1. Sensors - Lab Experience H. Scott Matthews April 9, 2003

2. Recap of Last Lecture(s)  Finished discussion of ‘mgmt systems’  Sensors interact with our environment and signal stimuli and changes  Sensor networks act as interfaces between sensors and our systems and practices  Historically, trend has been simple sensors connected to complex systems

3. Data Sources  Condition  Inventory  Accidents  Usage  Weather  Repair/Maint/Rehab Costs  User Costs  Benefits  MARR / discount rate  Planning Horizon/ Facility lifetime

4. Evolution of Systems  Increased data handling, analytic techniques (prob/stats, optimization, multi-obj analysis)  Computing power increased led to ability to look at larger scopes  In both problem area and application  Eventually went from mainframes to PCs - which sped up reporting time

5. Simple Sensor Example  Infrared Beam that reflects and sensor checks when beam broken  Used for ‘motion or passing through’ (mall)  Sensor connected to DC power source  Radio Shack $10, connect to alarm sys  Normally Open/Closed circuits  Watch multimeter as we make the sensor activate  What is happening? Why?

6. Implementation of Sensor  What kind of signal/system is this sensor generating (binary/boolean)  ‘Is it happening?’ - yes or no?  Could measure temperature?  Could measure temp cutoff (thermostat)  What other types of sensors/systems could/would work in a similar way?  Vehicle detector, occupancy,..  How would we connect to a mgmt system?

7. More Complex ‘Sensor’  Not really a ‘sensor’ but instead the communication method used by one  Simple radio antennas - transmit and receive  E.g. as used by wireless LAN on campus  Imagine this is ‘EZ-Pass’  What is EZ-Pass - RFID tag system to uniquely identify cars and automate toll collection  Uses a transponder to send/receive radio signals  Watch on scope and in LabVIEW as antennas send/receive signals

8. More Complex ‘Sensor’  When antennas close, signal is perfect  C=Lambda*F (from physics!)  5 kHz, 5V amplitude  What happens as antennas moved apart?  Frequency ok, amplitude lost  Why? Really low power!  Current in mA, Power = IV, (mW)  Wireless antennas on campus ~20W - 200 feet!  Assume this is how signal would work for EZPass  Could we each have a transponder that had a 5Khz signal? How would we uniquely identify each other?  What would we have to do differently?