This is a presentation on characteristics of an instrument which is a part of mechanical measurements and metrology.

1. Prepared by :
Kunj Thummar (140050119517)

2.  Static Characteristics : those characteristics of an
instrument which do not change with time are known
as static characteristics. Eg. error, hysteresis, etc.
 Dynamic characteristics : those characteristics of an
instrument which change with time are known as
dynamic characteristics. Eg. Measuring lag, overshoot,
etc.

3.  Accuracy : it may be defined as the ability of an
instrument or a system to respond to true value of a
measured variable under reference conditions.
 Static error : it is the difference between the indicated
value and the true value of the quantity or condition to
be measured.
 Static correction : it is the difference between true
value and the measured value of the quantity or
condition to be measured.

4.  Calibration : it is the procedure of making, adjusting
or checking a scale so that the readings of an
instrument or measurement system conform to an
accepted standard.
Calibration
curve
Error curve Correction curve

5.  Range and Span : A range is a region between the
limits within which an instrument is designed to
operate for measuring, indicating or recording a
measurand while span is the algebraic difference
between the largest and the smallest reading of an
instrument.
 Sensitivity : it is defined as the ratio of output response
to a specific change in input.
 Hysteresis : it is the maximum difference between two
outputs at same input value within the specified range
when input is continuously increased from zero and
continuously decreasd from maximum.

6.  Reproducibility : the reproducibility of an instrument
is the closeness of output readings foe the same input
when there are changes in the methods of the
measurement, observer, measuring instrument,
location, condition of use and time of measurement.
 Repeatability : the repeatability of an instrument may
be defined as the closeness of output readings when the
same input is applied repetitively over a short period of
time with the same measurement conditions, same
instrument and observer, same location and same
condition of use maintained throughout.

7.  Precision : it the measure of reproducibility of the
measurements for a given fixed value of quantity.
 Accuracy : it may be defined as the ability of an
instrument or a system to respond to true value of a
measured variable under reference conditions.

8.  Dead zone : it is largest change of input quantity for
which instrument does not indicate output.
 Drift : it is the gradual variation or undesired change in
output over a period of time, during which the input
doesn’t change.

9.  Threshold : it is defined as the minimum value of an
input which is required to cause a detectable change
from zero output.
 Resolution : the threshold defines the smallest
measurable input .
 Linearity : it is the ability of an instrument to
reproduce the input characteristics symmetrically.
 Loading effect : the incapability of a system to
faithfully measure, record and control the input signal
in undistorted form is called as loading effect.

10.  Dynamic response : the behavior of the system when
inputs vary with time and so does the output is called
dynamic response.
 Speed of response : it is the rapidity or fastness with
which an instrument responds to ant changes in the
input.
 Measuring lag : it is the retardation or delay in the
response of measurement system to change in
measured quantity.

12.  Dynamic error : it is the difference between the true of
the quantity changing with time and the value indicated
by the measurement system if no static error is
assumed.
 Fidelity : it is defined as the degree to which a
measurement system indicates changes in the measured
quantity without any dynamic errors.
 Overshoot : It is defined as the maximum amount by
which the pointer moves beyond the steady state.

13.  Dead zone : it is the largest change of measurand to
which the system doesn’t respond.
 Dead time : it is the time requires for the instrument to
begin to respond to a change in the measured quantity.