This topic describes dB/dBm Scaling for the 34465A/70A. Scaling features are different for the 34460A/61A and are described in the dB dBm Scaling Menus topic.
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This topic describes dB/dBm Scaling for the 34465A/70A. Scaling features are different for the 34460A/61A and are described in the dB dBm Scaling Menus topic. |
Press the Scaling softkey to open the default dB scaling menu:
Press the Function softkey to select a scaling function:
Scaling is set to OFF when you change measurement functions (for example, changing from DCV to ACV). You must re-enable scaling after changing measurement functions.
Each dB measurement is the difference between the input signal and a stored reference value, with both values converted to dBm:
dB = reading in dBm – reference value in dBm
The relative value must be from -200 to +200 dBm (default 0). You can either measure this value by pressing Measure Ref Value, or you can use the dB Ref Value softkey to specify a value.
dB scaling applies to ACV and DCV measurements only.
The dBm function is logarithmic, comparing power delivered to a reference resistance, relative to 1 milliwatt:
dBm = 10 x log10 ( reading2 / reference resistance / 1 mW )
The reference resistance value (Ref R) may be 50, 75, 93, 110, 124, 125, 135, 150, 250, 300, 500, 600 (default), 800, 900, 1000, 1200, or 8000 Ω. Press Ref R and use the front panel up and down arrows to make your selection.
dBm scaling applies to ACV and DCV measurements only.
% performs a percent change operation. The result is the percent change of the measurement from the reference value:
Result = ((Measurement – Reference) / Reference) * 100.
Press Measure Reference to use the first measurement as the reference value, or press Ref Value to specify the reference value.
% scaling applies to all measurement functions except Ratio, Continuity, and Diode.
For Mx-B scaling, the result is the measurement multiplied by the Gain (M) value minus the Offset (B) value.
The User Units softkey allows you to specify the custom alphanumeric label of up to four characters (for example, RPM or °C) for Mx-B scaled measurements.
Mx-B scaling applies to all measurement functions except Ratio, Continuity, and Diode.