10.6.2.10 Sensor Monitoring (pH
Sensor mV Only)
With configured pH measured variables, it
is possible to monitor a sensor connected
to the potentiometric input for fault states.
This check is disabled as standard.
Monitoring for sensor breakage: The
sensor breakage check (broken probe)
can identify a defective sensor by means
of its low internal resistance. Correctly
functioning pH sensors have very high
resistances with internal resistances in the
high M
Ω range. The DULCOMETER
®
D1Cb / D1Cc is capable of recognising
broken sensors from their internal resist‐
ance. This function should be deactivated
if very low resistance sensors are used.
Refer also to:
Ä Table on page 146
Check for presence: The "Check for avail‐
ability" identifies a disconnected sensor or
a broken cable. This function should be
disabled if pH sensors are used, which
have a high internal resistance across
their entire operating range.
10.6.2.11 Pause
"Normal" Pause function
If the pause contact is closed, the con‐
troller sets the control outputs to
‘ 0 ’
, as
long as the pause contact is closed or for
a subsequent delay period
‘ td ’
(if a min.
‘ td > 0 ’
is set). While the Pause contact
is closed, the controller records the
‘ P ’
term in the background.
PID control
An I term is generally only present if,
in the setting menu ‘ set control? ’
‘ Tn > 0 ’ has been set.
Exception: The mA-Outputs for the
measured value or correcting value
are unaffected by the Pause.
For PID control: An I term present when
closing the Pause contact is saved. Once
the Pause contact has been opened, the
control outputs
‘ td ’
remain
‘ 0 ’
for the
length of the delay period. The delay
period
‘ td ’
must be set in such a way
that, for example, during this period the
sample water, which contains sufficient
feed chemical (e.g. chlorine), for the typ‐
ical process, flows to the sensor.
For PID control: The control variable
issued following the Pause and the expiry
of the delay period
‘ td ’
consists of the
current P term and (
‘ Tn> 0 ’
) the stored I
term.
"Hold" Pause function
If the pause contact is closed, the con‐
troller sets the control outputs to the last
value, as long as the pause contact is
closed or for a subsequent delay period
‘ td ’
(if a min.
‘ td > 0 ’
is set).
While the Pause contact is closed, the
controller records the P term in the back‐
ground.
For PID control: The standard mA signal
outputs (measured value or correcting
value) are also frozen. After the Pause
contact has been opened, the control
output remain frozen for the delay
period
‘ td ’
. The delay period
‘ td ’
must
Operating Menus Independent of Measured Variables
134
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