Performace Terms Flashcards
What is a static characteristic
A term used to specify the performance of an instrumentation system when steady-state conditions occur
What is Accuracy
The extent to which the value indicated by a measurement system or element is wrong
How is accuracy expressed
As a percentage of the full-scale deflection (f.s.d.) e.g +/-1% 0f 10A = +/-0.1A
What is error
The difference between the result of the measured and true value of the quantity being measured e.g measured value - true vale
What is hysteresis error
The difference in outputs given by the same measurement according to weather the value is reached by a continuously increasing or decreasing change
What is non-linearity error
The error that occurs as a result of assuming a linear relationship between inputs and outputs when there isn’t one
What is insertion error
The error caused by the measurement device affecting the variable being measured by the process of measuring
What is Range
The limits to which the input can vary
What is dead band/ dead space
Is used if there’s a range of input values for which there is no output
What is precision
Is the degree of freedom of a measurement system from random errors
What is reliability
Is the ability of a measurement system to give the same value for repeated measurements of the same value of a variable
What is reproducibility
The ability of a system to give the same output for a constant input when the system is disconnected from its input and then reinstalled
What is sensitivity
How much the instrument output changes when the quantity being measured changes by a given amount e.g. output/ input
What is stability
The ability to give the same output when used to measure a constant input over a period of time
What is drift
The change in output that occurs over a period of time
What is dynamic characteristic
The behaviour between the time that the input value changes and the time that the measured value settles down to the steady state value
What is response time
The difference in time of the change of an input against the measured value by a system/ element as a percentage of the actual value e.g 95% of the input
What is rise time
The time taken for the output to rise to some specific percentage of the steady state output
What is Settling time
The time taken for the output to settle to within some percentage of the steady state value e.g. +/-2% of the steady state value
