Contact: ( Dr. Ashraf Aboshosha ) www.icgst.com, www.icgst-amc.com editor@icgst.com Tel.: 0020-122-1804952 Fax.: 0020-2

1. Analog and Digital Interface Contact: (Dr. AshrafAboshosha) www.icgst.com, www.icgst-amc.com editor@icgst.com Tel.: 0020-122-1804952 Fax.: 0020-2-24115475 Prepared by: Eng. Mohamed Hassan Supervised by: Dr. AshrafAboshosha

2. Big Picture Physical world Other Systems or ICs Digital Communication Analog Interfacing MSP430

3. Sensors • A device that converts a physical phenomenon into an electrical signal • Physical phenomenon • light, temperature, humidity, pressure, and etc. • Electrical signal • resistance, capacitance, current, voltage, and etc. • Maps a physical phenomenon change to a electrical signal change

4. Signal Path Produce a proper output voltage level Signal Conditioning (if necessary) Sensors • Amplification • Filtering Analog to Digital Conversion (ADC) • Light • Temperature • Acceleration • Humidity • Pressure • etc. 10011101 • Resistance • Capacitance • Current • Voltage • etc. Convert to voltage Converts voltage to digital number

5. Sensors We Have • Raw sensors • Produce raw electrical signal • Signal conditioned sensors • Have some signal conditioning circuit • Produce analog output • Mostly Voltage • Sometime Current

6. Sensors We Have • Digitalized sensors • Have some signal conditioning circuit • Convert analog to digital internally • Provide digital output

7. Our Focus Produce a proper output voltage level Sensors Signal Conditioning (if necessary) Sensors • Amplification • Filtering • Light • Temperature • Acceleration • Humidity • Pressure • etc. Analog to Digital Conversion • Resistance • Capacitance • Current • Voltage • etc. 10011101 Convert to voltage Converts voltage to digital number • We are not going to talk about signal conditioning • You can find many sensors that are signal conditioned and provide a proper analog output, or even digitalized • We will focus on how to understand these signal conditioned sensors and get the output we want

8. Some Raw Sensors • Temperature Sensors • Thermistors • Temperature-sensitive resistor • RTDs (resistive temperature devices) • Temperature-sensitive resistor • Thermocouples • Temperature => voltage (mV) • Pressure sensors • Piezoresistive • Resistancechange with applied pressure

9. Level is measured at the position of the interface between phases, where the phases are liquid/gas, solid/gas, or immiscible liquid/liquid and after reaching certain level,switch turns the equipment ON & OFF. Level is simply a measure of height. Level Switches

10. Types Of Level Measurement • Direct • Indirect

11. Direct Level Measurement • Direct methods employ physical properties such as fluid motion and buoyancy, as well as optical, thermal, and electrical properties. Direct level measurement does not require compensation for changes in level caused by changes in temperature. Direct level measurements show the actual level of the interface.

12. Indirect Level Measurement • Indirect level measurement involves converting measurements of some other quantity, such as pressure to level by determining how much pressure is exerted over a given area at a specific measuring point, the height of the substance above that measuring point can also be determined.

13. A dipstick used to measure the amount of fuel remaining in a tank. Dipsticks can also be used to measure the quantity of liquid in an otherwise inaccessible space, by inserting and removing the stick and then checking the extent of it covered by the liquid. Dipstick

14. Rotating paddle level sensors are a very old and established technique for bulk solid point level indication. The technique requires a low speed gear motor that rotates a paddle wheel. When the paddle is stalled by solid materials, the motor is rotated on its shaft by its own torque until a flange mounted on the motor contacts a mechanical switch Rotating Paddle Level Sensors

15. A sight glass or water gauge is a transparent tube through which the operator of a tank or boiler can observe the level of liquid contained within. Simple sight glasses may be just a plastic or glass tube connected to the bottom of the tank at one end and the top of the tank at the other. The level of liquid in the sight glass will be the same as the level of liquid in the tank. Today, however, sophisticated float switches have replaced sight glasses in many such applications. Sight Glass

