L2 Flashcards
Accuracy implies
Precision
If a measurement is accurate it must be also
Precise
is a quantitative or numerical indication of closeness with which a repeated set of measurements of the same variable agrees with the average of the set of measurement.
Precision of measurement
Characteristics that show the performance of an instrument are
Accuracy, sensitivity, precision, resolution etc.
It allows users to select the most suitable instrument for specific measuring jobs.
Characteristic of instrument
value of the measured variable change very fast.
Dynamic characteristic
are required to be considered for the instrument which
measure unvarying process condition.
Static characteristic
defined for the instruments which measure quantities which do not vary with time.
Static characteristic
value of the measured variable change slowly.
Static characteristic
degree of closeness with which an instrument reading approaches the true value
of the quantity being measured.
Accuracy
indicates the nearness to the actual/true value of the quantity.
Accuracy
ratio of changed in output of an instrument to the change in input
Sensitivity
ratio of magnitude of the measured quantity to the magnitude of response
Sensitivity / inverse sensitivity / deflection factor
degree of closeness by which a given value can be repeatedly measured
Reproducibility
is specified for a period of time
Reproducibility
signifies that the given reading that are taken for an input, do not vary with time.
Perfect reproducibility
the gradual shift in the indication over a period of time wherein the input variable does
not change.
Drift
caused of environment factor like stray electric field, stray magnetic field, thermal e.m.fs, changes in temperature, mechanical vibrations, etc.
Drift
3 categories of drift
Zero drift
Span drift / sensitivity drift
Zonal drift
the deviation from the true value of the measured variable.
Static error
involves comparison of an unknown quantity with an accepted standard quantity.
Static error
degree to which an instrument approaches to its expected value is expressed terms of error of measurement.
Static error
the largest changes of input quantity for which there is no output.
Dead zone
the input that is applied to an instrument may not be sufficient to overcome friction.
It will only respond when it overcomes the friction force.
Dead zone
measure of the reproducibility of the measurement that is given a fixed value of
variable.
Precision
measure of the degree to which successive measurements differ from each other.
Precision
the instrument has zero adjustment error, so when we take a readings, the instrument is
Highly precise
as the instrument has a zero adjustment error the readings obtained are precise, but they are
Not accurate
the smallest measurable input, below which no output change can be identified.
Threshold
while specifying ***, manufactures give the first detectable output change.
Threshold
defined as the ability of an intrument to reproduce its input linearly
Linearity
simply a measure of the maximum deviation of the calibration points from the ideal straight line.
Linearity
defined as ______=maximum deviation of o/p from idealized straight line / actual readings.
Linearity
most instruments are specified to function over a particular range and the instruments can be said to be linear when incremental changes in the input and output are constant over the specified range.
Linearity
the ability of an instrument to retain its performance throughout its specified
storage life and operating life is called as ***.
Stability
the minimum and maximum values of a quantity for which an instrument is
designed to measure is called its ** or **.
Range or span
sometimes the accuracy is specified interms of ** or ** of an instrument
Range or span
the constant error which exist over the full range of measurement of an instrument.
Bais
can be completely eliminated by calibration.
Bais
the zero error is an example of ** which can be removed by calibration.
Bais
the maximum allowable error that is specified in terms of certain value while
measurement.
Tolerance
specifies the maximum allowable deviation of a manufactured device from a mentioned value.
Tolerance
is a phenomena which depicts different output effects while loading and
unloading.
Hysteresis
takes place due to the fact that all the energy put into the stressed parts when loading is not recovable while unloading.
Hysteresis
when the input of an instrument is varied from zero to its full scale value and then if the input is decreased from its full scale value to zero, the output varies.
Hysteresis
the output at the particular input while decreasing and increasing varies because of
Internal friction / hysteric damping
the output at the particular input while decreasing and increasing varies because of
Internal friction / hysteric damping
instrumens rarely respond to instantaneous changes in the
measured variables, their response is slow or sluggish due to mass, thermal capacitance, electrical capacitance, inductance, etc. sometimes, even the instruments has to wait for some time till the response occurs
Dynamic characteristic
these types of instruments are normally used for the measurement of quantities that flactuate with time
Dynamic characteristic
the behaviour of such system, where as the input varies from instant to instant, the output also varies from instant to instant is called as _____ _____ of the system.
Dynamic response
defined as that part of the response which goes zero as the time
becomes large.
Transient response
is the response that has definite periodic cycle.
Steady state periodic/ response
the input that is subjected to a finite and instantaneous change
Step input
the input linearly changes with respect to time.
Ramp input
input varies to the square of time. This represent constant acceleration.
Parabolic input
input changes in accordance with a _______ function of constant
amplitude.
Sinusoidal input
defined as the rapidity with which an instrument, responds to the
changes in the measured quantity.
Speed of response
shows how fast and active the system is.
Speed of response
defined as the degree to which a measurement system is capable of faithfully
reproducing the changes in input, without any dynamic error.
Fidelity
every system requires its own time to respond to the changes in input.
Lag
defined as the retardation or delay, in the response of a system to the changes in input
Lag
as soon as there is a changes in the measured quantity, the
measurement system begins to respond.
Retardation lag
the response of the measurement system starts after a dead time, once
the input is applied, They caused dynamic error.
Time delay
the difference between the true value of the quantity that is to be
measured, changing with time and the measured value, if no static error is assumed.
Dynamic error
the difference between the true value of the quantity that is to be
measured, changing with time and the measured value, if no static error is assumed.
Dynamic error
