|
Parallel communication
A method of communications where data is transferred on several wires simultaneously.
Parity
Bit used to help check for data integrity during a data communication.
PCI (Peripheral Component Interconnect)
A high-performance expansion bus architecture originally developed by Intel to replace ISA and EISA. It is achieving widespread acceptance as a standard for PCs and workstations; it offers a theoretical maximum transfer rate of 132 Mbytes/s.
PCM (Pulse Coded Modulation)
A method of encoding information in a signal by varying the amplitude of pulses. The most common method of encoding an analog signal into a digital bit stream, usually 16 bits per sample.
Peer-to-peer
This is communication that occurs between similar devices. For example, two PLCs communicating would be peer-to-peer. A PLC communicating to a computer would be device-to-host.
PID
An I/O element used to drive an analog input toward a particular value (called the setpoint) and to keep the input very close to that value. PID loops include a gain term (abbreviated P for proportional, which is the inverse of gain), an integral term (I), and a derivative term (D). Temperature control is a typical application for a PID.
PLC (Programmable Logic Controller)
A class of industrially hardened devices that provides hardware interface for input sensors and output actuators. PLCs can be programmed using relay ladder logic to control the outputs based on input conditions and / or algorithms contained in the memory of the PLC.
PPR (Pulses per revolution)
This refers to the number of pulses an encoder produces in one revolution.
Profibus
Vendor-independent open fieldbus standard for use in manufacturing and building automation as well as process control. Utilizes a non-powered two-wire (RS485) network. PROFIBUS is standardized under the European Fieldbus Standard EN 50 170. Includes 3 versions - FMS, DP and PA.
PROM (Programmable Read-Only Memory)
A type of ROM that can be written (programmed) with a device programmer. These memory devices can be programmed only once, so they are sometimes referred to as write-once or one-time programmable devices.
PWM (Pulse Width Modulation)
A switch-mode control method used in amplifiers and drivers to control motor voltage and current to obtain higher efficiency than linear control. PWM refers to variable on/off times (or width) of the voltage pulses applied to the transistors.
|