A40: Hysteresis mode contact K1
A41: Hysteresis mode contact K2
These parameters allow selection as to whether the hysteresis values which are adjustable with P32, are set
symmetrically or one-sided at the respective switching point. At symmetrical hysteresis, half of the hysteresis’
value is effective below and half of the value above the switching point. The one-sided hysteresis works
downward with heating contact and upward with cooling contact (see fig. 1 + 2).
A50: Minimum action time contact K1 ”On”
A51: Minimum action time contact K1 ”Off”
A52: Minimum action time contact K2 ”On”
A53: Minimum action time contact K2 ”Off”
These parameters permit a delay in switching on/off the relay in order to reduce the switching frequency. The
adjusted time sets the entire minimum time period for a switching-on or switching-off phase.
A54: Delay after “Power-on”
This parameter allows a switching-on delay of relays after switching-on the mains voltage. This delay
corresponds with the time set here.
A55: Mutual delay of contacts K1 and K2
This parameter makes a mutual switching-on delay of relays possible, depending on whichever contact is
switched first.
A56: Alarm Delay after “Power-on” or setpoint changeover
This parameter allows a delay of the alarm after switching-on the mains voltage or after a setpoint
changeover with switching input E1.
A80: Temperature scale
Indication can be switched between Fahrenheit and Celsius. At conversion, the parameters and setpoints
maintain their numerical value and adjustment range. (Example: A controller with the desired value of 0°C is
switched to Fahrenheit. The new desired value is then interpreted as 0°F, which corresponds to a
temperature of -18°C).
NOTE: Indication limits with °F can be smaller than the actual measuring range!
Status messages
Message
Cause
Error elimination
_ _ _
Key-lock active
Change parameter P19 or A19
F1L
Sensor error,
short-circuit at sensor F1
Check sensor
F1H
Sensor error,
open-circuit at sensor F1
Check sensor
display flashes
Temperature alarm at too high or too low
temperature (if activated) see A31
EP, display
flashes
Data loss at parameter memory
(Contacts are switched off)
If error cannot be eliminated by
switching on/off, the controller must be
repaired
Summary of Contents for ST72-31.03
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