Minipa ET-2907 - AC Voltage Measurements; dB (dBm or dB V) Measurements

71
5.1.1 AC Voltage Measurements
All pushbutton features are available in this function. The On Screen
Menu Selection accesses decibel (dBm or dB) measurements.
5.1.2 dB (dBm or dB V) Measurements in AC Volts Function
The AC volts function allows you to display readings as deviations in
dB (decibels) above or below an established reference level.
Set up dB measurements by using the On Screen Menu Selection
buttons when measuring AC volts. The dBm (or dB V)value appears in
the secondary display and the AC reading appears in the primary display.
Normally, dB is measured as dBm, which is a measure of decibels
relative to 1 milliwatt. The meter assumes a resistance of 600
ΩΩ
ΩΩ
Ω in
making this calculation. This resistance can be set for any value from 1
ΩΩ
ΩΩ
Ω to 1999
ΩΩ
ΩΩ
Ω by using the set-up menu selection buttons. When
measuring dB V, the reference voltage can be set for any value from
0.1000 V to 5.0000 V by using the set-up menu selection buttons.
dB = 20 x log (Vx / Vr)
- For dBm, Vr is the voltage across the reference resistance at
1 milliwatt. For example, Vr would be 0.7746V with a 600Ω
reference resistance.
- For dB V, the reference voltage is 1 V.