The pressure range is the most complicated and confusing specification parameters to define for a pressure sensor. If you do not fully understand the different types of pressure that can be measured, you are likely to end up reading pressures inaccurately, or worse still, damaging the sensor before you have had a chance to correct the situation.
The two main questions that you need to ask yourself are, what is the range of pressure I need to measure over, and what baseline pressure will it be relative to?
Reference Pressure
If you are measuring the direct pressure of a gas or liquid process then you will need either a gauge (g, rel) or absolute (abs, a) reference pressure range depending on whether you need to track relative to atmospheric air pressure changes (zero output = atmospheric pressure) or measure independently of atmospheric pressure changes (zero output = perfect vacuum). This will define the baseline pressure required, and will dictate the type of pressure sensor needed, since typically a pressure sensor will be manufactured to only measure gauge or absolute pressure, and cannot be modified once it has been built.
Featured gauge reference pressure sensor products
Pneumatic air cylinder pressure transducer monitoring up to 150 psi with Arduino - Sensor for monitoring the amount of air pressure required to supply a pneumatic air cylinder from a compressor, and connecting to a Arduino board
16 bar, 200°C steam pressure transmitter and gauge - Combined pressure transmitter and indicator in one package with the option for use with high temperature media such as steam at 200°C
Featured absolute reference pressure sensor products
Ex rated ambient pressure sensor with 800-1100 mbar range - Could you give details of a high accuracy pressure sensor which measures ambient pressure (800 to 1100 mb) for environmental purposes.
Gas sensors testing barometric pressure sensor with RS485 Modbus RTU interface - We are looking to make high accuracy barometric measurements to use in the testing of gas sensors in an indoor laboratory environment at room temperature.
If you are measuring pressure between two points such as either side of an extraction fan, or across a filter, then you will need a differential pressure (dp) sensor.
Featured differential pressure sensor products
Differential Pressure Transmitters - Differential pressure transmitters for measuring the DP of fluids and gases across particle filters and along a length of pipe to monitor flow.
Wireless environmental sensors with custom MQTT SCADA system for energy management IoT platform - An energy management specialist required a multi-point wireless sensor network with specific accuracy requirements and a gateway that could output to their own MQTT-based SCADA system. This explains the selection of sensors and the dual gateway solution offered, covering both Modbus RTU and cellular MQTT options.
Pressure Units
Pressure ranges are typically specified by the manufacturer in bar (bar)or pounds force per square inch (psi) for medium to high pressures, and millibars (mbar), hectopascals (hPa), pascals (Pa) or inches of water column (inH2O, inWG, inWC) for low pressures. If your required pressure range is in other units then use a pressure converter to determine the pressure in common units.
Over-Range Pressure
It is important to think about the maximum pressure to be measured and the likely peak pressure that could be generated by the measured process. If there is a large difference between the two pressures then choosing a pressure sensor with a high overpressure rating to match the peak pressure is imperative to prevent calibration disturbance, mechanical damage or failure of the sensor.
Negative Pressure
Occasionally it is necessary to measure negative pressure or pressures below the baseline reference pressure. It is only possible to do this with a gauge reference or differential pressure sensor. For example you may want to measure suction or vacuum pressure which are pressures between full vacuum and atmospheric pressure. Another example of measuring negative pressure would be to apply a reverse the differential pressure across an air filter periodically, as a preventive maintenance measure to clean the air filter and improve air flow.
Compound Ranges
Negative pressure ranges can also be combined with positive pressure ranges to create a compound range or a bidirectional range. These can be used to combine vacuum and positive pressure ranges, or for measuring ventilation pressures in a duct where the air could be flowing in either direction.
Featured negative pressure sensor products
DMP343 Low Range Pneumatic Pressure Sensor - DMP343 pneumatic pressure sensor for measuring very low range pressures on pneumatic control systems, heating, ventilation and air conditioning systems (HVAC) .- Suction Pressure Sensors - Suction pressure sensors for measuring negative gauge reference pressure. Select pressure sensors for measuring the level of pressure below ambient atmospheric pressure.
Liquid Head Pressure
It is also very common to use pressure sensors to measure liquid level by measuring the liquid head pressure. These pressure ranges are often specified in meters or feet of water column. Due to the variance in liquid density it is also possible to have specifically scaled ranges, for example 1.078 bar for a 10 metre high tank which contains a liquid of a slightly different density to water.
Featured liquid head pressure sensor products
Wastewater holding tank submersible hydrostatic level monitoring pressure transmitter - Monitor liquid levels in wastewater holding tanks with a flush diaphragm sensor designed to prevent clogging from grease and particulate matter in hazardous zones.
BMS water tank 6mH2Og range 0-10V out submersible level sensor for commercial buildings - This submersible level sensor provides accurate and reliable water level measurement in BMS applications in commercial office buildings, with a 0 to 6 mH2O gauge pressure range and a 0 to 10V output signal.
Related Help Guides
- Determining the hydrostatic pressure range for a tank level sensor
- Measuring vacuum with negative gauge or absolute ranges
- What is the difference between gauge and absolute pressure measurement
- What is difference between working, burst and over pressure
- What is the difference between vacuum and absolute pressure
- What does negative and positive gauge pressure mean
- Measuring negative pressure using a positive differential pressure range
Related Technical Terms
- Bidirectional
- Burst Pressure
- FS – Full Scale
- Gauge Reference Pressure
- MSL – Mean Sea Level
- Negative Gauge Pressure
- Reference Pressure
- SG – Sealed Gauge
- Static Line Pressure
- Vented Cable
- Vented Gauge
Related Product and Application Guides
Barometric Pressure
Compound Pressure Ranges
Hydrostatic Pressure
Suction Pressure
Absolute Pressure
Low Pressure Range
Related Application Questions and Answers
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