Suppose the measured value of a quantity is x and its true value is a, then x-a=ε.
The error is expressed in the same units as the measured value x and ε is therefore referred to as the absolute error (the absolute value of the difference between the measured value and the true value).
The upper bound on the absolute value of the solution is then called the absolute error limit for the approximation ε(x*), which is simply the error limit for the cycle times.
Mathematical definition: the measurement does not consider the size of a certain quantity, but only considers the size of the error itself between the approximate value of the quantity and its accurate value. The absolute error has a plus or minus and a direction.
Calculation formula of absolute error: value of indication - standard value (the difference between the measured value and the real value)
For example, the analytical balance is used to weigh two objects with masses of 1.5268g and 0.1526g respectively. Assuming that the true values of the two objects are 1.5267g and 0.1525g respectively, the absolute error of weighing them is:
E1 = 1.5268-1.5267 = +0.0001g
E2 = 0.1526-0.1525= +0.0001g