Pressure is an important process variable because it sets critical conditions for boiling, chemical reactions, distillation, extrusion, vacuuming, and conditioning of air. Incorrect pressure or flow rate can cause major safety, quality, and productivity problems. Very high pressure or flow rate inside a sealed environment can also cause an explosion. In order to ensure that plants operate efficiently and safely, periodic calibration of pressure, level, and flow instruments is required.
Many factories and metrology laboratories use various pressure and flow-meter calibration instruments. This high-accuracy equipment is used to calibrate industrial devices like pressure transducers, pressure gauges, and transmitters, as well as instruments that measure and control flow.
Some of the important types of devices used with pressure calibrators are:
1) Pressure gauges: They are instruments used to measure pressure in liquids and gases. Some of the commonly used pressure gauges are glycerin gauges, electric contact gauges, differential gauges, test gauges and capsule gauges. These are usually used in commercial production plants.
2) Calibration standard pressure sensors: These pressure sensors, usually consisting of differential pressure manometers, gauges, pressure controller, transmitters, and vacuum gauges are very precise and are sometimes used in calibration standard labs for secondary reference.
3) Pneumatic calibration hand pumps: These pressure calibrators manually produce air pressure set points. Then, these are used to calibrate pressure equipment with the help of a pressure indicator.
4) Pressure calibrators utilizing electrical measurement: These measure electrical current as well as voltage in order to show the output signal produced by a pressure transducer.
5) Digital test gauges: These gauges are installed on both hydraulic and pneumatic calibration hand pumps to determine pressures with precision.
6) Precision manometers: These pressure calibrators are handheld instruments, which provide a selection of pressure units. They are powered by batteries.
7) High pressure calibration hand pumps: These instruments produce pressure in order to calibrate a test gauge or connect to an indicator.
For any transducers or measurement systems, which provide information on the amount of material transferred in a given time, flow meter calibration is necessary. In flow-meter calibration, measurements usually occur in units of mass per unit time (gravimetric measurement) or volume per unit time (volumetric measurement). These two types of measurements relate to one another by the density (mass per unit volume) of the flowing material. This third method is called comparison measurement.