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CONTROL SYSTEMS AND INSTRUMENTATION (Characteristic (static (accuracy…

- - - - no measurement can be made with perfect accuracy and precision
        
        Errror = Vi - Va
        
        Vi = indicated value
        
        Va = actual value
        
        systematic or cumulative error
        
        have the same magnitude & sign for a given set of conditions (instrument bias)
        
        ex : instrument error
        
        ex : loading error
        
        ex : environmental error
        
        accidental or random error
        
        due to random variations in the parameter or the system of measurement (by lack of consistency in the measured values when the same input is imposed repeatedly in the instrument)
        
        ex : presence of certain system defects - Change the tolerance
        
        miscellaneous type of gross error
        
        systematic / random error
        
        ex : human error
        
        ex : faulty component
        
        improper application of the adjustment
    - - accuracy of an instrument indicates how closely the reading of the instrument approaches the true value
        
        accuracy = (Result - Actual value x 100)/Actual value
      - precision is defined as the ability of the instrument to reproduce a certain set of readings within a given accuracy
    - - sensitivity of a measuring instrument is expressed as the ratio of the output to the magnitude of the input signal
        
        static sensitivity, K = change of output signal/change in input signal
    - - reproducibility is the degree of closeness with which a given value of a quantity is repeatedly measured within a close range
    - - drift is defined as the variation of output for a given input caused due to change in the sensitivity of a instrument due to certain interfering inputs like temperature changes, component instabilities, etc.
        
        zero drift
        
        sensitivity drift
    - - dead zone is the largest change input quantity for which a noticeable change in the output quantity is observed from zero reading / AREA OF SIGNAL WHEN NO ACTION OCCURS
  - - - periodic signals with time period
        
        varying cyclically with time or repeating itself after a constant interval
      - transient signal
        
        varying non- cyclically with time
      - random signal
        
        varying randomly with time, with no definite period and amplitude