NovaLynx Corporation
255-704-B
Page 11
April 2021
5.5
Offset Calibration (optional)
The generic calibration (Section 5.4) does not take into account the amount of water required to lift the
float off the bottom of the gauge. Since evaporation is the DIFFERENCE between readings (typically
measured once every 24 hours), it isn't necessary to adjust the offset. However, to match the readings
to the actual water level, add the offset to each scaled measurement in the Linear Scaling Assistant.
The amount of water required to lift the float is about 1.7 inches (varies from unit to unit). To find the
actual offset for a particular unit, measure the water level in the evaporation pan (using a tape
measure) and subtract the logger's reading at that level.
1.
Measure the water depth and calculate the offset:
Example:
8.00" Measured Depth – 6.30" Logger Reading = 1.7" Offset
2.
Add the offset to the generic calibration values:
Value 1 Scaled:
0 + 1.7" Offset = 1.70000
Value 2 Scaled:
9.444 + 1.7" Offset = 11.14400
3.
Program the new calibrations into the Linear Scaling Assistant.
5.6
Field Calibration (optional)
A two-point field calibration is easy to do provided there is an accurate way to measure the water
depth in the evaporation pan. The depth can be measured with a tape measure, ruler, hook gauge, or
by adding known amounts of water.
Connect a computer to the logger, run HOBOware, then open the Status window. In the Current
Readings section, set the Screen Refresh Interval to 1 second.
Use the calibration chart below to record your measurements:
Raw
Scaled
Units:
Volts
Inches
Value 1:
0.00000
1.70000
(1.7" offset added)
Value 2:
2.50000
11.14400
(1.7" offset added)
