ABB IIMLM01 Multibus Loop Module

Model Type: 6638230C1 Multibus Loop Module

Term Definition

A/D Conversion Analog-to-digital conversion. Process of generating a digital representation of the magnitude of an analog signal.

Basic Station An analog control station configuration that allows the operator to adjust the set point in

the automatic mode (closed-loop control) and the control output in the manual mode

(open-loop control). One of 3 station types available in the normal operating mode.

Bypass Operation An analog control station operating mode that provides control output for a process.

Bypass operation gives the operator direct control of the output if a primary module or

control I/O slave module failure occurs.

Cascade Station An analog control station configuration that allows an externally generated signal, such

as the output of an upstream controller, to control the set point. One of 3 station types

available in the normal operating mode.

Closed-Loop

Control System

A control system in which the controlled variable is measured and compared with a

standard (set point) representing the desired performance. From this comparison (feedback), the system compensates to eliminate any deviation between the set point and

the controlled variable.

Control Output The control system signal that influences the operation of a final control element.

D/A Conversion Digital-to-analog conversion. Process of generating an analog signal of a magnitude

that corresponds to a digital value.

Demand Output The desired control output of the analog control station when it is in bypass operation.

Manual Override An operator initiated mode which has similar functionality as bypass mode. This mode

is entered independently of the state of the primary module and CIS module. The SAC

station ignores all serial link communications with the module while in this mode. The

SAC station controls the process directly.

MFT Machine fault timer. Reset by the processor during normal operation. If not reset regularly, the MFT times out and the module stops.

Open-Loop

Control System

A control system where no function of the controlled variable is used for automatic control of the system. It is not a feedback control system.

PID Proportional plus integral plus derivative control action. Control action in which the output is proportional to a linear combination of the input, the time integral of input and the

time rate-of-change of input.

Primary Module Active module in a redundant configuration.

Process The collective predetermined functions performed in and by the equipment in which a

variable is to be continuously controlled.

Process Variable An input that is used by the control strategy of a control device.

Ratio Station An analog control station configuration that maintains a ratio between two variables.

The ratio of an externally generated wild variable times the controlled variable becomes

the set point that provides regulation of a third variable. One of three station types available in the normal operating mode.

RS-232-C and

RS-485

Two serial communication interface standards developed by the Electronics Industry

Association (EIA) specifying what signals and voltages will be used to transmit data

from a computer (DTE) to a modem (DCE).

Set Point Target set for a process variable or standard representing desired value of the process

variable.