acads (08-006) covered keywords process measurement, control, zero error, angular error, units of...
TRANSCRIPT
ACADs (08-006) Covered
KeywordsProcess measurement, control, zero error, angular error, units of weight, units of measurement, SI Measurements, range, span, upper range, lower range, accuracy, precision.
Description
Supporting Material
1.1.2.1 5.1.2.1.9 5.4.1.7
NIA97ADVANCED PROCESS AND MEASUREMENT CONTROL
Any sufficiently advanced technology is virtually indistinguishable from magic.
Arthur Clark
Path to becoming an I&C Techat Palo VerdePlant Systems
Advanced Process
NIA97
Foxboro
NIA98
Technical Skills
NIB43
Loops
NIA02
In Field (OJT)
Loop Calibration
The ‘100’ card
GPI
I&C
Tech
Other required training:
Site Access Training
RWP & Dress out
Respirator training & fit test
Conduct of Maintenance
Prints & Plant Drawings
Tagging
Electrical Safe Work Practices
Industry Events
I&C Select Training:
PPS, Excore
BOP/NSSS ESFAS
SESS/RK
RRS/SBCS
QSPDS
CEDMCS
DAFAS
VLPMS
Seismic
DFWCS
Fire Protection
PPC/PLC
GR
EHC/TSI
Gas Turbine
NIA97 Lessons• Measurement Fundamentals• Pressure instrumentation• Level instrumentation• Flow instrumentation• Temperature instrumentation• Pneumatic instrumentation• Calibrating & maintaining flow control
valves
Terminal Objective
• From memory the I&C Technician will define concepts and terminology related to the process measurement and control industry. Mastery will be demonstrated by successful completion of Lab Performance Exercises and written Exam.
Enabling Objectives• Define the term "measurement“• List two common engineering measurement systems• Define the following terms as they relate to process
measurement and control:– a. Range– b. Span– c. Linearity– d. Dead band– e. Hysteresis– f. Sensitivity– g. Conformity– h. Accuracy– i. Resolution
• Differentiate between "Zero Error" and "Angular Error"
Measurement is
• the determination of the size or magnitude of something.
• An observation that reduces the amount of uncertainty about the value of a quantity.
• A comparison of a quantity to some standard, called a unit
Who decides which units we will use?
Imperial or English Customary Weights & Measurements
1 inch = the length of 3 barleycorns (the word ‘inch’ comes from the word ‘thumb’ in some languages)
1 yard = the distance from the nose to the fingertip of Henry I
1 mile = the length of 1000 paces of a Roman legion
1 acre = a field of a size that a farmer can plow in a single day
1 grain = the weight of 1 barleycorn
1 pound = 7000 grains
(The Latin word for pound is Libra, hence the abbreviation LB)
1 gallon = the volume of 8 pounds of wheat
U.S. Customary Units• Similar to the old Imperial system• Based on many old local units derived over centuries, often
based on old Anglo-Saxon and Roman units• Length: The inch, foot, yard, and mile are declared units
based on historical customs• Volume: The ounce, quart, cup, pint, gallon, and barrel are
declared units based on custom• Weight: The ounce, pound, and ton are Avoirdupois weights
based on custom• Temperature: Degrees Fahrenheit based on historical custom.
The SI System1 meter = the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second
1 second = the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom
1 Kelvin = The Kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water."
1 kilogram = the mass of the international prototype of the kilogram
The Second• Same unit in nearly every system• Originally 1/86,400 of a mean solar day• Earth’s rotation is not sufficiently uniform• With the development of atomic clocks, the
second was redefined in terms of atomic time.
• the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom
Unit systems we do not use
• MKS-Meter/Kilogram/Second• CGS-Centimeter/Gram/Second• Both were replaced by the SI system in 1960
Bureau International des Poids et Mesures
The BIPM at Le Pavillon de Breteuil in Sevres, France
SI base units Base quantity Name Symbol length meter m
mass kilogram kg
time second s
electric current ampere A
thermodynamic temperature kelvin K
amount of substance mole mol
luminous intensity candela cd
KPa
• 1 Pascal = 1 Newton x 1 meter2
• 1 Newton = 1 kilogram x 1meter/sec2
• 1000 Pascal x 1 meter2 = 1 KPa
• 1 Kilopascal = 0.145 psi
• 1000 Kilopascal = 145 psi
Range Vs. Span
What is the range of the output of a Rosemont transmitter? What is the span?
Range: The region between the limits within which a quantity is measured
Span: The algebraic difference between the upper and lower limits of a range expressed in the same units as the range.
• URV – Upper Range Value – the highest quantity a device is adjusted to measure
• LRV – Lower Range Value – the lowest quantity a device is adjusted to measure
Terms• Accuracy• Precision• Resolution• Inaccuracy• Linearity• Scale• Total loop uncertainty• Repeatability• Tracability •Sensitivity
•Conformity
Accuracy vs. Precision
measure with a micrometer, mark with chalk
cut with an ax
Precision: How much you care to say about a particular item
Accuracy: How correct you are when you say something about that item
Resolution: The resolving power of a system, the smallest increment in a measurement
Zero, Span, Angularity & Gain
Static Calibration Errors
Input Ideal Output
(psig) (ma) (ma)
0 4 4
25 8 8
50 12 12
75 16 16
100 20 20
Ideal Calibration
05
10152025
0 25 50 75 100
Pressure
Cur
rent
Zero Adjustment Span Adjustment
Angular Error
05
10152025
0 25 50 75 100
Pressure
Cur
rent
Input Output
(psig) (ma)
0 4
25 8.25
50 12.5
75 16.75
100 21.0
Angular or Span Error
Angular Error
05
10152025
0 25 50 75 100
Pressure
Cur
rent
Input Ideal Output
(psig) (ma) (ma)
0 4 4
25 8 7.75
50 12 11.5
75 16 15.25
100 20 19
Would you adjust zero or span?
Zero Shift
05
10152025
0 25 50 75 100
Pressure
Cur
rent
Input Ideal Output
(psig) (ma) (ma)
0 4 3
25 8 7
50 12 11
75 16 15
100 20 19
Would you adjust zero or span?
Zero Shift
05
10152025
0 25 50 75 100
Pressure
Cur
rent
Input Ideal Output
(psig) (ma) (ma)
0 4 5
25 8 9
50 12 13
75 16 17
100 20 21
Would you adjust zero or span?
Zero
Based
Linearity
• Linearity-a behavior of a system in which the output varies in direct proportion with the input. In a linear circuit the output/input ratio is always the same
• Sensitivity-The ratio of the change in output magnitude to the change in input that caused it
• Conformity-(used when output is not linear from input) the closeness to which the output curve approximates a specified curve, such as a parabolic or logarithmic. Conformity is specified as independent, terminal-based, or zero based
• Repeatability Repeatability is the closeness of agreement among a number of consecutive measurements of the output for the same value of the input under the same operating conditions, approaching from the same direction. It does not include hysteresis.
Hysteresis
Uncertainty
222 %75.0.25%00.5%ncertaintyTotalLoopU
Transmitter +/- 0.5%
I2V
Converter +/- 0.25%
Indicator +/- 0.75%
Total Loop Uncertainty = 0.935%
On to Measuring Pressure