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Static and Dynamic Characteristic of Instrument - Coggle Diagram
Static and Dynamic Characteristic of Instrument
[3.1] Static Characteristic (do not change with time)
SENSITIVITY
Ratio of output to magnitude of input signal
Static sensitivity, K = change of output signal/change in input signal
DEAD ZONE
Largest change in input quantity for which a noticeable change in the output quantity observed from zero reading
-Occurs due to friction in instrument
ACCURACY-PRECISION
Accuracy
-how closely the reading approaches true value
Accuracy = ((Result - Actual Value)/Actual Value)*100
Precision
-ability to produce same output value every time
REPRODUCIBILITY
The degree of closeness with a given quantity repeatedly measured within close range
(The difference between largest and smallest result)
DRIFT
Variation of output for a given input caused due to change in sensitivity of instrument due to certain interfering inputs like temperatures changes, component instabilities, etc
Zero drift
Sensitivity drift
ERROR
No measurement with perfect accuracy and precision
Error = Vi - Va
Vi = indicated value
Va = actual value
Accidental or Random Error
Due to random variation in parameter or system of measurement
Miscellaneous Type of Gross Error
Systematic/random error
-Human error = observe/read
-Fault component/adjustment
-Improper application of instrument
Systematic or Cumulative Error
-Instrument Error = poor design
-Loading Error = act of measurement
-Environmental Error = condition in surrounding
[3.2] Selection Instrument
Convenience Aspect
-Suitable for the given application
-Adaptibility to different sizes input
-Safety in use
-Maintenance, repair, steady delivery
-Material durability & non-fouling design
Cost, Initial and Cumulative Total
-Initial cost
-Maintenance, repair, calibration, etc.
-Running cost
-Expected lifetime
Instrument's Qualities
-Accuracy & Precision
-Nature and type of data available
-Further data computation
-Dynamic response characteristic
-Susceptibility to environmental disturbances
[3.3] Dynamic Characteristic of Instrument
Dynamic characteristic
~ steady-state periodic
~Transient (lasting for a short time)
Most measuring system can be categorized
-first order system
-second order system
3.3.1 First Order System
-Model of 1st order system consisting a spring and dashpot in parallel along with a necessary connecting element AB, acted on by a force
-Element (Linear spring and Viscous damper)
-Zero mass
3.3.2 Second Order System
-Consist mass
3.3.3 Seismic devices-Spring-Mass Type
-Base of the devices or transducer attached to the object whose motion or vibration is to be measured
-Motion of mass relative to the frame or base, gives an indication of the motion of the motion of the object and output of instrument
Types of dynamic input signal
Transient Signal
Random Signal
Periodic Signal with Time Period
The assumption :
-The restoring element are linear
-Damping is viscous
-System is a single degree of freedom system
Can be determine by applying a known and predetermined input signal to its primary element and the studying output
