Philips pm2521 - 6.4.1.3. Decibel measurements (dBV~); dB MEASUREMENTS (STANDARD METHOD); dB MEASUREMENTS IN RELATIVE REFERENCE MODE (ZERO SET)

37
6.4.1.3. Decibel measurements (dBV~)
GENERAL
The dB function offers the possibility to measure the ratio between ac voltages, and to express this in decibels
(dB). Decibel measurements can be made in two ways viz.:
— dB measurements (Standard method),
— dB measurements in relative reference mode.
The r r elative reference mode enables selection of a predetermined relative reference zero level. Each subsequent
reading will indicate the positive or negative deviation from the relevant reference value.
Example:
5
ST 3014
Fig. 14. dB measurements
FUNCTION
AMPLIFIER
IN
OUT
V~
100.00 mV
10.000 V
dB
-17.7 dB
+22.2 dB
dB ZERO SET
00.0 dB +39.9 dB
ATTENUATOR
IN OUT
10.000 V
+22.2 dB
00.0 dB
100.00 mV
-17.7 dB
-39.9 dB
dB MEASUREMENTS (STANDARD METHOD)
— Select function V~ with the function selector.
it — Select the automatic ranging mode with pushbutton AUTO/MAN*.
Remark:
Manual ranging is indicated with a * on the display. In automatic ranging mode the UP level is 20200 and the
DOWN level is 01800.
— Connect the voltage source to the 0 and V terminal and measure the voltage.
Remark:
Take care that the maximum input voltage of 600 V rms is not exceeded.
600 V rms = +57,8 dB.
— Depress pushbutton dB (V~) once.
Remark:
The measured ac voltage is now expressed in decibels (dB).
0 dB = 1 mW, 600 £20,775 V is used as reference
— To leave the dB function and to jump to the V~function again, depress pushbutton dB (V~) twice.