Vacuum Sensors

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. 

Many vacuum sensors can perform additional pressure readings such as absolute, differential, gauge, compound, and sealed pressure. Absolute pressure is a pressure measurement relative to a perfect vacuum. Differential pressure is the difference between two input pressures. Gauge pressure, the pressure measured above the local atmospheric pressure, is the most common pressure measurement. Compound vacuum sensors can measure both positive and negative pressures. Sealed gauge pressure is relative to one atmosphere at sea level (14.7 psi), regardless of local atmospheric pressure. 

Selecting vacuum sensors requires an analysis of signal outputs. Analog voltage is a simple, usually linear function of the measurement. Analog current levels or transmitters are suitable for sending signals over long distances. Frequency outputs are encoded via amplitude modulation (AM), frequency modulation (FM), sine waves, or pulse trains. RS232 and RS485 are serial communication protocols that transmit data one bit at a time. Parallel outputs such as printer ports, Centronics ports, and the general-purpose interface bus (GPIB) transmit data in groups of bits. Common protocols include highway addressable remote transducer (HART^®), the process fieldbus (PROFIBUS^®), Foundation FIELDBUS, DeviceNet, and Ethernet. HART is a registered trademark of the HART Communication Foundation. PROFIBUS is a registered trademark of PROFIBUS International. Some vacuum sensors provide special digital or transistor-transistor logic (TTL) outputs. Others change the state of a switch or alarm.

Vacuum sensors provide features such as TTL-compatible switches, built-in audible or visual alarms, and temperature measurement outputs. Devices with temperature compensation include built-in factors that prevent pressure measurement errors due to temperature changes. Negative pressure outputs are available only with vacuum sensors that provide differential pressure measurements. 

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Part Numbers for Vacuum Sensors