Terms starting with V

The standard curve of the eye's daytime sensitivity to each wavelength, peaking in green at 555 nm.

V-shaped groove cut partway into a panel from both sides so boards snap apart along straight lines.

Any enclosed space where the gas pressure sits below the surrounding atmosphere, graded by how far below it goes.

Clear-topped box pulled to a vacuum over soapy geomembrane so leaks in seams and patches show up as bubbles.

Carburizing at low pressure in a vacuum furnace using pulses of hydrocarbon gas, then a gas or oil quench.

A sealed, pumped-down furnace that heats parts with no atmosphere, then quenches with pressurized gas or oil.

Standard graphic symbols for pumps, gauges, valves and traps used on vacuum system schematics.

The film of vapor that wraps red-hot steel at the start of a liquid quench and slows its cooling.

Pressure at which a liquid or solid is in balance with its own vapour, which decides what can go inside a chamber.

A plastic sheet under a slab on grade that slows ground moisture from rising into the concrete.

Unit of reactive power, the volt-ampere reactive, written lower case and usually scaled to kvar or Mvar.

Breakdown of total variation into the shares contributed by each source, such as lot, wafer, site and measurement.

Freight crew slang for a passenger train, after the glossy varnished finish of wooden coaches. Shop talk

Thin, sticky, amber-to-brown deposit from degraded oil that coats valves, bearings and coolers.

Variable air volume: a system that holds supply air temperature steady and varies the amount of air to each zone.

Code stating how a three-phase transformer's windings are connected and the phase shift between them.

To let gas back into an evacuated chamber, usually dry nitrogen, to bring it up to atmosphere. Shop talk

The amount of outdoor air deliberately brought into a space to dilute indoor contaminants, usually in cfm per person and per square foot.

A check that an item is good enough for its stated requirements, usually ending in pass or fail with no full calibration data.

Sinking or rising of the ground at a tide station, which changes the sea level trend the gauge records.

Voids filled with asphalt: the share of the aggregate voids occupied by binder rather than air.

Visual Fault Locator: a bright red laser pen that shows breaks, bends and bad connectors as visible glowing points.

Plated hole that connects copper on one layer of a board to copper on another.

Via placed directly in a component pad, filled and plated over so solder cannot drain down it.

Gas trapped in a hidden pocket inside the vacuum that bleeds out slowly and behaves like a small real leak.

Regenerated cellulose fiber, the main absorbent man-made fiber in spunlace wipes and hygiene products.

A fluid's resistance to flow, the lubricant property that sets how thick an oil film can build.

Number showing how little an oil's viscosity changes with temperature; higher means flatter.

Polymer additive that thickens oil more when hot than when cold, raising its viscosity index.

Flow regime in which molecules collide mostly with each other, so the gas moves as a continuous fluid.

Voids in mineral aggregate: the space between aggregate particles available for binder and air.

The change in reactivity caused by steam bubbles or voids forming in the coolant.

Gas pockets trapped inside solder joints, seen as light spots on X-ray, which weaken them and block heat.

Vacuum plasma spray: plasma spraying inside a low-pressure inert chamber to make oxide-free metal coatings.

Voltage transformer: an instrument transformer that steps high voltage down to a standard level for relays and meters.

Visual testing: inspecting welds by eye with gauges, lights and magnifiers, the first and most-used NDE method.