Table 4-9 Analog/Digital/Bluetooth Analyzer > Functions > Thd+N Ratio Menu - Keysight U8903B User Manual

4 Audio Analyzer Measurement Functions
Table 4-9 Analog/Digital/Bluetooth Analyzer > Functions > THD+N Ratio menu description
Menu Description
Press the Unit softkey to select the measurement unit.
– dB
Unit – ΔdB
– %
– x
Press the Format softkey to select the format of the returned measurement reading.
– Off
Selecting Off will return the measurement reading without any formatting (raw value).
– Linear
Format
Selecting Linear will return the measurement result by dividing the measured ratio by the reference ratio. The result is
returned in unit x.
– Delta
Selecting Delta will return the measurement result by deducting the reference ratio from the measured ratio. The result
will be returned in unit ΔdB.
This is only available for analog analyzer.
Set to 0dB
Press the Set to 0dB softkey to store the measured ratio as the reference ratio, and set the measurement reading format to
Delta.
Set resul t as ref. from Press the Set resul t as ref. from softkey to store the measurement result from the selected channel as the reference ratio.
Ref. Ratio Press the Ref. Ratio softkey to set the reference ratio value.
This is only available for digital analyzer.
Precision
Press the Precision softkey to enable or disable the precision mode.
Press the Freq Lock softkey to select the searching method for the fundamental frequency.
– Auto
Selecting Auto will allow the U8903B to search for the fundamental frequency automatically.
– Gen Lock
Selecting Gen Lock will allow the U8903B to search for the fundamental frequency based on the generator frequency
Freq Lock
value of the respective generator channel. You can select the generator channel by setting the Src Channel in the Meas.
Config. menu page. This Gen Lock method is only useful if you use the internal audio generator.
– Custom
If you have a known input signal, you can define the fundamental frequency value by setting the searching method to
Custom and setting the frequency value in Fund Freq.
Press the Fund Freq softkey to set the fundamental frequency value. This setting is only available when Freq Lock is set to
Fund Freq
Custom.
This is only available for analog analyzer.
Analog Notch Press the Analog Notch softkey to enable or disable the analog notch filter. This filter is used to emulate the analog notch
filter used in HP8903B.
THD+N level is defined as the square root of the sum of the squares of all the signal
harmonics components and noise amplitude, and it is expressed in Vrms. The THD+N level
can be computed as follows.
THD+N Level
196
= rms value of noise and distortion
Keysight U8903B User's Guide