Signals
A signal that uses binary (0 or 1) digits to represent continuous values or discrete states.
What is a digital signal?
A device having an output that changes to regulate a controlled variable in a specific manner.
What is a controller?
Measures the process variable.
What is a sensor?
______ is any variable property of a process. It is the part of the process that changes and, therefore, needs to be controlled.
What is a process variable?
Conformity to an indicated, standard, or true value, usually expressed as a percentage deviation (of span, reading, or upper-range value) from the indicated, standard, or true value, or the degree to which an indicated value matches the actual value of a measured variable. A mathematical relationship expresses the degree of conformity.
What is accuracy?
A continuous operating signal that is a continuous representation of a physical quantity, property, or condition. The signal may be transmitted as pneumatic, mechanical, or electrical energy.
What is an analog signal?
A term used broadly to describe any device that performs a measuring or controlling function. The process variables measured by the device may be used for indication, recording, or control.
What is an instrument?
The part of a loop (if needed) to convert the controller output signal to a suitable form.
What is a transducer?
The variable for which supply and demand must be balanced. It is a physical or chemical change of matter and/or conversion of energy.
What is a process?
The desired value where a process should be maintained. The value may be manually set, automatically set, or programmed. It is expressed in the same units as the controlled variable.
What is a set point?
A control signal that is on or off, open or closed, run or stop, etc.; one of two possible states or conditions.
What is a discrete signal?
A device that senses a process variable through the medium of a sensor and converts the input signal to an output signal of another form. The output of the device is a steady-state value that varies only as a predetermined function of the input (process variable). The sensor may or may not be integral with this device.
What is a transmitter?
The part of a loop or instrument that first senses the value of a process variable and assumes a corresponding, predetermined, and intelligible state or output. The sensor may be separate from, or integral with, another functional element of the loop. It is also known as a detector or sensor.
What is a primary element?
The process of adjusting an instrument by compiling a deviation chart so that the instrument output can be correlated to a known standard input value.
What is calibration?
With respect to calibration, the measurement point where minimum input value to the instrument is equal to the minimum output value of the instrument.
What is zero?
Information in the form of a pneumatic pressure, an electric current, or mechanical position that carries information from one control component to another.
What is a signal?
A drawing used to represent the interconnection of the control loop devices, their location in the process, and a traceable signal path between the devices.
What is a loop sheet?
Departure from a desired value, or the difference between the value of a specific variable and some desired value, usually a set point.
What is a deviation?
A process under control, whereby an instrument measures a process variable and the data is manipulated by a controlling device, which sends corrective data to a final control element to appropriately adjust the process variable; the process automatically repeats.
What is a control loop?
The set of values over which measurements can be made by a device without changing the device's sensitivity.
What is range?
A varying voltage or current that carries information about a measured physical quantity, like temperature, pressure, or flow rate, allowing it to be transmitted and displayed by an instrument
What is an electrical signal?
The primary source of instrument information when ordering, designing, installing, maintaining, and calibrating an instrument.
What is a specification sheet?
The component of a control system that directly regulates the flow of energy or material to the process. The device directly controls the value of the manipulated variable of a control loop. Often it is a valve.
What is a final control element?
A process and instrumentation drawing or diagram.
What is P&ID?
The difference between the upper and lower limits of a range that is expressed in the same units as the range. It is the difference of the URV and LRV.
What is span?