7 Reference
7.2 mV (oxidation-reduction potential [ORP]) measurement
180
HORIBA
7.2
mV (oxidation-reduction potential [ORP])
measurement
●
ORP principles
ORP is an abbreviation for oxidation-reduction potential.
ORP is the energy level (potential) determined
according to the state of equilibrium between the
oxidants (M
z+
) and reductants (M
(z-n)+
) that coexist
within a solution.
For one type of equilibrium in a solution:
M
z+
+ne
-
⇔
M
(z-n)+
••••••
①
If only
①
exists within a solution, a metal electrode
(platinum, gold, etc.) and a reference electrode are
inserted into the solution, forming the ORP measuring
system shown in Fig. 1. Measuring the potential (ORP)
that exists between the two electrodes enables the
potential to generally be expressed by the following
equation.
••••••
②
E: Electric potential E
0
: Coefficient R: Gas coefficient
T: Absolute temperature n: Electron count
F: Faraday constant a: Activity
Fig. 1 ORP measuring system
E
E0
RT
nF
‑‑‑‑
aM
z
n
–
(
)
+
aM
z +
‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑‑
ln
–
=
Potentiometer
Содержание D-25
Страница 2: ......
Страница 11: ...CONTENTS VIII HORIBA ...
Страница 31: ...1 Overview of the Meter 1 9 Using the protective cap D 53 54 55 20 HORIBA ...
Страница 75: ...2 Taking Measurements 2 9 Dissolved oxygen DO measurement D 55 64 HORIBA ...
Страница 139: ...4 RS 232C communications 4 5 Communication example using the HyperTerminal 128 HORIBA ...