|
Vacuum Gauges
Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure pressure are called pressure gauges or vacuum gauges more...
 Home
ATV Parts
Apparel & Merchandise
Automotive Tools
Aviation Parts
Boat Parts
Car & Truck Parts
 Air Conditioning and Heat
Air Intake & Fuel Delivery
Brakes
Charging & Starting Systems
Computer, Chip, Cruise...
Cooling System
Decals, Emblems, & Detailing
Emission System
Engines & Components
Exhaust
Exterior
Filters
Gaskets
Gauges
 Boost Gauges
Clocks
Fuel Gauges
Gauge Trim
Glow Gauges
Instrument Clusters
Oil Pressure Gauges
Other
Panel Gauges
Speedometers
Tachometers
Vacuum Gauges
Volt Meters
Water Temp Gauges
Glass
Ignition System
Interior
Lighting & Lamps
Other Parts
Safety & Security
Salvage Parts Cars
Suspension & Steering
Transmission & Drivetrain
Turbos, Nitrous,...
Wheels, Tires & Parts
Car Audio, Video
Manuals & Literature
Motorcycle Parts
Other Vehicle Parts
Personal Watercraft Parts
Racing Parts
Services & Installation
Snowmobile Parts
Vintage Car & Truck Parts
Wholesale Lots
A manometer is a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term manometer is often used to refer specifically to liquid column hydrostatic instruments.
A vacuum gauge is used to measure the pressure in a vacuum --- which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10e-11 mbar.
Zero reference
Although pressure is an absolute quantity, everyday pressure measurements, such as for tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other ad hoc reference. When distinguishing between these zero references, the following terms are used:
Absolute pressure is zero referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.;
Gauge pressure is zero referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted.;
Differential pressure is the difference in pressure between two points.;
The zero reference in use is usually implied by context, and these words are only added when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressures are often ambiguous, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 30 inHg (typical atmospheric pressure) − 26 inHg = 4 inHg.
Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the tire pressure goes up. Some standard values of atmospheric pressure such as 101.325 kPa or 100 kPa have been defined, and some instruments use one of these standard values as a constant zero reference instead of the actual variable ambient air pressure. This impairs the accuracy of these instruments, especially when used at high altitudes.
Read more at Wikipedia.org
|
|
Contact
