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~INSTRUCTION MANUAL
MODEL 661
AC/DC GUARDED
DIFFERENTIAL VOLTMETER
Page 2
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.INSTRUCTIO,N MANUAL
MODEL 661
AC/DC GUARDED
DIFFERENTIAL VOLTMETER
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Page 3
MODEL 661 DIFFERENTIAL VOLTWZTER
GENERAL DESCRIPTION
l-1. DESCRIPTION.
a.
one
ranges are from 100 microvolts full scale to 500 volts.
are from 1 millivolt full scale to 500 volts, and from 10 cps to 80 kc.
of error includes all stability considerations,
brated or manually restandardized for a full-year.
b.
lighted decimal points; 10 to 25-millivolt recorder ou;put;
voltages; floating operation up to 500 volts dc off chassis ground; line frequency reject-
ion greater than 46 db.
lems.
l-2.
.i~
a.
voltmeter.
with -fO.Ol% limit of error and from 100 microvolts full scale
10 microvolts.
Model 661 measures from 1 millivolt full scale to 500 volts with an accuracy of 23% of
' full scale.
SECTION 1.
The Keithley Model 661 AC/DC Guarded Differential Voltmeter is four instruments in
- dc potentiometer, ac potentiometer, dc VTV?d and ac VTVM. 'As a dc instrument, its
Features for convenient use include:
Also, full guarding for dc measurements minimizes leakage prob-
OPERATING MODES.
The Model 661 can be used as a dc potentiometer or as a dc conventional vacuum tube
As a pot&ntiometer,
Input resistance is infinite at null over all ranges.
Input resistance is 50 megohms from 0.5 to 500 volts.
it measures from 100 millivolts full scale to 500 volts
GEXERAL DESCRIPTION
.
As an ac instruments, its ranges
Since the limit
the unit need not be periodically cali-
i
five in-line readout dials with automatically
input polarity switch for dc
to
100 millivolts within
As a VTW?, the
The Model 661 can be used as an ac potentiometer or as a conventional average read-
b.
ing vacuum tube voltmeter.
to 500 volts over 50 cps to 10 kc with a limit of error of *(0.05% of reading + 0.005%
of the voltage range).
to 5.00 volts over 10 cps to 80 kc with an accuracy of 53% of full scale.
for the 1 volt to 500-volt ranges is 1 megohm, 45 Ticofarads.
r--
As B potentiometer,
As a VTVH, the Node1 661 measures from 10 millivolts full scale
____ .__,_ -_"_._-__l_~__i ._
it measures from 1 millivolt full scale
Input impedance
"
-..,. - ___.- -;.,
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__ __.____l,,_._.__
FIGURE 1.
Keithley Instruments Node1 661 AC/DC Guarded Differential Voltmeter.
0666R
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GENERAL DESCRIPTION
1-3. SPECIFICATIOSS.
AS A DC POTENTIO>ETER:
MODEL 661 DIFFF.P.ENTIAL VOLTmTER
_:
LIHIT OF ERROR:
50.01% of reading or 10 microvolts, whichever is greater, after 30-minute
warm-up.
LOXG-TERX STABILITY:
TEHPERATURE COEFFICIENT:
REPEATABILITY OR REVERSAL ERROR:
Wili operate within stated limit of error'for one year.
Does not exceed O.OO1%/°C.
-fO.OOl% or 10 micyovolts, whichever is greater, with
constant temperature and line voltage.
MAXIMUM NULL SEXSITIVITY:
INPUT RESISTANCE:
Infinite at null, from 0 to 500 Volts.
100 microvolts full scale with 2-microvolt resolution.
LINE STABILITY: Better than 5 ppm for 10% change in line voltage.
AS AN AC POTENTIO?I?,TER:
._
VOLTAGE RANGES:
WAVE-FORX RESPONSE: Averaging,
.
LIMIT OF ERROR (from 1 millivolt to 500 volts):
0.5, 5.0, 50.0 and 506.0 volts full scale.
calibrated in rms of a sine wave.
50 cps - 10 kc:
20 cps - 50 kc:
10 cps - 80 kc:
2(0.05% of reading + 0.005% of Voltage Range)
4(0.1% of reading +~ 0.01% of Voltage Range)
*(O.'S% of reading + 0.08% of Voltage Range)
MAXIMLM USABLE XULL SENSITIVITY:
LONG-TERM STABILITY:
TEMPERATURE COEFFICIENT:
Will operate within stated limit of error for one year.
Does not exceed 0.005%/°C.
REPEATABILITY: Within 0.01%.
INPUT IX'EDANCE:
One megohm, 45 picofarads except on the 0.5-volt range, where it is one
megohm, 50 pi&farads.
LINE STABILITY:
Better than 20 ppm for 10% change in line voltage.
AS A DC VACULJX !t7JBE VOLTXETER:
VOLTAGE RANGES:
NULL RAXGES:.
VTVM ACCURACY:
,
exclusive of noise and drift.
0.5 volt full scale to 500 volts in four decade ranges.
100 microvolts full scale to 100 volts in seven decade ranges.
53% of full scale on all ranges, except *5% on 100~microvolt range,
1 millivolt full scale with lo-microvolt resolution.
1.
2
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MODEL 661 DIFFERENTIAL VOLTXETER
GENERAL DESCRIPTION
OPEN CIRCUIT OFFSET:
ZERO DRIFT:
Less than 10 microvolts per 24 hours non-cumulative, after 30-minute warm-up.
INPUT RESISTANCE:
Less than 5 microvolts on the 100-microvolt null range.
50
megohms, 0.5 to 500-volt ranges;
10 megohms, O.l-volt range;
1 megohm, 0.1 to lo-miljivolt ranges.
LINE FRF,QUEXCY REJXTIOH:
Greater than 46 dc (peak-to-peak) above full scale for 2% of
full-scale change, lOO-microvolt through
l-volt range.
Greater than 70 db for 50% change,
.'
lOO-microvolt through lo-millivolt range.
AS AN
VOLTAGE RMGES:
NULL RANGES:
ACCURACY:
AC
VACULW TUBE VOLTKETER:
0.5
volt full scale to 500 volts in four decade ranges.
1 millivolt~full scale to 100 volts in six decade ranges.
-f3% of full scale from 10 cps to 80 kc on lo-millivolt to SOO-volt ranges,
except 25% of full scale from 20 cps to 50 kc on l-millivolt range.
INPUT IWEDWX: One megohm, 45 picofarads; 1 to SOO-volt ranges. One megohm, 50 pico-
farads; 1-ml-~:volt to 0.5-volt ranges.
GENERAL CHARACTERISTICS:
RECORDER OUTPUT:
output:
Output Resistance:
Noise:
Note:
FUNCTION:
FLOATING OPERATION:
INPUT ISOLATION:
Adjustable 10 to 25 millivolts dc for full-scale meter deflection.
300
ohms maximum
2 microvolts peak-to-peak referred to'input up to 1 cps.
Recorder used
must
have fully isolated input, 1010 ohms minimum to ground.
DC positive, negative, or ac, selectable by switch.
500 volts
dc maximum off chassis ground.
Circuit ground to chassis ground:
MAXINPl OVERLOAD: 500 volts, rms or dc.
COWECTORS: Input:
POWER:
105-125 or 210-250 volts (switch selected), SO-400 cps, 50 watts.
DI>EKSIONS, WEIGHT:
Binding Posts. Output: Banana jacks.
5-l/2 inches high x 17-l/2 inches wide x 13,-l/2 inches deep; net
weight, 25 pound's.
l-4. APPLICATIOXS.
108 ohms shunted by 0.05 microfarad.
a. Typical applications as a dc instrument include monitoring stability 'of most dc
standards, conducting power-supply stability and regulation checks, testing zener diodes
for stability and regulation,
and accurately measuring thermocouple outputs.
c
.~ ..~.
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GENERAL DGSCRIPTION
Typical applications as an ac instrument include uses~ in instrument maintenance
b.
' (stability checks and calibration),
and accuracy measurements,
ripple and hum determination, semiconductor circuit work,
ac power-supply verification, generator stability
MODEL 661 DIFFERENTIAL VOLTMETER
and oscillator monitoring.
1-5. .ACCESSORIES.
.
a. Model 6601A High Voltage Divider is a 1OO:l divider which extends the'& range of
the Model 661 to 5000 volts.
10 megohms.
The overall limit of error of the Model 661 with the Model 6601A is t0.02%.
The divider accuracy is ?O.Ol% and its input resistance is
Section 7 gives operating instructions for the Divider.
Modal 4000 Rack.Mounting Kit,
b.
Model 661 to fit standard 19-inch racks.
containing two brackets and a top cover, converts the
Rack mounted',
the Model 661 is 5-l/4 inches
high x 19 inches wide x 13-l/2 inches deep. Section 7 has asse&ly instructions.
1-6. EQUIPXENT SHIPPZD.
