HP 400D Operating And Servicing Manual page 14

11
Sect. Page 4
EXAMPLES:
Range Meter
Switch Scale
VOLTAGE MEASUREME NT
300 3
10 1
. 003 3
. 001 1
MEASUREMENT
DB
+40 db db
+40 db
db
+10 db db
-30 db db
-30 db db
-50 db db
•
-60 db db
NOTE: In case where a meter scale reading
•
below - 8 db is obtained, it is best
to switch to the next lower range on the instru-
ment so a reading will be obtained
portion of the scale where
may be obtained.
The same situation exists for voltage measurements.
When a reading is obtained in the lower 1/3 scale, the
range switch should be switched to the next lower
range to obtain a reading in the upper 2/3 scale.
c. Amplifier -
The instrument may be used to amplify small
With full-scale meter deflection, the
signals.
Actual
Meter
Indicates Level
1. 8 180
0.44 4.4
2. 3 . 0023
. 27 . 00027
+2 db +42 db
-7 db +33 db
-6 db + 4 db
o
db -30 db
-8 db -38 db
-9 db -59 db
+1 db -59 db
in
the upper
highest accuracy
amplifier open-circuit output is approximately
. 15 volt rms on all ranges. The response of the
amplifier is flat across the band from 1 0 cycles to
4 mc. The impedance, looking into the OUTPUT
terminals, is approximately 50 ohms over the entire
frequency range. To obtain maximum gain, proceed
as follows:
1) Turn the toggle switch to ON, and allow a warm­
of
up period approximately five minutes .
2) Set the VOLTS (range) switch at the . 001-
DB
volt position.
3) Connect to the OUTPUT binding posts the equip­
ment which is to receive the amplified signal. When
of
the impedance the load across the amplifier output
is approximately 50 ohms, the output voltage will
be approximately half the open-circuit voltage, or
approximately . 075 volt.
4) Connect the voltage to be amplified to the
binding posts. Up to . 002 volt may be applied to
the amplifier with the range switch at the . 001-
volt position.
NOTE
A mplification also may be obtained on the . 003,
. 01 , . 03, and . 1 volt ranges, but maximum gain
is available only on the .001 volt range because
of the 10 db loss per step inserted by the
switch as' the switch is tUl'ned in a clockwise
direction.
INPUT
DB VOLTS