Engineering Dictionary

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An alphabetical listing of General terms and items.

Palisade   Dico Tools
(1) A Defensive fence or wall of wooden stakes arranged vertically or obliquely in a row. See valli. (2) To surround or defend with a palisade. 

Pan   Dico Tools
The part of a work forming one side of a salient angle.

Pan Coupe   Dico Tools
When a salient angle is replaced by the straight line of a parapet, a pan coupe is formed.

Parados   Dico Tools
An earthwork parapet situated behind an infantry or gun position, protecting the rear from attack. (Fr. parare, to prepare; L. dorsum, back).

Parallax   Dico Tools
An optical illusion which occurs in analog meters and causes reading errors. It occurs when the viewing eye is not in the same plane, perpendicular to the meter face, as the indicating needle.

Parallel   Dico Tools
A siege trench dug parallel to the front of a fortress.

Parallel Transmission   Dico Tools
Sending all data bits simultaneously. Commonly used for communications between computers and printer devices.

Parapet   Dico Tools
(1) The top of a wall of either a fortification or fieldwork, either plain or battlemented. Used to provide protection to the defenders behind the wall. See battlement, crenel, embrasure, merlon, reveal. (2) A breastwork or wall used to protect the defenders on the ramparts of a fortification, either plain or provided with embrasures.

Parapet Walk   Dico Tools
See allure.

Paraportia   Dico Tools
Gates in Byzantine field fortifications (See the Strategikon for more details).

Parity   Dico Tools
A technique for testing transmitting data. Typically, a binary digit is added to the data to make the sum of all the digits of the binary data either always even (even parity) or always odd (odd parity).

Parol   Dico Tools
A wooden frame with sharp stakes projection horizontally from it, which was used to deter besiegers from scaling the parapets.

Pas De Sours   Dico Tools
Steps leading into the ditch of a permanent fortification.

Pashtib   Dico Tools
A raised platform of sandbags used to fill a defensive ditch. (Indian)

Passage   Dico Tools
An opening in the parapet of the covered way.

Pat   Dico Tools
An outwork in the shape of a horseshoe, used to cover the gate of a fortification. See demilune, halfmoon, horseshoe, moon.

Pele, Pele Tower, Pile Tower   Dico Tools
A castle almost unique to the Scotish/English border region, usually consisting of just a small tower, or fortified dwelling, suitable for defence against raiding parties rather than any type of real siege. Dating from 1100-1700 A.D., they are also found in Ireland, used both as a refuge and a stronghold. Some were provided with a surrounding or adjoining bailey which was called a barbkin or barmkin, which was used for the protection to the tenants and their livestock during raids. (L. palus, stake).

Peltier Effect   Dico Tools
When a current flows through a thermocouple junction, heat will either be absorbed or evolved depending on the direction of current flow. This effect is independent of joule I2 R heating.

Pendentive   Dico Tools
A triangular shape that adapts the circular ring of a dome to fit onto a flat supporting wall

Penstock   Dico Tools
A wooden dam, the water of which was used by the defenders of a fortification to destroy enemy positions in the ditch by opening the sluice of the dam and flooding the ditch.

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Pentagonal Sconce   Dico Tools
An earthwork fort of the 17th century, based on the bastioned trace plan, protected by; pitfalls and a palisade beyond the ditch surrounding the sconce, and horizontal storm poles on the top of the interior slope of the ramparts, as well as a wooden revetted breastwork which extended along the top of the ramparts. See bastion trace, sconce.

Perfectly Balanced Rotor   Dico Tools
A rotor is perfectly balanced when its mass distribution is such that it transmits no vibratory force or motion to its bearings as a result of centrifugal forces.

Perimeter   Dico Tools
The distance around the outside of a shape

Perimeter Wall   Dico Tools
See bailey wall, curtain wall, enceinte.

Peripheral   Dico Tools
A device that is external to the CPU and main memory, i.e., printer, modem or terminal, but is connected by the appropriate electrical connections.

Perpendicular Fortification   Dico Tools
A fortification introduced by Montalembert in 1776 A.D., consisting of four different lines of defence which were; firstly a tenaille trace, followed by two lines of counterguards, and finally a two storied circular multi-gun tower. Thus four consecutive breaches were needed to be made to subdue this type of fortification.

