Precision Water Level Instrument
Unidata Manual 6293 - Precision Water Level Instruments Issue 2.1
11
Model 6541-3 Metric Water Level with 100mm Pulley
(used for precision measurements)
3.1.2 When to Log
When you log data you save it in the memory of the logger. This is the
information that you record for later use. You can select what data to log, and
when to log it, so the time series of data that you capture will suit your project
and application. This is often a compromise between the memory size of the
logger, the data detail that you wish to record, and how often you can unload
and process the data.
The logger will read the 6541 at the scan intervals you select. You have the
option of time based logging (e.g. each 15 minutes), event based logging (e.g.
each time the water level changes 5mm) or a combination of time and events
(say once each day and each time the level changes 10mm).
Time Based Logging
The default method is time based logging and this is typically used for water
level measurement. The logging interval must suit the site conditions and
project. For reservoirs and groundwater aquifers, water level may change
slowly. In such cases logging the average water level each hour may be
adequate. In larger rivers logging each 15 minutes may be suitable. The water
level in smaller streams and drains can change rapidly and you may need to log
each 1 to 5 minutes to capture the maximum rates of change that can occur. For
rainfall or evaporation you may require hourly or daily totals or you may wish to
log detailed data from which you can derive maximum rainfall intensities
needed for design studies.
When you use Time Based Logging, memory usage is consistent and the time
and date when the memory will be full can be predicted.
Three parameters define the time element of the logged data:
