Vacuum sensors are used to measure vacuum or sub-atmospheric pressures. They produce electrical output signals and are available with packaging, signal conditioning, and compensation. Vacuum range is the most important specification to consider when selecting vacuum sensors. Units of measure include pounds per square inch (psi), kilo pascals (kPa), atmospheres (atm), bars, inches of mercury (inHg), centimeters of mercury (cmHg), inches of water (inH₂O), feet of water (ftH₂O), kilograms per square centimeters (kg / cm²), and ounces per square inch (oz / in²). Applications for vacuum sensors include chemical processing, freeze drying, helium leak detection, and sterilization. Vacuum sensors are also used in lamp, lighting, and laser products; cathode ray tubes (CRT); electron microscopes; high energy physics; optical, functional, and plasma-enhanced deposition; gas delivery manifolds; mechanical vacuum pumps; mass spectrometers; and metallurgical processes.