Hanna Instruments HI 93414 - Manual (Page 31)

31
FOUR-POINT CALIBRATION
To perform a four-point calibration, continue the
procedure with the following steps:
• Remove the third standard cuvette.
• Place the 750 NTU standard cuvette (or the
fourth prepared formazin standard) into the
holder, with the cuvette mark aligned with the
sign on the instrument top.
• Close the lid and press READ/TIMER . The
display will show blinking dashes and the icons
for cuvette, detectors and lamp will appear
during measurement.
• At the end of the measurement, the four-point
calibration is completed and the instrument
returns automatically to measurement mode.
OUT CAL RANGE FUNCTION
The instrument has an
Out Cal Range function to
prevent taking measurements in a range where the
calibration do not assure the best results. The range
where the calibration assures correct measurements
is up to 40 NTU for a two-point calibration and up
to 150% of the third point value for a three-point
calibration.
The display will show a blinking “
CAL” tag each
time the measurements are taken outside the
calibration range.
CALIBRATION ERROR MESSAGES
• If the value of the standard read during the
calibration is too far from the set value, the
instrument will display “
-LO-” or “-HI-” error
messages. Check if the correct standard is used
or prepare a fresh standard, if formazine is
used, and repeat the reading of the standard.