Hantek HDM3000, User Manual, Page: 51 / 93

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DB and DBM functions can be accessed through the second soft key in the [Math]
menu.
When the first soft key in the dB/dBm menu is enabled (as shown below), you will see
one of the following menus: When the function is dB:
When the function is dBm:
The dB scaling
Each dB measurement is the difference between the input signal and the stored
reference value (both converted into dBm) : dB = reading in dBm - reference value in
dBm
The relative value must be between -200 and +200 dBm (default is 0).You can
Measure the Value by measuring Ref Value, or you can enter a specified Value.
dBm scaling
The dBm function is a logarithmic expression that compares the amount of
electricity transferred to the reference resistor, relative to 1 mW:
dBm
= 10 xlog
10
(reading
2
/ reference resistance/ 1 mW)
Reference resistance values (Ref R) can 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 up
and down arrows on the front panel to select.
Mathematical Operations - Statistics
When the instrument takes measurements, it automatically calculates statistics for
those measurements.
The statistics menu can be accessed from the front panel menu through the third soft
key in the [Math] menu.