Example: A filling height is monitored for its rate of change. In
menu group
LIM address MODE is set to parameter TRD. The
switch on threshold value is set up in
SETP and has the value 3,
the reset value in
RESP is set to -2. The time cycle tm is set up
in menu group
TRDT.
In this example the relay is deactivated when the increase in
filling height (MW
E
-MW
A
) has exceeded the value of 3/time
unit. The relay is only powered up again when the lowering of
the level has reached a value of 2/time unit..
Operation of the alarm feature
ALARM:
If the parameter in
MODE is set to ALARM, then the relay operates
as a system alarm relay. The relay is only deactivated in a unit
fault condition, this can be:
- Cable open circuit as well as a short circuit on 2 wire
transmitters
- Sensor fault on 2 wire transmitters
(<3.6 mA or >21 mA)
- Certain hardware and software faults
(see fault finding)
Operation of the switch time delay
DELY:
Using this setting a time delay
DELY between switch threshold
SETP and activating the relay can be installed.
If the measurement value falls below the preset switch
threshold
SETP (without hysteresis) within the time delay DELY
then the switch delay time counter is reset to zero. The time
counter restarts after a new infringement of the preset switch
threshold
SETP.
This is also valid for minimum monitoring.
Measurement value
HYST
SETP
DELY
Relay deactivated (no power), yellow LED off
Process transmitter
58
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