34
SECTION 3,
continued
4. When the reading has stabilized, the standard number will
change to
2
.
5. Press
EXIT.
The adjusted offset value, the slope, and the
Store
and
?
icons will appear. Verify the offset value (isopotential
point) is within the range specified in the electrode manual.
6. To save the adjusted calibration and return to the reading
mode, press
ENTER
. To exit the calibration without saving it
and return to the reading mode, press
EXIT
.
3.3
ISE Calibration
Calculation for ISE values does not require temperature
compensation, so a temperature probe is not necessary for ISE
testing. However, a temperature probe will still function properly
and display the correct sample temperature. Use the 5-pin
temperature probe available from Hach, Cat No. 51980-00.
1. Prepare standards according to the electrode instruction
manual or the instructions for the standard. Use two to five
standards for calibration. Pour 25 mL of each standard into a
50-mL beaker.
2. Turn the instrument on. Select the desired channel and the
BNC connector (Setup 1). If necessary, press the
ISE/mV
key
to get into the ISE reading mode (the last concentration units
entered
will be displayed).
3. Press
CAL
. Functional keys will appear in the lower left part
of the display.
CAL,
?
, and flashing units will appear.
4. To change the units, use the arrow keys to scroll to the
desired choice (g/L, mg/L, µg/L, ppm, ppb, M). Press
ENTER.
5. Add ionic strength adjustor to 25 mL of the least
concentrated standard.
6.
Standard,
and
1
will appear in the upper display. If the meter
has been calibrated, the last value for standard 1 will appear.
The numeric keypad will become active.
7. Place the ISE electrode in the standard with the lowest value.
While measuring, stir the solution slowly and steadily.
