Tektronix 630 Instruction Manual

INSTRUCTION MANUAL

MODEL 630

POTENTIOMETRIC ELECTROMETER

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 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 Cleveland factory,

DDD 216-248-0400. You will be given assist-

ance and shipping instructions.

REPAIRS AND RECALIBRATION

Keithley Instruments maintains a complete re­pair service and standards laboratory in Cleve­land, and has an authorized field repair facility
in Los Angeles and in all countries outside the
United States having Keithley field repre­sentatives.

To insure prompt repair or recalibration serv­ice, please contact your local field representa­tive or the plant directly before returning the
instrument.

Estimates for repairs, normal recalibrations,
and calibrations traceable to the National Bu-

reau of Standards are available upon request.

MODEL 630 POTENTIOMETRIC ELECTROMETER

TABLE OF CONTENTS

CONTENTS

section

GENERAL DESCRIPTION . . . . . .

1.

1-L.
1-2.
1-3.
l-4.
1-5.
1-6.

2.

OPERATION . . . . . . . . . . .

2-l.

Description . . . . . .

Operating Modes . . . .

Applications. . . . . .

Specifications. . . . .

Accessories . . . . . .

Equipment Shipped . . .

Front Panel Controls

and Terminals . . . .

2-2.

Rear Controls and

Terminals . . . . . . .

2-3.
2-4.
2-5.
2-6.

Preliminary Procedures. .
Operating Procedures. . ,

Recorder Output . . . . ,

Effective Input Resis-

tance . . . . . . . . .

2-7.

Null Sensitivity and

Source Resistance . . .

2-8.
2-9.

3.

CIRCUIT DESCRIPTION . . . . . .

3-1.
3-2.
3-3.
3-4.
3-5.
3-6.

AC Effects on Measurement

Current Measurements. . .

General . . . . . . . .

Reference Voltage Supply.

Kelvin-Varley Divider . .

Null Detector . .

Oscillator. . . . .

Guarding . . . . .

.
.

.
.

.
.
.

.

. . 5

. . 5
. . 6
. . 6
. . 9

. . 9

. . 11
. . 11
. . 11

. . 13

. . 13

. . 13

. . 14

. . . . .

. . . . .

. . . . .

Page

.
.

.
.

.
.
.

.

14

15
16

1
1

1

2
2
3
3

5

Section Page

CALIBRATION . . . . . . . ., . . 21

5.

5-l.

5-2.
5-3.

General . . . . . . . . . . 21

Calibration Schedule. . . . 22

Kelvin-Varley Divider . . .

Verification. . , . . . . 22

5-4.

Input Divider Calibration . 23

5-S. Range Calibration , . . . . 23

5-6.

Reference Voltage Supply

Stability Test , . . . . 26

5-7.

6.

ACCESSORIES . . . . . . . . . , . 35

6-1.
6-2.
6-3.
6-4.

Oscillator Adjustment . . .

27

Model 6301 Guarded Probe. . 35

Rack Mounting . . . . . . . 35

Placing in Rack . . . . , . 36

Model 6013 pH Electrode

Adapter . , . . . . . . . 37

REPLACEABLE PARTS , . . . . . , . 39

7.

7-l. Replaceable Parts List. . . 39

7-2.

How to Order Parts. . . . . 39

Model 630 Replaceable

Parts List. . . . . . . . 40

Model 6302 Replaceable

Parts List. . . . . . . 48

Model 630 Schematic Diagram

1826lE . . . . . . . . . 51

Green Repair and

Calibration Form . . . . . 53

,4.

SERVICING . . , . . .
4-l.

4-2.

4-3.
4-4.
4-5.

General . . . . . .

Servicing Schedule.
Parts Replacement .
Troubleshooting . .
Adjusting Grid Bias

Cathode Follower.

4-b.

4-7.

4-a.

0 168il

Zener Diode Replacement . . . 20

Meter Adjustment . . . . . . 20

Adjusting Quadrature Control. 20

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

of

. . . . .

17

17
17
17
17

19

*Change Notice . . . . . . . . . . . Last

Page

*Yellow Change Notice sheet is included
only for instrument modifications affect-

ing the Instruction Manual.

MODEL 630 POTENTIOMETRIC ELECTROMETER

GENERAL DESCRIPTION

SECTION 1.

l-l.

potentiometer, It measures from 300 millivolts to 500 volts dc with 0.01% limit of error

from source resistances as high as lOlo ohms,

The upit need not be constantly calibrated or manually restandardized for a full year;

the limit of error is specified for one year.

in ut resistance of 1013 ohms,

10 5 ohms at 1% off null and to infinite resistance at null.
put resistance , .the Model 630 draws an absolute minimum of current to avoid loading and
polarizing the source.

lighted decimal points; one-volt,
ranges except the l-millivolt; input polarity switch;
off chassis ground; better than 60 db line-frequency rejection on the l-millivolt range.

Also, full guarding minimizes leakage problems.

l-2. OPERATING MODES. The Model 630 can be used as a five-dial potentiometer or as a

vibrating-reed electrometer.

500 volts full scale with *O.Ol% limit of error and from 1 millivolt full scale to 300

millivolts within 30 microvolts.
measure from 1 millivolt full scale to 500 volts within 23% full scale.

DESCRIPTION
The Keithley Model 630 Potentiometric Electrometer is a convenient, self-contained

a.

Using the guarded, vibrating-reed null detector,

F"'

Features for convenient use include:

c.

on the l-millivolt to l-volt ranges, increasing to over

one-milliampere output for full-scale deflection on all

As a potentiometer,

As a vibrating-reed electrometer, the Model 630 can

GENERAL DESCRIPTION

and below 300 millivolts within 30 microvolts.

the Model 630 has a minimum (slewing)

With this extremely high in-

5 in-line readout dials with automatically

floating operation up to 500 volts

it can measure from 300 millivolts to

1265R

FIGURE 1.

Keithley Instruments Model 630 Potentiometric Electrometer.

1

GENERAL DESCRIPTION

MODEL 630 PO'TENTIOMETRIC ELECTROMETER

l-3.

APPLICATIONS.
Due to its very high input resistance,

a.

the Model 630 is very useful in making accur­ate dc measurements from high resistance sources frequently encountered in electrochemical
and physical-chemical research.

It is especially useful for measuring potentials from
piezo-electric crystals, electro-chemical cells, grids and plates of tubes, biological
cells and pH electrodes.
fuel-cell studies,

silicon resistivity and capacitor charge measurements, and for mrasur-

The Model 630 is also ideally suited for making Hall-effect and

ing gate potentials of field effect transistors.

The null-detector output permits use with potentiometric recorders and digital volt-

b.

meters equipped with automatic print-out.
duct development,

inspection and production.

The Model 630 is

useful

in quality control, pro-

l-4. SPECIFICATIONS.

AS A POTENTIOMETRIC ELECTROMETER:

LIMIT OF ERROR:

ute warm-up.

LONG-TERM STABILITY:
TEMPERATURE COEFFICIENT:

?O.Ol% of reading or 30 microvolts, whichever is greater, after 30-min-

Accuracy is exclusive of null-detector drift.

Will operate within stated limit of error for one year.

Does not exceed 0.001% per OC.

REPEATABILITY:

MAXIMUM NULL SENSITIVITY:

INPUT RESISTANCE:

Within 0.0025% or 30 microvolts, whichever is greater.

1 millivolt full scale with 30-microvolt resolution.

Infinite at null, from 0 to 500 volts.

0 to 500 volts with DETECTOR INPUT Switch in OPEN position.

FLOATING OPERATION:
INPUT ISOLATION:

500 volts maximum off chassis ground.

Circuit ground to chassis ground: 108 ohms shunted by 0.05 microfarad.

AS A VIBRATING REED ELECTROMETER:

VOLTAGE RANGES:

NULL RANGES:

INPUT RESISTANCE:

O-5 volt full scale to 500 volts in four decade ranges.

1 millivolt full scale to 100 volts in six decade ranges.

1013 ohms or 1010 ohms selectable by switch, L-millivolt to l-volt

ranges; 1010 ohms, 5 to 500-volt ranges.
ELECTROMETER ACCURACY:
ZERO DRIFT:

Less than 2 millivolts per 24 hours after Z-hour warm-up.

f3% of full scale on all ranges, exclusive or noise and drift.

non-cumulative.

