1 Advanced Sensors Lecture 6 Sensors Technology AUE 2008 Bo Rohde Pedersen

2 Today's Lecture Piezo Acceleration Movement (IR)‏ Distance (IR)‏ Microphones

3 Piezo Sensor Generates a ”Voltage” High impedance app 1Mohm ( )‏ Mechanically tough

4 Applications Piezo Sensor

5 Applications of Accelerometer “Accelerometers are being incorporated into more and more personal electronic devices such as media players and gaming devices, like the Wii Remote, which has multiple accelerometers to provide another element of gameplay. In particular, more and more smartphones (such as Apple's iPhone and the Nokia N95) are incorporating accelerometers for step counters, user interface control, and switching between portrait and landscape modes. Another Apple product featuring an accelerometer is the iPod Touch.”Wii RemotesmartphonesiPhoneNokia N95iPod Touch Accelerometers can be used to measure vibration on cars, machines, buildings, process control systems and safety installations. They can also be used to measure seismic activity, inclination, machine vibration, dynamic distance and speed with or without the influence of gravity. accelerometers is in airbag systems for automobiles. In this case the accelerometers are used to detect the rapid negative acceleration of the vehicle to determine when a collision has occurred and the severity of the collision.

6 Principal of Accelerometer

7 Converting Mechanical Motion to Electrical Signals

8 Converting Mechanical Motion to Electrical Signals (II)‏ - Piezoelectric version - Optical - Laser measurements - Electromechanical Other ways of converting the motions to electrical signals?

9 Applications of Accelerometer (II)‏ Measures the Vibration Acceleration of Motion of a Structure

10 Accelerometers (vibration sensors) Frequency Range and Level Dynamic Range is the +/- maximum amplitude that the accelerometer can measure before distorting or clipping the output signal Frequency Response is determined by the mass, the piezoelectric properties of the crystal, and the resonance frequency of the case. It is the frequency range where the output of the accelerometer is within a specified deviation, typically +/- 5%.

11 Frequency Range of Accelerometer High Frequency Limit is the frequency where the output exceeds the stated output deviation. It is typically governed by the mechanical resonance of the accelerometer. Low Frequency Cut-off is the frequency where the output starts to fall off below the stated accuracy. The output does not "cut-off " but the sensitivity decreases rapidly with lower frequencies.

12 Passive Inferred Sensor: Movement Device:Detection Anglers: Connect GND to 0V and V+ to 5V. O/P connect to digital in. The device is measuring the temperature or the change in temperature

13 Passive Infrared Sensor: Driver Chip -Daylight adjusting -Filtering noise -Drivers for sensor KC778B is the main chip on the passive infrared sensor. Here are the features of the passive infrared sensor:

14 Long Distance Measurement Sensor The device sends out infrared light and detects the reflections Device:Block diagram:

15 Fasekorrelationsprincippet Principles of IR Distance Measurement Triangulating principle Light is sent out at a known angle from the transmitter and the receiver detects the direction of the light that is received (angle). Based on the receiving angle the distance is calculated. The triangulating principle is used for the short distance measurements in the range (um/mm) with high resolution. Time of flight principle In the principle Time of flight is a short pulse of light sent out. This pulse is reflected and the time from the pulse being sent out till it is received again is measured. This time is corresponding to the distance.

16 Output Signals

17 Measurement Spread Not the IR sensor we have!!

18 Microphones Technologies Electrodynamic (Coil in magnetic field)‏ Electrostatic (A capacitor that changes size)‏ Piezo Moving Coil Microphone Condenser Microphones

19 Examples of microphones Electrodynamic Benefits: Robust, high dynamic range Electrostatic microphone capsule Benefits: Size, low cost Electrostatic measuring microphone Benefits: Flat frequency response

20 Microphone Characteristics

21 Output Signals of a Microphone A microphone amplifier amplifies the signal to standard audio line level. A microphone amplifier includes typically extra filtering for low frequency noise. Frequency range is typically Hz

22 Links

23 Exercise 1.Connect the IR Distance Measurement Sensor to the Teleo board (analog in) and test the spread & range of the sensor (in cm). Review the Making Things page for Max implementation. s/acc_ir_dist_001.htm s/acc_ir_dist_001.htm 2.Connect the passive infrared sensor (digital in) and find out the spread and range for motion detection. Can it detect a piece of paper? How could you use it in practice? (installations / instrument interfaces)‏ 3.Model an installation space that will have three distinct active zones but will use only two passive infrared sensors. How would you do it?