In addition to the basic functions of Arduino compatibility and power management, Ardh@t -I has a barometric pressure sensor (or altimeter), which is designed to work in unison with the IMU for motion related applications, such as movement detection and platform stabilization.
The Ardh@t -E includes both pressure and humidity sensing (but without the IMU), for example for use in weather stations.
Both of these functions are performed by Bosch SensorTec integrated environmental sensors, the BMP280 and BME280 respectively, which also include on-board temperature sensors.
From the Bosch SensorTec website…
“The humidity sensor features an extremely fast response time which supports performance requirements for emerging applications such as context awareness, and high accuracy over a wide temperature range. The pressure sensor is an absolute barometric pressure sensor with features exceptionally high accuracy and resolution at very low noise. The integrated temperature sensor has been optimized for very low noise and high resolution. It is primarily used for temperature compensation of the pressure and humidity sensors, and can also be used for estimating ambient temperature.”
The BMP280 is largely compatible with the popular RTIMUlib, but requires some register changes as it was created for the BMP180, the predecessor of the BMP280.