Why doesn't the IntelliCAL™ LDO101/LBOD101 Luminescent/Optical Dissolved Oxygen (LDO) Probe's pressure reading match the pressure reported by the weather station, airport, or household barometer?

Document ID

Document ID TE2596

Published Date

Published Date 27/05/2017
Question
Why doesn't the IntelliCAL™ LDO101/LBOD101 Luminescent/Optical Dissolved Oxygen (LDO) Probe's pressure reading match the pressure reported by the weather station, airport, or household barometer?
Summary
LDO/LBOD pressure readings different than household/weather station barometers
Answer
The pressure that is measured by the IntelliCAL™ LDO101 Standard Luminescent/Optical Dissolved Oxygen probes is what is commonly referred to as "atmospheric pressure", which is the actual pressure at a given point within the Earth's atmosphere. All weather station pressures are reported as "mean sea level pressure" (MSLP), which is the pressure at (or corrected to) sea level. The MSLP is what is normally reported for weather reports used for internet, television, radio, and newspapers. Household barometers are traditionally set to match such local weather reports and most likely will not report the actual local atmospheric pressure. Since the LDO and LBOD probes do not report this MSLP pressure, they will not return the same pressure readings compared to most household/professional barometers or weather station reports.

In order to compare the pressure results obtained by the LDO and LBOD probes to these MSLP barometers, it is necessary to convert the pressure. See below equation. Otherwise, there are calculators available on the internet to do this conversion.

Mean Sea Level Pressure (hPa) = Atmospheric Pressure (hPA) / e -elevation / (temperature x 29.263)

Where:
Elevation = the elevation of the station in meters (m)
Temperature = current temperature in Kelvin (K)
The constant 29.263 is in units of meters per Kelvin (m/K)