Pr
o
Minent
®
Page 121
pH/Redox (ORP)
Checking the Redox (ORP) Sensor
The redox sensor is checked with the aid of a redox buffer solution. The standard buffer value is
set at the factory to 465 mV. If a different buffer is to be used (e.g. 220 mV), the default in the
complete operating menu (menu A) can be changed accordingly. Control is stopped and me ter-
ing is reduced to the set basic load during the test. The 0/4...20 mA output (measured value) is
frozen. If the test is concluded successfully, all error checks concerning the measured values are
restarted.
Possible
values
Initial value
Increment
Lower value
Upper value
Remarks
Buffer values pH 7
pH 0.01
pH -2
pH 16
Error messages
pH
4
when both
buffers too close
(<2 pH-values)
calibration pH
zero p.: -3.1 mV
slope at 25
°
C
53.70 mV/pH
calibration pH
calib. 2 active
please wait!
157 mV
calibration pH
buffer 2: 4.00 pH
mea. val: 4.00 pH
signal: 157 mV
calibration pH
calib. 1 active
please wait!
-3.1 mV
calibration pH
buffer 1: 7.00 pH
mea. val: 7.00 pH
signal: -3.1 mV
calibration pH
zero p.: -3.1 mV
slope at 25
°
C
58.32 mV/pH
calibration?
calibration pH
probe in buffer
buffer: 7.00 pH
calibration pH
probe in buffer
buffer: 4.00 pH
D2C2-pH-Re-MT-2-D
A
B
calibration
end?
check probe
measurement act.
please wait!
450 mV
check probe
ORP
buffer: 465 mV
signal: 450 mV
check probe
ORP
check probe
ORP
buffer: 465 mV
A
Possible
values
Initial value
Increment
Lower value
Upper value
Remarks
Buffer value
465 mV
1 mV
0 mV
1000 mV
–
Error messages
Condition
Remarks
Sensor ORP defective
10 % measured value
Clean sensor
measured value too low
< buffer value
repeat calibration
Sensor ORP defective
15 % measured value
Buffer too old
measured value too high
> buffer value
repeat calibration
Error message
Condition
Remarks
Buffer distance
Δ
Buffer <2 pH
During calibration procedure:
too small
Recalibrate buffer 2!
Return to permanent display:
pH zero point low
< –60 mV
Basic metering load
Warning, old zero
point and slope
retained
pH zero point high
< +60 mV
„
„
pH slope low
<45 mV/pH
„
„
pH slope high
>65 mV/pH
„
„
Measured value
pH unsteady
„
BA_DR_002_02_09_GB_Cooling.indd 121
BA_DR_002_02_09_GB_Cooling.indd 121
24.02.2009 11:56:11 Uhr
24.02.2009 11:56:11 Uhr