MANUAL CHANGES
ERRATA:
MODEL 400D
/
H
/
L
VACUUM
TUBE VOLTMETER
Sect.
11
Page 4-Subparagraph
"C"9
Amplifier:
Delete all of the information to the end of the section.
Replace with the following:
C.
AMPLIFIER
With full scale meter deflection, the amplifier open circuit
output is approximately
Ou15
volts rms on any range.
The
Model 400D
/
H
/
L thus is useful as an amplifier with input
signals less than approximately
0.1
volt.
Maximum gain will
be obtained with the RANGE switch on the
0.001
volt position.
Be careful not to overdrive the amplifier.
You should select
a range which gives
a
meter deflection near full scale.
Sig
nals more than about
2
times full scale will cause severe dis
tortion.
The impedance looking into the
O
UTPUT terminals is
approximately
50
ohms.
The frequency response and voltage calibration of the instru
ment may be affected by any external load impedance applied
to the output terminals.
The effect will be greater near the
edges of the nominal band pass of the amplifier.
You can quickly check the effect of the applied load:
Observe the meter reading obtained with the output terminals
open circuited and then note any shift of reading when the
external circuit is connected to the OUTPUT terminals.
If
this shift is negligible, the measurement is not being af
fected appreciably by the load.
When the nature of the in
put signal is changed; ioe., a different frequency or band
of frequencies is applied, repeat the quick check described
above
0
ADDENDUM:
For instruments with Serials Prefixed:
the manual for
Model 400D, Serial
and above; Model
400H,
Serial
6526
and above; Model 400L, Serial
6516
and above applies with all
corrections listed aboveo
12/15/59
1/6/60
