【9-Axis Offline Accelerometer Data Logger】WT901SDCL High-Precision Gyroscope+Angle (XY 0.05° Accuracy)+Magnetometer with Kalman Filtering, MPU9250 200Hz Inclinometer Sensor with 16G SD Card

Device and Hardware- Physically small, under 4x4 centimeters (excluding ears).- Internal circuitry is clean and well-assembled.- Battery lasted longer than expected, at least six hours in initial testing. (Fun fact: You can log data to the SD card with power connected.)- USB-C port is physically lose on my unit.- Included 32GB SanDisk SD card and a USB SD reader. (I'd recommend discarding the latter, mine broke on first use.)- Important note: When connected over USB, it will remain in sleep mode (and not stream data to host device) unless switched on.Documentation and Materials- Full documentation set with FAQ, datasheet, manual and protocol guide (latter required to decode data stream) are difficult to find, hidden away on a Google Drive link. However, some of these (the datasheet and manual) are shared on the Amazon product page and sent from the seller after purchase.- Their GitHub repository appears out of date (at least for this product).Onboard Data Logging- Data files are stored in a hexadecimal stream you'll either write code to translate or use their Windows software to playback/convert.- Time must be calibrated in the app. Based on my limited testing, it drifts approximately 30 seconds/day.- For data logging purposes, some settings (like sensors) are managed via the Windows app. However, others are controlled via a settings file in the SD root (such as scale and logging rate).Windows App- Windows app is unsigned! It worked well within a VMware Windows 11 virtual machine. However, lack of signing prevents any real-world deployment for me. Software available on Google Drive.- Apparently there is a new 2023 version, although hosted on a different Google Drive link I cannot (re)locate.- The Windows app is required to translate the native hexadecimal stream to a useful tab-delimited format. (Unless you write code to perform the same, of course.)Android App- APK on the Google Play Store is outdated (version 3). You can download version 4 from their Google Drive link.- Using multiple devices and versions, I've can update device configuration but never stream/record data successfully. At most, it’ll only capture the initial measurement sample and never stream updates.- I didn't see time calibration or file conversion on Android, just Windows.Recommendations for Witmotion Team- Host latest versions of software, manuals, datasheets on their website. Centralize common software and protocol documents into a single location so they remain current across products.- Please continually deploy latest Android apps to Google Play and sign your software.- Stand-alone data loggers should export information in human-readable format (such as CSV or tab-delimited). At least make it an option with perhaps a reduced log rate.

I like that the product can record data offline using an SD card, which can be viewed later for data analysis.

After the second order of these sensors (the first one died in testing) I am now also returning the pair included in my second. On the plus side, the pair of sensors included in my second order have survived initial testing. Unfortunately, I have found a significant issue with the internal clock drifting, regardless of charge level, which may not be so noticeable unless you have time dependent synchronization requirements. I left three stars because they do perform the measurements stated by the manufacturer and work well through the app, however, the synchronization doesn't work remotely which is presumably why you would purchase a SD data logging variety. I came to the conclusion this is more of a novelty sensor and not fit for my specific purposes...so much for a shortcut. If you want something done right, build it yourself.