OFFSET CALIBRATION
Immerse the RX probe in the buffer solution.
Wait for the reading stabilization on the
display. Press ENTER / MENU for 3
seconds and then use the ▼ ▲ keys to
move the cursor to Calibration and press
ENTER twice. The current reading of the
probe is shown on the display. Press
ENTER and adjust (if necessary) the buffer
reading value with the ▼ ▲ buttons and
then confirm by ENTER.