
Chapter 4 ________________________________________________________________ Operation
VAISALA ______________________________________________________________________ 101
0610-076
Figure 41 Relay Output Modes
Mode 4 is usually used if an alarm needs to be triggered when the
measured value exceeds a safe range. The relay is active when
measurement is in range, and is released if the value goes out of range
or the measurement fails.
NOTE
If the measurement of the selected quantity fails or the transmitter
loses its power, the relay is released.
Hysteresis
Hysteresis function is to prevent the relay switching back and forth
when the measured value is near to the setpoint values.
Relay is activated when the measured value passes the exact value of
the setpoint. When returning and passing the setpoint again relay is
not released before the value reaches the setpoint increased/decreased
by the hysteresis value.
Hysteresis should be smaller than difference of the setpoints.
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