Oscilloscope Reference Spectral math magnitude controls
Spectral math magnitude controls
Vertical units can be either linear or log. You can select from the following choices by clicking the Math
menu button. Then select the Spectral Analysis Setup command.
Mag tab
Select the d
esired scale type, Linear, dB, or dBm:
Linear. When the spectrum is linear magnitude the vertical units are the same as the source waveform.
Usually th
is is volts. However, it may also be watts or amperes.
dB. This sets the vertical scale of the magnitude spectrum to dB. Use the Reference Level Offset to set
which ver
tical position in the magnitude spectrum will be zero dB. The following equation applies:
dB = 20 log (|X| - Ref)
Where X is a complex data point in the spectrum and Ref is the Refe r ence Level Offset value.
dBm. This selects dB as described in the above equation, but also sets the Reference Level Offset to a
value that is equivalent to 1 mW of power into 50 ohms. Therefore, if the input units are volts, then the
value is set to 223.6 mV. If the input units are amperes, then the value is set to 40 mA. If the input
units
are watts, then the value is set to 1 mW.
Reference level
This sets the vertical position of the displayed spectrum.
Its value is the magnitude at the top of the display screen.
When
this control is adjusted, the spectral waveform along
with its zero reference m arker move vertically on the screen
as shown. This control does not change the spectral data.
x
xx
DSA/DPO70000D, MSO/DPO/DSA70000C, DPO7000C, and MSO/DPO5000 Series 765
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