10 15

ohms at.l% off null frop

Long term drift is

RISE TIME (10% to 90%): Less than 2.5 seconds on any range with 1010 ohm source resistance.
LINE-FREQUENCY REJECTION:

Greater than 60 db on the l-millivolt range, decreasing to 35

db on the 500-volt range.

2

1067R

MODEL 630 POTENTIOMETRIC ELECTROMETER

GENERAL CHARACTERISTICS:

GENERAL DESCRIPTION

LINE STABILITY:

Better than 5 ppm for 10% change in line voltage.

RECORDER OUTPUT:

output:

1 volt, 1 milliampere for full-scale meter deflection on all ranges except on

l-millivolt range, where it is 10% less.

Noise:

30 microvolts peak-to-peak referred to input up to 1 cps.

Note: Recorder used must have fully isolated input, lOlo ohms minimum to ground.
POLARITY: Positive or negative, selectable by switch.
CONNECTORS: Input:
POWER:

105-125 or 210-250 volts (switch selected); 50, 60 or 400 cps; 50 watts.

DIMENSIONS, WEIGHT:

Special Triaxial. output: Banana jacks.

5-l/2 inches high x 17-l/2 inches wide x 13-l/2 inches deep; net

weight, 24 pounds.
ACCESSORIES SUPPLIED:

Model 6302 Input Cable consisting of a mating plug and 3-foot

triaxial cable.

l-5.

more conveniently.

ACCESSORIES.

Model 6301 Guarded Probe with 3-foot connecting cable allows measurements to be made

a.

Using the Probe does

not

affect any Model 630 specification.

Model 4000 Rack Mounting Kit, containing two brackets and a top cover, converts the

b.

Model 630 to fit standard 19-inch racks. Rack mounted,

the Model 630 is 5-l/4 inch&s

high x 19 inches wide x 13-l/2 inches deep. Section 6 has assembly instructions.

C. Model 6013 pH Electrode Adapter,which has a Z-foot cable and triaxial connector,

accepts Leeds & Northrop and Beckman pH electrode connectors.

The Adapter allows accurate

and convenient,pH potential measurements with the Model 630.

l-6.

EQUIPMENT SHIPPED. The Model 630 Potentiometric Electrometer is factory-calibrated
and is shipped with all components in place. All units are shipped for bench use. Model
4000 Kit may be ordered for rack mounting;
The shipping carton also contains the Instruction Manual and the Model 6302 Mating

refer to Section 6 for assembly instructions.

Connec-

tor with 3-foot triaxial cable.

016GR

3

OPERATION

s303

?4ODEL 630 POTENTIOMETRIC ELECTROMETER

Reference Voleage Dials

5304

s305

S-306 It381

-

DETECTOR INPUT

Swirch (5102)

Receptacle

FIGUKlc L.

.JlOl

5103 5104

Switch

(S101) (R122)

I'W~~L OJU rronr: .raneL wncrols and Terminals.

CO"tL-01

Replaceable Parts List and schematic diagram.

Switch

(5104)

SwFtch
(5301)

The designations refer to the.

4

FIGURE 3. Model 630 Rear Panel

Controls

and Tarminzlr.

1265

MODEL 630 POTENTIOMETRIC ELECTROMETER

OPERATION

SECTION 2.

2-1. FRONT PANEL CONTROLS AND TERMINALS.

a.

polarity.

POLARITY Switch.

The Switch reverses the polarity of the internal rc,Ccrcncc voltage supply so

The POLARITY Switch turns the instrument on and sclccts

OPERATION

(See Figure 2).

the

input

both positive and negative voltages may be measured; it does not reverse the meter polar-

ity.

DETECTOR INPUT Switch.

b.

A 3-position toggle switch allows selection of

the

Model

630 input resistance and also allows checking the meter zero.

1) Setting the Switch to 10 10 OIIMS sets the input resistance at 1010 ohms for all

ranges.

Setting the Switch to OPh'N sets the input resistance at 1013 ohms for the l-milli-

2)

volt through l-volt ranges.

The input resistance remains

at

1010 ohms for the ranges

above 1 volt.

3) Setting the Switch to ZERO CK internally disconnects the input from the vibrating

capacitor and shunts the capacitor to the amplifier low. This allows meter zeroing on

any range without removing the input signal.
'c . NULL Switch.

ranges from 1.0 millivolt full scale to 100 volts.

The NULL Switch sets the null detector sensitivity for six decade

When the Switch is in the VTVM posi-

tion, the Model 630 operates as a vibrating-reed electrometer for the four ranges of the

RANGE Switch.

RANGE Switch.

d.

0.5, 5, 50 and 500 volts full scale.

Varley divider and the position of the decimal point light

The RANGE Switch adjusts the sensitivity of the VTVM in four steps:

It also determines the voltage acrws the Kelvin-

- which also serves as a pilot

light - between the five Reference Voltage Dials.

Reference Voltage Dials. Five in-line dials at the top of the front panel set the

e.

reference voltage when the Model 630 is used as a potentiometer.

have decade steps as indicated on the dial.

METER ZERO Control. The METER ZERO Control adjusts the meter needle to zero. The

f.

The last dial is continuously adjustable.

The first four switches

Control allows precise meter zeroing on all ranges when the DETECTOR INPUT Switch is set

to ZERO CK.

Input Terminals. The Model 630 uses a special triaxial receptacle for its INPUT

g.

Receptacle.

Model 6302 Input Cable.

The Control has a. range of approximately 120 millivolts.

The Receptacle is similar to a bnc connector, but requires using the furnished

Using a standard bnc conmctor could damage the INPUT Receptacle.

A set of binding posts marked LO and GND is provided for grounding the LO input terminal

to the chassis when desired.

The LO terminal and the shell of the triaxial INPUT Recep-

tacle are internally connected.
2-2.

a.

REAR CONTROLS AND TERMlNALS.
Fuse.

For LOS-125 volt operation, the Model 630 uses a l-ampere 3 AG fuse.

(See Figure 3)

210-250 volt operation, the Model 630 uses a 0.5-ampere 3 AG fuse.

0166R

For

5

OPERATION

MODEL 630 POTmTIOMETRIC ELECTROMETER

Power Cord.

b.

less otherwise specified on the rear panel.
3-prong plug provides a ground connection for the cabinet. A 3:2 prong adapter is provi­ded.

NULL DETECTOR OUTPUT.

C.

null detector.

COARSE ZERO Switch.

d.
tact potential of the vibrating-reed capacitor.
ten ZO-millivolt steps.

117-234 Switch.

e.
or 234volt ac power lines.

2-3.

power cord.

PRELIMINARY PROCEDURES.
Check the 117-234 Switch and the Fuse for the proper ac line voltage. Connect the

a.

Set the Model 630 front panel controls as follows:

b.

DETECTOR INPUT Switch
RANGE Switch
NULL Switch VTVM

Reference Voltage Dials

The Model 630 is designed for a 105-125 volt, 60-cps line source, un-

The 3-wire power cord with the NEMA approved

A screwdriver adjustment is provided for bucking out the con-

The screwdriver-operated slide switch sets the Model 630 for 117

POLARITY Switch

Two terminals, marked + and -,

The Switch has a i-100 millivolt span in

ZERO CK
500

-I.
ZWXJ

supply a dc signal from the

The decimal light between the third and fourth Dials will light. Allow the instrument
to'warm up 30 minutes to meet the specified accuracy on all ranges.

Set the NULL Switch to 1.0 MV.

c.

mally, using the COARSE ZERO Control on the rear panel is not necessary. Return the
NULL Switch to VTVM.

Check meter zero periodically.
per day,

DETECTOR INPUT Switch to ZERO CK disconnects the input signal source from the
instrument, avoiding polarization.

2-4. OPERATING PROCEDURES,

The Model 630 is used first as a voltmeter to determine the approximate value of

a.
the unknown voltage.
to 10.01%.

Vibrating capacitors are extremely sensitive to shock and vibration. when

making a measurement,place the Model 630 on a vibration free, rigid structure

or on some material which will minimize vibration.
the input cable and any attached circuitry; any cable flexure will generate
electrostatic charges which the Model 630 will detect.

which will cause inaccuracies in continuous readings.

It is then used in the potentiometric mode to determine the voltage

Zero the meter with the METER ZERO Control.

