Endress+Hauser Topclean S CPC30, Руководство по эксплуатации

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6 Commissioning Topclean S
76 Hauser
2. PFM (PFM; "pulse-frequency controller")
Pulse-frequency-modulated outputs are intended to control magnetic dosing pumps, for example.
As with PWM, PFM is output as a rhythmic signal by the relay.
The greater the calculated actuating variable, the higher the frequency of the related contact. The
maximum settable frequency 1/T is 120 min
-1
. The switch-on period t
ON
is a constant factor of the
entered frequency (see fig. 39).
For 100 % dosing, the ratio of switch-on period and switch-off period is 50 : 50.
Here, you can combine PFM with a second controlling method for a two-sided process as follows:
• a PFM relays
• a PWM relay
• a three-point step controller
C07-CPM153xx-05-06-00-en-004.eps
ƒig. 39: Left: pulse-width modulation (PWM)
Right: pulse-frequency modulation (PFM)
3. Three-point step controller ("3-point step")
With the Mycom S, this type of control is only possible for one process side (acid or base). With two-
sided processes, either PWM or PFM must be used for the other process side.
The three-point step controller can only be selected if an analogue input for the position feedback
of the valve or the actuator is available.
This type of actuator controller is intended for actuator drives (e.g. motor-driven valves, etc.) where
a motor must be controlled directly. For this, two relays are required: one "+relay" which, by
picking-up, opens the valve and one "–relay" which closes the valve. To set an actuating variable of,
for example, 40% (valve 40% open), Mycom S requires the input of the time that the "+relay" must
be picked up to completely open a completely closed valve (= "
motor run time ").
!
Note!
• If using a driven valve, gate valve or similar, you must determine the motor run time,
before
beginning with the menu settings.
• When commissioning your system, you need to fully open and close the valve so that Mycom S
can adjust the position feedback.
4. Analogue (via current output 2, 20 mA)
The current output can be used to output the analogue actuating variable for one or two-sided
processes and cannot be combined with the method described above.
• With one-sided processes, the actuating variable range 0% ... 100% (or –100 % ... 0%) is
represented on the selected current range (0 ... 20 mA or 4 ... 20 mA). The output current is
proportional to the actuating variable.
• With a two-sided process, the complete actuating variable range from –100% ... +100% is
represented on the given current range. A actuating variable of 0% leads to a current of 10 mA
(at 0 ... 20 mA) or 12 mA (at 4 .. 20 mA) (see fig. 40).
T
1
( f <)
T
2
(f >)
on on
off off
t
ON
t
ON
t
OFF
period T
time [s] time [s]
contact contact