7.4
Electrode monitoring »SCS«
The sensor check system SCS monitors the
pH and reference electrode to determine
measuring errors and total failure.
The SCS detects:
• pH electrode glass breakage
• Fine short circuits in the pH measuring
circuit, including, for example, moisture
or dirt bridges at clamping points
• Soiling or blocking of the reference
electrode
Two methods are applied to do this:
• Monitoring of high resistance in the
pH electrode. If a fault is detected (if the
electrode impedance is measured to be
< 1 M
Ω
), the fault message E 008 and the
fault contact are activated.
• Monitoring of the reference electrode.
If a fault is detected (if the reference
electrode impedance is measured to be
larger than the set threshold), the
maintenance message E 030 and the
maintenance contact are activated.
The sensor check system SCS can be
switched on or off in the »Sensor monitoring«
menu. When the SCS is switched on, it checks
automatically whether the pH electrode and/or
the reference electrode can be monitored in
the current installation (see note below).
Caution:
The maximum line length for
measuring cables CPK 71 and
DMK is 20 m.
If longer lines are used, the SCS
function must be disabled to
prevent false alarms.
Note:
Connection symmetrical with PM:
Monitoring of pH electrode and
reference electrode.
Connection asymmetrical / without PM:
Monitoring of pH glass electrode only.
→
Commissioning
→
Sensor monitoring
Function
Selection
Default
For two-circuit measurement
Delta window: maintenance required,
leads to error message E 035
pH:
0.00 ... 18.00 pH
Redox mV:
0 ... 3000 mV
Redox %:
0 ... 6000 %
2.00 pH
100 mV
20 %
Delay time until activation of error
message
0 ... 600 s
0 s
Delta window: device failure,
leads to error message E 019
pH:
0.00 ... 18.00 pH
Redox mV:
0 ... 3000 mV
Redox %:
0 ... 6000 %
4.00 pH
200 mV
40 %
Delay time until activation of error
message
0 ... 600 s
0 s
Activation of SCS
on / off
off
If »on« is selected (only for symmetrical measurement with PM)
Facility for setting the monitoring
threshold for the reference electrode
standard,
individual
individual
If »Standard« is selected
Degree of contamination for SCS
monitoring threshold for reference
electrode
low
(corresponds to 10 k
Ω
)
middle (corresponds to 25 k
Ω
)
high
(corresponds to 50 k
Ω
)
high
If »Individual« is selected
SCS monitoring threshold for
reference electrode 1
0.5 ... 100.0 k
Ω
50.0 k
Ω
SCS monitoring threshold for
reference electrode 2
(for two-circuit measurement only)
0.5 ... 100.0 k
Ω
50.0 k
Ω
PARAM
pm152e07.chp
mycom CPM 152
Instrument configuration
Hauser
41
