Adafruit BMP180, A Basic Sensor Measuring Barometric and Temperature Pressure

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/ 2018/6/14 19:04:23 / Tech

What is adafruit BMP180?

adafruit BMP180 is a basic sensor that is designed specifically for measuring barometric pressure, which also does temperature measurement on the side to help. It's one of the few sensors that does this measurement, and its fairly low cost so you'll see it used a lot.


You may be wondering why someone would want to measure atmospheric pressure, but its actually really useful for two things. One is to measure altitude. As we travel from below sea level to a high mountain, the air pressure decreases. That means that if we measure the pressure we can determine our altitude - handy when we don't want the expense or size of a GPS unit. Secondly, atmospheric pressure can be used as a predictor of weather which is why weather-casters often talk about "pressure systems"

 BMP180.jpg


Introduction of BMP180 adafruit

The BMP180 is a new generation of high precision digital pressure sensors for consumer applications. The BMP180 is the new digital barometric pressure sensor of Bosch Sensortec, with a very high performance, which enables applications in advanced mobile devices, such as smartphones, tablet PCs and sports devices.


The ultra-low power, low voltage electronics of the BMP180 is optimized for use in mobile phones, PDAs, GPS navigation devices and outdoor equipment. The ultra-low power consumption down to 3 μA makes the BMP180 the leader in power saving for your mobile devices. BMP180 is also distinguished by its very stable behavior (performance) with regard to the independency of the supply voltage. With a low altitude noise of merely 0.25m at fast conversion time, the BMP180 offers superior performance.


The I2C interface allows for easy system integration with a microcontroller. The BMP180 is based on piezo-resistive technology for EMC robustness, high accuracy and linearity as well as long term stability. Robert Bosch is the world market leader for pressure sensors in automotive applications. Based on the experience of over 400 million pressure sensors in the field, the BMP180 continues a new generation of micro-machined pressure sensors.

 

HOW BMP180 pressure sensor WORKS?

The BMP180 is a piezoresistive sensor that detects pressure. Piezoresistive sensors are made up of a semiconducting material (usually silicon) that changes resistance when a mechanical force like atmospheric pressure is applied.


The BMP180 measures both pressure and temperature, because temperature changes the density of gasses like air. At higher temperatures, air is not as dense and heavy, so it applies less pressure on the sensor. At lower temperatures, air is more dense and weighs more, so it exerts more pressure on the sensor. The sensor uses real-time temperature measurements to compensate the pressure readings for changes in air density.


The BMP180 outputs an uncompensated temperature (UT) value and an uncompensated pressure (UP) value. The temperature measurement is taken first, followed by a pressure measurement.

 

How to Operate BMP180 adafruit?

The BMP180 is designed to be connected directly to a microcontroller of a mobile device via the I2C bus. The pressure and temperature data has to be compensated by the calibration data of the E 2PROM of the BMP180.

 

The BMP180 consists of a piezo-resistive sensor, an analog to digital converter and a control unit with E2PROM and a serial I2C interface. The BMP180 delivers the uncompensated value of pressure and temperature. The E2PROM has stored 176 bit of individual calibration data. This is used to compensate offset, temperature dependence and other parameters of the sensor.

 BMP180 application schematics.jpg


For all calculations presented here an ANSI C code is available from Bosch Sensortec (“BMP180 _API”). The microcontroller sends a start sequence to start a pressure or temperature measurement. After converting time, the result value (UP or UT, respectively) can be read via the I2C interface. For calculating temperature in °C and pressure in hPa, the calibration data has to be used. These constants can be read out from the BMP180 E2PROM via the I2C interface at software initialization. The sampling rate can be increased up to 128 samples per second (standard mode) for dynamic measurement. In this case, it is sufficient to measure the temperature only once per second and to use this value for all pressure measurements during the same period.

 BMP180 temperature measurement.jpg

 

Pin configuration for BMP180 adafruit

Picture shows the device in top view. Device pins are shown here transparently only for orientation purposes.

