NAVI D-25 Instruction Manual page 195

7 Reference
7.2 mV (oxidation-reduction potential [ORP]) measurement
184
Operation check using standard solution
Standard solution is not used only for the calibration of
the meter, but to confirm whether or not the condition of
electrodes is good.
1.
Add 250 mL pure (de-ionized) water to one
packet of any of the previously listed standard
solutions and mix well. (When mixing, the
excess quinhydrone [a black powder] will float to
the surface of the solution.)
2.
Immerse a washed and dried ORP electrode in
the ORP standard solution and measure the mV
value.
3.
If the electrode and the meter itself are working
correctly, numerical values within ± 15 mV of
those listed in Table 1 should be obtained.
4.
If measurements falling within 15 mV of the
values listed above are not obtained using this
method, measure the solution again after
replacing
solution and removing any dirt from the surface
of the metal electrode by moistening a cotton
swab with alcohol or a neutral cleaning agent
and lightly rubbing the electrode or by soaking
the electrode in diluted nitric acid (1:1 nitric
acid).
5.
If measurements within 15 mV of the values are
still not obtained after re-measuring, the
reference electrode or the meter may be faulty.
Either replace the electrode or have the meter
inspected.
the reference electrode internal
HORIBA