Appendix 29: Audio Measurement Ranging; Manual Ranging; Auto Ranging - Keysight U8903B User Manual

Appendix 29: Audio Measurement Ranging

In order to obtain measurements with high accuracy and resolution, selecting the
appropriate audio measurement range is crucial. The U8903B is covered by switchable
attenuation or gain from the input circuits of the audio analyzer. The two types of audio
measurement ranging are manual ranging and auto ranging.

Manual ranging

Manual ranging is used to configure the level of the input signal to the optimum range for
measurements. This allows you to set the gain of the analyzer to amplify a low input signal
or attenuate a high input signal as required.
The U8903B provides the following input voltage ranges for both unbalanced and balanced
inputs:
– 140 V
– 100 V
– 32 V
– 10 V
– 3.2 V
– 1 V
– 320 mV
For optimum range, you should select the lowest range with its upper limit exceeding the
expected maximum input signal.

Auto ranging

The auto ranging mode automatically selects an appropriate range for each measurement.
Auto ranging determines the correct range to use according to the signal level to achieve
the optimum measurement accuracy for the input signal.
Auto ranging is suitable for measuring stable signals with levels that do not vary greatly. It
is however not suitable for signals with rapid-changing pulses or spikes. As auto ranging
needs to determine which range to use for each signal level, it may not be fast enough to
accommodate signals with rapid-changing pulses or spikes. This may result in ranging
errors leading to incorrect measurements.
Therefore in this case, manual ranging provides better and faster performance for your
measurement needs.
It is recommended to know the characteristics of the input signal and its level variation
before applying the manual or auto ranging mode.
Keysight U8903B User's Guide
Appendixes A
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