Understanding Pressure Measurements Absolute Pressure: • Base reference for pressure measurements, used in high-accuracy vacuum measurement, low pressure in distillation vacuum columns, and tank leakage checks. Gauge Pressure: • Difference between atmospheric pressure and absolute pressure, used in laboratories, instruments, and process tanks. • Used in air conditioning, air control, and process tanks. Differential Pressure: • Difference in pressure between two points of pressure, used in level measurement, overpressure measurement, flow and filtration, and leak detection. Units for Measuring Pressure: • BAR (at sea level), PSI (Pounds per Square Inch), PA (Pascal), Torr (pressure directed onto a 1mm cylinder of mercury), InHg (pressure exerted onto a one inch cylinder of mercury), and InH2O (measure of 1inch cylinder of water at gravity and 4°C). Absolute Pressure Gauges: • Sealed instruments, measuring the actual pressure applied regardless of atmospheric pressure change. • Differential Pressure Measurement: Measures pressure drop across a system, such as monitoring a filtration system within a pipeline.