This topic describes dB/dBm Scaling for the 34460A/61A. Scaling features are different for the 34465A/70A and are described in the Scaling topic.
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This topic describes dB/dBm Scaling for the 34460A/61A. Scaling features are different for the 34465A/70A and are described in the Scaling topic. |
The dB and dBm scaling functions, which apply to ACV and DCV measurements only, allow you to scale measurements relative to a reference value.
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.
The dB and dBm functions are accessed from the second softkey in the [Math] menu.
When the first softkey in the dB / dBm menu is enabled, as shown below, you will see one of the following menus:
When function is dB:
When function is dBm:
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 enter a specified value.
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.