West Control Solutions DataVU 5 - Manual (Page 25)

25
2 Device description
Operating
principle
The measurements from the analog inputs are acquired continuously in a
250msec sampling cycle, and then stored in the main memory. These
measurements also serve as the basis for limit monitoring.
Main memory
(FLASH
memory) The data stored in the main memory are regularly copied to the CompactFlash
card in 4 kbyte blocks. The main memory is written to as a ring memory, i.e.
when it is full, the oldest data will automatically be overwritten by new data.
The capacity of the main memory is sufficient for approximately 350,000
measurements. The instrument monitors the capacity of the main memory and
activates the “Memory alarm (internal)” signal if the level falls below a
configurable residual capacity.
CompactFlash
card For saving the data, CompactFlash cards (industrial grade) can be used with
the following storage capacities: 64/128/256MB.
The instrument monitors the capacity of the CompactFlash card, and activates
the “Memory alarm (CF card)” signal if the level falls below a configurable
residual capacity. This signal can be used, for instance, to operate a relay
(warning signal “Swap CF card”).
Data security The data are stored in coded form in a proprietary format. If the CompactFlash
card is removed from the instrument, no data will be lost immediately, as these
data are still stored in the FLASH memory. A loss of data will only occur if, after
the CompactFlash card has been removed, the FLASH memory is completely
rewritten as well, and no data have been read out through the interface.
Storage cycle Different storage cycles, ranging from 1sec to 32,767sec can be configured
for normal, event and timed operation under “configuration”.
The storage cycle determines the time intervals at which the measurements
are stored.
Stored value Under this parameter, separate configurations are made for normal, event and
timed operation, to decide which value is stored (average, momentary,
minimum, maximum, peak values).