Hanna Instruments HI 98401 - Manual (Page 8)

8
CALIBRATION
In order to obtain accurate measurements, frequent calibration is
recommended.
For better results, calibrate at a temperature close to that of the
solution to be tested (no more than ±3°C apart).
The instrument can be calibrated at 1 or 2 points. Two-point calibra-
tion is always recommended for better accuracy.
The first point of calibration is fixed at 100 ppm (HI 70703). The
second point can be selected between 10.0 (HI 70702) and 1000
ppm (HI 70701). If the sample to be tested has low ionic strength
(below 100 ppm), use HI 70702 for the second point. Likewise, with
sample concentrations above 100 ppm, use HI 70701 as the second
calibration point.
PREPARATION
• Use only clean beakers.
Prepare two calibration solutions by mixing
sufficient quantity of 50% HI 70703 (100
ppm) and 50% HI 7023 (TISAB) solution in
one beaker and then 50% of HI 70702 (10.0
ppm) or HI 70701 (1000 ppm) solution and
50% HI 7023 (TISAB) in the other.
• Attach the fluoride electrode (#3 on page 4), the reference
electrode (#2) and the temperature probe (#1) to their respec-
tive connectors on top of the meter.
• Switch the meter on by pressing the ON/OFF button.
Note: For best results, it is recommended to prepare two beakers for
each calibration point: one beaker to rinse and the second one
to calibrate. This minimizes contamination of the calibration
solutions.
Note: Use plastic beakers to minimize electromagnetic interference.
CALIBRATION PROCEDURE
Note: If the fluoride electrode is new, or it has not been used for a
few days, it must be soaked in a solution of HI 70702 (10 ppm
of F
- ) for at least 3 hours prior to calibration.
• Rinse the electrodes with deionized water and dry them attentively
with a non-abrasive cloth.
9
• Immerse the fluoride and the reference elec-
trode as well as the temperature probe to a
depth of at least 1 cm (½”) in the prepared
buffer solution. Make sure that the electrodes
are not touching the bottom of the beaker.
Immerse the temperature probe close to the tip
of the other electrodes.
• Press CAL. The display will show “CAL” and “BUF” together with
an intermittent “~” symbol. The upper display will show the
calibration point (100 ppm) with the temperature of the solution
shown on the lower LCD.
• When the CON symbol appears, it means that the calibration
solution has been recognized and the reading has stabilized. Press
CFM to confirm the first calibration point.
Note: If the value of the calibration solution
measured by the meter is too far from
the ideal value, the “ “ symbol
starts blinking to indicate an error in
the calibration procedure. Ensure that the calibration solution is
fresh and the correct one (in this case 100 ppm), and that the
electrodes are in good working condition if necessary follow the
electrode maintenance procedure. Repeat the procedure with
fresh and/or new solutions and electrodes.
• After pressing CFM, the display will show
the second point of calibration (10.0 ppm).
Two-point calibration is always recom-
mended, however, by pressing CAL one
can exit the calibration procedure at this point, having successfully
completed a one-point calibration.
• Press BUF to toggle between 10.0 and 1000
ppm and select the second calibration buffer.