Proline Promass 83E/F/O Description of Device Functions - FMC ...

7 Block OUTPUTS Device Functions Proline Promass 83
7.3.4 Information on the response of the relay output
General
If you have configured the relay output signal for “LIMIT VALUE” or “FLOW DIRECTION”, you
can define the requisite switch points in the ON VALUE and OFF-VALUE functions. When the
measured variable in question reaches one of these predefined values, the relay output switches as
shown in the illustrations below.
Relay output configured for “flow direction”
The value you entered in the function ON-VALUE defines the switch point for the positive and
negative directions of flow.
If, for example, the switch point you define is = 1 m 3 /h, the relay drops out at –1 m 3 /h and pulls
up at +1 m 3 /h. Set the switch point to 0 if your process calls for direct switchover (no switching
hysteresis). If low flow cut off is used, it is advisable to set hysteresis to a value higher than or equal
to the low flow cut off rate.
Switch-on/switch-off point
-Q Q
-1 0 +1
a
b
a = Relay energized
b = Relay de-energized
A0001236
Relay output configured for limit value
The relay output signal switches as soon as the measured variable undershoots or overshoots a
defined switch point.
Application: Monitoring flow or process-related boundary conditions.
Measured variable
m
A B C
n
n
m
m
n
o
o
o
t
A0001235
m = SWITCH-OFF POINT, n = SWITCH-ON POINT, o = Relay de-energized
A = Maximum safety (SWITCH-OFF POINT > SWITCH-ON POINT)
B = Minimum safety (SWITCH-OFF POINT < SWITCH-ON POINT)
C = Minimum safety (SWITCH-OFF POINT = SWITCH-ON POINT, this configuration is to be avoided)
Page 108 • MN0M023
Issue/Rev. 0.2 (12/12)