OVERVIEW OF VACCUM PRESSURE GAUGES
Dime Marine Services www.dimemarine.com
VACCUM PRESSURE GAUGES
A vacuum gauge is device used to measures pressure below the atmospheric pressure. At normal case the atmospheric pressure is set as zero and the vacuum pressure is given in negative values.
Vacuum pressure The atmospheric pressure usually called the standard pressure at sea level and is 101.325 kPa. The common units for expressing pressure is in bar or psi. Vacuum pressure (Pvac) is expressed in a negative value with respect to the atmospheric pressure. It is not the same as absolute pressure (Pabs), which is measured with respect to the absolute zero point. The different pressure definitions explained:
Absolute pressure Pabs: relative to the absolute zero point
Atmospheric pressure Patm: the pressure at sea level (1.01325 kPa)
Gauge pressure Pgauge: relative to the atmospheric pressure
Vacuum pressure Pvac: measured relative to atmospheric pressure.
Applications for Vacuum Gauges Practically all industries make use of vacuum, from pick and place in the maritime industry, automotive, food & beverage, manufacturing, pharmaceutical, chemical etc. The vacuum gauges are important devices to ensure optimal performance and safety of the system. They may be used for pick-and-place applications, keeping the workplace clean from pollutants, transport materials, etc.
Accuracy of vacuum gauges The accuracy is the difference between the real value and the value that is displayed on the dial. This is usually expressed as a percentage of the span. In cases with higher demands on the accuracy, the calibration of individual gauges may be necessary. The highest demand arises if the gauges are used as transfer standards in inter comparisons of primary pressure standards. Here, the achievable accuracy is limited by the stability of the gauge with time. Gauges based on different operating principles and different constructions show different stabilities. Furthermore, the stability depends on the handling of the gauge.
Pressure gauges for absolute pressure It is important to note that vacuum pressure gauges and absolute pressure gauges are not the same thing. Normal vacuum pressure gauges measure against the atmospheric pressure, while absolute pressure gauges measure with reference to the absolute zero point. In order to do so, these gauges contain a reference chamber with a near full vacuum. These are high end products that are for example used to monitor vacuum pumps or vacuum packaging machines.
----------------------------------------