03-19-2023, 11:54 PM
Dear all,
I was experimenting in the Lab with a SDoF system to see if we might be able to make measurements with multiple devices (using the remote control functionality) and re-align after export using the system time data in the meta folder. Both devices (an iPhone and a Samsung), were sitting on the vibrating mass.
I did the necessary post-processing in Excel, using the delta between the two but I cannot get the time realignment as close as I had hoped/expected. Here you can see the data for the two phones (iPhone first, Samsung second) when they were both on top of each other on the mass. I determined the delta (-8.440 s) using the system time values for each device and adjusted the time trace for the iPhone based on that to align the data.
As you can see below, they are still a little bit misaligned (but SO frustratingly close!). I noticed there may be some DC offset on both so detrended and subtracted the mean but, even tho' a bit better (and you can see they are measuring the same vibration), it is not good enough.
It would be possible to "fix" the issue with cross-correlation to find the additional time realignment required but I had hoped to get closer than this.
I wonder if anyone has any thoughts or comments on this.
Thanks, Ben
I was experimenting in the Lab with a SDoF system to see if we might be able to make measurements with multiple devices (using the remote control functionality) and re-align after export using the system time data in the meta folder. Both devices (an iPhone and a Samsung), were sitting on the vibrating mass.
I did the necessary post-processing in Excel, using the delta between the two but I cannot get the time realignment as close as I had hoped/expected. Here you can see the data for the two phones (iPhone first, Samsung second) when they were both on top of each other on the mass. I determined the delta (-8.440 s) using the system time values for each device and adjusted the time trace for the iPhone based on that to align the data.
As you can see below, they are still a little bit misaligned (but SO frustratingly close!). I noticed there may be some DC offset on both so detrended and subtracted the mean but, even tho' a bit better (and you can see they are measuring the same vibration), it is not good enough.
It would be possible to "fix" the issue with cross-correlation to find the additional time realignment required but I had hoped to get closer than this.
I wonder if anyone has any thoughts or comments on this.
Thanks, Ben