Bronkhorst Multibus Manual de usuario descargar pdf (Pagina 17)

BRONKHORST®

Page 17 Operational instructions for digital multibus instruments 9.17.023

4.4 S

ETPOINT

unsigned int

0…32000

1/1

4.5 FSETPOINT

float

1e-10…1e+10

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 SETPOINT MONITOR MODE

unsigned char

0…255



329

115/23

This parameter makes it possible to visualize the internal setpoint value.

Value

Description

Setpoint

Internal setpoint after Setpoint Exponential Smoothing filter

Internal setpoint after slope function

4.7 S

ETPOINT EXPONENTIAL

SMOOTHING FILTER

float

0…1



117/3

This factor is used for filtering the setpoint before it is further processed.

It filters according the following formula:

filter) exp. Setpoint(1filter exp. SetpointxY

−•+•=

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.

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