OEM OPM223 Operating Instructions Manual page 21

OPM223/253
Fig. 18:
A Panel-mounted instrument
B Field instrument
C Potential matching (PM) in the medium for symmetrical connection
The pH and ORP sensors can be connected both symmetrically and asymmetrically.
Generally, the following applies:
• No potential matching connection present: asymmetrical connection
• Potential matching connection present: symmetrical connection
The decision can also depend on the operating conditions.
!
Note!
• OPM223/253 is pre-programmed for symmetrical measurement with potential matching. If
you want asymmetrical measurement, you have to change the configuration in the A2 field.
• If the "asymmetrical" software setting was selected for a symmetrical connection, the
operating time of the reference electrode is reduced.
"
Caution!
In the case of a symmetrical connection, the potential matching pin must be connected and
always immersed in the medium.
Advantages of symmetrical vs. asymmetrical:
• Symmetrical measurement:
– No leak current since the reference and the pH/ORP electrode is connected with high
resistance
– Safe measurement under difficult process conditions (strong flowing and high-resistance
media, partially soiled diaphragm)
• Asymmetrical measurement:
– Use of assemblies without potential matching possible
PA/
S PM
NC
BN BNC BK
OPK1
B
A
BN
OPS12
Asymmetrical (without PML) and symmetrical (with PML) connection of ORP electrodes
PA/
S PM
NC
Ref
BN BNC
OPK1
A
BN
C
OPS12
Wiring
Ref
BK
B
C07-OPM2x3xx-04-06-00-xx-011.eps
21