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NXP MPL3115A2

A barometric pressure sensor, that can also estimate altitude. Available in SCK2.1 and SCK2.3.

Image Credit: NXP

Version

This sensor is available on the Urban Board of the SCK2.1 and SCK2.3. The SCK2.2 uses the ST LPS33K instead.

Working principle

The MPL3115A2 is a MEMS pressure sensor. It has a very thin silicon membrane that bends with the pressure of the air. The deflection of the membrane is measured and converted into a digital pressure value by the integrated electronics 1. The sensor also includes a temperature sensor, used to compensate the pressure readings.

Since atmospheric pressure decreases with height, the sensor can also estimate the altitude, by comparing the measured pressure with a reference pressure at sea level.

Usage and considerations

The sensor is on the Urban Board, and its readings are available as:

Metric Shell name Units Enabled by default
Barometric pressure MPL Barometric pressure kPa Yes
Altitude MPL Altitude m No
Internal temperature MPL internal temperature ºC No

You can check the readings with the read and monitor commands, and enable the other metrics with the sensor command:

read mpl barometric pressure
sensor mpl altitude -enable

Altitude estimation

The altitude is estimated using a standard reference pressure at sea level. Since the atmospheric pressure changes with the weather, the estimated altitude can change by tens of meters during the day, even if the kit doesn't move. Use it for relative changes over short periods of time, rather than as an absolute value.

Barometric pressure is used in meteorology: decreasing pressure generally indicates bad weather coming, while increasing pressure indicates good weather. It is also used to compensate other sensors that are affected by pressure.

Internal temperature

The internal temperature is the temperature of the sensor itself, which is affected by the heat of the electronics, so it is not a good measurement of the air temperature. For that, use the SHT3X.

Performance

Property Value
Sensor type Piezoresistive MEMS pressure sensor with digital interface (I2C)
Measurement range 20 kPa – 110 kPa (operational), 50 kPa – 110 kPa (calibrated)
Absolute accuracy ±0.4 kPa (50 – 110 kPa, 0 – 50 ºC)
Resolution 1.5 Pa (0.3 m in altitude)

Resources

References

  1. NXP Semiconductors. “MPL3115A2 I2C Precision Altimeter - Datasheet.” https://www.nxp.com/part/MPL3115A2. ↩