User Guide

16
STANDARD SUSPENSION
Presently, there are only two recognized pri-
mary standards: AMCO-AEPA-1 and formazine.
Hanna Instruments supplies HI 93703 with the
AMCO-AEPA-1 which has a much longer shelf
life at all concentrations (approximately six
months, if free from contamination). In addition,
no special handling or disposal is required and
a much higher stability of suspended particles
has been observed.
On the other hand, formazine is a very toxic
substance, generated by a known carcinogen,
its stability is poor (particles flocculate and
settle quickly). Lower concentrations change
value within a few days or hours after dilution
from stock solutions.
The consistency of HI 93703 readings by using
both standards has been separately estab-
lished by Advanced Polymer Systems and
Hanna Instruments.
Additional documentation about the formazine
standard and more complex calibration proce-
dures is available upon request.
VIEWING THE CALIBRATION DATE
• Turn the meter on and
wait for the display to
show "----".
• Press and hold the
DATE/⇒ key and a
"MM.DD" message
appears while the key
is held.
Note: The displayed date is the date that was
input by the user at the beginning of the
last calibration.