>The Model 661 AC/DC Guarded Differential Voltmeter is factorycalibrated and is shipped with all components in place. All units are shipped for bench
use. Model 4000 Kit may be ordered for rack mounting;
refer to Section 7 for assembly
instructions. The shipping carton also contains the Instruction Manual.
Page 7
.~ ..__... _ ../. I,..,. 1_1.---1”--11-“.1-
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ODEL
b
. -..-.
66l.[.DIWJERENTIAL VOLTMETER
c__-.-- -.---_L- _-.-
OPJATION-:
SECTION 2 OPERATION ..
on when it is set t,o the ON _ j
The FUNCTION Switch selects one of three operating modes for the
to measure positive or negative, dc voltages or to measure ac voltages.
NULL Switch.
decade ranges from 0.1 millivolt to 100 volts full scale.
position,
'f the RANGE Switch.
d.
,.5, 5, 50 and 500 volts full scale.
Varley divider and the position of the decimal point light -- which also serves as a
pilot light -- between the five Reference Voltage Dials. When the Model 661 is in the
ac operating mode,
(x0.1 to x1001 times the NULL Switch setting.
of the four RANGE settings is used.
e. Reference Voltage Dials.
reference voltage when the Model 661 is used as'an ac or dc potentiometer.
I
j f.
the dc mode only.
the other ranges,
a range of approximately *30 microvolts.
I g.
,to the low impedance terminal of the unknown voltage and the red HI Post is for connections
to the high impedance terminal.
vided for grounding theLO input terminal to: the chassis when desired.
are connected together internally.
/ / / I
'-2.
1
( a. Fuse.
210-250 volt operation,
b.
unless otherwise' specified on the rear panel.
?-prong plug provides a ground connection for the cabinet. An adapter for operation from
T-terminal outlets is provided.
c. NULL DETECTOR OUTPUT. Two terminals,Imarked + and -, c. NULL DETECTOR OUTPUT. Two terminals,Imarked + and -,
ull detector. ull detector.
the Model 661 operates as a conventional vacuum tube voltmeter for the four ranges
I
RANGE-MULTIPLY Switch.
METER ZERO Control.
Input Terminals.
REAR CONTROLS AND TFRMINALS.
!
For 105-125 volt operation,
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Power Cord.
The NULL Switch sets the null detector sensitivity for ,the seven
The NULL Switch functionsithe same for both ac and dc operating modes.
The Switch adjusts the sensitivity of the VTVM in four steps:
the full-scale null sensitivity is the product of the MULTIPLY setting
Five in-line dials at the top of the front
The METER ZERO Control adjusts the meter needle
The control is needed .on only the 0.1 and l.O-millivolt
the needle will normally be on zero without adjustment.
At the lower left front panel,
A second set of binding posts marked LO and GND is pro-
the Model 661 uses a 0.5-ampere 3 AG fuse.
The Model 661 is designed for a 105-125 volt,
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When the Switch is ,in the VTVM
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It also determines the voltage across the Kelvin-
The MULTIPLY setting is determined by which
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the black LO Post is for connections
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the Model 661 uses a l-ampere 3 AG fuse.
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The 3-wire power cord with the NEMA approved
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supply a dc signal from the supply a dc signal from the ~ ~
50-400 cps line source,
. - '1
panel set the
to zero for
null ranges; on
The control has
The LO terminals
For
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OUTPUT ADJUST. OUTPUT ADJUST.
etector-output.~-between-.~lO-and-25~.-mi~llivolts full---scale~.~-~------- etector-output.~-between-.~lO-and-25~.-mi~llivolts full---scale~.~-~-------
0465
A screwdriver control next to the OUTPUT terminals adjustcthe null A screwdriver control next to the OUTPUT terminals adjustcthe null
_.---_._ _.---_._
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(IPERATION MODEL 661 DIFFBRENTJALAOLT
e. 117-234 Switch. The screwdriver-ope
r 234-volt ac power lines.
-3. 'PRELIMINARY PROCEDURES.
a. Check the 117-234 Switch and the Fus,
,wer cord.
Set the Model 661 as follows:
b.
Power Switch
FUNCTION Switch
RANGE-MULTIPLY Switch
NULL, Switch
Reference Voltage Dials
s
the proper ac line voltage. Con
on
Des , red Operating Mode
500' .
VTVM
Zerb
_~
1
re decimal light between the third and fou\
arm up for 30 minutes to meet the specified accuracy on all ranges.
c. In the dc operating mode with the input terminals open, set the NULL Switc:
I and sero the meter with the METER ZERO Control.
le stability of the.Model 661 is such should be required in
iter a 30-minute warm-up.
:th Dials will light. Allow the inst,
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Then return the NULL Switch
r 117
ct the
ment tc
to 0.1
VTVM.
ght hou
NOTE /
There is no need to check the zero in 'the ac mode. If it is checked there 1
be approximately a lOO-microvolt offset.
offset does not occur when a signal isi applied.
-4. DC OPERATING PROCEDURES.
a. The Model 661 is used first as a VTVM to determine the approximate value of the un-
lown voltage. It is then used in the
1.01%.
The Model 6601A High Voltage
dc potentials only.
DC VTVM Operating Procedures.
b.
Eleven full-scale ranges are available:for'VTVM operation. When the NULL Switch;
1.
! is at VTVM, the RANGE-MULTIPLY Switch determines one of four full-scale ranges.~
ting the five Reference Voltage Dials at zero
on the seven null ranges.
the unknown voltage
impedance terminal of the unknown.
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I This has no effect on accuracy.~
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mode to determine the voltage to
Model 661 range to 5000 volts for
11
he
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By put-
meter deflection.
10465~
-.--l6)
Page 10
L- L--_.-
ODEL 661 DIFFERENTIAL VOLTMETER
‘“‘(
OPE.W.Ud
v/l 00000
LH LG
I-
0000
*
p/) 00000
1
‘y+zi$?J
.
A
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FIGURE 2.
measuring at ground and for floating.
In A, the unknown voltage has one terminal,at ground.
the Lo and GND Posts of the Model 661.
In B, the unknown voltage has both terminals off ground potential.
or off-ground potential must be less than 500;volts. Also note the shorting link is not
c. DC Potentiometric Operating Procedures.
Input Connections to Model 661.
The two diagrams show the input circuit for
jOTE
Potential 5
B
The shorting link is between
Note this floating
Avoid large overload voltages on the null detector. No permanent damage will
occur even with 500-volt overloads,
in the null detector.
capacitors,
Leave the RANGE-MULTIPLY Switch at the'last setting used in the VTVM operation.
1.
If the VTVM reading is negative, set the FUN
position.
Set the first two Reference Voltage D
2.
voltage found in the VTVM operation.
Set the NULL Switch to the initial
3.
null setting shown in Table 1. Adjust
the Voltage Reference Dials progressively
for zero meter deflection while increasing
the null detector's sensitivity with the
NULL Switch.
indicate the voltage being measured is
more
Dial Setting.
positive than the Reference Voltage
will disappear after about 5 minutes.
Deflections to the right
The offset, due to the polarization of the input filter
but some open circuit offset will be caused
!
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ION Switch to the opposite dc polarity
‘CT
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.ls to the first two digits of the unknown
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RANGE
MJLTIPLY Initial
Switch
Setting
500 v
50 v
5v
0.5 v
TABLE 1.~
and Settings for DC Potentials.
NULL Switch NULL Switch
Setting
100 v 10 MV
10 v 1.0 MV :
1v
100 MV
Recommended Null Sensitivities
---__
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Most Sensitiv
Setting
O.lMV j
0.1 MV
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OPERATION
MODEL 661 DIFFERENTIAL-~O&iET~
OTE
The most accurate resistors in the Kelvin- arley divider are in the first tyo
Reference Voltage Dials. Therefore, to obtain the most accurate readings,
the first two dials as much as possib e.
The value of the unknown voltage is re~ad directly from the Reference Vo
4.
a) The Dial reading will be within the specified limit of error if the!NULL
Switch is at the most sensitive setting (Table 1) for the range used and ifithe met
indicates as close to null as possible. Null does not have to be reached. '
b) When the first Reference Voltage Dial is used, only the five Dials need be
read
meter may be read as an approximation of a: sixth digit.
to
be within specifications (iO.Ol% of reading or 10 microvolts).
.
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se
tage Di
.'
However, the
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c) When the first Reference Voltage Dial is not used, read the voltage directly
from the remaining four Dials.
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d) Use the meter as a null indicator tjhen balancing voltages. When the first
Reference Voltage Dial is not used,
However,
quantative inaccuracies when the meter is Off null, (See paragraph 2-7). /
the loading effect of the Kelvin-Varley divider on the meter causes
the meter approximates a fifth dial reading.
some
8.
AC OPERATING PROCEDURES.
'5.
