Agilent Technologies e4418b Uncertainty Equation, Voltage Measurements Uncertainty, 1 j = ∑i +

Measurement Uncertainty Analysis – Power Reference Level Test

Measurement Introduction

	:
	MsUncertainty = 1 ⁄( 1±2PsPd)
	The equation above includes the worst-case mismatch magnitude 2PsPd and is in the
	form where various powers can be multiplied by the equation to find worst-case
	power levels with respect to mismatch.
Note	From the above mismatch uncertainty equation if Pd is zero, for example, the
	8478B sensor is exactly 50 ohms then there is NO mismatch uncertainty.
	This has not yet been achieved but efforts will be made in the future to try to
	achieve as near as possible to a ‘zero’ level of mismatch uncertainty and
	hence have negligible mismatch when calibrating products.

Uncertainty Equation

General form of uncertainty equation is:

N

N

N

u

2

(y ) =

c

2

iu

2

(x

) +



c

c

u(x

,x



2

)

∑

i



i

j

i

j



i

i

∑

= 1

=

1 j =∑i + 1

Hence,

u2(1mW)

CV0 ⋅ u(V0)

2

CV1 ⋅ u( V1)

2

CVcomp ⋅ u(Vcomp)

2

CR ⋅ u(R)

2

CCF ⋅ u(=CF)

2

CMs ⋅ u(Ms)

2

+++CRep ⋅ u(Rep) 2 CDrift ⋅ u(Drift)

2

Assuming that there is no correlation exists between the 8 input variables.

Voltage Measurements Uncertainty

Since the manufacturer’s data is used to determine the standard uncertainty, the

analysis used is the Type A method.

The 3458A DMM Uncertainty is calculated with reference to the Appendix ‘A’ of the

3458A Operating Manual.

+

B-4

+++Agilent E4416A/E4417A Service Guide