I have level data from a non-vented transducer in a water body and barometric pressure data from the same location. My elevation is 500 meters, how do I determine the true depth?
The true depth can be calculated by subtracting the actual atmospheric air pressure from absolute referenced level data.
Typically a non-vented depth transducer will have an absolute range, but this should be verified by checking the reading at zero depth, which should be around 10 mH20 or 1 bar, which would signify that the transducer does indeed have an absolute reference.
Featured non-vented reference hydrostatic level measurement products
S12S SDI-12 Coms IP68 Pressure and Temperature Sensor - Combined pressure and temperature sensor with a 1200 baud rate serial data interface as defined by the SDI-12 support group.
Absolute Unvented Reference Hydrostatic Liquid Level Sensors - Absolute unvented reference hydrostatic level sensors provide reliable liquid level measurement in challenging environments where traditional vented sensors are impractical.
If the reading is close to zero, it will most likely be a sealed gauge reference type instead, this means that it will have a fixed zero offset that will typically correspond 1 bar, which will need to be determined precisely by subtracting the zero depth reading from the actual atmospheric air pressure and then adding the result to all non-vented depth readings, e.g. if Zero depth = -50 mbar, Atmospheric pressure = 980 mbar, then 1030 mbar should be added to all the depth data to convert it to absolute readings.
If the barometric pressure is the actual pressure at that location without any meteorological adjustment for elevation you can simply subtract that reading from the absolute referenced level reading, but be careful to ensure all calculations are carried out in the same pressure units.
If the barometric pressure was obtained from a meteorological service or barometer it is most likely to be referenced to sea level and you will need to compensate it for the 500m elevation by using a barometric formula to calculate corrected pressure for elevation.
Featured barometric pressure measurement products
Near-atmospheric pressure transmitter for hazardous gas test chambers - Intrinsically safe pressure transmitter configured for a narrow, sub-atmospheric range to safely monitor dangerous gases in a test chamber.
IMPLR Low Range All Stainless Steel OEM Pressure Sensor - Low cost sensor for measuring small pressure ranges from 0-50 mbar (10 inH2O) to 0-1000 mbar (15 psi) of liquids or gases.
Related Help Guides
- Difference between vented and non-vented water level measurement
- Atmospheric pressure compensation for hydrostatic level sensors
- Using absolute pressure sensors to measure hydrostatic level
- Simulating 8000 foot altitude with a pressure gauge
- Measuring barometric pressure using a dp sensor
Related Technical Terms
- at – Technical Atmosphere Pressure Unit
- atm – Standard Atmosphere Pressure Unit
- inHg – Inches of Mercury at 0 degrees C Pressure Unit
- MSL – Mean Sea Level
Related Online Tools
- 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
Related Product and Application Guides
Related Application Questions and Answers
- Ex rated ambient pressure sensor with 800-1100 mbar range
- 1013 to 1400 mbar barometric pressure transmitter & readout
- Wind turbine USB PC logging pressure & temperature sensor
- Gas sensors testing barometric pressure sensor with RS485 Modbus RTU interface
- Atmospheric range for 4-20mA pressure sensor
- 5 to 20 psi absolute ambient 4 to 20 ma pressure transmitter
Contact us about this Converting non-vented depth readings & barometric pressure to true depth page to request more information, or to discuss your application requirements.