DAQ Dictionary: O-P

This edition of DAQ dictionary brings us closer to O and P. Data acquisition is a vast field, but every step gets us closer to completely mastering it.

OEM

Original Equipment Manufacturer. A company which makes basic computer hardware for other manufacturers to build into their products.

Offset Error

If you get a reading other than zero for a zero condition then you have an offset error: every reading will be inaccurate by this amount.

Ohm

SI unit of resistance, such that one ampere through it produces a potential difference of one voltage.

On-Off Control

A simple control system which is either on or off.

Output

Information leaving a device.

PAL

Phase Alternation Line.

PC

Personal computer. Generally applied to computers conforming to the IBM designed architecture.

PCI

Peripheral Component Interconnect. A local bus standard developed by in 1992. PCI cards plug into your computer and are configured through software. They do not have jumpers or switches.

PCMCIA

Personal Computer Memory Card International Association. The industry group that developed the specification for credit card-sized plug-in cards for laptop computers.

Peer-to-Peer Communication

A communication between networked devices in which any device can initiate data transfer.

PID

Proportional gain, integral action time and derivative action time. PID software, for example, compares an analog input value with a setpoint and if there's a discrepancy outputs an appropriate analog or digital control value, according to the PID calculations.

PI&D

Piping and instrumentation diagram.

Ping Utility

This is a test utility which sends a message to a defined port within your instrument. The instrument replies with a short data message. Virtually every unit on TCP/IP will support this action. If you cannot Ping your instrument, and it is on a TCP/IP network, you will not be able to talk to it.

PLC

Programmable Logic Controller.

Pole

A relay contact.

Port

The external connector on a device.

Positive Edge Trigger

Data acquisition starts when an input signal changes from a low to a high state.

Positive Temperature Coefficient

An increase in resistance due to an increase in temperature.

Precision

The repeatability of a measurement. The ability of an instrument to give the same reading under repeated identical conditions.

Protocol

A set of rules used in data communications.

Pulse

A temporary change in voltage of any length.