Null detector drift can be up to 2 millivolts

Setting the

It is not necessary to disconnect the input.

Also,

tightly tie down

Nor-

6

L265R

MODEL 630 POTENTIOMETRIC ELECTROMETER

OPERATION

FIGURE 4.

measuring at ground and for floating.

In A, the unknown voltage has one terminal at ground. The shorting Link is between

the LO and GND Posts of the Model 630.

In B, the unknown voltage has both terminals off ground potential. The floating or

off-ground potential must be less than 500 volts. Also note the shorting line is pe&

used.

The Model 630's high input resistance allows circuit measurements without causing

b.
circuit loading. (See paragraph 2-6.) On the l-millivolt to L-volt null ranges, the in­put resistance can be set to 1013 er 1010 ohms with the DETECTOR INPUT Switch. Use the
OPEN (1013 ohm input) setting for high source resistances; use the LOLO OHMS setting to

avoid pickup problems or to increase response speed.

resistance is 1010 ohms for either setting.

When making measurements on devices with high contact resistances (such as

silicon), completely isolate the power supply from ground to avoid measuring
the drop acress the contact resistance.

c. Voltmeter Operating Procedures.

1.
at VTVM, the RANGE Switch determines one of four full-scale ranges.
Reference Voltage Dials at zero,
six null ranges.

Input Connections to Model 630. The two diagrams show the input circuit for

On ranges above 1 volt, the input

NOTE

Ten full-scale ranges are available for VTVM operation. When the NULL Switch is

By putting the five

the Model 630 can then operate as a voltmeter on the

Connect the unknown voltage to the INPUT Receptacle, using the Model 6302 Input

2.
Cable or the Model 6301 Guarded Probe.

lead to the LO Terminal.

Switch the RANGE Switch to the most sensitive range for an on-scale meter deflec-

3.

tion.

When using the guarded probe, use a separate

7

OPERATION

Potentiometric Operating Procedures.

d.

NOTE

Avoid large overload voltages on the null detector. No damage occurs even
with 500~volt overloads, but some open circuit offset will be caused in the
null detector.

Leave the RANGE Switch at the last setting used in the voltmeter operation. If

1.

the voltmeter reading is negative, reverse the POLARITY Switch position.

Set the first two Reference Voltage Dials to the first two digits of the unknown

2.

voltage found in the voltmeter operation.

When switching between the 50-volt and SOO-volt ranges and when changing the

POLARITY Switch, the meter will sometimes temporarily read off-scale.

due to transients introduced when the circuit is interrupted and it does not

indicate a faulty instrument.

The offset will disappear after about 5 minutes.

NOTE

MODEL 630 POTENTIOMETRIC ELECTROMETER

This is

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. Deflections to the

right indicate the voltage being measured
is more positive than the Reference Vol-

tage Dial setting.

NOTE

The most accurate resistors in the Kelvin-Varley divider are in the first
two Reference Voltage Dials. Therefore,
dings, use the first two dials as much as possible.

The value of the unknown voltage is read directly from the Reference Voltage Dials.

4.
The dial reading will be within the specified limit of error if the NULL Switch

a)

is at the most sensitive setting (Table 1) for the range used and if the meter indi­cates as close to null as possible.

b) When the first Reference Voltage Dial is used,

read to be within specifications (*O.Ol% of reading or 30 microvolts).

meter may be read as an approximation of a sixth digit,

RANGE

Switch
Setting Setting Setting

I

I

500 50 0.5 5v v v v 100 100 10 1.0 Mv v v v

I

TABLE 1. Recommended Model 630 Null Sen­sitivities and Settings.

to obtain the most accurate rea-

Initial

NULL Switch NULL Switch

only the five Dials need to be

Most Sensitive

1.0 1.0 10 1.0 Mv Mv Mv Mv

However, the

c) When the first Reference Voltage Dial is not used, read the voltage directly

from the remaining four dials.

d) Use the meter as a null indicator when balancing voltages. When the first Ref-

erence Voltage Dial is not used,

8

the meter approximates a fifth dial reading.

0166R

MODEL 630 POTENTIOMETRIC ELECTROMETER OPERATION

2-5. RECOFDER OUTPUT.

Recommended recorder for use with the Model 630 is the Keithley Model 370. Any re-

a.

corder used must be able to float 500 volts off ground and its input must be fully isolated

(1010 ohm minimum leakage resistance to ground).

before attaching the recorder, set all Reference Voltage Dials to zero. Disconnect

b.

The Model 370 meets these requirements.

the unknown voltage and short the Model 630 high input to the low. Set the NULL Switch

to 10 MV.

Connect the recorder to the OUTPUT Terminals on the Model 630 rear panel. The

370 Recorder mates directly with the Model 630 using the 3701 Cable.

Set the Reference Voltage Dials to 10 millivolts to apply an accurate lo-millivolt

c.
potential to the null detector on the lo-millivolt null range.
scale recorder output of 1 volt at 1 milliampere.
corder may load the Model 630 output. On this range,

On the l-millivolt null range, the re-

output resistance is 100 ohms.

This will provide a full-

To obtain accurate results and/or

d.

to

prevent ,damage to the instruments, the recorder

must be able to float off-ground with the Model 630. Leakage and pickup between the two

instruments should also be minimized.

The Model 370 meets these requirements.

NOTE

On the l-millivolt range there is a 10% loading error if the recorder draws

1 ma of current. Thus the output for full scale deflection will be .90 volt,
1 ma.

1. Make sure neither recorder terminal is grounded. Use a 3-wire grounded power line

for the recorder.

If a 2-wire line is used,

connect the recorder chassis and the Model

630 chassis with a separate lead.

2. Minimize all sources of leakage between the output terminals, the recorder and

ground. Use polystyrene or Teflon-insulated cable where possible. If the connecting

wires are shielded, connect the shield to the LO Post.

3. Avoid long leads between the Model 630 and the recorder.

Do not short either Model 630 output terminal to the case; this may damage the
Kelvin-Varley divider.

2-6.

EFFECTIVE INPUT RESISTANCE.
The Model 630 input resistance varies. It can be set either 1013 or 1010 ohms for

a.
the l-volt and lower ranges, and it is 1010 ohms for ranges above 1 volt.
are not the Model 630's effective input resistances.

higher due to the potentiometric principle of operation.

Its input resistance is considerably

When reference voltage (Refer-

ence Voltage Dial setting) is much greater than meter readings the value is

Ri* =

Rn( Ed )

Equation 1

v

Where Rin is the effective input resistance of the Model 630;

Ed is the setting of the Reference Voltage Dials in volts;

'Rn is the input resistance of the null detector in ohms;

V is the null detector meter reading in volts.

1067R

These, however,

9

OPERATION

To find the loading effect the Model 630 will have on a circuit, use Equation 1 to

b.

MODEL 630 POTENTIOMETRIC ELECTROMETER

compute its effective input resistance. At null, where V = 0, the input resistance is
infinite. Off null, the Model 630 input resistance is usually much greater than the
source resistance, and loading will not be enough to affect the measurement accuracy.

graph in Figure 6 shows the Model 630 effective input resistance for the l-millivolt to

l-volt null ranges with the DETECTOR INPUT Switch set to OPEN.

Note that the input resis-

tance for a reading 1.0% off null is 1015 ohms.

NOTE

The

For a ful.ler treatment of paragraphs 2-6 and 2-7,

Product Note,

0.6

zo.5
0

:,o.,
”

0.3

0.2

"The Effective Input Resistance of Potentiometric Voltmeters."

send for Keithley Instruments

0.L

18

FIGURE 6.

tance.

Model 630 Effective Input Res

The graph shows the effective input
resistance for the l-millivolt to l-volt
ranges when the DETECTOR INPUT Switch is
set to OPEN. Percent off null is 160 V/Ed

as defined in Equation 1.

10

~llrluw /. F,rrecr or xxlL^ce KeSlStnnCc on

Model 630 Null Sensitivity.

The graphs are

for the two null detector input resistance
settings.
in equation 2.

Ideally, V = Vs - Ed as defined

The graphs indicate the per­cent of the actual difference between the
source and reference voltages the meter

will indicate.

