Xylem DH-21 - Manual (Page 96)

4-50 Using the Graphical “W ATER LOG” Software
DH-21
4.4.9 Zero Sensor Option
The “ W ATER LOG” software allows you to force the sensor to use a specific point as its zero
offset point. For example, placing the sensor in 5 feet of water and pressing Zero Sensor button
will cause the sensor to record levels with a -5.0 foot offset. Figure 4-33 shows the option
selected.
Figure 4-33. Zero Sensor Option
The Zero Sensor Option can also be used periodically to remove errors in pressure measurements
due to long-term drift. To do this, remove the sensor from the water and allow it to settle for
about 20 minutes (The sensor temperature will likely be changing rapidly so you must let it
settle). Issue the Zero Sensor Option and the pressure output will go to very near 0.0000.