User Manual

ADVANCED MEASUREMENT

dBm/dB Measurement

Applicable to

(NOT applicable to ACV+DCV)

Background

Using the ACV or DCV measurement result, the

GDM-8200A series calculates the dB or dBm value based

on a reference resistance value in the following way.

dBm 10 x log10 (1000 x Vreading

/ Rref)

dB dBm – dBmref

Parameters Vreading Input Voltage, ACV or DCV

Vref Reference voltage obtained by Rref/1mW

Rref Reference impedance simulating an output

load

dBmref Reference dBm value

Measure dBm

Activate dBm

Press the Shift key followed by the

key. The 1st display shows dBm,

and the 2nd display shows the

reference impedance.

dBm result

appears

dBm Indicates dBm measurement

600Ω

2nd display indicates the reference impedance

Select

reference

impedance

To change the reference impedance,

press the Up/Down key. The new

impedance appears in the 2nd display.

The following is the impedance list.

2 4 8 16 50 75 93

110 124 125 135 150 250 300

500 600 800 900 1000 1200 8000