0266R

MODEL 630 POTENTIOMETRIC ELECTROMETER

OPERATION

2-7.

the Model 630 is less affected.
tiometric electrometer for accurate measurements from a high resistance source.

where V, is the source voltage in volts;

With no source resistance, the null detector meter will read exactly the difference be-

tween the reference voltage and the source voltage (V = V, - Ed).
resistance, the meter will indicate only a portion of the difference between the two

voltages.

ings for the Model ,630. The curves are the percent the meter reads the voltage differ­ence. At loo%, V = V, - Ed.
indication as an absolute value becomes insignif+cant regardless of source resistance.
For instance, if the Model 630 is 0.1 millivolt off null on the l-millivolt range and the

source resistance is such that the meter indicates only 10% of actual value, the metier
will be within -09 millivolt. At .Ol millivolt off null, the meter will be within 9
microvolts.

NULL SENSITIVITY AND SOURCE RESISTANCE.

Source resistance affects null sensitivity. Because of its high input resistance,

a.

The following paragraphs show the value of using a poten-

The equation below gives the relationship of the meter reading to source resistance:

b.

Equation 2

R, is the source resistance in ohms;
V is the nuli detector meter reading in volts;

Ed is the setting of the Reference Voltage Dials in volts;

R,, is the input resistance of the null detector in ohms

For increasing source

This discrepancy becomes more important the more off null a reading is.

Figure 7 contains graphs showing the effect source resistance has on off-null read-

c.

Note that as the Model 630 approaches null, the meter

NOTE

When the Model 630 is as near to null as possible, the Reference Voltage Dial

setting is always correct within the instrument's specified limit of error.

2-8. AC EFFECTS ON MEASUREMENTS. The Model 630 has greater than 60 db line frequency re-

jection on its l-millivolt range.

sitivity and cause needle quiver or a zero shift.
the input. The component values depend on the source resistance.

might be a 109 resistor and a lOO-picofarad capacitor.

only about two seconds to the rise time.

Use a larger R or C if rise time is not important.

capacitor or one with as good an insulation resistance to avoid degenerating the
input resistance.

2-9. CURRENT MEASUREMENTS.

a. When used with a high-value precision resistor,

trometer can be used to accurately measure currents as low as lo-13 amperes.

Greater line frequency pickup may reduce off-null sen-

To reduce this, use an R-C filter at

A good compromise

ohm source, this adds

With a

NOTE

Always use a polystyrene

the Model 630 Potentiometric Elec-

1010

The choice

0266R

11

OPERATION MODEL 630 POTENTIOMETRIC ELECTROMETER

of the shunt resistor depends upon the

current to be measured and the setting of
the Model 630 (Refer to Table 2).

Current measuring procedure:

b.

Shunt the Model 630 input with a
seikcted resistor R. (See Table 2 for
resistor values).

Set the Reference Voltage Dial Set-

2.

ting to zero and the DETECTOR INPUT
Switch to OPEN.

Switch the Model 630 sensitivity

3.
to the lowest.setting to obtain an on­scale reading.

4. The Meter reading is the voltage drop V across the shunt resistor R.

Use the Model 630 as a potentiometer and bring the meter to a null with the Re-

5.
ference Voltage Dials. Record the Reference Voltage Dial reading Ed.

Calculate the current I, using the equation,

6.

Current Range Shunt Resistor NULL Setting

in amperes in ohms

10-13
10-13
10-12
10-12
10-12
10-11

I

10-11 10-11 10-11

TABLE 2.
Use in Current Measurements.

Recommended Shunt Resistors for

10 10

1011

109

1010
1011
108

109 1010 1011

in millivolts

1
10
1
10
100

1
10
100

1000

I

I, =-

where I,

c.
the above procedure is followed.
of measurement may be *4% plus the accuracy of the shunt resistor.

calculate the current to compensate for the loading effect of the shunt resistor.

is the current to be measured in amperes;
R is the shunt resistance in ohms;
V is the meter reading (from step 4 above) in volts:

Ed is the setting of the Reference Voltage Dials in volts.

It is recommended that shunt resistors no larger than 1011 ohms be used
a larger resistor the response is extremely slow.
enough

The accuracy of the measurement is i3% plus the accuracy of the shunt resistor, if

to

affect accuracy may not show up immediately due to the slow response.

However, when using a 1011 shunt resistor the accuracy

1

R

NOTE

(-

Ed v

Ed - V

An offset which 1s largFth

It is necessary to

.

12

0266R

MODEL 630 POTENTIOMETRIC ELECTROMETER

CIRCUIT DESCRIPTION

3-1. GENERAL.

SECTION 3.

The Model 630 Potentiometric Electrometer measures voltage by the potentio-

CIRCUIT DESCRIPTION

metric (null) method. The variable known voltage is an ultra-stable 500-volt reference
supply used in conjunction with a precision 5-dial Kelvin-Varley divider.

Electronic

referencing of the 500-volt output to a zener diode standard maintains the reference sup­ply's stability and accuracy. This method eliminates repeated manual standardization.
The difference between the divider output and the unknown voltage is indicated by the
null detector,
directly from the in-line dials of the Kelvin-Varley divider.

a vibrating-reed electrometer.

At null the unknown voltage can be read

The input and null detector

are fully guarded to avoid leakage.

NOTE

_.__ -_ __ l_..l...-__ - 1_1o ^-...

GUARDED,

VIBRATING-REED

NULL DETECTOR

INPUT

__-__- __.^ _~ _^..... -.

KELVIN-VARLEY

Guard

..,..,.. ..^. .

5.DIAL

DIVIDER

REFERENCE

VOLTAGE

SUPPLY

500 v

SUPPLY

Zener

Reference

Simplified Model 630 Circuit Diagram.

3-2.

FIGURE 8.

REFERENCE VOLTAGE SUPPLY.

Unregulated voltage from transformer T201 is rectified by a silicon half-wave
reziifier, D301, and is filtered by capacitors C302 and C303A.
to the regulator series pass tube, V3004.

Regulator tube V3005 is used to keep the

The voltage then is applied

screen of V3004 at a constant potential.

To obtain a stable, accurate voltage,

b.

divider network of wirewound resistors, R325 to R330.

justed with potentiometer R327 to better than 0.01%.

the 500-volt output of V3004 is sampled by a

The divider network ratio is ad-

Light modulator E302 compares the
sample voltage from the divider network to the voltage across zener diode, D302. Any dif­ference between the

amplifier, V3001.

two

voltages is chopped by E302 and amplified by a 2-stage ac-coupled

'L"ne amplified output of V3001 is converted to a dc signal by light
modulator ~301 and then is amplified by the two-stage differential dc amplifier, V3002
and V3003.

1165

The amplifier output is applied to the grid of the series tube, ~3004, to

13

CIRCUIT DESCRIPTION MODEL 630 POTENTIOMETRIC ELECTROMETER

nullify input variations.

The temperature-compensated zener diode, D302, is used as the basic reference since

c.

typical variations are limited to less than 20 ppm per year and 5 ppm per oC.

Capacitor C305 is used in the ac feedback circuit.

Thus, a

highly stable reference which eliminates manual standardization is provided with respect

to both time and temperature.

The regulated 500-volt output of V3004 is either applied directly to the Kelvin-

d.

The zener diode will also withstand shock and vibration.

Varley divider or it is divided to 50, 5 or 0.5 volts by very stable wirewound resistor
networks. The RANGE Switch, S104, determines which network is used.

The 50-volt range
divider consists of resistors R333, R334, and R335; the 5-volt, or R333, R337 and R338;
and the 0.5-volt of R333, R339 and R340. Using potentiometers R334, R337 and R339
accurately sets the voltage division on each range.

3-3. KELVIN-VARLEY DIVIDER.

The Kelvin-Varley divider precisely divides the reference voltage for nulling an

a.
unknown voltage. It is, in effect, a constant input impedance decade potentiometer, con­sisting of resistors R341 through R381.

The resistors within each decade are matched;

the decades are matched for each instrument.

Each decade of the Kelvin-Varley divider, except the first, R341 through R346,

b.

parallels two resistors of the preceeding string.

Between the two contacts of the first
Reference Voltage Switch, S303, the total resistance is 40 kilohms (80 kilohms in paral­lel with the 80 kilohms total resistance of the four remaining strings).

With the RANGE

Switch set at 500, 100 volts dc will appear across the contacts of Reference Voltage
Switch S304, 10 volts across S305,

1 volt across 5306, and 0.1 volt across R381.

3-4.

