vault backup: 2023-03-30 08:45:51

content/notes/10-orientation-sensors.md

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+---
+title: "10-orientation-sensors"
+tags: 
+- lecture
+- info305
+---
+
+
+Accelerometers 
+- Measures proper acceleration (acceleration it experiences relative to freefall. gravity), felt by people or objects 
+- Units: m/s2 or g 
+- Most smartphone accelerometers trade large value range for high precision 
+	- iPhone range: ±2g, precision 0.018g
+![g forces|300](https://i.imgur.com/l4DnMSN.png)
+
+Accelerometers 
+- Acceleration is measured on 3 axes 
+- Orientation of sensor (and coordinate system) varies among different device
+![|100](https://i.imgur.com/4SwveO3.png)
+
+Accelerometers 
+- Miniaturisation using a MEMS (Microelectromechanical systems)
+- Measuring flowing current over an differential capacitor indicates the acceleration
+![|300](https://i.imgur.com/UIS4zDV.png)
+
+Accelerometers 
+- Advantage: 
+	- Fast update rate 
+	- Relatively accurate 
+- Disadvantage: 
+	- Can’t easily identify certain kind of acceleration (small value range)
+	
+	
+	
+Compass / Magnetometer 
+- Measures the strength of earth’s magnetic field 
+- Strength is expressed in tesla [T] 
+- iPhone 4 magnetometer range: ±2mT 
+- Pro tip: prolonged exposure to a fridge magnet decalibrates your phones’ magnetometer for at least a week ;-)
+![field strength examples|300](https://i.imgur.com/00VV74x.png)
+
+![Error around metal/magnetic objects](https://i.imgur.com/YIJAcGS.png)
+
+
+	
+	
+	
+	
+Recap
+- Several improvements to traditional GPS 
+- AGPS for improved startup time and improved localisation using WIFI 
+- DGPS for improved localisation using reference stations with known error 
+- RTK GPS for improve localisation using DGPS and phase analysis 
+
+- Accelerometers for measuring gravity along multiple axis (typically 3) 
+- Usually implemented with MEMS 
+- Typically limited in value range (in mobile devices)

content/notes/info-305.md

@@ -24,5 +24,5 @@ tags:
 - [x] [[07-location-sensors]]
 - [x] [[08-proximity sensors]]
 - [x] [[09-location-sensors-3]]
-- [ ] 
+- [ ] [[10-orientation-sensors]] 
 # Info