380
P. Liu
where
∂ f
∂ x i
is the error transfer coefficient and x i is the error of the direct
measured value. If the direct error satisfies the normal distribution, the
standard deviation of the indirect error is:
σ y =
∂ f
∂ x 1
2
σ 2
x 1
+
∂ f
∂ x 2
2
σ 2
x 2
+
∂ f
∂ x 3
2
σ 2
x 3
+ · · · +
∂ f
∂ x n
2
σ 2
x n