TB 9-6625-2020-24
20. Ac Decibels
a. Performance Check
(1) Position dBm/dBV jumper (fig. 2) in dBm position.
(2) Press TI VOLTS AC TRUE RMS, dB, and 200 V pushbuttons.
and LOW.
(3) Connect calibrator OUTPUT HI and LO to TI VOLTS/
(4) Set calibrator for a 77.46 V, 100 Hz output. If TI does not indicate between
+39.5 and +40.5, perform b below.
(5) Set calibrator for a 77.46 mV, 100 Hz output.
(6) Press TI 200 mV pushbutton. If TI does not indicate between -19.5 and -20.5,
perform b below.
(7) Set calibrator for a 0.7746 mV, 100 Hz output. If TI does not indicate between -
59.5 and -60.5, perform b below.
(8) Position dBm/dBV jumper (fig. 2) in dBV position.
(9) Press TI MAX dB pushbuttons and set calibrator output for settings listed in
table 12. TI will indicate within limits specified.
Table 12. dBV
Test instrument
Calibrator output settings
Test instrument
MAX dB
indications
pushbuttons
Voltage
Min
Max
-10
1 mV
20 Hz
-59.5
-60.5
-10
1 mV
2 kHz
-59.5
-60.5
-10
1 mV
10 kHz
-58.5
-61.5
-10
100 mV
10 kHz
-19.5
-20.5
+10
1V
20 Hz
-0.5
+0.5
+30
10 V
10 kHz
+19.5
+20.5
+50
100 V
10 kHz
+39.5
+40.5
b. Adjustments
(1) Press TI 200 V pushbutton.
(2) Connect multimeter INPUT HI to TP1108 (fig. 2) and LO to TI LOW.
(3) Set calibrator for a 77.46 V, 100 Hz output. Adjust R1201 (fig. 2) until
multimeter indicates 00.0 mV dc.
(4) Disconnect multimeter from TI.
(5) Adjust R1518 (fig. 2) until TI indicates +40.0 (R).
(6) Set calibrator for a 77.46 mV, 100 Hz output.
(7) Press TI 200 mV pushbutton. Adjust R1521 (fig. 2) until TI indicates -20.0 (R).
(8) Set calibrator for a 0.7746 mV, 100 Hz output. Adjust R1102 (fig. 2) until TI
indicates -60.0 (R).
(9) Press TI 2 V pushbutton.