Bronkhorst Multibus - Manual (Page 23)

BRONKHORST ®
Page 23 Operational instructions for digital multibus instruments 9.17.023
5 CONTROL PARAMETERS
The controlling algorithm for the valve handled by the micro-controller consists of several parameters which can be
set via the BUS/RS232. Although many parameters could be accessed via BUS/RS232, Bronkhorst advises not to
change these parameters because during manufacturing they have got optimal values for their purposes. Changing of
controller settings should be performed by or under supervision from trained service personnel only.
The picture below shows the basic controller diagram of the digital instrument. It consists of a standard PID controller
with a number of add-ons.
Basically, when a faster or slower controller response is needed, only the controller speed (Kspeed) or PID-Kp has to
be changed.
Data Type Range read/write Secured DDE Proc/par
5.1 PID-K
P
float 0…1E+10 RW  Y 167 114/21
PID controller response, proportional action, multiplication factor.
5.2 PID-T
I
float 0…1E+10 RW  Y 168 114/22
PID controller response, integration action in seconds.
5.3 PID-T
D
float 0…1E+10 RW  Y 169 114/23
PID controller response, differentiation action in seconds.
5.4 C
ONTROLLER SPEED
(Kspeed)
float 0…3.40282E+38 RW  Y 254 114/30
This parameter is the controller speed factor. PID-Kp is multiplied by this factor.
5.5 O
PEN FROM
Z
ERO RESPONSE
unsigned char 0…255 RW  Y 165 114/18
Controller response when starting-up from 0% (K
open
,
Kp multiplication factor when valve opens).
Value 128 is default and means: no correction.
Otherwise controller speed will be adjusted as follows:
Zero) from Open (128 1.05 * response old response New − =
K
open
K
normal
K
stable
S
+
-
Sensor
Control Valve
Flow
Setpoint
K
p
P
I
D
K
speed
+
+
+