Thermo Fisher Scientific Alpha pH 1000 - Manual (Page 39)

34
The output relay of the pulse length controller is clock-timed. The switching period T remains
constant. Depending on the divergence from the limit value, the switch-on time t
ON
is increased
or decreased in accordance with the proportional range Xp.
The following applies:
t
ON
+ t
OFF
= T (Const.)
greater divergence
→ greater t
ON
Xp exceeded → t
ON
= T (relay remains picked up)
Relay
ON
tON tOFF
Pulse Length T
OFF
Time [s]
Controller signal of Pulse Frequency Controllers
The output relay of the pulse frequency controller is clock-timed. The pulse duration t
ON
remains
constant at 250mS.
Depending on the divergence from the limit value, the frequency (
1
/
T
) is increased or decreased
in accordance with the proportional range Xp.
The following applies:
t
ON
= Const. (250 msec.)
greater divergence
→ greater f (greater frequency)
Xp exceeded → max. frequency