Are you ordering the wrong pressure range for a pressure sensor?

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?

Contents

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

Solar-powered pressure sensing for remote wastewater networks - This system combines a battery-powered wireless pressure sensor with a solar-charged IoT gateway to deliver frequent data uploads to the cloud.
Water jetting high pressure pump 1600 bar/23000 psi 4-20mA pressure sensor - Rugged, all-welded stainless steel pressure sensor with 4-20mA output for demanding high-pressure applications up to 1600 bar. Ideal for water jetting, hydrodemolition, and industrial cleaning.

Featured absolute reference pressure sensor products

IMP Low Cost Pressure Sensor - Versatile low price pressure sensor with a wide selection of electrical and mechanical options for customisation.
Absolute Reference Voltage Output Pressure Transducers - High voltage output absolute pressure transducers are essential for precise pressure measurements in applications where a perfect vacuum serves as the reference point.

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

Heating appliance chimney draft and barometric pressure testing using differential and absolute sensors - Very low, bi-directional chimney draft pressure and barometric pressure sensor for testing preformance of wood stoves in a research environment.
Low Range DP Voltage Output Transducers - Low range differential pressure transducers are essential for monitoring and controlling air movement in a variety of applications, including ventilation systems, air extraction systems, and building management systems.

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

DPS200 HVAC Differential Pressure Transmitter - Differential air pressure sensor with a 10 volt or a 4-20mA output for building ventilation applications. Ranges from 0 to 6 mbar up to 0 to 1000 mbar.
DCT531P RS485 Modbus RTU Flush Pressure Sensor - RS485 Modbus RTU serial interface pressure sensor with exposed all welded stainless steel 316L flush diaphragm in ranges from 100mb up to 40 bar gauge or absolute.

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

Hazardous Area Externally Fitted Hydrostatic Liquid Level Sensors - Ensure safe and accurate liquid level measurement in hazardous environments with our selection of externally mounted hydrostatic level sensors.
Wash water break tank submersible level transducer with 1.6 m range and 4-20mA output - Monitor wash water levels in break tanks with this submersible 4-20mA transducer. Features high accuracy, 5m vented cable, and robust design.

How do you choose the correct pressure range for a pressure sensor