The Model 661 is used first as a VTVM to determine the approximate value of the
a.
iknown voltage. It is in the potentiometric mode to determine the voltage more,accurate
,e ac operation is similar to the dc operation: except for the null multipliers. :
AC VTVM Operating Procedures.
b.
Ten full-scale ranges are available for VTVM operation. When the NULL Switch is
1.
at VTVM, the RANGE-MULTIPLY Switch determines: one of four full-scale ranges.
ting the five Reference Voltage Dials
on six null ranges. The full-scale range for'these six ranges is the NULL Switch set- ~
ting times the MULTIPLY setting of the RANGE-MULTIPLY Switch.
RANGE-MULTIPLY Switch is at 50 V and the NULL Switch is at 10 MV, the full-scale null
range is 100 millivolts. Table 2 lists the switch settings for optimum results for the,
ten ac voltmeter ranges.
at
zero,, the Model 661 can then operate as a VTVM
For example, when the i
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F5y put-
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When changing the RANGE-MULTIPLY Switch to lower multiplier values, make sure the RANGE
values on the Switch are higher than the input voltage. Otherwise,
will be overloaded.
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Connect the unknown voltage to the!input terminals, using the LO Post fdr the
2.
low impedance terminal of the unknown. Referito Figure 2.
the ac converter
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Y.
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Switch the RANGE-MULTIPLY Switch to the most sensitive range for an on-scale
meter deflection. The meter will always showa deflection in the + direction.
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Page 12
@EL 66kDIFFERENTIAL VOLTMETER
OPERATION-/
RANGE-MULTIPLY
Switch: Setting
:500 volts
50 volts
: 5 volts
: 0.5 volt
100 volts
"10 volts
1 volt
100 millivolts
: 10 millivolts
1 millivolt
ITABLE 2.
perter is
pperating
re possible for the same ranges.
c. AC Potentiometric Operating Procedures.
1.
Set the first two Reference Voltage Dials to the first two digits of the unknown voltage found in the VTVM operation.
2.
Voltage Dials to read zero on the meter.,
sensitive range possible.
Switch Settings for AC VoltmeterRanges. Using the above settings,~the conoperated at as high a level as possible.
conditions, although alternate settings of the NULL and RANGE-MULTIPLY Switches
Leave the RANGE-MULTIPLY Switch at the'last setting used in the VTVM operation.
Set the NULL Switch to the least sensitive range.
.
/
500
5
50 F
0.5 v
500 ir
50 ;
3 v
O.$ v
0.5 v 10 MV
These settings are for the best
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Increase the null sensitivity to the most
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Keep resetting the Reference
NULL Switch
Settine
VTVM
VTVM
VTVM
VTVM
1v
1v
1v
1V
100 MV
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Do not set the NULL Switch beyond the'10 l&
mode.
Beyond this range, the meter will probably fluctuates excessively because of in-
stability of the ac input.
0.01% does not often occur.
3. I The Model 661 is an average reading device for ac voltages. It is calibrated to!
read the true rms value of a pure sine wave.
in reading,
the fundamental.
harmonic.
,6. RECORDER OUTPUT.
a. Recommended recorders for use with the Model 661 are the F. L. Moseley Autograf
10 series recorder and the Minneapolis Honeywell recorder (lOmv-0-1Omv scale, 50 kilohms
lput resistance). Any recorder used must be able to float 500 volts off ground and its ;
lput must be fully isolated (lOlo
Before attaching the recorder, I set all Reference Voltage Dials to zero.
b.
le unknown voltage and short both Model 661 input terminals.
1 Mv.
Better than 0.01% is readable on the lo-millivolt NULL Switch position.
An ac amplitude stability which is.~ better than
/
which depends on the harmonics present and of their phase in relation to
Table 3 indicates the range,of error for a,given percentage of a
ohm minimum leakage resistance to ground).
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Connect the recorder to the OUTPUT terminals on the Model 661 rear panel.
1
position for the ac operating
,Wave form distortion can cause an error
Disconnect ;
Set the NULL Switch to
*---....-
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Page 13
~PEkiT10~
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Harmonic
Percent
%/Distortion
MODEL 661 DIFFERE~~AL;JV~LTMFT~R
Maximum Percent
of Error from True
RMS Value /
Any even
harmonic
.
lird harmonic
ifth harmonic
ABLE 3. Error Caused by Distortion from Sine Wave.
Set the Reference Voltage Dials to 10 millivolts to apply an accurate lo-millivolt !
C.
ltential to the null detector on the lo-millivolt null range.
:ale recorder output which can be matched to the recorder's range between 10 and 25 milli-
bC
)lts by adjusting-the OUTPUT ADJUST Control.
.
ml
ir
To obtain accurate results and/or to 'pre
d.
1st be able to float off-ground with the Mode
lstruments should also be minimized.
Make sure neither recorder term&l
1.
is grounded.
line for the recorder. If a 2-wire line i
is used,
the Model 661 chassis with a separate lead.
Minimize all sources of 'leakage be-
2.
tween the output terminals, the recorder
and ground. Use polystyrene or Teflon-
insulated wire where possible. If the :
connecting wires are shielded, connect j
the shield to.the LO Post.
Avoid long leads between the Model/
3.
661 and
4.
connect a IO-microfarad capacitor between~ th
panel.
the recorder.
If difficulty is encountered in ofi-g,
Use a 3-wire grounded power
connect the recorder chassis and
0.1
0.5
1-o
2.0 i
0.1 /
0.5
1.0
2.0 .
0.1
0.5
1.0
2.0 ;
!
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ver
1: ’
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rbc
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It damage to the instruments, thk recorder
361. Leakage and pickup between:the two
FIGURE 3.
the Model 661 and the recorder may be necessary when using the O.l-millivolt null detector range.
lnd measurements,
Xl and GND terminals on the.Model 661 front
This will provide a full-
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Recorder Filter.
0,000
0.000 to -0.001
0.000 to -0.005
0.000 to -0:020
+0.033 to -9.033
+0.167 to -0.168
+0.328 t6 -0.338
+0.X167 to -0.687
+0.020 td -0.020
+0.099 to -0.101
+0.195 to -0.205
+0.380 to -0.420
A filter between
such as unstable readings,
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Page 14
I,-- .,.._
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MODEL 66 JIPPEREKPIAL MLTMFTBR
Kelvin-Varley divider.
O.l-millivolt null.range, place a
Refer to Figure 3 for this connection.
2-7. EFPPCTS DDE To KELVIN-VARLEY OUTPUT RESISTANCE.
!
a. When the Model 661 is used for nulling on the O.l-millivolt range, the last Reference Voltage Dial may appear to be inaccurate. The apparent error is due to a voltage
drop across the Kelvin-Varley divider. This effect involves only the null detector sensitivity and not the accuracy of the Dial setting.
as possible, the Reference Voltage Dial setting is correct within the instrument’s spec-
ifications. There is no effect present at null.
The effect is most apparent on the 0.1, 1 and lo-millivolt null ranges; a O.l-milli-
b.
volt off-null setting of the reference voltage will not produce a full-scale meter deflection. This is because the Kelvin-Varley divider output resistance is significant cornpared to the shunt resistance across the null detector meter. The IR drop across the
divider will cause the meter to be in error from 1% to 6%, depending upon the Reference
,Voltage Dial settings. On the lOO-millivolt range the maximum error is 1%. The effect :
Icannot be observed on the other null ranges of ,the Model 661.
c. The amount of deflection on the meter is jequal to the ratio
Rn, /
Rn, +; Rkv i
where OR
2-8.
is the shunt resistance across the meter (50 megohms for the 100 to l-volt null
._
ranges, 10 megohms for the lOO-millivolt range,
millivolt ranges) ;
Rk is the output resistance of the
x2.4 kilohms at Reference Voltage
a minimum of 100 ohms at settings
LOADING AND OFF-NULL RESISTANCE.
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When the Model 661 is as near to null
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and 1 megohm for the 10 to O.l-
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Kelvin-Varley divider, which is a maximum of
Dial settings of 2 4 5 4 5 and 2 5 4 5 5 and
of 4 ,9 9 9 8 and 0 0 0 0 2.
I I I
I
I
I
01 r’RATION’
.’
, _.___ ~..A
1
/
a. The input resistance of the voltmeter for the seven dc null ranges varies from 50
to 1 megohm as given in the Specifications. This resistance, however, is not the effective input resistance of the Model 661.
to the potentiometric principle of value is given by
is the effective input resistance of the Model 661;
Fd is the setting of the Reference Voltage Dials in volts;
R, is the shunt or input resistance of the null detector meter in ohms;
V is the null detector meter reading in volts.
_l_l_--__i 1-i --..
46% ___
Its input resistance is considerably higher due
Rink - ‘v
Equation 1
c
-.I-
-----.ll
J
Page 15
bE!!~TIO~
MODEL 661 DIFPERENIIAL MLTMEIER
4-
To find the loading effect the Model! 661 [will have on a circuit,
b.
