HP 400D Operating And Servicing Manual page 7

Sect.
I
Page
1
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I.I
GENERAL
DESCRIPTION
Throughout
this
manual, where reference
is
made
to the 400D
the information applies equally to
the
400H.
The
major differences
between
the
two
in-
struments are tolerance refinements
and
a more
accurate meter movement in the Model
400H.
The
Model
400D Vacuum Tube
Voltmeter is
an
accu-
rate ard
sensitive average-req)onding
rms calibrated
voltmeter
which
will
measure
a-c
voltages
from
0.001
volt
full
scale
to
300
volts
full
scale
over
a frequency
range
of
10 cycles
to
4
megacycles. It has
an input
impedance
of
10
megohms, effectively preventing
disturbance
to circuits
under
test.
The
distinctive
features of this voltmeter
make
it
valuable
for
mea-
suring.gain, network response,
and ou@ut
level
witl
speed
and
accuracy.
The
wide frequency range makes
it
suitable
for
audio,
r-f,
and
video measurements.
The
sensitivity
of
t}re
voltmeter
is sufficient in
many
instances
to
measure hum
and noise
level directly.
The
400D
voltmeter also may
be used as an audio
level (VU) meterl
as a
high-gain
broadband
ampli-
fier
to give increased sensitivity to
oscilloscopes,
bridges,
and
other
equipment
requiring additional
o
Table
1-1.
Ranges
Switch
Designator
Voltage
Range
Decibel.
Range
-60
.0001
-50
.003
-40
.01
-30
.03
-20
.1
-10
.3
10
3
+10
10
+20
30
+30
100
+40
300
+50
0
to
0.001
0
to
0.003
o
to 0.01
0
to
0.03
0to0.1
0to0.3
0to1
0to3
0to10
0to30
0
to
100
0
to
300
-72
to
-58
-62
to
-48
-52
to
-38
-42
to
-28
-32
to
-18
-22to
- I
-l2to+
2
-
2to+12
+
8to+22
+18
to
+32
+28
to
+42
+38
to
+52
GEl{TRAT DTSCRIPTIO]{
sensitivity;
and
to detect
nulls.
In
conjunction
with
an
oscilloscope, the
voltmeter
may be used
to monitor
waveforms,
and
in conjunction with
an oscillator,
may
be used
to
measure wide ranges
of
L
and
C as
well
as moderate ranges
of R and
Z.
The 400D
also
may be used
as an indicating device to measure
coil
Q.
T.2
DAMAGE IN
TRANSIT
If
upon
initial
inspection
this instrument is
found
to
be
damaged
in
any
way, refer to CLAIM
FOR
DAMAGE
IN
SHIPMENT
for
the
necessaly instruc-
tions.
(See
last page in instruction
manual.
)
I.3
POWER LINE
YOTTAGE
When
the instrument leaves the factory normally
it
is
wired
for
115-volt operation.
ff it is
desired
to
operate
the
instrument from
a
230-volt
source, refer
to the
transformer conversion
data
on
the schematic
diagram
for
the
correct procedure.
As
shown on
the schematic diagram, the alteration
changes
the
primary
windings of the transformer
from
a
parallel (for 115-volt
input)
to
a
series (for
230-volt input) arrangement.
I.4
POWER
CABTE
The
three conductor power cable supplied with this
instrument
is
terminated
in
a
polarized three-prong
male connector recommended by the National elec-
trical
Manufacturersr
Association.
The
third
con-
tact is
an
offset
round
pin,
added
to
a
standard two-
blade connector,
which grounds the
instrument chas-
sis
when used
with the appropriate receptacle. To
use
this
NEMA connector
in a standard two-contact
re-
ceptacle,
a three-prong
adapter should be
used.
The ground connection emerges
from
the adapter
as a short lead which
should be
connected
to
a
grounded receptacle
box
for
the
protection of oper-
ating personnel.