Learn the method of utilising a differential pressure (DP) sensor for barometric pressure measurement.
- Barometric pressure is the pressure of the surrounding atmosphere.
- It can be measured using a differential pressure (DP) sensor.
- DP sensors work by measuring the difference in pressure between two points.
- One side of the sensor must be evacuated to create a reference pressure.
- The other side of the sensor is then exposed to the atmosphere.
- The difference in pressure between the two sides of the sensor is then measured by the sensor.
- DP sensors can be rescaled to output a signal that is proportional to the barometric pressure over a specific range.
Featured differential pressure sensor products
Barometric pressure is the pressure of the surrounding atmosphere which is constantly changing due to the local weather conditions. Since barometric pressure only varies by a narrow range at a particular location, it is usual to scale the output signal over an elevated and narrow band of pressure to improve the resolution of barometric pressure readings.
Measuring atmospheric pressure is normally achieved by using a absolute referenced pressure sensor which has a vacuum trapped on the reverse side of the sensing diaphragm, and an output range which corresponds to the lowest and highest barometric pressure. A common pressure range for this purpose is 800 to 1200 mbar absolute, which can be used in most applications at ground level across the globe.
A differential pressure sensor is designed for pressure to be applied to both sides, and the mechanical design and fittings are designed to be used over a wide range of pressures including the barometric range and vacuum range. It is therefore possible to apply full vacuum to the negative side of the dp sensor, to create an absolute reference, and then leave the positive side open to atmosphere to allow the barometric pressure to be measured.
The vacuum on the negative side can be created by connecting a vacuum source from a pump to continuously maintain an absolute reference during operation, or a vacuum can be applied and then sealed off, using a suitable isolation valve able to provide a leak tight vacuum seal.
The atmospheric pressure applied to the positive side connection of the dp sensor, will now be measured relative to full vacuum, in the same way as an absolute pressure sensor.
DP sensor often include the ability to rescale the output signal via push buttons, potentiometers, digital interface or HART coms. Using the rescaling functionality it is possible to set zero output to 800 mbar, and the full range output to 1200 mbar, creating a higher resolution output signal for barometric pressure measurement.
Featured differential pressure sensor products
Here are the steps involved in measuring barometric pressure using a DP sensor:
- Evacuate one side of the sensor to create a reference pressure.
- Expose the other side of the sensor to the atmosphere.
- Measure the difference in pressure between the two sides of the sensor.
- Rescale the output signal if necessary.
Related Help Guides
- Measuring liquid level in a sealed tank with a hydrostatic pressure sensor
- Measuring the difference in air pressure between rooms
- Measuring negative pressure using a positive differential pressure range
- Measuring liquid level in a tank using a dp sensor
- Measuring density of a liquid using a dp sensor
Related Technical Terms
- at – Technical Atmosphere Pressure Unit
- atm – Standard Atmosphere Pressure Unit
- Barometric Pressure
- Differential Pressure
- Dry/Dry
- inHg – Inches of Mercury at 0 degrees C Pressure Unit
- MSL – Mean Sea Level
- Static Line Pressure
- Wet/Dry
- Wet/Wet
Related Online Tools
- DP Flow Transmitter Output Calculator
- High and Low Side Pressure to Differential Pressure Calculator
- Gauge + Barometric to Absolute Pressure Calculator
- Suction Pressure to Vacuum Calculator
- US Standard Atmosphere Altitude and Pressure Calculator
- ICAO Standard Atmosphere Altitude and Pressure Calculator
- Elevation, Station (QFE) and Sea Level (QNH) Pressure Calculator
