Characteristics of the instrument

1)static characteristics:

Accuracy: is how close is the measurementto 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 algebric difference between largest and smalleat reading of the range.

suppose thermometer operate between 0-100 Degree cl.then range=100-0=100°C

Stability : Output is constant when theinput 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 overallsensitivity 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 ameasurement system responds to changes in themeasured quantity.

Measuring lag:It is the retardation or delay in the response of ameasurement system to changes in themeasured 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.

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