Precision Water Level Instrument
Unidata Manual 6293 - Precision Water Level Instruments Issue 2.1
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proposed.
Significant source of error can occur at sites such as reservoirs and bores where
large variations in water level are recorded. When the float movement exceeds
10 metres, special components or designs may be required. This is because the
net weight of the floatline transfers from one side of the pulley to the other. In
extreme cases the float may be lifted from the water by the weight of the line on
the opposite side of the pulley and
run away
.
The endless floatline is an alternative that eliminates the transfer of weight from
one side of the float to the other, and the errors so induced. It also solves the
problem of line “run away”.
6.9 Causes of Error
The main causes of error in float line level measurement are:
•
Float line shift.
•
Submergence of counterweight.
•
Instrument lag.
•
Temperature change.
Other minor causes relate to humidity and water saturation of wooden
supporting structures and the expansion of such structures resulting from
changes in temperature and water content.
Note:
Causes of error, corrections and error reduction are fully described in
Appendix C – Float Systems