U U
sed to compute the effective input resistance: At null, the input resistance is infin-
i i
0 0
; ;
0 0
‘2 ‘2
e e
r r
rn, rn,
m m
DC DC
2, 2,
UI UI
4: 4:
0: 0:
[pickup will be observed as needle
[pickup will be observed as needle
Off null, the input resistance is usually high compared to the internal resistance ;
te.
f the unknown voltage, and the loading will not be enough to affect the measurement acuracy. For example, the Model 661 input resistance is lOlo
ials are set at 1.0000 volt on the l-millivolt null range for a reading off null by 10% i
f full scale.
THERMAL EMF PRECAUTIONS.
-9.
mf errors for measurements using the most sensitive null ranges.
ead to 0.5 microvolt, thermal emf’s can introduce considerable errors into the measureents.
icroyolt range, Par extensive measurements in the microvolt region, request the article,
C Microvolt Measurements, from Keithley Instruments or its representative. ,I
-10.
nknown voltage, ~the Model 661 employs a chopper-stabilized null detector operating at
2-&s chopping rate with a 3-section R-C filter at the input. Very large ac components
n the measuring lines, however, may reduce off-null sensitivity. Also, heavy 60-cps
ode1 661, additional filtering is requir
win-T filter is effective. For an ac va
er.
In general, use pure copper leads throughout the system when measuring in the
AC EFFFCTS ON DC MEASURFMENIS. I To minimize errors from ac signals present in the
s
Observe standard thermocouple techniques to reduce thermal
Quiver.
Quiver.
I
equation 1 may be i
ohms if the Reference Voltage
I I
Since the Model 661 can
! 1
If ac components affect measurements by the If ac components affect measurements by the
Par Par an ac signal of a single frequency. a an ac signal of a single frequency. a
xq : xq :
abl frequency, use an ordinary low-pass fil-
--1_1
I
:
i
Xange Input Resistance
500 volts
50 volts
5 volts
0.5 volt
100 volts
10 volts
1 volt
0.1 volt
10 millivolts
1 millivolt 1 megohm
0.1 millivolt
‘ABLE 4. Null Detector Input on
x3 Ranges.
50 megohms
50 megohms
50 megohms
50 megohms
50 megohms
50 megohms
50 megohms
10 megohms
1 megohm
1 megohm
12
I--...-
Page 16
/MODEL 661 DIPPBRENIIAL WLTMEIER
./
. .--_ . . . . ~--
CIRCUIT DPSCRIF’TION
SICTION 3.
)_._~___
CIRCUIT DF.SCRIPTION~
~_~--._-.--
~Dc.16~p~~~~~-~~-~~~cv~T~
-1.
,tentiometric method.
The Model 66?Dif&zial Voltmeter measures voltaae bv the
The ultra-stable 500-volt reference voltage supply (see Pipure 4)
j used with the S-dial Kelvin-Varley divider to null the unknown voltage. The difference
stween the divider output and the unknown voltage is indicated by the null detector -’
chopper-stabilized vacuum-tube voltmeter. At null the unknown voltage equals the referIce voltage and can be directly read from the five in-line dials of the kelvin-Varley
ivider. The input and null detector are fully guarded to avoid leakage.
i
INPUT
TERMINALS
G”ARLx3
NULL
DETECTOR
) !
KELiIN.VARLEY
DIVIDER
REFERENCE
“OLTAG E
SUPPLY
PIGURE 4.
Simplified DC Circuit Diagram of the Model 661.
/ j
;3-2., AC OPFRATING CIRCUIT.
mode as in the dc operating mode.
The Model 661 uses much the same circuit in the ac operating
The major difference is that the ac signal is converted
to dc before it is compared to the reference voltage supply. See Figure 5. An ac attenu-
,ator reduces all ac input signals to one range -
converter converts the ac signal to a dc signal,
deflection.
by the null detector.
This signal is compared to the reference voltage supply output and compared
The reference voltage supply operation for all ac ranges is equiva-
.-
the 0.5-volt range.
equivalent to 5 volts dc at a full scale
The ac
lent to the S-volt dc operating range.
‘IGURE 5. Sim-
Input
* ATTENUATOR
AC
AC-DC
* CONVERTER
*
DETECTOR
NULL
jlified AC Cir:uit Diagram of
:he Model 661.
REFERENCE
a
b465~
,~ -_~--
Page 17
.,
MODEL,661,DIFFERENTIAL VOLTMETER
. ..REPIACEArlLE PARTS
.
._ ~~. SECTICN 7.
7-l.
REPLACEABLE PARTS LIST.
Model.661.
ufacturer,
The List gives the circuit designation, the part.description,. a suggested man-
the manufacturer's part number and the Keithley Part Number.
The Replaceable Parts List describes the components of the
indicates the figure pictaring the part.
REPLACEABLE PARTS
The last column
The name and the address of the manufacturers
listed in the "Mfg. Code" column are in Table 11.
7-2.
HOW TO,ORDER PARTS.
a. For parts orders; include the instrument's model and serial number, ,the Keithley
.~Part Number',
the circuit designation and a description of the part.
All structural parts
and those parts coded for Keithleymanufact,ure,(80164) $ust be~'&dered from Keithiey
Instruments, Inc.,
Parts List,
Order parts through your nearest Keithley representative or the Sales Service Depart-
b.
completely describe the part,
or its representative.
In ordering a part not listed in the Replaceable
its function and its location.
ment, Keithley Instruments, Inc.
ampere
Ceramic, disc MtF
Ceramic, tubular
,.m ~_,
Mfg.
MY
.~milFf. .,.. (P-3) .~~~
Manufacturer
Metal Film
Mylar
Composition
P
Deposited Carbon Poly
pjco (lo-l*)
Polystyrene
Electrolytic, Aluminem Ref.
Electrolytic, Metal Cased
Electrolytic, tubular
Electrolytic, tantalum
farad
V
Figure
kilo (103)
J
.TAB!h LO.
Abbreviations and Symbols
EJW
WWVar
Reference'
micro
(10-6)
ohm.
volts
watt
Wirewound
Wirewound Variable
Page 18
REPLACEABLE PARTS
(Refer to Schematic Diagrams 187593, 187603 and 173423)
MODEL 661 DIFFERENTIAL VOLTMETER
MODEL 66i REPLACEABtE PARTS LIST
--
' Cl016
CAPACITORS
Circuit Mfg. 'Mfg.
Dksig.
Cl001
Cl002
Value Rating
0.1 IJ.f
0.1 pf
C1003' 605 I.lf
Cl004
Cl005
Cl006
Cl007
Cl008
Cl009
Cl010
Cl011
Cl012
Cl013
Cl014
Cl015
.05 IJ.f
. lO@f
10 pf
.002 IJ.f
680 pf
40120 pf
0.47 pf,
.002 pf
10 pf
.0047 pf
1.0 pf
125 Ff
4 bf
Cl017
Cl018
Cl019
600 pf
.05 pf
0.1 pf
Type
100 v Poly
100 " Poly
100 " Poly
600 v My
15 "
15 v-
ETB
ETB
1000 v . CerD
1000 "
CerD
450 " EMC
600 v
MY
1000 " CerD 72982 801Z5V202P C22-.OQ2M
15 "
1000 "
ETB 56289 TE1155 C3-1OM
CerD 72982
600 v ETB 13050 24009
15 "
250 v
6v
600 v.
100 "
ETB 73445. ~426 C3-125M
ETB
ETT
MY
Poly
Code
00656
00656
Part No.
lPJ..104J Cl29-'.lM
lPJ-104J Cl29-.lM
lPJ-5035
562.89
56289
6PS-S50
TE1155 c3-10M
56289 TEl155 C3-1OM '
72982
801Z5V202P C22-.002M
72982 801X5R681K C22-680P
56289 TVL2762 C36-40/20M
14655 WMF6P47 ClOl-.47M
81125V472P C22-.0047M
14655
05079
56289
BBR4-250
TEZ600-6C2 C133-600M
6PS-S50 C62-.05M
lPJ-104J C129-.lM
.
Keithley Fig.
Part No. Ref.
Cl29-605M
C62-.05M
C12-1M
C27-4M
c2001
c2002
cioo3
c3001
Not Used
.Ol &If
-01 k!f~
Not Used
C3002 Not Used
c3003 20 pf
c3004
c3005
C3006
c3007
C3008
c3009
c3010
c3011
40/20 pf
1.0 IJ.f
Not Used
Not Used
.002 pf
Not Used
.05 pf
4 kf
C3012 50 pf 6v
c3013 .0047 Nf
',' * 'k3014
c3015
.022 pf 260 v ETB
.05 pf 600 v
300 v
300 "
450 "
CerT 01884 MPX103K3 C61-.OlM
CerT 01884 MPX103K3 C61-.OlM
EMC 37942 FPl44 C36-20M
450 " EMC 56289 TVL2762 C36-40/20M
1000 v
ETB
1000 " CerD 56289
600 v
250 v
MY
ETB
ETB
1000 "
CerD
MY
13050 Z4009B Cl4-1.OM
5GAD22 C72-.002M
56289
14655
56289 TEllOO
72982
13050
56289
6PS-S50 C62-.05M
BBR4:250 C27-4M
c17-5OH
811Z5V472P
C22-.0047M
.EIWlA C6-.022M
6PS-S50
C62-.Q5M
c
42
0966R
Page 19
MODEL 661 DIFFERENTIAL VOLTMGTER
<
Circuit
Desig.
