The'" N Counter - HP 3320A Operating And Service Manual

Model 3320A/B
Section IV
Q3 (RESPONSE
CONTROL)
+v
r--+--~~---/_---,
cIc
OUTPUT TO
COMPARATOR
IC2
t---T----i~~PO"'R
.4.
IC I
SIGNAL
'/1J)1
r - 1® ®
I ,
,
,
- - ' \ " 'EE'BACK :
T H E R M O P I L E - - - - - - : . . •
THE THERMOPILE IS A SOUARE-LOW
DEVICE THAT CONSISTS OF SEVERAL
ntlN FILM THERMOCOJPLES IN SERIES.
THE TWO HALVES OF THE THERMOPILE
HAVE CLOSELY MATCHED CHARACTERISTICS.
(I VOLT AT POINTeD PRODUCES ABOUT 70rrH
Of de AT POINT
®
I
Figure 4-17. AC/DC Converter In The Amplitude Section.
031RESPONSE CONTROL)
ONt>+OHt I
de OUTPUT
- r - -
TO MODULATOR
T
'09(RESPON$E
t
¢.
CONTROLl
QB
IIREsflONSE
CONTROL)
r----j+
COW'ARATOR
o
IOtRESFONSE CONTROL)
>.,...--t--i.-~--_/
'<5
aClde
CONVERTER
i--(2
I
I
I
t +5V
,
L_
FROM
<lIITPUT
AMPLIFIER
FROM _
t.lOOULATQR OFF
OVERLOAD
SIGNAL
(gz~~OLS T--i.-_
ATTENJATOR)
-1!lV
deREfERENCE R53
FROM A M P L I T U O E · - - - - - - - ' M . - - - - - - - '
SECTION
Figure 4-18. AC/DC Converter With Overload Circuits.
the response to be remotely programmed to FAST. FAST
response requires these four switches to
be
open.
4-70.
The.,.
N
Counter.
4-71. Refer to Figure 4-10 for the block diagram of the
VTO Phase Lock Loop containing the .,. N Counter. The
purpose of the VTO Phase Lock Loop is to provide an
output frequency to the amplitude section. The range of
the output frequency from the VTO depends on the
position of the vernier control switch:
voltage at
TP2
exceeds about +2.5 volts, IC5 sets the
Monostable Flip-Flop. This causes K2 to close shorting the
converter input to ground and the output attenuator to
provide at least 40 dB of attenuation. While the Monostable
Flip-Flop is set, the voltage at TP2 approaches 0 volts. At
the end of 5 seconds, the Monostable returns to its normal
state. If the overload condition still exists, the Monostable
is set again. The resistor and diode between the output of
QI J and the de reference pulls the dc reference line
negative during overload. This reduces the 20 MHz signal
out of the Modulator.
4-{j9. The response is set to SLOW for the standard 3320B.
TItis requires the four response control switches shown in
Figure 4-18 to be closed. Options 003. 004 and 007 allow
Vernier
In
Out
VTO Output
20 to 32.9999 MHz
20 to 32.99 MHz
4-11