Halma ALICAT SCIENTIFIC M Series, Operating Manual

Page: 18 / 47

Process Control
January 2023 • Rev. 0 • Standard Devices User Manual
18
Idle Connection Response
MENU
→
CONTROL
→
Setpoint Setup
→
On Comm Timeout
If the communication connection is timed out, the controller
can either set a zero setpoint, or maintain the last setpoint
given. The timeout time is infinite by default and can be
manually defined ( page 27 ).
Setpoint on Power-Up
By default, the controller remembers its last setpoint across
power cycles, but a specific setpoint can be configured to be
used on every power-up. It is possible to also configure the
power-up setpoint to follow the ramp rate.
Power-Up Setpoint Value
MENU
→
CONTROL
→
Setpoint Setup
→
Power Up Setpoint
→
Value
By selecting
Fixed Setpoint
and entering a value, the
device moves to the same setpoint every time after power-up,
ignoring whatever the setpoint was before being powered off.
If the setpoint is digitally provided more than every few
minutes, use a fixed setpoint on power-up to avoid wearing
out non-volatile memory in the device.
Power-Up Setpoint with Ramping
MENU
→
CONTROL
→
Setpoint Setup
→
Power Up Setpoint
→
Ramp
This designates if the device follows the ramp rate or not after
powering on. The device can either honor the ramp rate and
ramp up (
Honor from 0
) or jump immediately to the power-up
setpoint (
Jump from 0
) .
For more information on ramping, see Setpoint Ramping
( page 18 ). This functions the same as the power-up option
in Ramping Options . Changing one overwrites the other.
Setpoint Limits
MENU
→
CONTROL
→
Setpoint Setup
→
Setpoint Limits
The setpoint limits menu configures upper and lower
limits for selecting a setpoint. By default, the limits are the
controller's measuring range, but more strict limits may be
beneficial in certain applications.
Over a serial connection, the controller rejects requests of
a setpoint outside the limit and an error is returned. When
using an analog setpoint signal, setpoints that are outside of
the setpoint limits are treated as if they were at the nearest
limit. For example, if you request a setpoint via analog that is
below the lower limit, the controller sets the setpoint at the
lower limit.
!
Caution: Flow controllers that have non-zero
lower setpoint limits cannot be set to stop flow
until the lower limit has been cleared.
✓
Note: When changing from one control loop variable
to another, the controller remembers setpoint limits
as percentages of full scale. For example, a 10-SLPM
limit on a 20-SLPM controller (50% of full scale) will
become a limit of 80 PSIA (50% of 160 PSIA) if the
control loop is changed to absolute pressure.
Setpoint Ramping
MENU
→
CONTROL
→
Setpoint Ramp
Setpoint ramping regulates how quickly the controller reaches
a new setpoint. It is often used to prevent bursts of pressure
or flow from damaging delicate instruments at the start of a
process.
To activate setpoint ramping, set a maximum ramp rate and
configure when to enable the ramping function.
Ramp Rate
•
Ramp
changes the maximum rate of change.
•
Units
changes the engineering units used.
•
Set By Delta / Time
allows for more
detailed control of the ramp rate including
changing the value of the time period.
Setting a maximum ramp rate.
Configuring delta / time ramping.
S etpoint ramping menu .
Power-up setpoint menu .
Setting a minimum setpoint.
Setpoint limits menu .
Communication timeout menu .