Agilent Technologies e4419b, e4418b manual Mismatch, Voltage measurement Uncertainty

Measurement Uncertainty Analysis – Power Reference Level Test

Measurement Introduction

A normal distribution is assumed, as the 3458A Manual has not specified the type of distribution used on the measurement.

Both V0 and V1 values are calculated by subtracting Vref from Vcomp as measured at the output of the 432A using a 3458A DMM. The approximate values of Vcomp and Vref for no power (V0) and for 1mW power (V1) are 5V with the DMM on the 10V scale.

For the 3458A DMM, the specified accuracy for the 10 volt scale is:

8ppm of Reading + 0.5ppm of Range

with;

0.15ppm of Reading + 0.01ppm of Range per °C (temp coefficient Tcal ±5 °C)

±8.75 ppm of Reading + 0.55ppm of Range Therefore,

U(Vcomp) = U(Vref) = ±	8.75 ⋅ 5	+	0.55 ⋅ 10
	1000000----------------------		------------1000000-----------

=±49.25uV

For V0 and V1, two measurements are taken, so the uncertainty is equated to the RSS of using two DMMs;

Voltage measurement	Uncertainty
U(Vcomp)	49.25 ∝V
U(V0)	69.65 ∝V
U(V1)	69.65 ∝V

Mismatch

The Mismatch uncertainty was previously determined as being:

MsUncertainty(magnitude) = 2PsPd

Note	This is the worst-case uncertainty for mismatch and occurs when the
	incident and reflected waves are 180 degrees out of phase.

Agilent E4416A/E4417A Service Guide B-5