Measurement Introduction - Agilent Technologies 4418B Service Manual

Measurement Uncertainty Analysis – Instrument Accuracy Test

Measurement Introduction

Measurement Introduction
In the Instrument Accuracy test the DUT measures power levels output from the test
station from –25dBm to +20dBm.
A modified 8482A sensor is used to perform this measurement; it has had its
thermocouple sensor (RF to DC converter) removed. This allows extremely accurate
DC levels to be injected into the sensor from a 3245 Universal Source. The output
from the universal source is measured at the head of the sensor by a 3458 DMM. In
effect there is now zero measurement uncertainty associated with the Universal
Source, as the 3458 DMM has assumed all the uncertainty.
In this test, DC signals are injected into the modified sensor. These are made in 5dB
steps, from –25dBm to +20dBm. A conversion from voltage to power is required to
achieve this. The measurement setup is shown in Figure A-1.
Figure A-1: Measurement Setup
Power Meter
DUT
Universal Source
B-2
T-Piece to measure DC
Drive Accurately
8482
DVM
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