nidaqmx - add_ai_microphone_chan - input parameters

[KelvinTao]

Hi All,

Working on a aquisition system and was hoping for some clarity on some input parameters for nidaqmx. I am referencing: https://nidaqmx-python.readthedocs.io/en/latest/task_collections.html#nidaqmx.task.collections.AICha...

The add_ai_microphone_chan method has a optional "max_snd_press_level" input parameter that is noted as "Is the maximum instantaneous sound pressure level you expect to measure. This value is in decibels, referenced to 20 micropascals."

I want to know if this impacts the output from the sensor or if there is any internal logic.

EX:

Mic sensitivity: 50 mV/PA

Input Range (9234) +/- 5 V

This correspondes to an ACTUAL max dB of 134 dB.

What happens then if I input a max_snd_press_level = 90 dB? Does setting this change anything?

Thanks

K

[santo_13]

That helps the DAQmx driver determine the appropriate input voltage range if your HW supports multiple ranges. You must also provide the sensitivity of the mic and only with that DAQmx can determine the correct input range.

[KelvinTao]

My hardware is the cDAQ 9171 with a 9234. I am unsure if this has a selectable range. 

https://www.ni.com/docs/en-US/bundle/ni-9234-specs/page/specs.html Indicates a minimum is 5 V.

Much Thanks,

K

[santo_13]

Even if your hardware supports only one range, I recommend configuring the max dB SPL in case you switch to a much more capable HW in the future, and your code will be stable.