1. ISAT 303-Lab3-1  Measurement of Condition: Lab #3 (2005):  List of parameters of condition: –Linear distance, angular displacement, vibration, displacement, humidity, viscosity, etc  Transducer – takes input of a form of energy (characteristic e.g. light beam, magnetic field, eddy current) and generates an output that is a different form of energy (characteristic e.g. voltage) from the input

2. ISAT 303-Lab3-2  Measurement of Condition: Non-Contacting Displacement Sensors  Displacement sensors measure the distance traveled by a target object as it moves from one position to another.  The transducers can also be used to measure external dimensions of objects, such as thickness, height, width or diameter.  Two basic types: –Contact type: dial gages, micrometers and LVDT –Non-contact type: »semiconductor laser displacement sensors: reflected light »inductive (eddy current) sensors: magnetic field attenuation »capacitive transducers: current decrease with plate separation »acoustic transducers: sonic waves reflection (e.g. sonar) »microwave devices: reflected  -waves (e.g. radar)

3. ISAT 303-Lab3-3  Displacement Sensors Used in This Lab: Comparative Summary

4. ISAT 303-Lab3-4  Laser Sensors: Operating Principles  Displacement laser sensors consist of a sensor head and a controller.  A laser within the sensor head emits a focused light on the the target.  Light reflected back from the target is focused on an optical position detector. Sensor head  The unit’s output is proportional to the displacement (along the laser’s line of sight) of the target.  The controller unit contains a power supply, adjustment circuitry and signal conditioning.

5. ISAT 303-Lab3-5  Inductive Sensors: Operating Principles  An oscillator generates a strong focused magnetic field.  When the target enters the field, eddy currents are induced in its surface  The current produces its own magnetic field which reduces the amplitude of oscillations.  The change in amplitude is converted into a DC output of the sensor which is related to how close the target is to the sensor head. Near Far Sensor head Magnetic field Metal target Target displacement Far Near Far Oscil- lator output Sensor output 0v0v Displacement Output, Volt

6. ISAT 303-Lab3-6  Inductive Sensors: Factors Influencing Sensing Range  Mechanical factors –core size and shape –material of the target –target size –manufacturing tolerance and other variations  Environmental factors –ambient temperature –electromagnetic (RF) noise –adjacent sensors or magnetic fields –electrical company power surges

7. ISAT 303-Lab3-7  Displacement Sensors: Sample Manufacturing Applications  Non-contacting dimensional gaging: critical dimensions in precision parts (circuit boards, engine components, sheet thickness, flatness, runout)  Motion and vibrations: small high frequency monitoring (disk head movement, machine vibration monitoring, robot motion verification and safety)  Coating and film thickness: precise measurement of thickness of coatings on metal parts (paint, resins)  Presence and absence of objects: electronic assembly, filling and packaging (damaged shrink wrapping and misfeeding)

8. ISAT 303-Lab3-8  Accuracy:  Accuracy – closeness of agreement between a measured value and the true value  Accuracy is often given (specified) as a % of full scale output –E.G. if device range is 0 to 5 volts and accuracy is +/-5% of F.S. –Then uncertainty is =/- 0.25 volts (.05 x 5) –Therefore at readings of below FS, % uncertainty will be greater than 5% (per example above) –At readings close to lower end of range, % uncertainty will be unreliable  Implications for selecting measuring systems ?????

9. ISAT 303-Lab3-9  Inductive (EddyDisplacement CATEGORYCurrent) SensorLaser Sensor Detected objectElectricallyAny opaque or conductive materialtranslucent material Detecting rangeVery short (0-10 mm)Typical (10-400 mm) ResolutionVery high (.3-1 mm)Ultra high (.01-.2 mm) Response timeFast (0.05 -1 ms)Very fast (.001-.05 ms) EnvironmentalExcellentTypical resistance Detection pointLargeVery small