BMP180 bottom view

BMP180 bottom view.jpg


BMP180 pins configuration

in No

 Name

 Function

1

 CSB*

 Chip select

2

 VDD

 Power supply

3

VDDIO

 Digital power supply

4

 SDO*

 SPI output

5

SCL I2C

 serial bus clock input

6

 SDA I2C

 serial bus data (or SPI input)

7

 GND

 Ground


Key features of BMP180

Pressure range: 300 ... 1100hPa (+9000m ... -500m relating to sea level)

Supply voltage: 1.8 ... 3.6V (VDD)

1.62V ... 3.6V (VDDIO)

Package: LGA package with metal lid

Small footprint: 3.6mm x 3.8mm

Super-flat: 0.93mm height

Low power: 5µA at 1 sample / sec. in standard mode

Low noise: 0.06hPa (0.5m) in ultra low power mode

0.02hPa (0.17m) advanced resolution mode

- Temperature measurement included

- I2C interface

- Fully calibrated

- Pb-free, halogen-free and RoHS compliant,

- MSL 1

 

Parameter

Technical data

Pressure range

300 ... 1100 hPa

RMS noise expressed   in pressure

0.06 hPa, typ.   (ultra low power mode)

0.02 hPa, typ.   (ultra high resolution mode)

RMS noise expressed   in altitude

0.5 m, typ. (ultra   low power mode)

0.17 m, typ. (ultra   high resolution mode)

Relative accuracy   pressure 
  VDD = 3.3 V

950 ... 1050 hPa/ ±0.12 hPa

@ 25 °C/ ±1.0 m

700 ... 900 hPa/ ±0.12 hPa

25 ... 40 °C/ ±1.0 m

Absolute accuracy
  p = 300
…1100hPa
  (Temperature = 0…+65°C, VDD =   3.3. V)

Pressure: -4.0 ...   +2.0 hPa
  Temperature:
±1   °C, typ.

Average current   consumption (1 Hz data refresh rate)
  Peak current

3 μA, typical (ultra-low   power mode)

32 μA, typical (advanced   mode)

650 μA, typical

Stand-by current

1.62 ... 3.6 V

Supply voltage   VDDIO

1.62 ... 3.6 V

Supply voltage VDD

1.8 ... 3.6 V

Operation temp.
  Range full accuracy"

-40 ... +85 °C
  0 ... +65 °C

Pressure conv. Time

5 msec, typical   (standard mode)

I²C date transfer rate

3.4 MHz, max.

Package type / pin.   No

LGA / 7

Package dimensions

3.6 x 3.8 x 0.93 mm³

 

Applications for Adafruit BMP180

- Indoor navigation

- GPS-enhancement for dead-reckoning, slope detection, etc.

- Sport devices, e.g. altitude profile

- Weather forecast

- Vertical velocity indication (rise/sink speed)


INSTALLING Adafruit BMP180 Arduino LIBRARY

Before starting programming Adafruit BMP180, you need to download and install the Arduino library. A ZIP file of the Adafruit BMP180 Arduino library can be downloaded from this link

It takes care of all the math for calculating the true temperature and pressure readings, as well as the math for calculating altitude.        


Notes for BMP180

Give it air: Remember that the BMP180 needs access to ambient air to measure its pressure, so don't put it in a sealed case. Providing a small vent hole should be adequate.

But not too much air: On the other hand, exposure to fast-moving air or wind can cause momentary pressure variations that will affect your readings. Shield the device from strong air currents.

Give it the right voltage: The BMP180 will operate on voltages from 1.8V to 3.6V. We recommend operating it at 3.3V. Never connect the “+” header to voltages higher than 3.6V!. Note that it is safe to connect the SCA and SDL pins to an I2C port on a 5V Arduino, as the pullup resistors on the BMP180 board will keep the voltage below 3.6V.

Keep it cool: Because an accurate temperature reading is needed to measure the pressure, try not to expose the device to rapid temperature changes, and keep it away from nearby hot parts and other heat sources.

Keep it dry: The BMP180 is sensitive to moisture. Don't submerge it or allow it to contact liquid water.

Don't blind it: Surprisingly, the silicon within the BMP180 is sensitive to light, which can enter the device through the hole on the top of the chip. For maximum accuracy, shield the chip from ambient light.



Tip:

Have the need to download the BMP180 datasheet pdf? Directly you can search and get it from HQEW.NET.

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