Transmitter 9135 – pH/redox measurement
Page 47
S/CONTROLLER Menu
The built- in proportional controller, abbreviation
controller P. The controller output Y activates the
limit switch relays. Y value may correspond to a
control by impulse or a control by frequency. The Y
value is determined by the parameters below :
•
A setpoint
(W)
: corresponds to the pH value to
control.
•
A neutral zone
(ZN)
: may be programmed and
positioned symmetrical ly
±
50% about the
setpoint. Within this neutral band the control
element (valve, dosing pump) is always inactive.
•
A proportional band
(XP)
: represents the
regulation slope. A XP value equal to 100% is
defined as a Y controlling value of 100% for a
5 pH (or 1000 mV in redox) drift according to the
neutral zone extremity.
•
A power factor
(Exponent)
: which calculates a
controlling value from a lineary (exponent = 1) or
an exponential function.
The value of Y in pH corresponds to the equation
below :
5
]
)
2
ZN
+
(W
-
pH
[
*
XP
100
=
Y
Exponent
Y value is represented as follows :
Z N
14.0 pH
+1500 mV
0.0 pH
-1500 mV
(XP=100%)
(XP=200%)
2.5
pH
(XP=50%)
100%
50%
0%
0.0
5.0
W
Y