16. It is used to measure liquid levels in the tank in which a float rests on the surface of liquid and follows the changing level of liquid. Float Level Sensor

17. Ultrasonic transmitters work on the principle of sending a sound wave from a peizo electric transducer to the contents of the vessel. The device measures the length of time it takes for the reflected sound wave to return to the transducer. A successful measurement depends on reflection from the process material in a straight line back to the transducer Ultrasonic / Sonic

18. The Metritape sensor comprises an elongated metallic base strip having electrical insulation on the edges and back of the strip to define an un-insulated zone along the length of the base strip, and a resistance wire or ribbon helically wound around the insulated base strip, with the helical turns bridging the insulated edge por­tions being spaced from the underlying un-insulated zone of the base strip. Resistance Tape

19. Hook- Type level Indicator consists of a wire of corrosion resistance alloy bent into U-shaped with one arm longer than the other. The shorter arm is pointed with 60 degrees while the longer is attached to a slider on a Vernier scale, which moves over the main scale and shows the reading. Hook- Type Level Indicator

20. Displacer level detector works on the Archimedes Principle which states, “A body wholly or partially immersed in fluid is buoyed up a force which is equal to weight of the fluid displaced”. By detecting the apparent weight of immersed displacer the level of the fluid is measured Displacer Level Sensor

21. Advantages • High accuracy • Reliable for clean liquids • Can be mounted internally or externally • Externally mounted can be disconnect from main unit for maintenance • Adoptable to liquid interface measurement

22. Disadvantages • These have limited ranges and devices exceeding 1.2m in length are difficult to measure • Cost of these increases appreciably for externally mounted units as pressure increases • External units may require heating to avoid freezing • External units may be in error due to temperature difference between vessel fluid and level chamber fluid

23. Key questions to ask before selecting a level measurement sensor: 1. Are you measuring a liquid or solid? 2. What is the application’s temperature and pressure ranges? 3. Is point level or continuous measurement required? 4. What level measurement range do you need? Level Measurement Sensor Selection:

24. 5. Is the measured material electrically conductive? 6. Will the material coat or build up on surfaces? 7. Does turbulence, foam, or vapor occur at the surface of the liquid? 8. Will you need contact or non-contact level measurement? 9. What kind of output do you need–analog, relay, digital display, etc.? Level Measurement Sensor Selection:

25. Switches A switch is an electrical device usually electromechanical used to control continuity between two points

26. Types of Switches Hand switches: Hand Switches are actuated by human touch. Process Switches: Process Switches are actuated by changes in some physical process(temperature ,level , flow etc.) Limit Swiches:Limit Switches are actuated by machine motion.

27. Liquid Level Switches A floating object can be used to actuate a switch mechanism when the liquid level in an tank rises past a certain point.

28. Nuclear Level Switches Both source and detector are outside of the vessel, with no intrusion at all except the radiation flux itself. The radioactive sources used are fairly weak and pose no immediate health threat to operations or maintenance personnel.

29. Nuclear Level Switches

30. Float Level Switches All float operated liquid level controls operate on the basic buoyancy principle which states "the buoyancy force action on an object is equal to the mass of liquid displaced by the object."

31. Difference Between Sensor, Switch & transducer Sensor: Tell us the value Switch: Turns something ON or OFF Transducer: A sensor that can send a signal

32. Temperature Sensors

33. Brief Overview • Types of Sensors and how they work • Sensor Applications • Advantages and Disadvantages • Sensors that will work with our project

34. Types of Temperature Sensors • Thermocouples • Resistance Temperature Detectors (RTDs) • Thermistors • Infrared Sensors • Semiconductors

35. Thermocouples • Two wires of different metal alloys. • Converts thermal energy into electrical energy. • Requires a temperature difference between measuring junction and reference junction. • Easy to use and obtain.

