Справочник Пользователя для National Instruments FP-3000
Chapter 4
Block Reference
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National Instruments Corporation
4-3
control blocks to switch smoothly from manual to automatic mode. It also
has a faultstate behavior that allows the block to react if communications
fail between itself and the upstream block.
has a faultstate behavior that allows the block to react if communications
fail between itself and the upstream block.
PID (Proportional–Integral–Derivative)
The PID block implements a PID control algorithm. When at least one PID
block is present in the device, the Process LED reflects the state of the
PID(s) present. In Fieldbus, a PID block must be connected to an upstream
block (such as an AI block) and a downstream block (such as an AO block)
before it can be used for control. These software connections are
established by using a host Fieldbus configuration system, such as the
NI-FBUS Configurator.
block is present in the device, the Process LED reflects the state of the
PID(s) present. In Fieldbus, a PID block must be connected to an upstream
block (such as an AI block) and a downstream block (such as an AO block)
before it can be used for control. These software connections are
established by using a host Fieldbus configuration system, such as the
NI-FBUS Configurator.
DI (Discrete Input)
The DI block reads data from discrete input channels. This block performs
simple filtering and processing of the raw data from the input channel and
supports limit alarming.
simple filtering and processing of the raw data from the input channel and
supports limit alarming.
DO (Discrete Output)
The DO block writes to a discrete output channel. This block supports
cascade initialization to allow upstream control blocks to determine the
current state of the process before assuming control. It also has a faultstate
behavior that allows the block to react if communications fail between
itself and the upstream block.
cascade initialization to allow upstream control blocks to determine the
current state of the process before assuming control. It also has a faultstate
behavior that allows the block to react if communications fail between
itself and the upstream block.
CDO (Complex Discrete Output)
The CDO block serves the same purpose as the DO block and adds a
number of parameters to support interlocking at three levels of priority.
number of parameters to support interlocking at three levels of priority.
Table 4-1. CDO Block Interlock Priorities
Input
(Descending Priority)
Notes
Safeguard Close
(
(
SAFEGUARD_CL
)
Safeguard Close takes priority over any other interlock input.
Safeguard Open
(
(
SAFEGUARD_OP
)
Safeguard Open takes priority over every other interlock input and is
used to force the block to an open state (
used to force the block to an open state (
Discrete_State_1
).