12
Notes:
1. In case of Over-range and Under-range PV Error condition, the Output-2 Relay is kept continuously ON to drive the motor for turning the
valve in Reverse (Close) direction completely.
2. For Temperature Sensor (Thermocouple and RTD Pt100) inputs, under Sensor Break (open) condition; the Valve Position is dependent
upon the ‘Valve Position Strategy’ selected by the user in PAGE-12 parameter list (Refer
Sub Section : Sensor Break Protection
later).
3. For DC Linear inputs, in the input open condition, the Upper Readout displays value corresponding to 0 (zero) level signal. For example,
consider 4-20 mA input signal scaled to display 0.0 to 100.0. The Upper Readout then shows approximately -25.0 (corresponding to 0
mA) upon input open.
4. In case of 3-wire RTD sensor input, if the compensating lead (connected at rear panel terminal number 3) is not connected or gets open,
the controller does not indicate PV error but the measured value is not compensated for the lead resistance.
5. In case Tuning operation is in progress, the controller automatically aborts the Tuning operation upon detecting the PV error condition.
6.
In case Profile Cycle is running, the controller automatically holds the Profile Cycle upon detecting the PV error condition. (The front
panel indicator PRF glows continuously to indicate the Profile Cycle Hold status.)
7. In PV Error conditions, the respective alarm (if selected in PAGE-11 parameter list) gets activated. (Refer
Section 7: Alarm Parameters
for further details)
ALARM STATUS UNDER PV ERROR CONDITIONS
The alarm status under PV error conditions depend upon the type of the PV error and the ‘Alarm Type’, as described below:
•
Under-range
Since this error occurs when the PV falls below the minimum range specified for the selected ‘Input Type’, the alarm signal
is generated by comparing the set alarm limits with the minimum range value. This means that the alarm gets activated if
the set ‘Alarm Type’ is either ‘Process Low’ or ‘Negative Deviation’ or ‘Window Band’.
• Over-range
Since this error occurs when the PV exceeds the maximum range specified for the selected ‘Input Type’, the alarm signal is
generated by comparing the set alarm limits with the maximum range value. This means that the alarm gets activated if the
set ‘Alarm Type’ is either ‘Process High’ or ‘Positive Deviation’ or ‘Window Band’.
• Open (Input sensor open or broken)
For Thermocouple and RTD Pt100, the input sensor open error is treated as Over-range. However, for DC Linear inputs
(mV/V/mA), the input sensor open error is treated as Under-range (as the measured PV under input open condition
corresponds to the 0 level signal).
The Table 2.3 below summarizes the alarm status under various PV error conditions. The alarm ON status means the alarm is
activated and OFF means the alarm is not activated.
User Manual
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Message
PV Error Type
Over-range
(PV above Max. Range)
Under-range
(PV below Min. Range)
Open
(Sensor open / broken)
Table 2.2
Figure 2.2
P P I
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FWD
PRF
REV
M
A
