Tektronix 421 Instruction Manual
INSTRUCTION MANUAL
MODEL 421
LOG N PERIOD AMPLIFIER
WARRANTY
We warrant each of our products to be free
from defects in material and workmanship. Our
obligation under this warranty is to repair or
replace any instrument or part thereof (except
tubes and batteries) which, within’ a year after
shipment, proves defective upon examination.
We will pay domestic surface freight costs.
To exercise this warranty, call your local
field representative or the factory, DDD 216.
795-2666. You will be given assistance and
shipping instructions.
REPAIRS AND RECALIBRATION
Keithley Instruments maintains a complete re-
pair service and standards laboratory in Cleve-
land, and has an authorized field repair
facility in Los Angeles.
To insure prompt repair or recalibration serv-
ice, please contact your local field representative or the plant directly before returning the
instrument.
Estimates for repairs, normal recalibration?,,
and calibrations traceable to the National Bureau
of Standards are available upon request.
m)DEL 421 IOG n PERIOD AMPLIFIER
!lABLE OF CONTENTS
Section
1.
GEBERAT, DWCRIPJ!ION. ............
l-l.
l-2. Features................l- 1
1-3.
l-4. Equipment Shipped. ...........
2.
OPJSRATION.
2-l. Front Panel Controls ..........
2-2.
2-3.
2-4. Operating Procedures ..........
z-2. mmping.................2- 2
CIRCUIT DESCRIFTION. .............
3.
y-1.
;:;:
3-4.
General. ...............
Specifications
.............
..................
Rear Chassis Controls and Terminals.
Input Connection
- .
Recording.
General. ................
Log n Amplifier Circuit.
Period Circuit
Power Supply
...............
............
........
.............
..............
Page
.1-l
.1-l
1-2
1-3
2-1
2-1
.. 2-1
2-2
2-2
2-3
3-l
3-l
3-1
3-2
3-3
4.
WU'iTENANCE
4-2. Electrometer Tubes
4-6.
4-7. Calibration of Period Circuit. .....
REPLACEABLEPARTS .............
5.
5-2. How to Order Parts ...........
Change Notice
*Yellow Change Notice sheet is included only for instru-
ment modifications affecting the Instruction Manual.
Calibration of Log n Amplifier
Model 421 Replaceable Parts List
Schematic Diagrem
..................
...........
16298D
........ 5-y
.....
..5- 1
.... 5-2
4-l
k-1
4-1
4-Z
5-l
last
page
0563
vo.3
i
1-l
GENERALDF!SCRIPmOM
MODEL 4211~~)
n PERIOD AMPLIFIER
GENE@& DESCRIFTION
l-3.
SP.ECIFICAlTONS.
OC.
RANGR
ZFAO DRIFT:
RISE TIME:
imum setting):
ACCURACY:
LIKEA.R-LCS RELAlTONSHIp: Within 2s of
within
Single scale, from lo-l2 to 10m4
Less than
l/6
decade in 24 hours after a one-hour warmup.
Seconds to 9C$ of final current value (DAMPING control at min-
Current Change
Amperes
10-12
to 1o-ll
10-n to 10-5
With No Significant
External Capacitance Across Input
3 seconds
1 second
Within 0.2 decade.
5s
of full scale from lo-5 to lo- ampere.
MODEL 421 MG n PERIOD AMPLIFIER
empere; positive currents only.
With 5000 pf
6 seconds
2 seconds
11 scale from lo-l2
to 10-5 ampeve
4:
ouTpuTs:
1) Zero at lo-l2
empere, increasing as 8 negative voltage 10
volts per decade to -80 volts at 10" ampere: up to one mil-
liampere may be drawn.
2) Recorder output of 50 millivolts full scale is supplied for
servo rebalance recorders.
RAITGE: Single scale, from -30 to infinity to
3%
at
-6
ACCURACY:
RESPONSE SPEED:
FiEEOVETfY TIME:
OuTcPum:
1) Minus one volt for -30 second period; zero for Infinite per-
seconds.
3 seconds maximum to 9% of final value.
10 seconds maximum.
iod; +lO volts for 3-second period.
2) Recorder output of 50 millivolts full scale is supplied for
servo rebeLlance recorders.
+3 seconds.
FOLARIzING FOTSNTIAL:
TABLE 1 (Sheet 1). Model 421 Specifications
l-2
+225 volts for ion chambers.
0563
MODEL 421 LOG n PERIOD AMPLIFIER
CONNEC~RS: Input: Type HN (UG-560/U) receptacle.
+225 volts:
All Outputs:
TUBE CO- One EA52, one OA2, one CG3, one 12AU7, two 12AX7, one
12~~7, ITOIW 5886, one 6~~6, one 6~~4, two 6x16, one 6~4, one ~Y&JA.
TR4NSISMR COMPLEMENT:
Amphenol 80-C receptacle.
Microphone receptacles.
One 2~1183, four 2~1381, one 2N1535.
GEXERAL DESCRIPTION
POWER:
ACCESSORIES SUPPLIED:.
ACCFSSOFUES AVAILABLE:
tubes in a plug-in can (replacement spare).
DIMENSIONS:
mxr WEIGIIT: 23 pounds.
1-J+. FxqJnMENT SHIPPED. The Model 421 Log q Period Amplifier is factorycalibrated and is shipped with all components in place.
also contains the Instruction Manual and a set of six mating input and out-
put plugs.
l-5. REGISTRATION CARD.
of the Instruction Manual. Please fill it out and mail it when you receive
the instrument.
