AEM 30-2500 AQ-1 Data Logging System - Manual (Page 20)

Page 20 10-2500 AQ1 Instructions RevD 102512.doc
Size
Cards up to 32GB are approved for use with the AQ-1. SD cards 4GB and above
may take longer for Windows to mount/recognize due to the file system required
(FAT32) for high capacity cards.
Speed
SD/SDHC cards are rated as Class 2, Class 4, Class 6, or Class 10. The class
can typically be identified by the Class number within a circle logo on the label of
the card. Note: Class 2 cards commonly do not have the class number on the
label. The AQ1 Data Logger comes with a 2GB Class 2 SD card that is suitable
for most cases. Extremely high total logging rates may require use of a class 4,
6, or 10 SD/SDHC Card.
If using a Class 4 or higher card, the "Total Data Rate" can be increased by
clicking the Total Data Rate link label in the lower left pane of the AQ-1 software.
Use caution when increasing the “Total Data Rate”. Data will be lost if the Total
Data Rate exceeds the capability of the SD/SDHC card. An error message will
be displayed during .LOG file conversion if data has been lost.
Total Data Rate
This is the data rate (bytes/second) at which data will be written to the SD card
during logging. This rate increases as you enable channels for logging or
increase their sampling rate. It decreases when you disable channels or reduce
their logging rate.
Fragmentation and Speed
The memory of a card is divided into minimum memory units. The device writes
data onto memory units where no data is already stored. As available memory
becomes divided into smaller units through normal use, this leads to an increase
in non-linear, or fragmented storage. The amount of fragmentation can reduce
write speeds, so faster SD memory card speeds help compensate for
fragmentation.
Brand
AEM does not recommend any specific brand but it is always suggested to use a
"name brand" card made by a reputable manufacturer. Cards by less than
reputable manufacturers may not adhere to the SDA specification resulting in
data loss.
Figure 26. SD Card Speed Classes