HP 415E User Manual

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Model 415Е
4-22. This high input impedance effectively nearly
doubles the output voltage ої а source compared with an
amplifier which matches the source resistance. It
should be emphasized thatthe transformer turnsratio
in the 415E is chosen for lowest noise figure rather
than to match impedances.
4-23. INPUT BIASING.
4-24. When the 415E input switch is set to one of the
biased positions XTAL IMPED/BIASED, or 4.5 MA
or 8.7 MA), a bias source is connected in series with
INPUT connector. Ап emitter follower, А101, in
this bias circuit provides bolometer protection by
limiting transients when abolometer or crystal detec-
tor is connected or disconnected. Three calibrated
levels of bias are available: 1 volt into 1000 ohms
(XTAL IMPED/BIASED), or 4.5 ma and 8.7 ma into
200 ohms, selected with the INPUT switch, А181.
These bias levels are set within a specification, +3%, by
adjusting the DC voltage potential of the positive power
supply with resistor A3R54. A single adjustment suf-
fices since 1% resistors accurately determine the
ratios between the 3 bias levels. The positive DC
voltage is typically 13.2 volts DC but may be as low
as +12 volts DC or as high as +14 volts DC for proper
adjustment.
02152-4
Section IV
Paragraphs 4-22 to 4-27
4-25. POWER SUPPLY.
4-26. The regulated power supplies are fed by either
an internal battery, BT1 (Option 01 instruments only),
or aconventional AC supply consisting of transformer
T2 and rectifier diodes AS3CR4and A3CR5. The power
supply must provide two regulated outputs: +13 volts
and -1.71 milliamperes offset current. Тһе voltage
reference diode ASCR10 (temperature compensated by
diodes A3CR7 and A3CR8) and transistor A3Q17 form
a constant currentsource toprovide the offset current.
The voltage reference diode АЗСВІО and transistor
АЗО16 forma shunt-type regulator maintaining a nomi-
nal -7.5 volts.
4-27.
In
the
LINE/ON
position,
about
3
ma
"trickle
charge"
is
supplied
through
A3R52
to
the
battery
BT1
(Option
01
only).
If
the
POWER
switch
is
set
to
BAT-
TERY/ON
position,
battery
current
passes
through
diode
АЗСН6
to
the
regulators.
The
BATTERY/
CHARGE
position
allows
recharging
of
the
battery
by
placing
A3R52
and
A4R2
in
parallel.
About
20
ma
to
30
ma
then
flows
to
the
battery
depending
upon
the
charge
condition
of
the
battery.
4-3/4-4

HP 415E Specifications

General

Brand	HP
Model	415E
Category	Measuring Instruments
Language	English