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Instrumentasi Sistem Pengaturan - 01 1 Instrumentasi Sistem Pengaturan Pengantar Sistem Instrumentasi Ir. Jos Pramudijanto, M.Eng. Jurusan Teknik Elektro FTI ITS Telp. 5947302 Fax.5931237 Email: [email protected]

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Page 1: Instrumentasi Sistem Pengaturan - Website Personalpersonal.its.ac.id/files/material/2982-jos-ee-Instr_S108 - 01... · Instrumentasi Sistem Pengaturan - 01 1 Instrumentasi Sistem Pengaturan

Instrumentasi Sistem Pengaturan - 01 1

Instrumentasi Sistem Pengaturan

Pengantar Sistem Instrumentasi

Ir. Jos Pramudijanto, M.Eng.Jurusan Teknik Elektro FTI ITS

Telp. 5947302 Fax.5931237Email: [email protected]

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Objektif

• Mengetahui konfigurasi sistem instrumentasi;• Perbedaan dari sensor dan tranduser;• Mengetahui pentingnya manfaat pengukuran;• Akurasi dari sensor;

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A Instrumentation systems includes all the components necessary for producing a measurement.

Instrumentation Systems

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Bicycle Speedometer

Sensor: A Magnet attached to one of the spokesTransducer: The Hall Effect device that produces an electrical pulse as the magnet passesSignal Conditioning: A circuit compares the pulses to a timer and determines the period. A correlation based on the measured period and wheel diameter is used to determine velocity.Output Stage: A digital signal is sent to the LCD displays and the velocity appears on the screen

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Measurement: Comparison between a standard and what we want to measure (the measurand).What is the standard?

Width of a man’s thumb =1 inchLength of a man’s foot = 1 footLength of a man’s belt = 1 yard

There is a need for an unchanging standard for physical parameters

length(m), time(s), mass(kg), temperature(K), etc.

Other parameters can be defined in terms of these standard parameters (velocity = length/time)Oversight of standards and definitions (IEEE)

What is a Measurement ?

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Sensor – converts some physical quantity into an electrical quantity

Transducer – converts one form of energy into another

What is a Sensor and Transducer ?

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Sensors and Actuators

Transducers:a sensor is an electronic transducer that converts a physical quantity into an electrical signal,an actuator is an electronic transducer that converts electrical energy into a physical quantity.They are essential to digital control systems.

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TradeGetting what you pay forGetting parts that fit

DesignDesign parameters are based on experimental measurement (ex. max. temperature = 140oC)Analysis based on measurement (Testing: Does the part fail under max load at T = 140oC?)

ControlSafety (stall sensors on an aircraft wing measure lift)Economy (fuel system controls on an automobile)

Why is Measurement so Important ?

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Strain gauge

Strain-gauge Measurement System

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Oxygen Sensor

Airflow Sensor

Water Temperature

Oil Pressure

Accelerometer

CO Sensor

Automotive Measurement System

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Ultrasound Transducer

Biomedical Measurement System

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Direct comparisonMeasure length with a rulerMeasure mass with a balanceMeasure pressure with a deadweight pressure gage

Indirect comparisonUse of a measuring systemRequires calibrationMeasure temperature with a thermometerMeasure velocity with a bicycle speedometer

How Do we Measure with Sensor ?

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There is always some uncertainty in measurementsUncertainty: A likely bound on the error

The application prescribes the required accuracySignificant consequencesCore temperature of a nuclear reactor vs. outdoor temperatureFunctionalityMeasurement of lens curvature on eyeglasses vs. curvature of a wide-angle mirror

Error Definition: Difference between the actual value and the measured valuePrecision errorBias error

How Accurate is the Sensor ?

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Precision Error

RandomCauses measurement to be randomly above or below the the average value

Estimated by statistical methodsEstimation based on standard deviation

Example: Darts

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Bias Error

SystematicConstant fractional or total error

Can not be estimated by statistical methodsEstimation based on an understanding of sources of error

Example: Darts