Issue Details

I have a NI-9217 C Series module placed in the NI cDAQ-9184 chassis. I want to read temperature data from the thermocouple, but I have problems with the module's response time when I program it in LabVIEW.
When I use the DAQ assistant VI I measure the data with a delay of about 0.5 seconds. When I use DAQmx VIs I have a delay of about 3 seconds. Using Test Panels of NI MAX the device acquires data immediately almost with no delays. I would like to know what can be the reason for this. Is there a way to have no delays in acquisition using DAQmx VIs in LabVIEW?
 

Solution

The programming method used in LabVIEW strongly affects the behavior of the device. DAQmx VIs in LabVIEW help you to program the hardware in various ways. At the first sight, the code can be more complicated than using the DAQ assistant VIs, but these functions give more functionality to meet the requirements of your task.
The best way to use DAQmx VIs if there are no specific tasks is the classical DAQ programming method.
You can find many examples in LabVIEW's shipping example list for a variety of tasks. These examples help to easily understand the right Software configuration method of your device to make the acquisition more correct and avoid delays in measuring data. 
To find an example for acquiring Temperature data you can open the NI Example finder by going to Help >> Find Examples.

In the opened menu select Browse according to: Task and find the needed example for acquiring Temperature data by following these steps
Hardware Input and Output >> DAQmx >> Analog Input >> Thermocouple - Continous Input


This example uses the classical method of using the DAQmx VIs to acquire Analog Input Temperature data. It can be easily modified according to a specific task and prevents delays in the acquisition of data. 

 

Additional Information

It is recommended to use "While loop" and control its execution time according to the task by using "Timing" functions rather than using "Timed Loop" for continuous acquisition.