Miscellaneous Electronic Components
Within each enDAQ sensor there are a variety of electrical components that can affect overall performance.
In this article
SD Cards
The enDAQ sensors use high-end SD cards to handle the fast write speed the device requires. Our legacy devices (LOG-XXXX) use cards that are part of Swissbit's S- 300u series. More recent devices (part numbers starting with 'S' or 'W') have a processor with more RAM and therefore can use a SD card with a slightly slower write speed. We use several different SD cards but if you're looking to replace one, we recommend ATP's AF16GUD4A-BBBIM for 16 GB devices, ATP's AF8GUD4A-BBBIM for 8GB devices, and ATP's AF1GUDI-OEM for 1GB devices.
Warning
Please note that we have only qualified specific SD cards for operation with the enDAQ. Although there are many other cards available, they often don't have the required write speed, temperature range, or reliability. Therefore they can cause the device to be unable to properly record data which will result in blocks of time with no data.
That being said, customers often look to replace the SD card anyways. If you'd like to switch out the card you can follow the steps listed below. Please note that the warranty will be voided.
- Make sure you are properly grounded to avoid ESD.
- Unscrew and slowly lift the top plate.
- Locate the micro SD card.
- Carefully slide the SD card backward until it lifts up.
- Remove and replace the SD card.
- Repeat steps 1-4 in reverse order.
Note:
Although the enDAQ devices operate as USB storage devices, they do not provide the same high speed USB transfer rate. This is due to the fact the device’s onboard memory is not directly accessed by the PC, it must “go through” the internal CPU. Expect transfers of large files to take several minutes. The transfer speed currently is 1.4 MB/s.
Analog Filters
The enDAQ sensor each have analog low-pass filters to prevent aliasing. But these filters can also be utilized to reduce high-frequency vibration data that may not be a concern to the user. The filters are part of Maxim's MAX7400 series, all are 5th order filters. The piezoelectric devices use a Butterworth filter, and the piezoresistive devices use a Bessel filter. For more information on filtering, visit our blog.
Oscillator
Timestamps are generated from Abracon's ABS06-32.768KHZ-1-T oscillator which has a frequency tolerance of ±10 ppm. This means over the course of 1 week (604,800 seconds) the timestamps will be accurate to within ±6 seconds.
Note:
The device will lose its clock settings if the battery dies. In this situation, the files will display as if they were recorded on 1/1/2000 or a similar looking date. Reconfiguring the device in the enDAQ Lab will set the clock to the correct date and time.
USB
The USB transfer speed on the device is 1.4 MB/s. This speed is independent on the USB cable/port used and is limited by the USB driver in the processor.