Value Rating . Type
CAPACITORS (Cont'd)
Mfg.
Mfg. Keithley
Code Part No. Part No.
REPLACEABLE PARTS
Fig.
Ref.
c4001 * 10 pf
C4002
100 pf
c4003 1.0 uf
c4qo4 .OOl pf
c4005
.OOl pf
~4006 56 pf
c4007
100 jlf
C4008 .' 1.0 vf
c4009
c4010
c4011
C4012
c5001
100 pf
100 pf
2
Pf
.OOl pf
1.2-3.5 pf 850 v Trimmer 74970
C5002 1.2-3.5 pf
c5003 47 pf
c5004
c5005
C5006
c5007
C5008
c5009
c5010
1.2-3.5 pf 850 v
1.5 pf 600 v
2.2 pf
18 pf
820 pf
820 pf
0.25 yf
600 v
25 v
200."
1000 " CerD
1000 v CerD
75 "
25 v
200 y
15 v
15 "
200 "
1000 "
CerT
ETT
MY
ETT
ETT
MY
EAl
EAl
MY
CerD
71590
05079
99120
72982
72982
08804
05079
99120
56289
56289
13050
72982
850 v Trimmer 74970
600 v CerT 80164
600 v
600 v
500 ",
500 v
400 v
Trimmer
CerT
CerT
CerT
Mica
Mica'
MY
74970
80164,
80164
71590
84171
84171
13050
TCZ
WLOO-25C2Ul
AZ2-105Z
c77-1OP
C96-100M
C119-1M
801Z5V102P C22-.OOlM
8OlZ5V102P C22-.OOlM
69F-381-G7
WlOO-25C2Ul
AZ2-105Z
C137-56M
C96-100M
C1'19-1M
89D217 d93-100M
89D217
C93-100M
MWLA C115-2M
801Z5V102P C22-.OOlM
189-lo-4
189-l-4
C121-1,2-3.5P
Cl21-1.2-3.5P
C123-47P
189-l-4
C121-1.2-3.5P
C123-1.5P
301-034COH0229B C123-2.2P
TCZ-18
C77-18P
DM19-821J C97-820P
DM19-821J C97-820P
SMLA
C73-.25M
c5011
C5012
c5013
c5014
c5015
C5016
c5017
,C5018
. c5019
C6001
C6002
C6003
C6004
C6005
C6006
.:"C6007
C6008
C6009
1.2-3.5 pf
1.5 pf
Not Used
1.4-7.3 pf
4.7 pf
4.7 pf
Not Used
2.2 pf
2.2 pf
40 )If
.OOl pf
1.0 IJ.f.
0.25 IJ.f
500/500 pf
330
pf
2.7 pf
1000 IJ.f
40 pf
850 v
600 v
850 v
Trimmer 74970
CerT
Trimmer
600 v CerT
600 v
600 "
600 v
1000 "
400 "
150 "
100 "
20 "
12 "
350 "
CerT
CerT
CerT
CerD
MY
EMC 53021
CerD
J ~'
EMC
EMC
80164
74970
80164
80164
80164
80164
72982
13050
72982
05397
56289
53021
189-l-.4 C121-1.2-3.5P
C123-1.5P
189-l-4
C121-1.4-7.3P
C123-4.7P
C123-4.7P
Cl23-2.2P
Cl23-2.2P
801Z5V102P C22-.OOlM
SMAA C73-.25M
505-2603-01 C20-500-500
831X5R331K
C22-330P
C80-2:7M
DFP
505-1022-01
C24-1OOOM
C19-40M
L*
'0966R
43
I
Page 20
REPLACEABLE PARTS MODEL 661 DIFFERENTIAL VOLTMETER
DIODES
Circuit
Desig.
DlOOl
D3001
b3002
D3003
D3004
D3005
Type
Silicon
Silicon -
Not Used
Not Used
Silicon
Silicon
D3006 Not Used
D3007
Not Used
D3008 Not Used
D3009
D4001
D4002
D4003
D4004
D4005
D4006
D4007
SFliCOIl
Silicon
Silicon
Zener
Not Used
Silicon
Zener
Silicon
Mfg.
Number
lN645
lN3256
Code
01295 RF-14
02735 RF-22
182378 08520
lN3256 02735
lN3157
1~645
lN935
lN709
lN914
lN715
lN914
12954 DZ-24
01295 RF-14
04713
12954
01295
12954
01295
Keithley Fig.
Part No.
Ref.
RF-25
RF-22
DZ-7
DZ-21
RF-28
DZ-22
RF-28
D6001
D6002
D6003
D6004
D6005
D6006
D6007
D6008
D.6009
D6010
D6011
., ..,
Silicon
Silicon
Silicon
Silicon
Zener
Zener
Sil'icon
Silicon
Zener
Silicon
Zener
lN3253
lN3253
lN3253
lN3253
IN709
lN3027
lN1563A
lNl563A
lN709
1~645
17935
:
02735
02735
02735 RF-20
02735 RF-20
12954 DZ-21
12954 DZ-16
04713 RF-19
04713
12954
01295 RF-14
04713
RF-20
RF-20
RF-19
DZ-21
DZ-7
44
.
0966R
Page 21
.~MODEL 661 DIFFERENTIAL VOLTMETER
REPL&EAB',E PARTS
MISCELLANEOUS PARTS
Circuit
Desig.
BTlOOl
DSlOOl.
DS2001
DS2002
DS2003
DS2004
ElOOla
'ElOOlb
.
E1002a
E1002b
E1003a
E1003b
E3001a.
E3001b
Mfg.
Keithley
Fig.
Description Code Part No. Ref.
.
Sodium Bias Cell 1.35 v (Mfg. No. PX-13) 37942
Neon Lamp (Mfg. No. NE-P1) 08804
Neon Lamp (Mfg. No. NE-2P)
Neon Lamp (Mfg. No. NE-2P)
08804
08804
BA-16
FL-6
PL-2
PL-2
Neon Lamp (Mfg. No. NE-2P) 08804 PL-2
Neon Lamp (Mfg. No. NE-2P) 08804 PL-2
Light Modulator 89164
Light Modulator 80164
Light Modulitor
80164 1513
Light Modulator 80164
Ligfit Modulator
80164
Light Modulator 80164
1513
1513
1513
1514
1514
Light Modulator 80164 1512
Light Modulator 80164
1514
E3002a
E3002b
FlOOl(117v)
FlOOl(234")
._-.
F6001
.---
F6002
..--
JlOOl
JlOO2
51003
51004
54001
-.--
56001
__._
.
-i-m
Light Modulator 80164
Light Modulator
Fuse,
Fuse,
slow blow, 1 amp (Mfg. Type MDL)
slow blow, 0.5 amp (Mfg. No. 312.500)
Fuse Holder (Mfg. No. 342012)
Fuse (Mfg. Type 361.002)
Fuse Holder (Mfg. No. 387001)
Fuse,
fast acting (Mfg. No. 36101.5)
Fuse Holder (Mfg. No. 387001)
Binding Post (Mfg. No. PF31RC)
Binding Post (Mfg. No. PF31BC)
Binding Post (Mfg. No. PF3lBC)
Binding Post (Mfg. No. PF3lBC)
80164
71400
75915
75915
75915
75915
75915
75915
91407
91407
91407
91407
Connector
Connector
Connector
Connector
Stiorting Link (Mfg,.No.' 938-L)
24655,
1514
1514
FU-10
FU-6
FH-3
FU-12
FH-l
FU-26
FH-1
BP-8R
BP-8B
BP-8B
BP-8B
CS-167
cs-166
BP-6
Ml001
. .
', 0966R'
Meter 80164 MB-38
c
Page 22
Circuit
Desig.
.
MISCELtANEOUS PARTS (Cont'd)
.,
Mfg.
Description Code
Keithtey,
Fig.
Part No. Ref.
