LD301 – Operation and Maintenance Instruction Manual
2.4
PID
First, the error is calculated: PV-SP (DIRECT ACTION) or SP-PV (REVERSE ACTION), then the MV
(manipulated value) is calculated, according to the algorithm of the PID. The PID output signal may
follow a user-determined curve, in up to 16 configurable points. If the table is enabled, there will be a
display indication with the F(X) character
Auto/Manual
The Auto/Manual mode is configured in CONTR/INDIC. With the PID in Manual, the MV can be
adjusted by the user in the LOW LIMIT to HIGH LIMIT range in the CONTR/LIM-SEG option. The
POWER-ON option is used here to determine in which mode the controller should be upon powering it
on.
Limits
This block makes sure that the MV does not go beyond its minimum and maximum limits as
established by the HIGH-LIMIT and LOW-LIMIT. It also makes sure that the Rate-of-Change does not
exceed the value set in OUT-CHG/S.
Output
It calculates the current proportional to the process variable or manipulated variable to be transmitted
on the 4-20 mA output depending on the configuration in OP-MODE. This block also contains the
constant current function configured in OUTPUT. The output is physically limited to 3.6 to 21 mA. The
current output complies with NAMUR NE-43.
Current Trim
The 4 mA TRIM and 20 mA TRIM adjustment is used to make the transmitter current comply with a
current standard, should a deviation arise.
User Unit
It converts 0 and 100% of the process variable to the desired engineering unit readout available for
display and communication. It is used, e.g., to get a volume or flow indication from a level or differential
pressure measurement, respectively. A unit for the variable can also be selected.
Totalization
Used for flow application to totalize the accumulated flow since the last reset, the last reset, getting the
volume or mass transferred. In the lack of power, the totalized value is saved and continues totalizing
after its re-establishment.
Display
The two indications configured in the DISPLAY alternates between the primary and secondary variable
as configured by the user.
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