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Instrumentation and Control
Citation preview
11/21/2014
1
FUNDAMENTALS OF
INSTRUMENTATION AND CONTROL
PHILOSOPHY
CALIBRATION CONCEPT
PENDAHULUAN
• Setiap instrumen memiliki paling sedikit satu
masukan (input) dan satu keluaran (output).
InputTekanan
Sinyal
Sinyal
OutputSinyal
Pembacaan
Daya
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PENDAHULUANKalibrasi adalah menera instrumen dengan memakai instrumen
standar. Tujuannya adalah menepatkan hubungan antara input dan
ouput instrumen.
PENDAHULUAN
CALIBRATION DAN RE-RANGING
CALIBRATION adalah mengecek dan mengatur untuk
menepatkan kerja instrumen dalam rentang tertentu (biasanya
dari minimum hingga maksimum)
RE-RANGING adalah menyetel nilai minimum dan maksimum
sehingga diperoleh nilai sensitivitas tertentu
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Hubungan Input-Output
Hubungan Input-Output
Pressure Transmitter
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ZERO ADJUSTMENT
Pressure Transmitter
Span Shift
Pressure Transmitter
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Effect of Linerarity
Pressure Transmitter
Effect of Hysteresis
Pressure Transmitter
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Typical Calibration Errors• If the technician “blocks and equalizes” a DP instrument and it
properly reads zero, its calibration is probably good across the entire range.
• If the DP instrument fails to read zero during this test, it definitely needs to be recalibrated.
Documentation
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LRV and URV Setting
LRV and URV Setting
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ADC Error
LRV and URV Setting
DAC Error
PRACTICAL CALIBRATION STANDARD
1) Electrical Standard
– Weston cell, 1.0183 V, low uncertainty
and low drift. Sensitive to vibration.
– High accuracy digital voltmeter
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PRACTICAL CALIBRATION STANDARD2) Temperature Standard
– For RTD and thermocouple
PRACTICAL CALIBRATION STANDARD3) Pressure Standard
– Deadweight Tester
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PRACTICAL CALIBRATION STANDARD3) Pressure Standard
– Deadweight Tester
PRACTICAL CALIBRATION STANDARD3) Pressure Standard
– Deadweight Tester
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PRACTICAL CALIBRATION STANDARD3) Analytical Standard
– A typical self-calibration system
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INDIVIDUAL CALIBRATION
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Disadvantages of Individual Calibration Advantages of Individual Calibration
a. The entire loop is not verified within
tolerance
b. Possible mistakes on re-connect or
install
c. Less efficient use of time to do one
calibration for each loop instrument
as opposed to one calibration for
the loop.
a. Correct instrument will be
adjusted
b. More compatible with
multifunction calibrators
LOOP CALIBRATION
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Loop Calibration Disadvantages Loop Calibration Advantages
a. Wrong instrument may be adjusted to
bring the loop within calibration.
b. Not as compatible with multifunction
calibrators used for “paperless” data
collection
a. Entire loop, including sensor, is
verified within tolerance
b. Mistakes on-reconnect or install can
be minimized
c. More efficient use of time to do one
calibration for loop as opposed to one
calibration for each loop instrument.
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