PlOOl
~SlOOl
_--_
Cord Set, 6 feet (Mfg. No. 4638-13)
Rotary Switch, less components, NULL 80164
Knob assembly, Null 80164
53001 Rotary Switch,
----
Knob assembly, Function
S3002 Rotary Switch,
----
Knob assembly,
. s3003 Rotary Switch,
----
----
Rotary Switch,
Dial assembly,
s3004 Rotary Switch,
----
----
s3005
----
----
S3006
---_---
Rotary Switch,
Dial assembly,
Rotary Switch,
Rotary Switch,
Dial assembly,
Rotary Switch,
Rotary Switch,
Dial assembly,
93656
co-5
14838A
less components, FUNCTION 80164
SW-175
80164 14838A
less 'components, RANGE 80164
Range 80164
less components, Readout
80164 SW-174
SW-191
171438
with components, Readout 80164 18810B
O-4, Readout 80164
less components, Readout 80164
with components, Readout 80164
O-9, Readout
80164 14828A
less components, Readout 80164
with components, Readout
O-9, Readout
less components, Readout
with components, Readout
O-9, Readout
80164
80164 148288
80164
80164 18816~
80164
14827A
SW-118
18811B
SW-170
18817~
SW-170
14828A
s3007 Rotary Switch,
----
---S.3006
-___
----
T3001
Rotary Switch,
Dial assembly,
Switch, lever SPST, ON
Rotary Switch, less components, METER ZERO
Knob assembly, Meter Zero
Transformer
less components, Readout
with components, Readout
O-10, Readout
80164
80164
80164
SW-174
18810B
191858
80164 17116A
80164
RPl9-15K
80164 15110A
80164
TR-62
46'
0966R
Page 23
MODEL 661 DIFFERENTIAL VOLTMSTER
.~
REPLACEABLE PARTS
RESISTORS
m
, R1019
Circuit
Desig. Value
RlOOl
R1002
R1003
R1004
R1005
R1006
R1007
R1008
Rl009
RlOlO
RlOll
R1012
R1013
R1014
R1015
R1016
R1017
R1018
R1020
50 Ma
1.5 Ma
220 kn
5 kQ
50 kQ
12.5 Ma
505 kn
220 kR
470 kQ
3 kfi
3 k0
900 kQ
220 kR
15 kfi
1 Ma
10 kfi
1.5 MR
200 kR
1.5 MQ
15 k0
Rating
l%, 2 w
l%, l/2 w
.lcyL, l/2 w
l%, l/2 w
l%, l/2 w
l%, 1 I?
l%, l/2 w
lO%, l/2 w
LO%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
LO%, l/2 w
!a, 2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
l%, l/2 w
lO%, l/2 w
lO%, l/2 w
Type
DCb
DCb
Comp
DCb
DCb
DCb
DCb
Comp
DCb
DCb
DCb
DCb
Comp
WWVar
Comp
Comp
Comp
DCb
Comp
Comp
Mfg. Mfg.
Code
91637 DC-2
79727
01121
79727 CFE-15
79727
91637 DC-1
79727 CFE-15
01121 EB
79727
79727 CFE-15
79727
79727 CFE-15
01121
12697 43C2
01121 EB
01121
01121
79727
01121 EB
01121
Part No. Part No.
C,FE-15
EB
CFE-15
CFE-15
CFE-15
EB
EB
EB
CFE-15
EB
Keithley
Ri4~-50M
Rl2-1.5M
Rl-220K
R12-5K
R12-50K
Rl3-12.5M
Rl2-505K
Rl-220K
R12-470K.
Rl2-3K
R12-3K
Rl2-900K
Rl-220K
RPl9-15K
Rl-1M
Rl-1OK
RlL1.5M
Rl2-200K
Rl-1.5M
Rl-15K
Fig.
Ref.
R1021
R1022
R1023
R1024
R1025
R1026
RI027
R1028
R1029
R1030
Rl031
R1032
R1033
R1034
' R1035
R1036
R1037
R1038
Rl039
R1040
10 MS-l
100 kn
70 kQ
450 kR
2.2 MR
10 Ma
8.2 k0
3.3 Ma
10 MQ
3.3 MR
1.2 kR
100 kn
220 kR
12 kR
1 kn,
2 k0
40 kn
1.5 MQ
4:7 MO
500 n
10%; l/2 w
lO%, l/2 w
l%, l/2 w
l%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
LO%, l/2 w
lO%, l/2 w
lO%, l/2 w
10%; lf2.w
lO%, l/2 w
lo%, l/2 w
lO%, l/2 w
lO%, l/2 w
l%, l/2 w
l%, lf2.w
lo%, l/2 w
l%, l/2 w
lO%, 5' w
Comp
Comp
DCb
DCb
Comp
Comp
Comp
Comp
Comp
Comp
Comp
Comp
Comp
Comp
Comp
ww
DCb
Comp
DCb
WWVar
01121
01121
79121 CFE-15
79727
01121 EB
01121 EB
01121 EB
01121
01121
01121
01121 EB
01121
01121 EB
01121 EB
01121
01686 E-30
79727
01121
79727
71450
EB
EB
CFE-15
EB
EB
EB
EB
EB
CFE-15
EB
CFE-15
AN
Rl-1OM
Rl-10OK
Rl2-70K
R12-450KRl-2.2M
Rl-1OM
Rl-8.2K
Rl-3.3M
Rl-1OM
Rl-3.3M
Rl-1.2K
Rl-100K
Rl-220K
Rl-12K
Rl-1K
R58-2K
Rl2-40K
Rl-1.5M
R12-I;.7M
RP3-500
0966R
c
47'
Page 24
REPLACEABLE PARTS
.
. :
MODEL 661 DIFFERENTIAL V'YLTMETER
C
RESISTORS (Cont'd)
Circuit Mfg. Mfg.
Desig. Value Rating
R1041
;:;;:
R1044
R1045
R1046
R1047
Rl048
R2001
R2002
R2003
R2004
R2005
'~2006
R2007
R2008
R2009
R2010
80 i-i
1500 n
200 n
1 kn
450~kR
1 &!l
lv.14 Ma
100 MO.
150 kR
220 kfl
100 k0
Not Used
Not Used
220 kn
150 kfl
.50 kR
150'kR
50 kfi
ix, l/2 "
l%, l/2 "
a
lO%,
I%,
20%,
I%,
20%,
10%,~1/2 w
Id%, l/2 "
lO%, l/2 Y
lO%, l/2 "
lO%, l/2 w
l%,
1%;1/2 "
3%, l/4 w
l/2 w
l/2 w
.2 w
l/2 w
l/2 w
l/2
"
TYPO
ww
ww
Comp
DCb
CompV
DCb
Comp
Comp
Comp 01121
Comp
Comp
Comp
DCb
DCb
CbVar
Code
01686
01686
01121
79727
71450
79727
75042~
01121
01121
01121
01121
79727
79727
80164
Part No.
E-30
E-30' R58'1500
EB
CFE-15 R12-450K
CTS RP31-1K
CFE-15 Rl2-1.14M
GBT
EB
EB Rl-220K
EB Rl-100K
EB
EB
CFE-15
CFE-15
Keithley
Fig.
Part No. Ref.
R58-80
Rl-1K'
R37-100M
Rl.-15OK
.
Rl-220K
Rl-150K
R12-50K
R12-150K
RP38-50K
R2011
R2012
R2013
R2014
R2015
~R300i
R3002
R3003
R3004
R3005
R3006
R3007
R3008
R3009
R3010
R3011
R3012
R3013
' rR3014
* R3015
1.8 MR
1.8 MR
Not Used
100 k0.
100 kn
220 n
820 kR
150 kfl
Not Used
1 Ma
1 MO
50 kQ
1 MR
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
1%,.1/2 "
l%, l/2 "
lO%, l/2 w
10%: l/2 "
lO%, l/2 "
lO%, l/2 "
lO%, l/2 "
lO%, l/2 "
lO%, l/2 w
lO%, 2 "
lO%, l/2 "
DCb
DCb
camp
Comp
Comp
Comp
Comp
Comp
Comp
Camp
Comp
79727
79727
01121
01121
01121
01121
01121
01121
01121
01121
01121
:
CFE-15
CFE-15
Rl2-1.8M
R12-1.8M
EB. Rl-1OOK
EB
Rl-100K
EB R1-220
EB Rl-820K
EB Rl-150K
EB
Rl-lM
EB Rl-lM
HB R4A-50K
EB Rl-1M
48
0966R
Page 25
; MODEL 661 DIFFERENTIAL VOLTMETER
REPLACEABLE PARTS
RESISTORS (Cont'd)
Circ&t Mfg. Mfg.
Desig. Value Rating
.
R3016
.R3017
R3018
.R3019
R3020
R3021
R3022
'R3023'
~3024
R3025
Not Used
Not Used
470 k0
4,70 k0
1 Ma
Not Used
3.3 kn
1 MO
10 Ma
150 kQ
lD%, l/2 w
lo%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lo%, l/2 w
lO%, l/2 w
Type
Comp
Comp
Comp
Comp 01121 EB
Comp
camp
Comp
Code
01121
01121
01121
01121
01121 EB Rl-1OM'
01121
*
R3026
R3027
R3028
R3029
R3030
R3031
R3032
R3033
R3034
R3035
680 ks2
'270 kSl
2.2 Ma
5.6 k0
65.4 kfi
3 kR
1 MR
220 kn
125 l$
200 n
lO%, l/2 w
lO%, l/2."
lO%, l/2 w
lO%, l/2 w
O.l%, 50 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, 2 w
Comp
Comp
Comp
Comp 01121
ww
Comp
Comp
Comp
WWVar
01&l
01121
01121
91637
01121
01121
01121
01121
71450
Keithley Fig.