PFA   Dico Tools
A fluorocarbon polymer used for insulation of electrical wires .

PH Junctions   Dico Tools
The Junction of a reference electrode or combination electrode is a permeable membrane through which the fill solution escapes (called the liquid junction).

PH(S) (Standard PH Scale)   Dico Tools
The conventional standard pH scale established on the basis that an individual ionic activity coefficient can be calculated from the Debye-Hckel law for primary buffers.

Phase   Dico Tools
A time based relationship between a periodic function and a reference. In electricity, it is expressed in angular degrees to describe the voltage or current relationship of two alternating waveforms.

Phase Difference   Dico Tools
The time expressed in degrees between the same reference point on two periodic waveforms.

Phase Proportioning   Dico Tools
A form of temperature control where the power supplied to the process is controlled by limiting the phase angle of the line voltage.

Piazza Bassa   Dico Tools
A casemate set in a flank of a work from which artillery was used to enfilade the curtain and to cover the ditch.

Pictish Tower   Dico Tools
A round tower dating from the early Iron Age which was attributed to the picts. Chiefly found in the Shetlands, Orkneys and Northern Scotland.

Picts House   Dico Tools
An earthen house ascribed to the Picts.

PID   Dico Tools
Proportional, integral, derivative. A three mode control action where the controller has time proportioning, integral (auto reset) and derivative rate action.

Piece Maitress   Dico Tools
The French phrase for the architecturally dominant feature of a castle, which in most castles was the keep or donjon, or can be applied to the great gatehouse which took the position of the keep.

Pieced Rampart   Dico Tools
A rampart which was modified by replacing the crenels with embrasures so that cannons could be fired through the parapet. See embrasure.

Pier   Dico Tools
A vertical supporting structure, such as a pillar

Piezoelectric Accelerometer   Dico Tools
A transducer that produces an electrical charge in direct proportion to the vibratory acceleration.

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Piezoresistance   Dico Tools
Resistance that changes with stress.

Pile   Dico Tools
a long, round pole of wood, concrete, or steel driven into the soil by pile drivers

Pile Driver   Dico Tools
A noisy machine that repeatedly drops a heavy weight on top of a pile until the pile reaches solid soil or rock or cannot be pushed down any farther

Pile Tower   Dico Tools
See pele.

Pixel   Dico Tools
Picture element. Definable locations on a display screen that are used to form images on the screen. For graphic displays, screens with more pixels provide higher resolution.

Place   Dico Tools
A word used in military architecture when referring to a fortification or a fortified town.

Place Des Armes, Place Of Arms   Dico Tools
An enlargement of the covered way where troops could assemble for sorties, and were used as command posts; if the work was salient it was situated at the outer point of the covered way, while if the work was re-entrant it was situated at the inner point.

Plane Separation   Dico Tools
Of a balancing machine, is the operation of reducing the correction plane interference ratio for a particular rotor.

Plastic   Dico Tools
A synthetic material made from long chains of molecules; has the capability of being molded or shaped, usually by the application of heat and pressure

Platinel   Dico Tools
A non-standard, high temperature platinum thermocouple alloy whose thermoelectric voltage nearly matches a Type K thermocouple (Trademark of Englehard Industries).

Platinum   Dico Tools
A noble metal which in its pure form is the negative wire of Type R and Type S thermocouples.

Platinum 10% Rhodium   Dico Tools
The platinum-rhodium alloy used as the positive wire in conjunction with pure platinum to form a Type S thermocouple.

Platinum 13% Rhodium   Dico Tools
The platinum-rhodium alloy used as the positive wire in conjunction with pure platinum to form a Type R thermocouple.

Platinum 30% Rhodium   Dico Tools
The platinum-rhodium alloy used as the positive wire in conjunction with platinum 6% rhodium to form a Type B thermocouple.

Platinum 6% Rhodium   Dico Tools
The platinum-rhodium alloy used as the negative wire in conjunction with platinum-30% rhodium to form a Type B thermocouple.

