25
80-1403-01, Rev. 3
To set the 0% signal level:
HART
Modify parameter DemRngLwr
BCP
dem0pctma
LOCAL
Apply the desired 0% value then press
and hold “CALIBRATE” and DEM 0% until
the “ACKNOWLEDGE” LED lights. If the
“DEMAND” LED lights, the signal is not
within the acceptable range.
To set the 100% signal level:
HART
Modify parameter DemRngLwr
BCP
dem100pctma.
LOCAL
Apply the desired 100% value then press
and hold “CALIBRATE” and DEM 100%
until the “ACKNOWLEDGE” LED lights.
If the “DEMAND” LED lights, the signal is
not within the acceptable range.
PARALLEL SIGNAL CONNECTIONS
Foundation Fieldbus devices are permitted
to be connected in parallel for normal operation.
Analog/HART devices can be connected in parallel
with limitations as described in Parallel Connected
Operation (page 15).
DEMAND SIGNAL
CHARACTERIZATION
The DCM-3 can interpret the Demand as
representing the desired output shaft position as
a linear relationship or as a nonlinear relationship.
The choices are Linear, Square, Square Root, and
Special. Refer to SETTING DEMAND SIGNAL
CHARACTERIZATION (page 25) for more details
concerning each selection.
To choose the relationship:
FF
Modify parameter Demand Curve.
HART
Modify parameter Dem Curve.
BCP
demfunc
LOSS OF DEMAND SIGNAL (L.O.S.)
If Demand is an analog signal, a possibility
exists that the signal will drop below acceptable
level and is considered invalid. This condition is
called Demand L.O.S., and creates an alarm. The
threshold for invoking the L.O.S. alarm is adjustable.
DCM‑3s are typically configured to stop the actuator
during L.O.S. conditions. This is called L.O.S. Stay
In Place. The DCM‑3 can be configured to travel
the output shaft to a predetermined position. This
is called L.O.S. Go to Position. Under the L.O.S.
condition, the STAT and DEMAND LEDs will light.
When the input signal is corrected, the actuator will
automatically resume normal operation.
The DCM‑3 can be configured to suppress
the alarm even if the Demand signal is below the
alarm threshold. This is called L.O.S. PAT mode.
To set the threshold level:
HART
Modify parameter DemLimLwr.
BCP
demlos
To set the action on L.O.S.:
HART
Modify parameter LOS Mode.
BCP
demlos
To set the predetermined position to run to if in
the L.O.S. condition:
HART
Modify parameter LOS Pos.
BCP
demlosgtp
DEMAND OPERATING MODE
The Demand Op Mode can be changed to
select a source of Demand signal other than the
typical source.
The Demand Op Mode parameter can have
the following values:
Follow:
Follow the analog Demand signal. This mode
is not available in Foundation Fieldbus systems. In
analog/HART systems, this is the correct mode if an
analog signal is being used as Demand.
Hold:
Use the digital value transmitted by the
Foundation Fieldbus or HART network. This is the
correct mode for Foundation Fieldbus systems. In
analog/HART systems, this mode can be used if
the control system can write a digital value to the
Demand parameter.
RunRET:
Run the motor so the output shaft
retracts until an over-travel limit is reached. This
is a diagnostic mode that should only be used for
closely controlled tests.
RunEXT:
Run the motor so the output shaft
extends until an over-travel limit is reached. This
is a diagnostic mode that should only be used for
closely controlled tests.
Stay:
Run the motor to preserve present position.
This mode is for special circumstances.
Stop:
Remove power from the motor.
FF
Modify parameter Op Mode.
Whenever the Transducer Block is placed
in AUTO, Op Mode returns to Hold. Hold
allows the actuator to accept the digital
Demand signal from the control system.
HART
Modify parameter Op Mode.
BCP
opmode
When the DCM-3 is installed in a system using
analog control, Demand Op Mode should be set to
Follow.