The input signal is attenuated,
a specially constructed capacitor,

NULL DETECTOR.
The Model 630 uses a null detector which has a vibrating capacitor at the input.

a.

if necessary, and filtered. This signal is modulated by

VClOl, having one stationary plate and one moveable

plate. The signal is then amplified and applied to the meter.

b. Input resistance is greater than 1013
OPEN for the l-millivolt through l-volt ranges.
input signal is attentuated by resistors RlOl through R104.
input resistance is a constant lolo ohms.

ohms when the DETECTOR INPUT Switch is

set

For null ranges greater than 1 volt, the

Therefore,

above 1 volt, the

To maintain high resistance, switching with

the DETECTOR INPUT Switch (SlO2) is done using reed relays, KlOl to K103.

c. The null detector has full-scale sensitivity from 1 millivolt

volt, resistors RlOl through R104 divide the input by a 5OO:l ratio.

to

1 volt.

The full-scale

Above 1

sensitivity is determined by which of six feedback resistors, R147 through R152, is in

the circuit.

nents.

A twin-T filter, tuned for 94 cps, is connected between the plate and grid of

tube V1002.

negative feedback for frequencies other than 94 cps.

An R-C filter - R107 and capacitor Cl01 - decreases the ac input compo-

The filter, consisting of R130, R132, R133, CllO, Cl11 and C112, provides

The vibrating capacitor, VClOl, is

driven at 94 cps to further minimize ac pick-up effects.

The vibrating capacitor VClOl converts the difference between the input signal and

d.
the Kelvin-Varley divider output into an ac voltage, which is amplified by tubes VlOOl,
V1002, and half of V1003. The amplified voltage is demodulated by a bridge, diodes ~106
through D109,

and filtered by resistor R144 and capacitor Cl21.

The dc voltage is fed

to

14

0166R

MODEL 630 POTENTIOMETRIC ELECTROMETER

through a cathode follower, half of tube V1003, and drives the meter.

VClOl has a moveable plate driven by an electromagnet which varies the distance

1.
between the two plates. Since the capacitance varies in inverse proportion to the dis­tance between the plates,

If a charge is placed on the capacitor its value is

2.

a time varying capacitance is produced.

CIRCUIT DESCRIPTION

Q = CE

where Q is the charge;

C is the capacitance;
E is the wltage across the capacitor.

In terms of the voltage, the equation becomes E = Q/C. If Q is constant and C varies
periodically,,E must also vary. Therefore, an ac voltage which is proportional to the

magnitude of the input voltage will be produced.

Resistors R147 through Rl52 form the feedback network, which divides the output

e.

voltage for all voltmeter and null ranges except the 500-volt and l-volt ranges.

output is fed back for these two ranges. The feedback voltage is returned to the low
end of the vibrating capacitor to provide stability.

The Model 630 uses a "driven guard" at its input:

f.

applied to the second conductor of the input cable. The potential between the input high

and low is the difference between the applied and feedback voltages.

capacitance charges only to the difference between the two voltages. This reduces the
effect of cable capacitance,

The zero-control network consists of a 1.35-volt mercury battery, BlOl, and resis-

g.

tors R109 through R123.

volts in 20-millivolt steps.

millivolt span.

providing faster response speed.

The rear panel COARSE ZERO Switch,

The front panel METER ZERO potentiometer, R112, has a 220

the feedback voltage is also

Therefore, the cable

S103, has a span of Cl00 milli.

Equation 3

Total

h. The recorder output is developed across the top end of meter MlOl. It is one volt
for a full-scale meter deflection for all ranges above 1 millivolt. However, using a re­corder with a l-milliampere movement reduces the output to 0.9 volt on the l-millivolt
range since the output impedance is 100 ohms on this range.

3-5. OSCILLATOR.

The oscillator drives the vibrating capacitor and bridge demodulator and supplies

a.
the filament voltage for ,tubes VlOOl and V1002.

The output of transistor Q203,

b.
to zener diode D207. Any voltage difference is amplified by transistors Q235 and Q206,
operating as a differential voltage amplifier.
istors 4204, Q202, and 4201 and applied to the regulator, Q2U3.

A dc-to-ac converter forms the voltage to drive the vibrating capacitor, VClOl, and

c.

the bridge demodulator, diodes D106 through D109.

ing network to supply an interrupted dc voltage to transformer T202.
from the transformer supplies feedback to the network to sustain switching action.

sistor R213 determines the feedback magnitude.

0166R

connected as a regulator, is divided and compared

The signal is further amplified by trans-

Transistors Q207 and Q208 form a switch-

An extra winding

Re-

15

CIRCUIT DESCRIPTION

MODEL 630 POTENTIOMETRIC ELECTROMETER

3-6. GUARDING. Guarding is accomplished by floating the null detector and the input
circuitry at a voltage equal to the input voltage from a low impedance source.

This full
guarding eliminates leakage between the input terminal and ground. Such leakage in an
unguarded circuit is difficult to avoid, under laboratory conditions, and can result in
sizeable errors.
of 108

ohms will introduce 1% error. A guarded circuit eliminates this element of error.

For example, in an unguarded circuit with a 1-megohm source, leakage

16

OL66R

MODEL 630 POTENTIOMETRIC ELECTROMETER

SERVICING

SECTION 4.

4-1. GENERAL. Section 4 contains the maintenance and troubleshooting procedures for the

Model 630. Follow these procedures as closely as possible to maintain the accuracy and

stability of the instrument.

4-2. SERVICING SCHEDULE.
care required of high-quality electronic equipment. No part should need replacement un­der ordinary use except a pilot lamp, fuse or, occasionally, a vacuum tube.

4-3. PARTS REPLACEMmT.

The Replaceable Parts List in Section 7 describes the electrical components in the

a.
Model 630. Replace components only as necessary, and use only reliable replacements
which meet the specifications.

Replace resistors within any one of the first three Kelvin-Varley divider decades

b.
only as an assembly.
tors R341 to R368.
and resistors R329 and R330 are also parts of assemblies.
part number (see Section 7) and replace all resistors in the assembly.
portance in maintaining power supply stability,
Instruments, Inc.,
replace the zener.
Instruments, Inc.,

Refer to the Replaceable Parts List for the part number for resis-

Resistors R325, R326 and R328, resistors R333, R335, R338 and R340

or its representative.

If replacing the vibrating capacitor, VClOl, order only from Keithley

or its representative.

The Model 630 needs no periodic maintenance beyond the normal

SERVICING

Reorder using the Keithley

Because of its im-

order zener diode D302 only from Keithley

Refer to paragraph 4-6 for instructions

to

4-4.

63::

Table 3 lists equipment recommended for troubleshooting.

located or repaired, I contact Keithley Instruments, Inc. or its representative.

TROUBLESHOOTING.
The following procedures are for repairing troubles which might occur in the Model

Use these procedures to troubleshoot and use only specified replacement parts.

If the trouble cannot be readily

Instrument Use

Keithley Model 153 dc Microvolt-Ammeter,

3% accuracy, minimum 200 megohm input

resistance,
Keithley Model 610B Electrometer
Keithley Model 50211 Ohmmeter
Hewlett-Packard 200CD Oscillator
Tektronix Type 503 Oscilloscope
Grid-modulated tube tester

TABLi? 3. Equipment Recommended for Model 630 Troubleshooting. Use these instruments

or their equivalents.

1 volt to 500 volts.

Circuit checking

Check grid bias at cathode follower
Check resistance

Check frequency
Check wave forms

Test vacuum tubes

d

0166R

17

SERVICING

MODEL 630 POTENTIOMETRIC ELECTROMETER

I

eter rattle, drift, or er-

Excessive drift on most
sensitive range

Line voltage variations
cause measurements to be
out of specifications

Reference voltage supply
drifts after 30-minute

warm-up, requiring frequent

adjusting of the range con­trols, R327, R334, R337 and
R339

Difficulty

is observed on all null

Probable cause Solution

Tube VlOOl, V1002 or V1003

is faulty

-6v power supply is drift­ing or oscillator circuit

is faulty

Faulty VClOl
Battery BlOl is faulty
Tube V3005 is defective

V3001, V3002, V3003 or
V3004 is defective

One of the divider resis­tors, R325 to R330, is
changing value rapidly dur­ing warm-up

Check tubes;
tY

Check power supply stability

PC104, and oscillator fre­quency (paragraph 5-7). If

faulty component cannot be

located, return instrument

to

factorv.

