Instrumentation terminology

instrumentation

#1

Range of an Instrument

The range of an instrument means the value of minimum measurable value to maximum measurable value.

Lower Range Value(LRV) of an Instrument

The lowest value of the measured variable, that a device is adjusted to measure. For a calibrated instrument, the lowest measurable value or the input value for a zero percent output of the value of instrument is termed as LRV.

Upper Range Value(URV) of an Instrument

The highest value of the measured value, that a device is adjusted to measure. For a calibrated instrument, the highest measurable value or the hundred percent output of the value of instrument is termed as URV.

Span of an Instrument

It is the difference between URV and LRV is known as span or sometimes range of the instrument.

                            SPAN = URV-LRV

Sensitivity of an Instrument

Sensitivity of an instrument is defined as the change in output of the instrument per unit change in parameter being measured. Instrument may have constant or variable sensitivities,they have a linear or nonlinear output.

Resolution of an Instrument

Resolution is defined as the smallest change that can be detected by the Instrument. Resolution is the fineness to which an instrument can be read.

Response of an Instrument

The time taken by an Instrument to approach its true output when subjected to a step input is referred to as its response.

Linearity of an Instrument

The ability of a measuring instrument to provides an indication having a linear relationship with a defined quantity. The instrument response graph will be straight line for a linear instrument.

Hysteresis of an Instrument

While checking the response of an instrument, the inputs are given in the ascending and ascending orders. Taking the response of the instrument there will be two different curves starting and ending at same points. This difference in response of an instrument is called hysteresis.

Accuracy of an Instrument

Accuracy is the degree of closeness of the measured value to the true value of variable being measured.

Precision of an Instrument

Precision is the repeatability of an Instrument with which repeated measurements of the same variable can be made under same conditions.