RMS velocity calculation from accelerometer data

[MGolm.1]

Hello everyone. I'm working on a vibration sensor with RMS velocity output based on measurements from an accelerometer with +-16g maximum acceleration range. There is a simple equation for calculation RMS velocity range and that is : VRMS=Apeak/2*pi*f*sqrt(2). Apeak would be 16g. The bandwidth that i want to cover is 10...1000Hz. So the RMS velocity would be variable based on frequency range. Now i want to know that what would be the maximum RMS velocity in mm/s for this range of frequency and +16g?

As it seen from above equation it should be something like 17.658mm/s, but i have a vibration sensor from PCH company as my reference and they declared in their datasheet that their maximum acceleration range is +-18g and at the same time they declared this device can measure maximum 100mm/s RMS velocity in 10...1000Hz frequency range. I'm pretty confused about these two issues. I really appreciate if anyone can describe some useful hints about the issue. Thank you.

[Eleon BORLINI]

Hi @Community member​ , are you using this formula below?

In the "worst" frequency point (1000Hz), for the +-18g sensor the V_range value is 39mm/s... I believe they declared the peak to peak velocity and not the rms value... You should double your vale to take into account that the ranges is +-16g (17.658mm/s*2 = 35,3mm/s), but otherwise I believe you are correctly calculating the V_rms value

Regards

[barteksieczka]

Hi,

I have a similar task, but I'm having trouble with data acquisition. I set up the ADXL345 to 3200 Hz, connected to the STM32 using I2C. I want to sample data at a frequency of fs = 256 Hz, so I call the function to retrieve data in an interrupt occurring at that frequency. I send this data to a PC application via UART, which plots graphs for me.

The problem is that I have many repeating samples (about 50 samples are needed to change the value) - unfortunately, I can't afford this because the results and graphs will be incorrect.

Have you encountered such an issue, or could you share the solution you used?