Platinum 67   Dico Tools
To develop thermal emf tables for thermocouples, the National Bureau of Standards paired each thermocouple alloy against a pure platinum wire (designated Platinum 2 prior to 1973, and currently Platinum 67). The thermal emf's of any alloy combination can be determined by summing the "vs. Pt-67" emf's of the alloys, i.e., the emf table for a Type K thermocouple is derived from the Chromel vs. Pt-67 and the Alumel vs. Pt-67 values.

Plinth   Dico Tools
The original purpose of the plinth was to increase the effect of the machicolations, and was not so much to counter the endeavours of sappers as to deflect projectiles thrown down from the walls above. The upper section of the plinth was concave and the lower oblique; the effect of this shape deflects projectiles thrown from above in a fan-shaped trajectory. See batter, spur, talus.

Pointed Arch Machicolation   Dico Tools
A machicolation dating from the 14th to the 15th century, which was supported on buttresses which extended down to the foundations. The type of machicolation had two distinct advantages

Pointed Merlon   Dico Tools
A merlon typical of the mudjar military architecture, having a pointed apex. See merlon, moorish merlon, mudjar merlon.

Poisson Ratio   Dico Tools
The ratio between the strain of expansion in the direction of force and the strain of contraction perpendicular to that force v = -Et/E1.

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Polarity   Dico Tools
In electricity, the quality of having two oppositely charged poles, one positive one negative.

Polarization   Dico Tools
The inability of an electrode to reproduce a reading after a small electrical current has been passed through the membrane. Glass pH electrodes are especially prone to polarization errors caused by small currents flowing from the pH meter input circuit and from static electrical charges built up as the electrodes are removed from the sample solution, or when the electrodes are wiped.

Polygonal Fortification   Dico Tools
A fortification designed by Montalembert in 1777 A.D. which consisted of faces with salient angles of little depth, and powerful caponiers armed with; 27 cannons in casements and a large number of infantry loopholes.

Polygonal Keep   Dico Tools
A keep which was built on a polygonal plan and was designed to overcome the problems associated with square and rectangular keeps, whose corners were vulnerable to battering, and their cubic shape created dead ground by their reduced field of fire, and they were also more susceptible to attack by undermining. See keep, transitional keep.

Pomerium, Pomoerium   Dico Tools
A street like open space which runs parallel to the inside base of the fortified wall of a city.

Port   Dico Tools
A signal input (access) or output point on a computer.

Porta Decumana   Dico Tools
The rear gate of a Roman fortification, situated in the wall opposite the main gate (porta preatoria) usually situated in one of the shorter walls.

Porta Praetoria   Dico Tools
The main gate of a Roman fortification, normally situated in one of the shorter walls opposite the porta decumana or rear gate.

Porta Principalis   Dico Tools
The name given to the two gates on either of long sides of a Roman fortification which was connected by the via principalis.

Porticullis   Dico Tools
A heavy grating of iron or iron reinforced wooden bars, suspended on chains which were worked by winches; used to cover an entrance to a castle. The porticullis could by dropped quickly down vertical grooves in entryway called coulisses, or at any other important entrance in the event of attack. Some castles had the machinery for raising and lowering the porticullis, usually a windlass, was accommodated above the entry, in a chamber situated between the flanker towers and was only accessible through one of them. This chamber was often put to domestic use despite the obstruction of the windlass and often the machinery for moving the drawbridge as well. Some gateways were provided with a succession of porticullises, at some distance apart. See gatehouse, successive porticullis. (L. porta, gate; coulisse, gutter).

Positive Temperature Coefficient   Dico Tools
An increase in resistance due to an increase in temperature.

Postern Bridge   Dico Tools
A bridge crossing a moat or ditch from the postern gate. See postern.

Postern Tower   Dico Tools
A tower which was used to defend as well as sometimes incorporating the postern gate. See postern.

Postern, Postern Gate   Dico Tools
A small secondary entrance, sometimes concealed, and usually at the rear of a castle. Used as a sally port for sorties, and as a route of escape. See sally port.

Potential Energy   Dico Tools
Energy related to the position or height above a place to which fluid could possibly flow.

Potentiometer   Dico Tools
1. A variable resistor often used to control a circuit. 2. A balancing bridge used to measure voltage.

