analog measurements using daq

[Miaa]

Hello there ,

I just want to make sure that i am not missing any steps in reading an analog signal using a USB DAQ board. So basically I go in the front panel and use the DAQmx icon as you can see it in the attached doc image.jpg, shown by "Physical channel". I connect the transducer output to the USB DAQ AI0 pin and other settings as shown on the DAQ assistant panel. 

One question here is that what should be my Acquisition mode ? sample to read and Hz values ? The signal i am reading using a DAQ board is the output of a sensor which is varying at the interval of 30 sec's. Kindly, let me know if i need to change any settings.

The second confusion is do i have to set anything using drop down menu ( see image_1.jpg ) the way i have it set right now is shown in top right hand side of image_1.jpg.

The third comment is that the introduction of noise between the 30 sec interval is too much. I have the coupling capacitors for power supply , stability capacitor for transducer but do let me know what can are the other options to view a crisp image.

[PBear]

Hi Miaa,

In general, you want your acquisition to be about 10 or more times the frequency of your signal. So if you have a 100Hz signal, you'll get a good picture of it sampling at 1000Hz or more. For the samples to read, you'll want to keep that around 10% of your sampling rate. Your Acquisition mode depends on your application: do you need to acquire a set number of samples and then end the task or do you need to continuously take in samples? Your For Loop surrounds your entire DAQmx code instead of just the DAQmx Read. This will reconfigure your board every iteration and clear the resource which will give you poor performance. You also don't need to open any of the DAQmx VIs so don't worry about the Task/Channels control.

National Instruments provides some great resources for succesfully programing your DAQ device. First, the example finder (Help\Find Examples...) has great examples for many analog, digital and counter applications. Look under "Hardware Input and Output\DAQmx\" There's also an excellent tutorial on our Developer's Zone entitled "Getting Started with DAQmx" Please follow the links below.

Getting Started with NI-DAQmx: Main Page
https://www.ni.com/en/support/documentation/supplemental/06/getting-started-with-ni-daqmx--main-page...

Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications
https://www.ni.com/en/support/documentation/supplemental/06/learn-10-functions-in-ni-daqmx-and-handl...