Aktakom AM-1108, User Manual

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Warning
 Do not apply more than DC 1000 V or AC 750 rms voltage; the meter will possible be damaged though the value
could be displayed.
 Indicator “ ” is on display for safety note when 30 V ac and/or dc voltage present at the input terminals
 The meter beeps constantly if the input voltage is more than AC 750V rms, which is over the meter’s range.
dBm Measurements in AC Volts Functions(See Figure 3-2)
The ac volts functions allow you to display readings as deviations in dB (decibels) above or below an established level.
Set up dB measurements with the following procedure:
1. Make an ac volt measurement to be used as a reference point.
2. Press to select dB. The dBm value appears in the primary display and the ac volts reading appears in the secondary
display.
3. Press again to turn dB off.
Normally, dB is measured as dBm, which is a measure of decibels relative to 1 milliwatt. The meter assumes a resistance of
600 in making this calculation. This resistance can be set for any value for50
Ω ， 75 Ω ， 93 Ω ， 100 Ω ， 150 Ω ， 300 Ω ， 600 Ω ，
800 Ω
，
1200 Ω
，
2400 Ω , using the meter’s setup capabilities (see Chapter 5.) to change the resistance.
Figure 3-2.dBm Measurements
Note
If dBm is displayed, check that the reference resistance value closely matches the
impedance of the system being measured.
dB is calculated with the following formula:
10
20 log
Vx
dBm
Vr
 

 
 
＝

For dBm, Vr is the voltage across the reference resistance at 1mW. For example, Vr would be 0.7746 V with a
600-
Ω reference resistance.
Measuring DC Voltage (See Figure 3-3)
1. Set the rotary switch to position, and “DC”, “V” will be on display.
2. Insert the black lead into “ COM ” terminal, and the red lead to into the “ Ω V ” terminal.
3. Connect the leads to the tested power.
4. Read the measuring results from the screen.