• setOversampleRate(byte) receives a value from 0 to 7. Check table

59 above. Allows the user to change sample rate from 1 to 128.

Increasing the sample rate significantly decreases the noise of each

reading but increases the amount of time to capture each reading. A

oversample of 128 will decrease noise to 1.5Pa RMS but requires

512ms per reading. The datasheet recommends oversample of 128

for basic applications.

The MPL3115A2 has a large number of features. Checkout the datasheet

for more info. This library covers the fundamentals. Help us out! Please add

or suggesting more features on the MPL3115A2 github repo.

Pressure vs Altimeter Setting

If you grabbed a few pressure readings and became confused when you

checked your local weather conditions, you’re not alone. The absolute

pressure that the MPL3115A2 pressure sensor outputs is not the same as

what weather stations refer to as pressure. Weather stations report

pressure in lots of different units:

• millimeters Mercury (mmHg)

• inches Mercury (inHg)

• millibars or hectopascals (hPa)

• pounds per square inch

• atmospheres (Atm)

• kilogram per centimeter

• inches of water

In barometer mode, the MPL3115A2 outputs pressure readings in Pascals.

This is most closely related to millibars or hectopascals. But, why does the

sensor not agree with the station around the corner? This is because many

stations report pressure in a few different formats. Have a look at all these

numbers for the Boulder/Denver area. The key is that your local weather

station is probably reporting the Altimeter setting.

Thank you National Oceanic and Atmospheric Administration (NOAA)! Did

you know they’re headquartered here in Boulder, CO?

• Station pressure - This is the pressure that is observed at a specific

elevation and is the true barometric pressure of a location.

• Altimeter setting - This is the pressure reading most commonly

heard in radio and television broadcasts. It is not the true barometric

pressure at a station. Instead it is the pressure “reduced” to mean

sea level using the temperature profile of the “standard” atmosphere,

which is representative of average conditions over the United States

at 40 degrees north latitude.

• Mean sea level pressure - This is the pressure reading most

commonly used by meteorologists to track weather systems at the

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