1-6.
follow the instructions given at the back of the ma~lual for reporting the
defect.
105-125 volts or alO-250 volts, 50-60 CPS, 50 watts,
set of six mating plugs.
Model 4102 Input Assembly, two 5886 electrometer
B-314 inches high x 19 inches wide x 12 inches deep.
TABLE 1 (Sheet 2).
The registration card is attached to the front cover
DAMAGE IN SHTPMENT. If *he Model 421 is damaged or faulty when received,
yodel 421 Specifications.
The shipping carton
0563
l-3
MODEL 421 MG n PERIOD AMPLIFIER
SECTION 2. OPERATION
2-1. FRONT PANEL CONTROIS.
OPEXKCTON
a. ON-OFF.
the instrument on. The pilot light is directly above the switch.
OPERATE - SE72 10-5 - SET lo-=.
b.
the log n amplifier to function as a logarithmic micro-microsmmeter. The
switch also allows the amplifier to be oalibrated at two points, 10-5 and
1oJl
log n amplifier to lo-11 ampere when the PPERATE switch is in SET lo-11
position.
log n amplifier to 10
quick dissipation of spurious charges which sometimes accumulate on the input terminal. It also allows the amplifier to recover quickly from large
overloads.
balance to read lo-12 ampere on the meter when the RECOVER switch is depressed.
circuit is normal with the period input connected to the log n amplifier
output.
log n amplifier to the period circuit. When the switch is at CHECK 00, the
period meter should readoo .
ampere.
C. SET 10-l-l.
d. SET 10-5.
e. RECOVER.
f. AMPLIFIRR RALANCE SET 10-12. This potentiometer adjusts the amplifier
OPERATE-CHiXKw.
g.
In the CHECK W position, the switch removes the signal from the
The ON-OFF control is a double-throw toggle switch which turns
In OPERATE position, the switch allows
The SET lo-11 potentiometer on the front panel adjusts the
The StT 10'5 potentiometer on the front panel adjusts the
-5
ampere when the OPERATE! switch is in SST 10-5 position.
The RECOVER switch shorts out the feedback diode and allows
With this switch in OPERATI? position, the period
h. SEToo.
OPERATE-CHECK 00 switch is at CHECKoo .
2-2.
(Amphenol 82-805).
chambers through an Amphenol %C receptacle.
amplifier meter deflection, and one milliampere can be drawn without upset-
ting the circuits, through a microphone-type receptacle (Amphenol 80 PC2F).
ect connection to servo rebalance recorders.
approximately 50 ohms.
0563
REAR CHASSIS CONTROLS ANDTERMINALS.
a. INPUT. The INPUT is a RN series receptacle, Military type US-560/U
b. +225.
C. &I V IOG N OUTPUT. Minus 80 volts are developed for full-scale log n
d. 50MVMGNOUTHJT.
This potentiometer adjusts the period meter to 00 when the
A polarizing potential of ~225 volts can be supplied to ion
Fifty millivolts are provided for convenient, dir-
The internal resistance is
2-l
Ol?ERATION
MODEL 421 MG n PERIOD AMPLIFIER
e. 10VPERIODOUTKIT.
for a +3 second period.
f. 50 MV PERIOD OUTHJT.
direct connection to servo rebalance recorders. The internal resistance is
approximately 50 ohms.
g. DAmmG.
lifier.
wise.
2-3. INHJT COI'TIWTION.
a. The current source should be connected to the INHIT with the high impedance side of the current source associated with the central conductor of
the RN type receptacle.
since spurious input signals will occur caused by capacitance changes and
generation of static charges.
b. The lead-in cable should be Polyethylene-, Polystyrene- or Teflon-
insulated coaxial cable; the plug should have Teflon insulation. For large
cables, Amphenol 82-804 plugs are recorunended; for small cables, Amphenol
82-816 plugs are recoxmnended. During the preparation of the cable and plugs,
it is essential that all high impedance surfaces be kept scrupulously clean
to avoid leakage. With graphite coated cables, it is necessary to avoid
tracking graphite onto the high impedance surfaces of the cut end of the
insulation and onto the Teflon surface of the plug.
Maximum damping is obtained by rotating the control fully clock-
The control varies the response time over a ten-to-one ratio.
The damping control slows the response of the log n amp-
Ten volts are developed by the period circuit
One milliampere can be drawn.
Fifty millivolts are provided for convenient,
Avoid movements of the cable during measurements,
,
2-4. OWm moc!EmTREs.
a. Turn on the power switch, After a &minute warmup, check the amplifier balance by depressing the RECOVER switch. The log n meter should
read lo-l2 ampere; if necessary, adjust the meter-pith the AIQLIFIER BALANCE
contra
to lo-
ATS switch to 10-Y position.
with the SET 10-5 control.
b. Check the period circuit by putting the OPERATE-CRFCK DC) switch in
CHECK 00 position. If the period meter does not read-, adjust the SETW
control for the correct reading.
c. Occasionally recheck the calibration of the log n amplifier andthe
period circuit. Adjust if necessary.
ments should be necessary.
2-5. DAMPING.
a. The speed of response, or the time constant of the ion chamber and the
log n amplifier, depends upon the speed of response of the circuitry of the
instrument and also upon the capacitance of the current source and its connecting cable. Because of the method of negative feedback applied to the
log n amplifier, the significance of the external input capacitance is de-
Turn the log n and set the log n meter
il
with the SET 10'
erz"""' to SET 10
Check calibration by turning the OPER-
If necessary, adjust the meter to 10-5 ampere
After warmup, only infrequent adjust-
2-2
0563
Loading...