The datalogger stores two types of records in the database, a detection record and an event record.
The detection record is a summary of the event which can include multiple scans of the same tag. The record is created when the tag is no longer seen (empty scan) or another tag is detected.
D 2013-10-25 11:17:57.13 00:00:00.28 HA 900_226000054864 A2 2 225
The records consist of:
detection record indicator "D"
date and time of start of detection
duration in hundredths of a second
H for HDX, F for FDX (dual mode reader)
A for ISO animal format, R for read-only, W for writeable tag
tag number (manufacturer code and unique ID)
- antenna number (multiple antenna reader only)
number of consecutive detections
number of empty scans before the detection (arrival interval) ("." if over 65,000)
The number of consecutive detections should be more than one to assure reliable operation. If the tagged animal is only scanned once and that detection is missed you will not get any data. If the tag is scanned a few times per event then if it misses once there is no harm. Multiple detections increase reading efficiency.
An empty scan is where the HDX reader sends out a charge pulse and does not detect a tag in the listen cycle The reason this is useful is that if the number is small and the tag number is the same, this indicates the tag is "stuttering". Each time the tag leaves the field (and an empty scan occurs or a new tag is seen) the detection record is written to memory.
If a tag is stuttering, usually because it at the edge of the scan zone where the charge pulse is weakest, this will generate lots of repeated detections very close together, possibly hundreds or thousands per day if the fish stays near the edge of the field. Our readers have a minimum gap parameter that you can set to ignore short gaps when scanning of the same tag. This creates one long detection record instead of many small ones.
An event record starts with the letter E and has the event message ("Battery low") with a timestamp.
Detection or event records are sent together in an upload. With the command line you can type UPD or UPE to only list detection or event records.