A vacuum pressure transducer or sensor is used to measure vacuum or sub-atmospheric pressures. Vacuum means pressure below atmospheric. Since true vacuum is never attained, the measurement is in respect to a near absence of gas pressure. Vacuum can be measured using a conventional pressure sensor; however they typically do not resolve extremely low concentrations of gas due to poor signal-to-noise ratio. Vacuum sensors rely on physical properties of gaseous molecules.
Vacuum Sensor Designs
Sensors that work in the vacuum range use some kind of physical displacement or material property change in order to make a measurement. Medium to high vacuum sensors use properties of the environment, such as thermal conductivity and ionization, to make a measurement.
Pressure Readings
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 is the pressure measured above the local atmospheric pressure. It is the most common pressure measurement.
- Positive and negative (vacuum) pressures can be measured using a compound vacuum sensor.
- Sealed gauge pressure is relative to one atmosphere at sea level.
Operating Temperature
Temperature and pressure are directly related to each other. If the temperature of the operating environment increases the pressure in the system will increase. In order to prevent equipment damage, it is important to know the extreme temperature ranges of the area.
Vacuum Transducers Features
Vacuum sensors provide features such as:
- Temperature measurement outputs allow the user to observe the temperature of the system and adjust temperature and/or vacuum level as needed.
- Temperature compensation includes 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.
- Built-in audible or visual alarms that signal when the switch or sensor has been turned on or off.
Performance Specifications
Vacuum range is the most important specification to consider when selecting a vacuum pressure transducer. Vacuum range is the span of pressures from the lowest vacuum pressure to the highest vacuum pressure. High-vacuum is a lower pressure than low vacuum.