Hach-Lange MTC10130 - Manual (Page 5)

1. Connect the
probe to the
meter. Make sure
that the cable
locking nut is
securely
connected to the
meter. Turn the
meter on. 2. To significantly
reduce the
stabilization time
for reducing-type
samples, put the
platinum disc in
Reducing Solution
for ORP
Electrodes for
3-10 minutes
before the initial
sample
measurement. 3. Rinse the probe
with the sample. 4. Put the probe in
the sample and
stir gently. Make
sure that the
reference
junctions are
completely
submerged. Do
not put the probe
on the bottom or
sides of the
container. Shake
the probe from
side to side in the
sample to refresh
the reference
junction. 5. Push Read.
The display will
show "Stabilizing"
and a progress
bar as the probe
stabilizes in the
sample. The
display will show
the lock icon when
the reading
stabilizes. If
necessary for the
application, record
the sample pH
and temperature.
6. Repeat steps
3-6 for additional
measurements. 7. When
measurements
are done, store
the probe (refer to
Storage
on page 11).
Measurement—conversion to SHE reference procedure:
For some applications, it is customary to report redox potential readings relative to the
standard hydrogen electrode (SHE), also called normal hydrogen electrode (NHE). To do
this, select the value in
Table 1 that corresponds to the temperature of the solution
measured. Substitute that value Eref into the equation and solve for E
h
:
E
h
= E + E
ref
where:
E
h
= oxidation reduction potential of the sample relative to the SHE
E = potential developed by the ORP/Redox electrode
E
ref
= potential developed by the reference electrode portion relative to the SHE
( Table 1 ).
Table 1 shows the potentials, E
ref
, developed by the reference electrode portion relative
to the SHE at various temperatures.
Table 1 Standard potential of reference electrode
Temperature (°C) Electrode potential in mV (E
ref
)
80 163.1
75 167.7
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