Power Supply   Dico Tools
A separate unit or part of a circuit that supplies power to the rest of the circuit or to a system.

PPM   Dico Tools
Abbreviation for "parts per million," sometimes used to express temperature coefficients. For instance, 100 ppm is identical to 0.01%.

Precinct   Dico Tools
The space enclosed by fortified walls. See bailey, enceinte.

Presidio   Dico Tools
The Spanish term for a place of defence such as; a fort, garrison or garrison town, or just a guard house. (L. praesidium, garrison).

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Pressure   Dico Tools
A force applied or distributed over an area

Priest Cap   Dico Tools
A fortification; so named because of its similarity to the shape of priest's cap, also known as a 'swallow tail'.

Primary Device   Dico Tools
Part of a flowmeter which is mounted internally or externally to the fluid conduit and produces a signal corresponding to the flowrate and from which the flow may be determined.

Primary Standard (NBS)   Dico Tools
The standard reference units and physical constants maintained by the National Bureau of Standards upon which all measurement units in the United States are based.

Primary Standards   Dico Tools
Aqueous pH buffer solutions established by the National Bureau of Standards within the 2.5 to 11.5 pH range of ionic strength less than 0.1 and which provide stable liquid junction potential and uniformity of electrode sensitivity.

Principal Axes   Dico Tools
The axes of maximum and minimum normal stress.

Principia   Dico Tools
The headquarters of a Roman fortress or auxiliary fort which was situated at the junction of the via praetoria and via principia.

Probe   Dico Tools
A generic term that is used to describe many types of temperature sensors.

Process Meter   Dico Tools
A panel meter with sizeable zero and span adjustment capabilities, which can be scaled for readout in engineering units for signals such as 4-20 mA, 10-50 mA and 1-5 V.

Program   Dico Tools
A list of instructions that a computer follows to perform a task.

Prom   Dico Tools
Programmable read-only memory. A semiconductor memory whose contents cannot be changed by the computer after it has been programmed.

Promontory Fort   Dico Tools
See cliff fort.

Proof Pressure   Dico Tools
The specified pressure which may be applied to the sensing element of a transducer without causing a permanent change in the output characteristics.

Proportioning Band   Dico Tools
A temperature band expressed in degrees within which a temperature controller's time proportioning function is active.

Proportioning Control Mode   Dico Tools
A time proportioning controller where the amount of time that the relay is energized is dependent upon the system's temperature.

Proportioning Control Plus Derivative Function   Dico Tools
A time proportioning controller with derivative function. The derivative function senses the rate at which a system's temperature is either increasing or decreasing and adjusts the cycle time of the controller to minimize overshoot or undershoot.

Proportioning Control Plus Integral   Dico Tools
A two-mode controller with time proportioning and integral (auto reset) action. The integral function automatically adjusts the temperature at which a system has stabilized back to the setpoint temperature, thereby eliminating droop in the system.

Proportioning Control With Integral And Derivative   Dico Tools
Three mode PID controller. A time proportioning controller with integral and derivative functions. The integral function automatically adjusts the system temperature to the set point temperature to eliminate droop due to the time proportioning function. The derivative function senses the rate of rise or fall of the system temperature and automatically adjusts the cycle time of the controller to minimize overshoot or undershoot.

Protection Head   Dico Tools
An enclosure usually made out of metal at the end of a heater or probe where connections are made.

Protection Tube   Dico Tools
A metal or ceramic tube, closed at one end into which a temperature sensor is inserted. The tube protects the sensor from the medium into which it is inserted.

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Protocol   Dico Tools
A formal definition that describes how data is to be exchanged.

PSIA   Dico Tools
Pounds per square inch absolute. Pressure referenced to a vacuum.

PSID   Dico Tools
Pounds per square inch differential. Pressure difference between two points.

PSIG   Dico Tools
Pound per square inch gage. Pressure referenced to ambient air pressure.

PSIS   Dico Tools
Pounds per square inch standard. Pressure referenced to a standard atmosphere.

Pulley Drawbridge   Dico Tools
A drawbridge raised and lowered by ropes or chains via a pulley system. See drawbridge.

Pulse Width Modulation   Dico Tools
An output in the form of duty cycle which varies as a function of the applied measurand.

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