Bronkhorst Multibus - Manual (Page 17)

BRONKHORST ®
Page 17 Operational instructions for digital multibus instruments 9.17.023
4.4 S
ETPOINT
unsigned int 0…32000 RW N 9 1/1
4.5 F
SETPOINT
float 1e-10…1e+10 RW N 206 33/3
Setpoint of the instrument can be operated by two parameters at the same time:
1. Setpoint is used to tell the PID controller in the instrument what the wanted amount of mass flow or pressure
is. Signals are in the same range as the measured value, only setpoint is limited between 0 and 100 %.
Setpoint can be given either via optional field bus or RS232 or via the analog interface. The parameter control
mode selects the active setpoint for the controller. See that paragraph for more detailed information.
2. With the use of parameter Fmeasure, also Fsetpoint is often needed. This parameter is R/W as variable in
FLOW-BUS proc33, par3. Fsetpoint is a float (in the capacity in which the instrument was calibrated, see also
Fmeasure). The last received setpoint by the instrument will be valid. It is not advised to use setpoint and
Fsetpoint at the same time.
Relation between setpoint and Fsetpoint is calculated as follows:
in text 32000
capacity0% capacity
capacity0% fsetpoint
setpoint •






−
−
=
Reading back actual values of Fsetpoint is also possible. When a value has been send to proc1, par1
(integer setpoint), then this will be converted to the float setpoint for direct reading in the right
capacity and unit
4.6 S
ETPOINT MONITOR MODE
unsigned char 0…255 RW  Y 329 115/23
This parameter makes it possible to visualize the internal setpoint value.
Value Description
0 Setpoint
1 Internal setpoint after Setpoint Exponential Smoothing filter
2 Internal setpoint after slope function
4.7 S
ETPOINT EXPONENTIAL
SMOOTHING FILTER
float 0…1 RW  Y 73 117/3
This factor is used for filtering the setpoint before it is further processed.
It filters according the following formula:
filter) exp. Setpoint (1 filter exp. Setpoint x Y
0 0
− • + • =
1
y
Default value = 1 (off)
This filter is in the control loop so it affects the response time.
For MBC-II type of instruments this parameter affects the analog setpoint signal.
For MBC3 type of instruments this parameter affects both analog and digital setpoint signals.