36. Thermocouple Applications • Plastic injection molding machinery • Food processing equipment • Deicing • Semiconductor processing • Heat treating • Medical equipment • Industrial heat treating • Packaging equipment

37. Thermocouples Advantages Disadvantages • Simple, Rugged • High temperature operation • Low cost • No resistance lead wire problems • Point temperature sensing • Fastest response to temperature changes • Least stable, least repeatable • Low sensitivity to small temperature changes • Extension wire must be of the same thermocouple type • Wire may pick up radiated electrical noise if not shielded • Lowest accuracy

38. Resistance Temperature Detectors (RTDs) • Wire wound and thin film devices. • Nearly linear over a wide range of temperatures. • Can be made small enough to have response times of a fraction of a second. • Require an electrical current to produce a voltage drop across the sensor

39. RTD Applications • Air conditioning and refrigeration servicing • Furnace servicing • Foodservice processing • Medical research • Textile production

40. RTDs Advantages Disadvantages • Most stable over time • Most accurate • Most repeatable temperature measurement • Very resistant to contamination/ • corrosion of the RTD element • High cost • Slowest response time • Low sensitivity to small temperature changes • Sensitive to vibration (strains the platinum element wire) • Decalibration if used beyond sensor’s temperature ratings • Somewhat fragile

41. Thermistors • A semiconductor used as a temperature sensor. • Mixture of metal oxides pressed into a bead, wafer or other shape. • Beads can be very small, less than 1 mm in some cases. • The resistance decreases as temperature increases, negative temperature coefficient (NTC) thermistor.

42. Thermistors • Most are seen in medical equipment markets. • Thermistors are also used are for engine coolant, oil, and air temperature measurement in the transportation industry.

43. Thermistors Advantages Disadvantages • High sensitivity to small temperature changes • Temperature measurements become more stable with use • Copper or nickel extension wires can be used • Limited temperature range • Fragile • Some initial accuracy “drift” • Recalibration if used beyond the sensor’s temperature ratings • Lack of standards for replacement

44. Infrared Sensors • An infrared sensor intercepts a portion of the infrared energy radiated by an object. • Many types Optical Pyrometers, Radiation Pyrometers, Total Radiation Pyrometers, Automatic Infrared Thermometers, Ear Thermometers, Fiber optic Thermometers, Two-Color Pyrometers, Infra-Snakes, and many more.

45. Infrared Applications • Manufacturing process like metals, glass, cement, ceramics, semiconductors, plastics, paper, textiles, coatings. • Automation and feedback control • Improve safety in fire-fighting, rescues and detection of criminal activities. • Used to monitor and measure human body temperatures with one second time response. • Reliability and maintenance needs from building heating to electrical power generation and distribution

46. Infrared Sensors Advantages Disadvantages • No contact with the product required • Response times as fast or faster than thermocouples • No corrosion or oxidation to affect sensor accuracy • Good stability over time • High repeatability • High initial cost • More complex - support electronics required • Emissivity variations affect temperature measurement accuracy • Field of view and spot size may restrict sensor application • Measuring accuracy affected by dust, smoke, background • radiation, etc.

47. Semiconductors • Are small and result from the fact that semiconductor diodes have voltage-current characteristics that are temperature sensitive. • Temperature measurement ranges that are small compared to thermocouples and RTDs, but can be quite accurate and inexpensive.

48. Semiconductor Applications • Hard Disk Drives • Personal Computers • Electronic Test Equipment • Office Equipment • Domestic Appliances • Process Control • Cellular Phones

49. Thermal Sensor Vendors • Minco • Pyrotek • Omega • Watlow • Texas Instrument • National Semiconductor • Maxim

50. Determining Factors • Low Power • Serial Interface • Small • Accurate • Wide temperature range Extras • I2C Interface • Temperature Alarms