D
3.0 DataHog2
3.1 Internal (on-board) Memory
The D loggers all have solid state, battery backed Random Access Memory.(RAM).
This stores all the logged data and also calibration factors etc. The on-board lithium cell
should provide back-up power for approximately ten years. Because of this memory back-
up, data is retained when the main batteries are flat or disconnected for replacement, but no
logging is possible from this back-up power. It should be noted though that it is good
practice to offload data from the unit before the main batteries are exhausted if at all
possible.
Depending on the model of 5000 series, the RAM may hold up to 11,001 records of data and
time (1 record includes date, time and a measurement of each channel) or nearly 30,000
measurements each with a time and date stamp, in 121,020 bytes. The amount of spare
memory can be checked in Options 1 then 5 from the Main Menu. The following table gives a
useful guide to the number of bytes used per channel and records available at different
logging intervals:
TABLE OF INTERNAL (ON-BOARD) MEMORY SIZE AND USAGE
The internal memory of your D is split between a few locations required for housekeeping
and the bulk of the storage capacity which is devoted to data storage. The data is stored in a format
that is constant. Basically the data from each channel that has been gathered at one time is stored
together with the date and time at which the data was obtained. Thus the channel data (from 1 to 8
channels) plus the time is a set number of records. Clearly the fewer the number of channels in use, the
greater the number of records available for storage. The table below shows the maximum number of
records for different numbers of channels in use and illustrates the time before memory is full at different
logging intervals.
Channels
Bytes per
record
Records
available
Logging
1 min.
Interval
10 min
30 min
2 hrs
1
11
11,001
7.6 days
10.9 wks
32.7 wks
2.5 yrs
2
15
8,068
5.6 days
8.0 wks
24.0 wks
1.8 yrs
3
19
6,369
4.4 days
6.3 wks
18.9 wks
1.5 yrs
4
23
5,261
3.6 days
5.2 wks
15.6 wks
1.2 yrs
5
27
4,482
3.1 days
4.4 wks
13.3 wks
1.0 yrs
6
31
3,903
2.7 days
3.8 wks
11.6 wks
46 wks
7
35
3,457
2.4 days
3.4 wks
10.2 wks
41wks
8
39
3,103
2.1 days
3.0 wks
9.2 wks
37 wks
9
43
2,814
1.95 days
2.8 wks
8.3 wks
33 wks
10
47
2,574
0.78 days
2.5 wks
7.6 wks
30 wks
11
51
2,372
1.64 days
2.3 wks
7.0 wks
28 wks
12
55
2,200
1.52 days
2.2 wks
6.5 wks
26 wks
16
71
1,904
1.18 days
1.4 wks
5.0 wks
20 wks
13