Part No: Part No. Ref.
EB Rl-470K
EB Rl-470K
EB Rl-1M
Rl-3.3K
EB
EB
EB
EB
EB
EB
RH-50
EB
EB
EB
EB
P252-200
til-1M.
Rl-150K
Rl-680K
Rl-270K
Rl-2.2M
Rl-5.6K
R37-65.4K
Rl-3K
Rl-1M
Rl-220K
(1)
RP22-200
R3036
R3037
R3038
R3039
R3040
R3041
R3042
R3043
R3044
R3045
R3046
R3047
R3048
R3049
R3050
125 kfi
4 ksl
1 kR
9 kQ
250 kn
1 kR
32.33 kR
91 kQ
1 kfi
2.563 k0
930 kn
1 k0
250.9 R
*
9: .~
O.l%, 2 w
O.l%, l/2 w
l%, l/2 w
.l%, l/2 w
O.l%, l/2 w
lo%, 5 w
O.l%, l/2 w
l%, l/2 w
lO%, 5 w
O.l%, l/2 w
l%, l/2 w
lO%, 5 w
O.l%, l/2 w
O.l%, l/4 w
O.l%, l/4 w
ww 80164
ww 80164
DCb 79727
DCb
79727
ww 80164
WWVar
71450
ww 80164
DCb
79727
WWVar 71450
ww 80164
DC!,
WWVar
79727 CFE,-15 Rl2-930K
71450
ww 01686
ww 01686
ww 01686
CFE-15
CFE-15
AW
CFE-15
AW
R12-1K
Rl2-9K
(2)
RP34-1K
(2)
Rl2-9lK
RP34-1K
(2)
AW RP34-1K
1250
(2)
7009 R95-*
7009 R95-*
R3051 to
R3056
40.kn
80164
(3)
*Nominal value, factory set.
(l)R3034, R3036 and R3037 comprise a matched set;Keithley Part No. 15436A.
(2)R3040, R3042, R3045 and R3048 comprise a matched set, Keithley Part No. 154328.'
(3)Part of a Switch Assembly, Keithley Part No. 18810B.
b.
0966R-
. .
49
Page 26
REPLACEABLE PARTS
MODEL 661 DIFFERENTIAL VOLTMETER
RESISTORS (Cont'd)
Circuits
DeSig*
Value .Rating
TYPa
Mfg. Mfg.
Code
Part No. Part No. pef.
Keithley Fig.
R3057 to
R3067 8 kQ .02%, l/2 w
.
ww
80164 RlOO-8K
R3068 to
R3078
1.6 ko
.04%, l/2 w
biw
80164 R99-1.6K
R3079 to
R3089
R3090
R3091
320 fl
750 n
*
O.l%, l/2 .w
-x0%, 4 w
l%, lj2 w
ww
01686 7044 R&7-320
War 12697 58M RP49-750
DCb 79727 CFE-15
R12-*
R3092 to
R3099
-
R3100
R4001
R4002
R4003
.
R4004
'R4005
Not Used
3.3 kQ lO%, l/4 w camp 01121 CB R76-3.3K
1.5 MO
1.5 kQ
348 kn
3.33 MCI
3.33 MO
l%, l/2 w
lO%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
DCb 79727 CFE-15 R1~2-1.5M
Comp
MtF
01121
EB Rl-1.5K
07716 CEC, T-9
R113-348:;
DCb 79727 CFE-15 Rl2-3.3M
DCb
79727
CFE-15 R12-3~.3M
R4006 1 kfi
R4007 390 R
R4008
150 0
R4009 5 kR
R4.010 2 k0
R4011
R4012
i4013
R4014
R4015
1 MR
2.2 kR
10 kfl
10 kR
8.2 kfl
.R4016
R4017
R4018
R4019
~4020
33 kR lO%, l/2 w
1.8 kR
2.21,kR
412 n
IO%,
IO%,
IO%,
l%,
lo%,
l%,
lO%, l/2 w
l%,
lO%, l/2 w
lO%, 1 w
lo%, l/2 w 220 R
*Nominal value, factory set.
. ..., -
l/2 w
l/2 w
l/2 w
l/2 w
l/2 w
112
w
112
w
Comp
Comp 01121
Comp 01121
01121
EB Rl-1K
EB Rl-390
EB
Rl-150
DCb 79727 CFE-15 Rl2-5K
WWVar
DCb
Comp
DCb
camp
Comp
80294
797i7
01121
79727
01121
01121
Camp 01121
01121
01121
07716
07716 CEC, T-9
30675-l-202 RP35-2K
CFE-15
EB
CFE-15
EB
GB
EB
EB
HB
CEC, T-9
R12-1M
Rl-2.2K
R12-10K
Rl-1OK
R2-8.2K
Rl-220
Rl-33K
R3-1.8K
R113-2.21K
R113-412
50
0966R
Page 27
. MODEL 661 DIFFERENTIAL VOLTMETER
REPLACEABI,E PARTS
RESISTORS (Cont'd)
Circuit
Desig.
* R4021
R4022
R4023
" R4024
R4025
R4026~
-ti4027
R4028
R4029
R4030
.
.x4031
,R4032
@I?3
'R.5001
R5002
R5003
R5004
R5005
Value Rating
57.6 n
.180 kn
2.21 kn
100 n
l%, l/2 w,
l%, l/2 w
lx-,
lO%, l/4 w
Not Used
1.2
kn
I%, 112 w
"48 kn
2.21 kn
180 kn
180 ksl
I%, l/2 w
l%, 112 w
l%, l/2 w
Id?, l/2 w
lO%, 2, w
909 kn
110 kQ
5 kn
990 kn
1MG
l%, l/2 w
1x, l/2 w
lO%, l/4 w
l%, l/2 w
.S%,
l/2
l/2
w
w
Mfg. Mfg. Ke-ithley
Type
MtF
DCb
MtF
ww
MtF
MtF
Code
07716
79727
07716
80294
07716
07716.
DCb 79727
DCb 79727
Comp
COmp
MtF
MtF
ww
MtF
WI?
01121
01121
07716
07716
80294 273-l-502
07716
01686 7020-W
Fig.
Part No.
CEC, T-9
Part No.
R113-57.6
Ref.
CFE-15 R12-180K
CEC, T-9 Rll3-2.,21K _
271-l-101 RP45-100
CEC, T-9
Rll3-1.2K
RllZ-48K
CEC, T-9
CFE-15~
CFE-15
EB
HB
CEC, T-9
CEC, T-9
R113-2.21K
R12-180K
Rl2-180K
Rl-150
p3-47
R113-909K
Rl13-11OK
RP44-5K
CEC, T-9
R113-990K
R118-1M
RSOOG
R5007
R5008
R5009
R5010
R5011
@OOl
R6002
R6003
R6004
R6005
R6006
R6007
RGOOS
R6009
R6010
.
R6011
" R6012
R6013
R6014
RG015
9.76 kn
500 n
976 n
1 kn
37.4 n
1MI-l
500 cl
100 kn
1.5 kn
820 n
220 n
47 kn
8.2 kn
16.67 kn
15 kfl
3k
1.5 n
330 n
560 n
10 kn
300 cl
l%, l/2 w
lO%, l/4 w
l%, l/2 w
lO%,
l/4
w
~I%, l/8 w
l%, l/2 w
l%, 5 w
lO%, l/2 w
5%, 3 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
l%, l/2 w
17, l/2 w
l%, l/2 w
l%, 5 w
5%,3w
l%, l/2 w
lO%, l/2 w
l%, l/2 w
MtF
ww
MtF
ww
MtF
07716
80294 273-l-501
07716 CEC, T-9
~80294 273-l-102
07716
MtF 07716
ww
91637
camp 01121
ww
Camp
Comp
camp
Comp
DCb
DCb
DCb
w
'ww
44655
01121
01121
01121
01121 EB
79727 CFE79727 CFE79727 CFE-
31637
'44655
DCb 79727
Comp
01121
DCb 79727
CEC, T-9
R113-9.76K
RP44-500
R113-976
RP44-1K
CF.A
CEC, T-9
RS-5
EB
4400
EB
EB
EB
R88-37.4
R113-1M
R4A-500
Rl-100K
R92-1.5K
Rl-820
Rl-220
Rl-47K
Rl-8.2K
,15
15
15
R12-16.67K
R12-15K
R12-3K
RS-5 R4A-.1.5
4400 R92-330
CFE-15 R12-560
EB
Rl-1OK
CFE-15 ,Rl2-300 *
*Nominal value, factory Set.'
