Characteristics of the instrument

Characteristics of the instrument

1)static characteristics:

Accuracy: is how close is the measurement to the true value.
  Percentage error = (( indicated value –true value ) / true value )x 100%
precision:it is a successive difference between the two reading.
An instrument can  be precise but inaccurate.
Range : The total range of values an instrument is capable of measuring. For
a standard thermometer this is 0 to100°C. so range is 0-100°C
Span:it is a algebraic difference between largest and smallest reading of the range.
suppose thermometer operate between 0-100 Degree cl.then range=100-0=100°C
Stability : Output is constant when the input is constant.
Tolerance:is the maximum error. A1000kW resistor with a tolerance of ±5% has an actual resistance between 950and 1050KW.
Sensitivity :change of a output according to input.Overall sensitivity – a measurement
system consists of a number of devices.
If the sensitivities of these devices areK1, K2, K3, etc., then the overall sensitivity is the product of theindividual sensitivities, K1xK2xK3xetc.
Resolution : If we increasing the input signal from zero there is a smallest change in input signal needed to produce a change in the output signal.
Linearity:change of a output proportional to input.
Hystresis:This refers to the situation where different readings are sometimes observed for the same inputbecause the input was Given from different directions
Repeatability: An instrument is repeatable if it produces a particular output when a certain input is applied in spite of thepassage of time.

2)Dynamic characteristics:

Speed of response:It is defined as the rapidity with which a measurement system responds to changes in the measured quantity.
Measuring lag:It is the retardation or delay in the response of a measurement system to changes in the measured quantity.
Dynamic error:It is the difference between the true value of the quantity changing with time & the value indicated by the measurement system. if no static error is assumed. It is also called measurement error.
fidelity

:it is formation of a ouput in the form of acceptable or suitable form.

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