Hach-Lange SI794 D tr User Manual - Manual (Page 81)

Pulse frequency controller (PFC)
The pulse frequency controller is used to operate a frequency-
controlled actuator (metering pump). It varies the frequency
with which the contacts are switched on. The maximum pulse
frequency [pulses/min] can be defined. It depends on the
actuator.
The contact ON time is constant. It is automatically calculated
from the user-defined maximum pulse frequency.
ON time
Pulse frequency (Y = 20%)
1
0
Output signal (relay contact) of pulse frequency controller
1
0
Pulse frequency (Y = 80%)
81