Endress+Hauser silometer FMC 671 Z, Operating Instruction, Page: 41 / 68

Two-point operation
with one relay If a particular level or volume range has to be maintained, this can be achieved by setting
an appropriate maximum (or minimum level) and hysteresis. For example, the relay is
set to maximum fail-safe mode.
•
Set the switch point to maximum permissible volume or level.
•
Set the hysteresis to the level or volume difference you want to control.
The level rises until the maximum is exceeded, at which point the relay triggers and the
pump is switched off. The relay energises again when the maximum level – hysteresis
has been reached.
•
Maximum level – hysteresis
The pump switches on again.
Procedure
Step Matrix Entry Significance
1 V1H0 e.g. 1900 Switch point 1 = 1900
2 - »E« Register entry
3 V1H1 1 Maximum fail-safe mode
4 - »E« Register entry
5 V1H2 e.g. 400 Hysteresis = 400, the relay energises again at level = 1500
6 - »E« Register entry
Level
Hysteresis
e.g. 400
Switchpoint
e.g. 200
Relay de-energised energised de-energised time
BA063E36
z18 d20 z20
z22 d24 z24 z18 d20 z20
z22 d24 z24 z18 d20 z20
z22 d24 z24
Fig. 7.1:
Range switching with minimum
fail-safe mode
Level
de-energised energised de-energised
Switch point
e.g. 1900
Hysteresis
e.g. 400
Relay time
z18 d20 z20
z22 d24 z24 z18 d20 z20
z22 d24 z24 z18 d20 z20
z22 d24 z24
BA063E37
600
1500
Fig. 7.2:
Range switching with maximum
fail-safe mode
Silometer FMC 671 Z/676 Z Chapter 7: Limit Switches
39