I

Replace VClOl

I

Replace BlOl

I

Check tube; replace if faul­ty

Check tubes; replace if faul,

I

w

Return the instrument for
factory check-out

replace if faul

Measurements out of toler­ance on all ranges

Measurements are out of

specifications on one
range other than 500-

volt range

TABLE 4.

Zener diode, D302, is un­stable

Light modulator, F,302,
is defective

Out of calibration

One of the divider resis- Return the instrument for
tars, R325 to R330, is

Resistor in the range di­vider network is faulty

(Sheet 1).

Model 630 Troubleshooting

Return the instrument for
factory check-out

I

Check light modulator by re­placing.

Refer to paragraph 5-5 for
recalibration

factory check-out

Paragraph 3-2 d points out

the resistors used for each
range.
ranges within specifications
by calibrating with the po­tentiometers in the network.
See paragraph 5-5. If this
does not work, check indivi­dual resistors.

Try to bring the

18

MODEL 630 POTENTIOMETRIC ELECTROMETER

SERVICING

Difficultv

Measurements are Out of
specifications
ges other than 500-volt

Excessive ac interference
Non-symmetrical response

on polarity switching and
low sensitivity on most
sensitive ranges

Instrument does not respond
to a signal and offset on
all ranges

Greatly increased sensiti­vity on 10 and 100 null
ranges and 5, 50 and 500V
VTVM ranges

500V supply operates but
null detector is completely
inoperable

on all ran-

Probable cause

Resistor R333 is faulty

R131 out of adjustment
Oscillator frequency has

drifted

Relay K102B is defective

Relay KlOlB is defective

Fuse F201 is blown

Solution

Replace the faulty resistor

Adjust oer oaragraoh 4-8
Check frequency.

approximately 94 cps.
to paragraph 5-7).

Check operation of relay. 11
faulty replace with Keithley
relay or return t0 factory

Check operation of relay. If
faulty replace with new relay
from Keithlev

Check for possible short in

-6v supply (~~104).

Reset to

(Refel

or return to

Keasurements are Out of
specifications on any range
tihen the Reference Voltage
Dials are at anv settine
other than 4 9 9 9 10 -

TABLE 4.

Paragraph 6-2 describes how to remove the Model 630 :over.

b.

the troubleshooting, check the vacuum tubes.
difficulty.
ing a tube does not correct the trouble, continue the procedures.
not necessitate recalibration of the instrument.

c. Table 4 contains the mwze ccnnm~n troubles which might occur.
ted in the Table do not clear up the trouble,
a point-by-point check of the circuits. Refer to the circuit description in Section 3

to find the more crucial components and to determine their function in the circuit. The

complete circuit schematic, 18261E, is found in Section 7,
4-5. ADJUSTING GRID BIAS OF CATHODE FOLLOWER.

V1003 (Figure 15), should be -3 volts. Use the Keithley Model 610B to check this value
i5"/,.

If necessary, adjust the DC BAL potentiometer, R157 (Figure 16), to this value.

All tubes can be readily tested on a grid-modulated tube tester.

(Sheet ).

One of the Kelvin-Varley
divider resistors is
faulty

Model 630 Troubleshootir :.

Normally,

the difficulty will have to be found through

The grid bias of the cathode follower,

See paragraph 5-3

Before proceeding with

replacing tubes will clear up the

If replac-

Replacing tubes does

If the repairs indica-

0166R

19

SERVICING MODEL 630 POTENTIOMETRIC ELECT&OMETER

4-6.

ZEhXR DIODE REPLACEMENT.

resistors R325 to R330.

The values of resistors R329 and R330 (Figure 20) are determined

Zener diode, D302, is a reference for the voltage divider,

by the reference voltage across diode D302. When the zener is replaced, the value of

these two resistors may have to be changed.

4-7. METER ADJUSTMENT.

Potentiometer R155 (Figure 16) is the internal meter sensitivity adjustment. It

a.

sets the current through the mater to indicate a full-scale deflection for a full-scale

applied voltage.

Warm up the Model 630 for 30 minutes.

b.

Set the NULL Switch to the l-volt range and
set the Reference Voltage Dials to 1.0000. Adjust potentiometer R155 until the meter
reads full scale.

4-8. ADJUSTING QUADRATURE CONTROL.

Large quadrature components in the

a.

null detector can cause poor ac rejection,

sluggish response, and, in some cases, un-

symmetrical readings on the most sensitive
ranges. Use the QUAD ADJ potentiometer,

Rl31 (Figure 16),

ents when necessary.

to buck out these compon-

While a large com­ponent is troublesome, the quadrature need
not be completely eliminated.

To adjust the potentiometer, set the

b.
Reference Voltage Dials to zero and the
DETECTOR INPUT. Switch to ZERO CK. Attach

an oscilloscope to the junction of Cl16 and
R134 (from pin 6 of V1002, Figure 15). Ad­just potentiometer, R131, for the correct

wave form (Figure 9).

FIGURE 9. Wave Form with Rl31 Adjusted.
A Type 503 Oscilloscope was used; horizon-

tal sweep was 5 mseclcm; vertical, 2 v/cm.

20

0166R

MODEL 630 POTh'NTIOMETRIC ELECTROMETER

SECTION 5. CALIBRATION

5-1. GENERAL.

CALIBRATION

The following procedures are recommended for calibrating the Model 630.

a.

equipment recommended in Table 5.
ibrating an fO.Ol% instrument
tact Keithley Instruments, Inc.,

The following procedures are covered:

b.

calibrate adjustment,

and oscillator adjustment.

If the Model 630 is not within specifications after the calibration, follow the

c.

troubleshooting procedures or contact Keithley Instruments, Inc., or its representative.

Instrument

Electra Scientific Industries Model SV194B
Voltage Calibrator, i-0.005% accuracy with
corrections on certificate

Electra Scientific Industries Model RV722
Decade Voltage Divider; terminal linearity
21 ppm; certificate corrected to kO.2 ppm

Electra Scientific Industries Model LC875B
Lead Compensator

voltage range calibration, reference voltage supply stability test

- are not available or if difficulty is encountered, con-

If proper facilities - especially important for cal-

or its representative to arrange for factory calibration.

Kelvin-Varley divider verification, divider

Use

Range voltage calibration

Voltage divider for range calibration

Range voltage calibration

Use the

Hewlett-Packard Model 200CD Oscillator
Keithley Instruments Model 15OB Microvolt

hmeter
Keithley Instruments Model 241 Regulated

High Voltage Supply
Keithley Instruments Model 662 Guarded dc

Differential Voltmeter
Keithley Instruments Model 370 Recorder

Tektronix Type 503 Oscilloscope

Weston Instruments Model 3 Type 7 Saturated

Standard cell

Weston Instruments Model 66 Oil Bath

TABLE 5.

equivalents.

Equipment Recommended for Model 630 Calibration.

Monitor oscillator frequency
Null detector for range calibration

Voltage supply for range calibration

Check voltages in Kelvin-Varley divider

Recorder for reference voltage supply

stability
Check wave forms

Range calibration and reference voltage

supply stability

Range calibration end reference voltage

Use these instruments or their

1067R

21

CALIBRATION

MODEL 630 POTENTIOMETRIC ELECTROMETER

Circuit

Control

Divider Calibrate

Quad Adjustment
Meter Calibrate
DC Balance

Oscillator

500-volt Calibrate R327 20 5-5
50-volt Calibrate R334 20 5-5
5-volt Calibrate R337 20 5-5

0.5-volt Calibrate R339 20 5-5
TABLE 6.

ure picturing the location and the paragraph describing the adjustment.

5-2. CALIBRATION SCHEDULE.

a. Recalibrate the Model 630 yearly. This normally means performing the voltage range

calibration (paragraph 5-5). The other verifications need not be done.

b.

or if components in the divider have been replaced. Also make the voltage range calibra-

tion after verifying the divider accuracy.

Model 630 Internal Controls. The Table lists all internal controls, the fig-

Verify the Kelvin-Varley divider (paragraph 5-3) only if trouble is suspected in it,

Desig.
R104 15 5-4

R131 16 4-8
R155 16 4-7
R157 16 4-5
R210 18 5-7

Fig.
Ref. Paragraph

Refer to

Check the reference voltage supply stability (paragraph 5-6) only if trouble is

c.

suspected in the supply or if some of its components have been replaced.

