IoTClass Inside the measurement
A closer look · 01

Sensor

Look inside
a sensor.

Barometric pressure sensor

A barometric sensor measures air pressure. In a pressure sensor with a diaphragm, that mechanical part moves as pressure changes. Compact MEMS sensors combine the mechanical sensing structure with electronics that condition its signal, convert it to a digital reading, and apply corrections. An IoT device can use the pressure reading to estimate relative height, since pressure falls as height increases.

Weather changes pressure too. Keep a recent local baseline and check another clue before treating a pressure change as movement between floors.

01

Recognize the element

Recognize the element: Barometric pressure sensor

BMP280 pressure sensorA cropped conceptual BMP280 breakout board shows the pressure-sensor package and pin header. Generic exterior shapes identify the sensor, without specifying internal construction or wiring. Not to scale. Conceptual BMP280
The BMP280 is the pressure side of the motion lab. Compare its pressure readings with a recent baseline before interpreting a height change.
02

Peel the teaching model

From case to sensing element

Choose a layer to see the measurement path. The enclosure and board layout are invented teaching choices, not a particular product.

The full text version below describes every layer. All measurement explanations are available without 3D.
Conceptual, not to scale
Case: lid and openingThe BMP280 has a metal lid. The opening in this teaching model is illustrative. [BMP280: Key parameters]

Drag to rotate; pinch to zoom. With the view focused: arrow keys rotate, + / − zoom, 1–3 choose a layer, Home resets rotation and zoom. Step advances to the next layer; Reset returns to the case and default view. Layer buttons select a view directly. The page does not move on its own.

Layer 1 of 3 / Outside

Case: lid and opening

The BMP280 has a metal lid. The opening in this teaching model is illustrative. [BMP280: Key parameters]

Teaching view: The silver lid has a small opening above the sensing parts. This is the pressure sensor’s outer package; its readings can be compared with a local pressure baseline.

The measurement to rememberAir pressure falls as height increases, but weather also changes pressure. Compare readings with a recent baseline and another clue before deciding that the sensor moved. [Gravity, Brownian Noise, Bandwidth · Pressure and weather drift]

Full text version · every layer

1 · Case: lid and opening

The BMP280 has a metal lid. The opening in this teaching model is illustrative. [BMP280: Key parameters]

Teaching view: The silver lid has a small opening above the sensing parts. This is the pressure sensor’s outer package; its readings can be compared with a local pressure baseline.

2 · Interface: pressure readout

The BMP280 combines a pressure-sensing element that changes resistance under pressure with a chip that converts its signals into digital readings. [BMP280 §3: Functional description]

Teaching view: A small pressure-sensing chip sits beside a dark readout block on the package base. The readout converts the sensing signal into digital pressure readings.

3 · Element: pressure die and height changes

In this simplified example, pressure bends a thin membrane and strains resistive sensing parts, changing their resistance. The membrane shape and strain marks illustrate the principle rather than the BMP280’s exact construction. [BMP280 §3: Functional description]

A pressure change alone cannot distinguish a height change from weather drift. [Gravity, Brownian Noise, Bandwidth · Pressure and weather drift]

Teaching view: The purple membrane and gold strain marks represent the pressure-sensitive part of the chip. The blue rim supports it. These shapes illustrate the sensing principle rather than the BMP280’s exact internal layout.

Explore the layers in order to follow the teaching model.

03

Listen

Package narration

Read transcript
Sam is adding a floor change alert to a connected delivery cart. He first takes a pressure reading while the cart is still at desk height. Consider a pressure sensor that uses a thin silicon diaphragm over a sealed vacuum cavity. Air pushes on the diaphragm, bending it. Resistors built into the silicon change resistance under that stress. Connected as a bridge circuit, they turn the resistance changes into a small voltage. Electronics amplify and convert that signal into a pressure reading. As Sam takes the cart upward, air pressure falls, so he can estimate height relative to his starting point. The course assumes pressure noise of zero point one two pascals. Near sea level, multiplying by eight point three two centimetres per pascal gives about one centimetre of height noise. That calculation describes noise under an assumption, not guaranteed height accuracy. Sam initially thinks a pressure change always means the cart moved. Weather changes pressure too. Before using the floor alert, he moves the cart through a known height and checks the estimate against a tape measure, using a fresh local baseline. The takeaway: pressure can estimate a height change, but it needs a recent baseline and a check against known height.

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