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INSTRUMENTASI INDUSTRI

INSTRUMENTASI INDUSTRI. Instrumentation System. A Measuring system is required to compare a quantity with a standard or to provide an output that can be related to the quantity being measured The quantity to be measured is detected by an input transducer or sensor .

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INSTRUMENTASI INDUSTRI

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  1. INSTRUMENTASI INDUSTRI

  2. Instrumentation System • A Measuring system is required to compare a quantity with a standard or to provide an output that can be related to the quantity being measured • The quantity to be measured is detected by an input transducer or sensor. • The detected quantity may be converted to a mechanical or electrical form of energy Output Input Display Signal conditioner Sensor Recorder Measurand

  3. Instrumentation System Control and feedback Power source Sensor Perceptible output Primary sensing element Variable conversion element Signal processing Output display Measurand Calibration signal Data storage Data transmission Radiation, electric current, or other applied energy Dashed lines are optional for some applications

  4. Clinical Instrument ECGInstrument EMGInstrument Blood PressureInstrument ．．．．．． ．．．．．． Clinical Instrument • Black box • Need many kinds of Instruments • Expensive

  5. PC A/DConverter LCD Sensor ProcessCircuit Oscilloscope Clinical Instrument (cont.) surface electrodepressuretransducerphotocoupler temperature sensorpressure gauge strain gauge ：

  6. Definitions • Measurand (Physical quantities): • Position, displacement • Temperature • Force • Pressure,… • Concentrations, chemicals,…, • Sensor: • is a device that detects a change in a physical stimulus and turns it into a signal which can be measured or recorded • Signal conditioning: • Amplifying, wave shaping, filtering, rectifying,… • Transducer: • is a device that transfers power from one system to another in the same or in a different form.

  7. Output Input Measured valueof variables True valueof variables Observer Process,machine orsystem beingmeasured Purpose of Measurement Systems Measurement System Lecture 2

  8. States of process or system Empirical Space Curves or values Abstract Space Measurement Theory Measurement is a mapping of a source set in the empirical domain space onto an image set in the abstract range space. Lecture 2

  9. Essential Requirements • Descriptive provide relationship between output and state. • Selective provide desirable information only. • Objective be independent of arbitrary observers. • Validated represent the true value. Lecture 2

  10. Types of Measurements • Manufacturing measurements discretely monitoring products quality. • Performance measurements providing performance evaluation as needed. • Operational measurements continuously monitoring operation process. • Control measurement continuously providing feedback signals. Lecture 2

  11. Output Input Measured valueof variables True valueof variables Essential Elements Measurement System SensingElement ConditioningElement ProcessingElement DisplayingElement Lecture 2

  12. Sensing Elements • In contact with the information carrier or medium • Giving a signal output related to the quantity being measured • Examples: • strain gage, R depends on mechanical strain; • thermocouple, V depends on the temperature; • LVDT, L depends on the displacement. Lecture 2

  13. Signal Conditioning Elements • Prepares sensor outputs suitable for further processing. • Mostly use various conditioning circuits. • examples: • deflection bridge, converts an impedance change into a voltage change • amplifier, amplifies millivolts to volts Lecture 2

  14. Signal Processing Elements • Converting conditioned output into forms more suitable for presentation. • Calculating secondary variable from measurable variables. • Examples: • analog-to-digital converter • analog or digital filter • signal compensation Lecture 2

  15. Data Display Elements • Display and/or store measured signals in recognizable form. • Use of analog and/or digital form. • Examples: • visual display units, like Oscilloscope • analog chart recorders • digital data array Lecture 2

  16. Precise readings Accurate readings True value Accuracy and Precision • Accuracy deviation of the output from the true value indicates the closeness of measured and true values • Precision degree of reproducibility of a measurement indicates the repeatability of measures values Lecture 2

  17. Definition of Accuracy Accurate is a property of a complete measurement rather than a single element. Accuracy is quantified using measurement error: E = measured valve – true valve = system output – system input Lecture 2

  18. True Value Measured Value Sensing Element Conditioning Element Processing Element Presentation Element I O K1 K2 K3 K4 Ideally: Measurement System Gains Gain is defined as the ratio of output to the input. Each element, as well as the entire system, has its specific gain! Lecture 2

  19. True Value Measured Value Sensing Element Conditioning Element Processing Element Presentation Element I O K1 K2 K3 K4 Measurement Error None of the elements can be perfectly manufactured and integrated in the system it results error! Lecture 2

  20. Sources of Measurement Errors • Improper sensing position • Improper element calibration • Improper data acquisition method • Improper sampling rate • Elements non-linearity • Environment effects Lecture 2

  21. Error Reduction Techniques(1) The mosteffectivemethodof reducingmeasurement erroris to: Set the sensing element at the right position. Lecture 2

  22. Error Reduction Techniques (2) An effectiveand usefulmethodof reducingmeasurement erroris to: Calibrate each element to eliminate or reduce bias. Lecture 2

  23. Error Reduction Techniques (3) Anothereffectivemethodof reducingmeasurement erroris to: Setup a proper sampling rate for data acquisition. D Lecture 2

  24. Error Reduction Techniques (4) An effectiveand usefulmethodof reducingmeasurement erroris to: Compensate sensing element non-linearity. I U C U(I) C(U) U C C I U I Lecture 2

  25. Another effectivemethodof reducingmeasurement erroris to: compensate the environmental effects • Environmental effectsisolation: • Environmental inputcancellation: Error Reduction Techniques (5) Lecture 2

  26. Part II: Learn from Example Assume a temperature measurement system was used to monitor the temperature in this classroom. This measurement system uses a thermocouple (gain: 40 V/C) as its sensing element, a signal amplifier (gain: 1 V/mV) as its signal conditioning element, and a visual indicator (gain: 25 C/V) as its display element. Please try to: • Design the measurement system, and present the design using a system block diagram. • Determine the gain of the measurement system. • Estimate the measurement error if the thermocouple gain is 40.04 V/C, the amplifier gain is 0.999 V/mV, and the indicator gain is 25.025 C /V. Lecture 2

  27. KARAKTERISTIK PENGUKURAN

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