5-3. KELVIN-VARLEY DIVIDER VERIFICATION.

There is no in-field calibration for the Kelvin-Varley divider; its accuracy can

a.

only be verified.

manufacture,

S304, is matched to *0.00125%. The resistors in the switches are checked as a set to an
accuracy of better than 0.0025%.
ching the string at Keithley Instruments.

b. Kelvin-Varley Divider Accuracy Verification Procedures.

1.

error to match the Model 630 under test.

the Model 630 to the HI terminal of the Model 662.

Be careful of high voltages when working within the Model 630. Up to 900 volts

dc is present at various points.

2.
iO.Ol%. This procedure, however, only indicates the Kelvin-Varley divider accuracy.
The errors of the two instruments may be additive, causing a false verification. The
most accurate way is to use standard procedures for checking a Kelvin-Varley divider

or to return the Model 630 to Keithley Instruments, Inc., for checking.

each resistor within the first two Reference Voltage switches, S303 and

Use the Model 662 Differential Voltmeter or equipment with better limit of

Set the dials to random settings on both instruments. Settings should match to

The divider accuracy depends upon matching resistors and switches. At

Individual resistors cannot be replaced without remat-

Connect the Low end of potentiometer R38L of

Connect both LO terminals.

NOTE

22

1265R

MODEL 630 POTENTIOMETRIC ELECTROMETER

If any resistor fails to test out,

3.

the entire divider string will have to he rc-

matched at the factory.

5-4.

INPUT DIVIDER CALIBRATION.

Above 1 volt the input is divided by a constant 5OO:L

ratio. R103 is pre-selected to approximate this ratio and R104 is adjusted to trim to

this ratio more closely.

'accuracy

on the l-volt and Lower ranges but appears in error for the higher ranges.
check the divider ratio,
put.
it does not,

5-5.

The Model 630 meter should have a full scale deflection on its 500-volt range.

trim R104 (Figure 15) until the meter indicates full scale.

RANGE CALIBRATION.

A misadjustment will show up if the Model 630 maintains spccificrl

'To

use the Model 241 to apply a 500-volt signal to the Hodel 630 in-

a. The reference voltage supply has a 500-volt output which can be attenuated to 50, 5

or 0.5 volts.

This voltage is then divided by the Kelvin-Varley divider to provide the
accurate buckout voltage. Each of the four voltage ranges is set by internally adjusting
potentiometers R327, R334, R337 and R339 (Figure 20).

The ranges are calibrated by applying an accurate voltage to the Model 630 for each

b.

setting of the RANGE Switch.

The Model 630 is set to furnish the equivalent buckout vol­tage, and the internal range potentiometer is adjusted until the voltmeter indicates a
null.

If

I

SUPPlY

d b

I

Mode, -~ --

i ‘C 8/,B

I

d I u-+-z Detector ]

o Compensator

9.9 lm

EXte"dGT

(5 and 0.5"

OlllY)

I

--+
_ Model

- sv 194B
Calibrator

p+Cd

I

Model R'J722

FIGURE 10.

Block Diagram to Establish System Accuracy for Model 630 Range Calibration.

Fully guard the entire system to prevent leakage errors.

to shunt the null detector.

See Table 5 for recoanended equipment.

Use a l-kilohm copper resistor

1067R

23

CALIBRATION

MODEL 630 POTENTIOMETRIC ELECTROMETER

NOTE

The accuracy of the Model 630 calibration will be no greater than the
accuracy of the voltage source used for calibrating.

Unless the user is

familiar with techniques for obtaining accuracy greater than 0.002%

(20

PPm) >

it is better to return the Model 630 to the factory for range

calibration.

The most critical part in range calibration is establishing a reference source

c.

whose accuracy exceeds 0.002%..

Use the Model SV194B Voltage Calibrator for the 500, 50,
5 and 0.5-volt outputs. Establish the accuracy of these outputs by determining the cor­rections for the calibrator's CALIBRATION and OUTPUT dials at these outputs.
accuracy can be determined to approximately 10 ppm. Added

to

the accuracy of the standard

The system's

cell, total accuracy should be approximately 12 ppm. Note that this depends upon proper-

ly executed procedures.

Procedures to Establish System Accuracy.

d.

Set up the system shown in Figure 10.

1.

Use the 9.9-megohm extender for only the

0.5 and 5-volt output.
Establish the corrections for the CALIBRATION dial setting for Model SV194B out-

2.
puts of 500, 50, 5 and 0.5 volts.
the Model RV722 Divider to a voltage equal to that of the standard cell.

Model SVl94B ratio dial until the null detector indicates a null.

Set the Model 241 Voltage Supply to 500 volts.

Adjust the

The difference be­tween the settings of the Model RV722 Divider and the ratio dial is the Model SVl94B
correction factor at 500 volts.

With this correction, the 500 volts may be set to

within approximately 12 ppm.

Connect the null detector to the 50, 5 and 0.5-volt taps of the Model SVl94B Cal-

3.

ibrator in that order.

Set the Model RV722 Divider to corresponding voltages.

Use the

9.9-megohm extender for the 5 and 0.5-volt outputs. (See Figure 10). The difference
read on the null detector is the correction factor for each of the three voltages.
These voltages may also be set to within 12 ppm.

Use the four correction factors for calibrating the Model 630 range setting.

4.

f. Procedures for Range Calibration.

Set up the system shown in Figure 11.

1.

10 ppm.

Use the dial correction factors found for each output.

was properly determined,

the input voltage to the Model 630 should be correct to 20 ppm.

The standard cell should be certified to

If the system accuracy

set

500-volt Range Calibration: Set the Model 630 controls as follows:

2.
DETECTOR INPUT Switch 1010 OHMS

RANGE Switch

500

Reference Voltage Dials 4 9 9.9 9 10

NULL Switch VTVM

POLARITY Switch

Adjust the Voltage Calibrator to apply 500 volts to the Model 630.

+

Turn the Model 630
NULL Switch to 10 MV and adjust the 500 V CAL potentiometer, R327 (Figure ZO), for
null on the Potentiometric Electrometer.

24

0166R

MODEL 630 POTENTIOMETRIC FLECTROMETER

CALIBRATION

FIGURE 11. Block Diagram for Model 630 Range Calibration. Fully guard the entire system

to

prevent leakage errors. See Table 5 for recommended equipment.

50-volt Range Calibration: Set the Model 630 controls as follows:

3.
DETECTOR INPUT Switch 1010 OHMS

RANGE Switch 50
Reference Voltage Dials 4'9.9 9 9 10
NULL Switch 10 Mv

POLARITY Switch +

Adjust the Voltage Calibrator to apply 50 volts dc to the Model 630. Adjust the 50 V

CAL potentiometer, R334 (Figure ZO),

for an off-null reading on the Model 630 equal to

the correction factor at 50 volts.

5-volt Range Calibration:

4.
DETECTOR INPUT Switch

RANGE Switch
Reference Voltage

set the Model 630 controls as follows:

1010 OHMS

'5

Dials 4.9 9

9 9 10

NULL Switch 1Mv

POLARITY Switch +

Adjust the Voltage Calibrator to apply 5 volts dc to the Model 630. Adjust the 5 V CAL

potentiometer, R337 (Figure 2o), for an off-null reading on the Model 630 equal to the
correction factor at 5 volts.

0.5~volt Range Calibration:

5.

Set the Model 630 controls as follows:

1067~

DETECTOR INPUT Switch 1010 OHMS

RANGE Switch
Reference Voltage

NULL Switch

POLARITY Switch

Dials .4 9

0.5
9 9 9 10

0.1 MV

+

25

CALIBRATION

MODEL 630 PO'TENTIOMETRLC ELECTROMETER

Oil Bath;

I
I

t

- I

-

- I

- I

,-------

FIGURE 12. Circuit Diagram for Model 630 Reference Voltage Supply Stability Test.
voltage across the 530-ohm resistor is slightly higher than the standard cell.

Model 150B

H

Null

Recorder

The

Use the

lo-kilohm potentiometer to shunt the divider voltage down. All resistors are wirewound.

See Table 5 for recommended equipment.

Adjust the Voltage Calibrator to apply 0.5 volt dc to the Model 630. Adjust the 0.5 v

CAL potentiometer, R339 (Figure ZO), for an off-null reading on the Model 630 equal to
the correction factor at 0.5 volt.

