-acquisition of data, as shown in the image below.

If you change to a control by right clicking > change control channels can be set by the user and the maximum purchase price will go as planned.

Concerning

Jamie

Tags: NI Software

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