User Guide

19
TWO POINT CALIBRATION
A two point calibration is recommended for
best accuracy. As a second point use pH 4.01
if you are going to measure acid samples (pH 7
or less), use pH 9.18 or pH 10.01 if you are going
to measure alkaline samples.
Two point calibration at pH 6.86 and pH 4.01
or pH 9.18 (NBS):
• Proceed as described in “One point calibra-
tion at pH 6.86” but do not quit calibration by
pressing the CAL key at the end.
• After the first calibration point
is confirmed, immerse the pH
electrode and the temperature
probe into the second buffer
solution (pH 4.01 or pH 9.18)
and shake briefly.
Note: the electrode should
be submerged approxi-
mately 4 cm (1½") into the
solution. The temperature
probe should be located as
close as possible to the pH electrode.
• Select the second buffer
value on the secondary
display by pressing the
°C
or
°C
key.
• When the “READY” and
“CON” symbols blink on the
display the reading is stable
and the calibration can be
confirmed.
• Press the CFM key. If the
reading is not close to the
selected buffer solution,
“WRONG
BU
F
2
” and “WRONG ”
will blink alternatively. If
the reading is close to the
selected buffer, the slope and
the offset are calibrated.
°C
HI 7004
4 cm
(1½
")
ºC
READY
CON
CFM
WRONG
WRONG
2
BUF