HP 3478A Technical Manual page 110

3478A 3478A
generator which is syncronized by the ALE clock (from generator which is syncronized by the ALE clock (from
the A/D Controller). the A/D Controller). The hybrid The hybrid receives all it
information from ports P10 through P14 of the A/D information from ports P10 through P14 of the A/D
Controller (U462 pin Controller (U462 pins 27 s 27 to 31
transferred over the A, B, C, D, and E lines (U403 pins 5 transferred over the A, B, C, D, and E lines (U403 pins 5
through 9) of the hybrid. through 9) of the hybrid.
2.The S-4, S 2.The S-4, S + 4, S-3, S +2, S-l, S + , S-0, and S + 4, S-3, S +2, S-l, S + , S-0, and S
+0 currents are developed using resistors RA2 through +0 currents are developed using resistors RA2 through
RAIO in conjunction with the slope switches. RAIO in conjunction with the slope switches.
3.The A/D comparator is also inside the A/D 3.The A/D comparator is also inside the A/D
Hybrid and its input is connected to the output of the A/D Hybrid and its input is connected to the output of the A/D
Integrator. Integrator. The comparato The comparator upda
each clock pulse. each clo ck pulse. Since t Since the
connected to a latch, the out- put is transferred to a TTL connected to a latch, the out- put is transferred to a TTL
driver during each driver du ring each clock pulse. clock pulse.
buffer which connects the output of the latch to the A/D buffer which connects the output of the latch to the A/D
Con- t Con- troller. roller. 4. 4. Dependent Dependent on t
hybrid connects the DC/Ohms Input Amplifier's output or hybrid connects the DC/Ohms Input Amplifier's output or
the AC to DC Converter's output to the A/D Integrator's the AC to DC Converter's output to the A/D Integrator's
(U401) input resistor (RAI in (U401) input re sistor (RAI in U403).
input switches inside the hybrid. input switches inside the hybrid.
b. b. A/D Integrator A/D Integrator (U401 (U401 and associate
The A/D Integrator consists of an amplifier (U401) with The A/D Integrator consists of an amplifier (U401) with
capacitor feedback capacitor feedback (C410). (C410).
inverting, the output slopes of the integrator will be inverting, the output slopes of the integrator will be
positive for negative input currents (and vice versa). positive for negative input currents (and
c. c. A/D A/D Controller Controller (U462) (U462). . The A/
the operat the operation of t ion of the A/D he A/D Converter.
control of the runup and rundown operation, and control of the runup and rundown operation, and
selecting the correct currents (S-4, S + 4, etc.). selecting the correct current
receives all its control s control
to 31). ). The information is is The information
r updates its tes its output output during
he comparator's comparator's output output is is
The TTL driver is a The TTL driver
on the funct he function selecte ion selected, the
U403). This is done by the This is done by the
and associated circuitry d circuitry). ).
Since Since the the amplifier amplifier is is
vice versa).
The A/D D Controller Controller controls controls
Converter. This includes the This includes the
s (S-4, S + 4, etc.). Refer to Refer to
paragraph 7-F-77 for more information on the A/D paragraph 7-F-77 for more information on the A/D
Controller. Controller.
d. d. Voltage Reference Voltage
provides three stable reference voltages: -10 OV, + 10V, provides three stable reference voltages: -10 OV, + 10V,
and a buffered -IOV. and a buffered -IOV. The circuitry
17, is explained as follows: 17, is explained as follows:
1. 1. The -O1V reference voltage is used by The -O1V reference voltage is used by the A/D Hybrid
(U403) to develop stable and ac- curate S-4, S + 4, S-3, (U403) to develop stable and ac- curate S-4, S + 4, S-3,
etc. currents. etc. currents. The
non-inverting amplifier (U405) using feedback resistors non-inverting amplifier (U405) using feedback resistors
in U403 and a 7V reference diode (zener diode U461). in U403 and a 7V reference diode (zener diode U461).
during
The 7V reference diode is connected to the amplifier's The 7V reference diode is connected to the amplifier's
positive terminal and determines the stabilty of the positive terminal and determines the stabilty of the
reference voltage. The diode voltage is reference voltage.
is a
the case of the diode has internal heaters to keep the the case of the diode has internal heaters to keep the
diode temperature diode temperature as
d, the
feedback resistors for U405 are in U403 for good feedback resistors for U405 are in U403 for good
stability. stability.
2. 2. The buffered -IOV The buffered -IOV is used by
stable -10V stable -10V power supply
X1 gain non-inverting amplifier U404 and the -10V X1 gain non-inverting amplifier U404 and the -10V
reference voltage. reference voltage.
3. 3. The + 10V reference volt The + 10V
Hybrid (in conjunction with the -10V reference) to Hybrid (in conjunction with the -10V reference) to
develop develop the
reference voltage is also used by the Ohms Current reference voltage is also used by the Ohms Current
Source to develop a stable ohms current (see paragraph Source to develop a stable ohms current (see paragraph
7-F-21). 7-F-21).
inverting amplifier U402 and feedback resistors in U403. inverting amplifier U402 and feedback resistors in U403.
7-F-50. 3478A 7-F-50. 3478A Logic
7-F-51. General. 7-F-51. General.
divided into two circuit areas: Chassis Common Cir- divided into two circuit areas: Chassis Common Cir-
7-F-15 7-F-15
Reference. . The The Voltage
The circuitry, shown
The reference reference voltage
The diode voltage is very stable since
as constant constant as
is used by the A/D Hy
power supply. . The voltage is develope The voltage is developed by
reference voltage is u age is used by
the S-4, S S-4, S + 4, + 4, S-3, et S-3, etc. c. currents.
The reference The reference voltage voltage is is developed
Logic Circuitry Circuitry
The 3478A Logic Circuitry can be The 3478A Logic Circuitry can be
TM 11-6625-3071-14 TM 11-6625-3071-14
Voltage Reference Reference
, shown in Figure 7-F- in Figure 7-F-
the A/D Hybrid
voltage is is developed developed by by
very stable since
as possible. possible. The The
the A/D Hybrid as a brid as a
d by
sed by the A/D the A/D
currents. The + The + 10V 10V
developed using using