096GR'
51
,
Page 28
'REPLACEABLE PARTS MODEL 661 DIFFERENTIAL VOLTMETER
. :
Circuit
Desig. Value RatFng
R6016
R6017
R6018
RGd19
R6020
R6021
R6022
. .
3.3 kn
1.2 ko
10 k-2
4.7 kn
200 n
3 k~
600
n
lO%, l/2 " Comp
lO%, l/2 w Comp
lO%, l/2 w Comp
lO%, l/2 " Comp
l%, l/2 w
l%, l/2 w
l%, l/2 w
iircuit
Desig.
94001
Q4002
Number
.2N963
2N706
Q4003 2N2951
Q4004
2N2951
RESTSTORS (cont'd)
Mfg.
'We
Code Part No. Part No. Ref.
01121
01121
01121
01121 EB
DCb 79727
DCb
DCb
79727
79727 CFE-15 R12-600
TRANSISTORS
Mfg.
Code
01295
i6331
16333 TG-26
16333
. .
Mfg.~
Keithley
,' EB Rl-3.3K
EB Rl-1.2K
EB
Rl-1OK
Rl-4.7K
CFE-15
R12-200
CFE-15 Rl2-3K
Keithley
Part No.
TG-27
TG-28
TG-26
Fig.
Fig.
Ref.
Q6001.
46002
Q6003
46004
46005
96006
46007
96008
Q6009
Q6010
Circuit
Desig.
VlOOl
v1002
v2001
; 1
2N2270
2N2270
Al294
Al294
2N1535
2N1183 02735
2N1381
2N1381 01295
2N1381 01295
2N1381 01295
95303
95303
73445
73445
.04713
01295
TG-25
TG-25
TG- 29
TG- 29
TG-7
TG-11
TG-8
TG-8
TG-8
TG-8
, Keithley
Number
7025
73445
Part No.
EV-7025
6ckl8 Oobll EV-6cM8
12AU7
73445
.
EV-12AU7
Fig.
Ref.
' .
v3001
V3002
v3003
7025
7025 ~,
7025
*Nominal value, factory set.
52 '
73445
73445
73445
EV- 7025
EV- 7025
m-7025
b.
0966R
Page 29
-. ‘i
Cxrcuit
Desig.
Number
VACUUM TUBES (Cont'd)
Mfg.
Code
-
Keithlcy Fig.
Part No.
Refi
.-
v3004
v3005
v400
1
6C1.16
OG3
7586.
.
.
(Refer to Schematic Diagram 16321B for circuit designations)
.
00011 :
73445
86684 W-7586
MODEL 6601A REPLACEABLE PARTS LIST
:TERMINALS
Circuit
Desig.
.~.----_.
Jl'O 1
-I
Description
Receptacle, hn modified
Plug, hn, Mate of JlOl, Mil No. UG-SVA/U '.
(Mfg. No. 7908)
5102
Bind& Post, HI OUTPUT (Mfg. No. DF31RC)
5103 Bind.ing Post, LO OUTPUT (Mfg. No.. DF3lBC)
RESISTORS
Circuit
Desig. Value Rating
.
RlOl
R102
.R103
R104
R105
'2Mfl
2MI-l
2Im
2Mn
2
Mn
O.l%,lw. Ww 54294
O.l%, 1 w
O.l%, 1 We
O.l%, 1 w
O.l%, 1 'w ww
Type
ww
ww PllG
ww
Ev-
6CM6
EV-OG3
---
Mfg.
Code
'Keithley
Part No.
80164 . cs-79
91737
58474
58474
Mfg. Mfg.
CS-80
BP-8R-
BP-8B
Keithley Fig.
Code Part No. Part No.
Pi16 R91-2M
54294
54294
54294
54294
,PllG R91-2M
R91-2M
PllG R91-2M
P116 R91-2M
-_
I
Fig.
Ref.
Ref.
R106
'R107
200
n
100 n 0.1% 1 w ww
R108 ,'cl kn
*Nominal value, factory set.
or~~~~~~~-,~~~~~-~~.~.~~~=~~=,-~-~ svm;n=u;i-J0011
Sylvania Elfctric Products, IX.
Buffalo,Operations of Sylvania, Milwaukee; Wis.
Electronic Systems
Buffalo, N. Y.
. .*
0656
1IT:IT'i7?;2: .I -D.,.~,~.-u=:3 :~._.<.. .-..jrT~
Aerovox'Corp.
New Bedford, >lass.
TABLE 2 (Sheet 1).
for Elanufacturers, Cataloging Handbook 114-l.)
096GR
. .
lO%, 2 w
l%, l/2 w DCb
,-.,.... ~_.,~ =,-. C.CI-I.-.
I_. _L. __-...
Code, List of
Susyested >lanuEacture.rs.
Wwvar
71450 AW RP3-200
54294 P-36
'79727
CFE-15 R12-1K
-meTz.rsnn
R90-100K .
--1..
-x.&pLpT..~y
01121 Allen-Bradley Corp.
01295. +exas Instr&ents, Inc.
Transistor Products Division
Dallas, Texas
(6
.,',
ased
- .
on,Fedcral Supply C~d~3
)I
53
I
. ..--~~~.INTX~~~=~2--~~~.~.~~.~~~.~,~~~..~iiZ:,i __. -.;~,~ii ~.~ii.,/ _,-
.
I
‘I
Page 30
REPLACEABLE PARTS
. . .
MODEL 661 DIFFERENTIAL VOLTMETER
..,.
11686 RCL Electronics, Inc.
Riverside, N. J.
3794'2 Mallory, P. R., and Co., Inc.;'
Indianapolis, Ind.
31884 Dearborn Electronic Laboratories, Inca. 44655 Ohmite Mfg. Co.
Orlando, Fla.
32735 Radio Corp. of America
Commercial Receiving Tube and
53021 Sangamo Electric Co'.
Skokie, Ill.
Springfield, 111.~ c
Semiconductor Division
Somerville, N. J.
54294 Shallcross Mfg. Co.
Selma, N. C.
Cl4713 Motorola, Inc.
Semiconductor Products Division
Phoenix, Arizona
05079 Transistor Electronics, Inc.
Bennington, Vt.
05397 Union Carbide Corp.
Linde Division
Kemet Dept.
56289 Sprague Electric Co.
North Adams, Mass.
58474 Superior Electric Co., The
Bristol, Corm.
71400 Bussman Mfg. Div. of
McGraw-Edison Co.
St,. Louis, MO.
Cleveland, Ohio
71450 CTS Corp.
07716 International Resistance Co.
Elkhart, Ind.
Burlington, Iowa
71590 Centralab Division of
08520 Electronic Devices, Inc.
North Ridgeville, Ohio
Globe-Union, Inc.
Milwaukee, Wis.
08804 Lamp Metals and Components
Department G. E. Co.
.72982 Erie Technological Products, Inc.
Erie, ?a.
Cleveland, Ohio
73445 Amperex Electronic Co. Division of
12697 Clarostat Mfg. Co., Inc.
Dover, N. H.
North American Philips Co., Inc.
Hicksville, N. Y.
12954 Dickson Electronics Corp. 74970 Johnson E F Co.
Scottsdale, Ariz. Waseca, Minn.
13050 Potter Co.
75042 International Resistance Co.
Wesson, Miss. Philadelphia, Pa.
14655 Cornell-Dubilier Electric Corp.
75915 Littelfuse, Inc.
Newark, N. J. Des Plaines, 111.
16333 Motorola Inc. 79727 Cbntinental-Wirt Electronics Corp.
Solid State System Division
Philadelphia, Pa.
Phoenix, Ariz.
80164, Keithley Instruments, Inc.
24655 General Radio Co.
..West Concord, Mass. ,: : " :,. " ~,
Is
TABLE 2 (Sheet 2)
for Manufacturers
Code List of Suggested Manufacturers.
Cataloging Handbook H4-1.)
:
Cleveland, Ohio i
r
(Based on Federal Supply Code
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a
54
0966R
Page 31
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80294 Bourns Laboratories, Inc. 91637 Dale Electronics, Inc. . ,.-I..
Riverside, Calif.
64171 Arco Electronics, Inc. 91737 Gremar Mfg. Co., Inc.
Great Neck, N. Y.
66684 Radio Corp. of America 93656 Electric Cord Co.,
.Electronic Components and Devices
Harrison, N. J.
,
.
95303 RCA Electron Tube Division
91407 Superior Electric Co., The
Oak Park, Ill. Cincinnati, Ohio
Columbus, Nebr.
Wakefield, Mass.
Caldvell, N. J.
of Radio Corp. of America
:
TABLE 2 (Sheet 3).
Code List of Suggested Manufacturers. ,(Based on Federal 'Supply Code
for Manufacturers, Cataloging~Handbook 114-l.)
.
0966i
Page 32
i ’
Page 33
.,.
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