This article explains the fieldbus block parameters defined in the Foundation fieldbus.
Foundation Fieldbus Blocks Parameters
- Analog Input
The Analog Input (AI) block takes the manufacturer’s input data, selected by channel number, and makes it available to other fieldbus blocks at its output. - Discrete Input
The Discrete Input (DI) block takes the manufacturer’s discrete input data, selected by channel number, and makes it available to other fieldbus blocks at its output. - Manual Loader
The Manual Loader (ML) block has an output whose value is not set by the block algorithm. The output, OUT, may be set by the operator in Man mode or by a computer in ROut mode. - Bias/Gain
The Bias Gain (BG) block is intended to allow several unit controllers, such as boiler masters, to be set by one controller output, such as a plant master. It may also be used for biased external feed forward control. - Control Selector
The Control Selector (CS) block is intended to select one of two or three control signals in a manner determined by SEL_TYPE, when the block is in Auto mode. - PD Control
The Proportional Derivative (PD) block is exactly like the PID block, described below, with the exception of having a BIAS instead of a RESET term. The BIAS term has special bumpless mode switching behavior. - PID Control
The Proportional Integral Derivative (PID) block is key to many control schemes. As long as an error exists, the PID function will integrate the error, which moves the output in a direction to correct the error. - Ratio
The Ratio (RA) block setpoint (SP) is the ratio of its output to its input. A ratio SP of 0.5 produces an output that is one half of its input. The input is either a ‘wild’ flow or the output of a blend pacing controller. The output will be used as the setpoint for a secondary flow controller. Other uses are possible, of course. An input from the secondary measurement is used to calculate the actual ratio, which is displayed as the PV. - Analog Output
The Analog Output (AO) block converts the value in setpoint (SP) to something useful for the hardware found at the channel (CHANNEL) selection. - Discrete Output
The Discrete Output (DO) block converts the value in the discrete setpoint (SP_D) to something useful for the hardware found at the channel (CHANNEL) selection. - Device Control
The Device Control (DC) block is designed to permit setpoint control of discreate devices with multiple states. - Output Splitter
The Output Spliter (OS) block provides the capability to drive two control outputs from a single input. Each output is a linear function of some portion of the input. Back calculation support is provided using the same linear function in reverse. Cascade initialization is supported by a decision table for combinations of input and output conditions. This block would normally be used in split ranging or sequencing of multiple valve applications. - Signal Characterizer
The Signal Characterizer (SC) block has two sections, each with an output that is a non-linear function of the respective input. The non-linear function is determined by a single look-up table 21 arbitrary x-y pairs. The status of an input is copied to the corresponding output, so the block may be used in the control or process signal path. An option can swap the axes of the function for section 2, so that it can be used in the backward control path. - Lead lag
The Lead Lag (LL) block provides dynamic compensation of the IN parameter. The block can provide lead, lag, or both. The LEAD_TIME and LAG_TIME parameters may be configured to obtain the desired input/output relationship. There is no support for control status propagation or back calculation because this block belongs in the measurement path. - Deadtime
The Deadtime (DT) block provides the capability to delay a continuous signal by some specified amount of time. This block receives one input and produces one output delayed by the amount of time specified by the DEAD_TIME parameter. The FOLLOW parameter is used to bypass the delay action based on an external event. - Integrator
The Integrator (IT) block integrates a variable as a function of the time or accumulates the counts from a Pulse Input block.
The block may be used as a totalizer that counts up until reset or as a batch totalizer that has a setpoint, where the integrated or accumulated value is compared to pre-trip and trip settings, generating discrete signals when these settings are reached. - Setpoint Ramp Generator
The Setpoint Ramp Generator (SRG) block provides a “Guaranteed soak” function that stops the timer when the deviation between the generated setpoint and an external variable is larger than a configured value.
When operating in manual mode, the operator can pause the timer, select one point on the profile, advance or return the position in time. The first point of the profile can be balanced to the controller’s BKCAL_OUT value. - Input Selector
The Input Selector (IS) block provides selection of up to four inputs and generates an output based on the configured action. This block normally receives its inputs from AI blocks. The block performs maximum, minimum, middle, average and ‘first good’ signal selection. - Arithmetic
The Arithmetic (AR) block designed to permit simple use of popular measurement math functions. The math algorithm is selected by name, chosen by the user for the function to be done. - Timer
The Timer/Counter (TMR) block provides timing functions. - Multiple Discrete Input Block
The Multiple Discrete Input (MDI) block makes available for the FF network eight discrete variable of the I/O subsystem through its eight output parameters OUT_D1/D8. - Multiple Discrete Output Block
The Multiple Discrete Output (MDO) block makes available to the I/O subsystem its eight input parameters IN_D1/D8. - Multiple Analog Input Block
The Multiple Analog Input (MAI) block makes available for the FF network eight analog variable of the I/O subsystem through its eight output parameters OUT_1/8, whose values must be expressed in engineering units. - Multiple Analog Output Block
The Multiple Analog Output (MAO) block makes available to the I/O subsystem its eight input parameters IN_1/8.
To read basic concept of Foundation Fieldbus Foundation Fieldbus Overview.
Foundation Fieldbus Loop Configuration Examples