How To Measure Power - Keysight Technologies N774 C Series User Manual

4 User Interface Reference

How to Measure Power

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Big Num
If you are only interested in the measured numbers and not in the
graphical view, you may exit the graph by clicking on the Big Num option.
This option hides the graph and only the big sized measured numbers are
displayed on the Control Instrument page.
The Power Value
For each port, the optical power is measured and returned or displayed.
The power reading represents the average optical power over the selected
averaging time. The power meter can continuously self-trigger new
measurements or be configured to wait for external software or hardware
triggers.
How to Set the Power Unit
The Power Unit setting allows you to select either W, dBm or dB as the
units in which power is displayed or returned. For returning large amounts
of logged data, the fastest data transfer is achieved using W units.
What are the Power Units?
The SI unit for power measurement is Watt (W).
You can also measure power in dB or dBm. Values returned in these units
are derived from measurement in Watts.
By selecting dBm, the following calculation is made:
Where,
P is the power value returned in dBm, and
dBm
P is the input signal level in Watts.
input
Power, in units of dBm, is measured relative to 1 mW. It is an absolute
power measurement.
Power, in units of dB, is measured relative to a particular reference power
value.
The following calculation is made:
Keysight N774xC Series Multiport Power Meter User's Guide