Endress+Hauser RTA421 - Applications - Alarm Set Point Monitor; Silo Level Monitoring Example

7. Applications
7.1 Alarm set point monitor
The level in a 10 m high silo is to be displayed front end and
also monitored for a minimum level of 2 m (20%) and a
maximum level of 8 m (80%). The hysteresis in order to avoid
unnecessary relay switching in the area of the set points is 2%
in both cases. The minimum level must also be set with a 10
sec time delay.
Example:
Input signal and display:
- Sensor signal 0-20 mA equals 0-10 m
Set point 1:
- Minimum monitoring
- Switch threshold 20% (2 m)
- Hysteresis 2%
- Time delay 10 s
Set point 2:
- Maximum monitoring
- Switch threshold 80% (8 m)
- Hysteresis 2%
- Time delay 0 s
Setting up:
SP 1
SP 2
Menu group Address Set up value
Analogue input Input range
RA NG
0-20
Set point monitor LI 1
Operating mode MO
Switch threshold SP 1
Hysteresis HY 1
Time delay DL Y1
MI N
20
2
10
Set point monitor LI 2 Operating mode MO 2
Switch threshold SP 2
Hysteresis HY 2
Time delay DL Y2
MA X
80
2
0
Contactor
39