5-6.

REFERENCE VOLTAGE SUPPLY STABILITY TEST.
The reference voltage supply,

a.

consisting of the power transformer and the main sup­ply (printed circuit PC92), is factory calibrated for an output of 500 volts dc greater
than 0.002%. The 500-volt output is adjustable to meet specifications. If the stability
of the supply is not within specifications,

then troubleshoot for a faulty component.

Routine calibration of the Model 630 does not require a stability test of the ref-

b.
erence voltage supply. However, a stability test is recommended if one of the components
in the supply is replaced.

For the 24-hour test, the 500-volt output of the reference voltage supply is divided

c.

and compared to a 1.02-volt saturated standard cell using a sensitive null detector.

Var-

iations between the reference voltage supply and the standard cell are detected by the

Model 150A and are recorded on a recorder.

Refer to Figure 12 for the block diagram of

the test circuit.

In using the test circuit,

d.

Saturated standard cells,

1.
ture coefficient and require a controlled environment during use.
ton Oil Bath, which is maintained at ~350 M.OloC, is used for the test.

the following points are important.

though extremely stable with time, have a high tempera-

Therefore, the Wes-

Unsaturated
standard cells have a lower temperature coefficient, but they do not have the long term
stability required for this test.

The resistor divider network is constructed from wire of the same spool for an

2.

extremely close temperature coefficient match (4 ppm, typically).

26

Additional stability

1067R

MODEL 630 POTENTIOMETRIC ELECTROMETER

CALIBRATION

results when the resistors are immersed in an oil bath to hold the ambient temperature
variations

Procedures for the Reference Voltage Supply Stability Test.

e.

After the saturated standard cell and the resistor divider network are placed in

1.

to

+O.Ol%.

the oil bath, allow sufficient time for the cell to stabilize at ~35°C. (Consult Keith-

ley Instruments, Inc., or its representative for details.) Connect the standard cell
to the circuit after turning on the 500-volt supply. Set the Model 630 controls as
follows:

DETECTOR INPUT Switch

1010 OHMS
RANGE Switch 500
Reference Voltage Dials 4 9 9.9 9 10
NULL Switch 10 Mv
POLARITY Switch

OFF

Connect the resistor divider network across the Model 630's reference voltage supply,

the positive side of the divider input to the wiper arm of the last Reference Voltage
Switch, S306, and the negative side of the divider to the LO terminal on the Model 630
front panel.

Connect the Model 150B and the recorder as shown in Figure 12. Set the Model 1500

2.

to the 3-volt range.

Advance the Model 630 POLARITY Switch to -I- to put 500 volts across
the divider. If the Model 150B reads two volts, the standard cell and the divider vol­tages are improperly connected in series. If the circuit is correct, the Model l50B

will read zero. Increase the Model 15OB's sensitivity to the O.l-millivolt range. If

it reads more than 20 microvolts, adjust the 500 V CAL potentiometer, R327 (Figure 20),
shunting the divider.

NOTE

Any adjustment of potentiometer R327 requires all other ranges to be calibrated,

After l-hour warm-up,

3.

the drift of the entire system should not exceed i-25 micro-

volts in 24 hours.

5-7. OSCILLATOR ADJUSTMENT.

The oscillator circuit drives the light modulator, vibrating capacitor and bridge.

a.

demodulator. Before adjusting the oscillator, make sure the reference voltage supply
is operating correctly.

Connect the Type 503 Oscilloscope Vertical Input to the plate and low side of tube

b.

V1003 (Figure 15) and the Horizontal Input to the Model 200CD Oscillator. Adjust the

oscillator frequency to approximately 94 cps with potentiometer R210 (Figure 18). The

Model 630 oscillator is then adjusted for minimum meter noise - normally within a cycle

of 94 cps.

Disconnect the Oscilloscope before adjusting potentiometer R210. The

Oscilloscope will cause a small loading error.

1067R

27

CALIBRATION

MODEL 630 POTENTIOMETRIC ELECTROMETER

R30 1

0302

Q203

Cl22

(hid,

(Refer to Figures 15 and 16)

PC-103

FIGURE 13. Top view of Model 630 Chassis.

28

Null Detector Input
(Refsr to Figure 17)

Front panel faces to the right.

0166

MODEL 630 POTENTIOMETRIC ELECTROMETER

CALIBRATION

'IGURE 14. Bottom view of Model 630 Chassis.

13 shows the top view.

0166

Front panel faces to the right.

Figure

29

CALIBRATION

MODEL 630 POTENTIOMETRIC ELECTROMETER

Cl01

Cl15

Clll.-elj

Cl10 ----+

Cl19 -".q

A

OS101

Cl06

Cl07 Cl13

I

-cl08

+D104

~V1002

*cl16

Cl09

c12oa-+

c117nn"y

Dlb9

VCiOl Djoy166

I

;

Re-

Fl [GURE 15.

Capacitor,

D108

Tube and Diode Locations on Printed Circuit PC-103.

fer to Figure 16 for Resistor Locations. Hidden from view, in locations A and B

are, potentiometer Rl04, resistors R124 and R154, and capacitors Cl03 and C105.

30

0166

MODEL 630 POTENTIOMETRIC ELECTROMETER

R107-

CALIBRATION

Rl33 -mm..&

R130,

R158

29

R141

i,j

R109
thru
R118

0166

KeS1StOr

Diode and Tube Locati

on lx-L”J.

R15.1 R108

Keter

to Figure 13 tar Capacitor,

31

CALIBRATION

MODEL 630 POTENTIOMETRIC ELECTROMETER

I,

tector Input.

32

Locations

on Null De

'IGURE 18.

Component bzations on -6.3 vo

ower Supply, PClO4.

0166

MODEL 630 POTENTIOMETRIC ELECTROMETER

CALIBRATION

D301

I

v3003

I

c 5

P

,~_,,,., I‘....

008
C306

VW0 1

GURE 19.
,fer to Figure 20 for Resistor

Capacitor, Diode, Modulator and Tube Locations on Printed Circuit Board PC-92.

Locations.

CALIBRATION MODEL 630 POTENTIOMETRIC ELECTROMETER

R307

R33111

R30

9

R310
R308

4

“:“kc

R30 2

I

R312 R314

R303 R305 R315

I I I I I

,m

R313

R317

R316

-

R318

R319

R332

R328

-

?osition

R324

FIGURE 20.

.iii‘::*&

R339

Resistor Locations on Printed Circuit Board PC-92.

Capacitor, Diode, Modulator and Tube Locations.

R3.33

R325

Position

R326

Position

-R330

positiac

c

R334

R327

Refer to Figure 19 for

34

0166

MODEL 630 POTENTIOMETRIC ELECTROMETER

SECTION 6. ACCESSORIES

6-1. MODEL 6301 GUARDED PROBE. (Figure 21)

The Model 6301 is a guarded probe and shielded lead to make measurements with the

a.

Model 630 nvxe convenient.

furnished with 3 feet of low-noise cable,

plug connects directly into the Model 630 Input Receptacle.

It does not alter any Model 630 specification.

terminated by a special triaxial type plug.

ACCESSORIES

The lead is

The

b. Using the Model 6301 Probe allows point by point measurements.

Its operation witli

the Model 630 is explained in paragraph 2-4.

6-2. RACK MOUNTING.

The Model 630 is shipped for bench use with four feet and a tilt-bail

(See Figure 22)

The Model

4&% Rack Mounting Kit converts the instrument to rack mounting to the stan&nd EIA (RET@)

19-inch width.

To convert the Model 630, remove the four SC~BWS at the bottom of each side of the

b.
instrument case. Lift off the top cwer assembly with the handles; save the four screws.
To remcwe the feet aid tilt bail from the bottom cover assembly, turn the two screws near

the back. The two pawl-type fasteners will release the cwer and allow it to drop off.

Remove the feet and the tilt bail and replace the cwer (2).

c. Attach the pair of rack angles (3) to the cabinet with the four screws (4) previou

y removed.

Insert the top cwer assembly (1) in place and fasten to the chassis with t

S-

he

FIGURE 21.
probe tip,

Keithley Instruments Model 6301 Guarded Probe with the Model 630.

the Model 6301 can have banana plug, alligator clip, and bnc-type connections.

Unscrew tip to make the connection.

1265

m

Besides the

35

ACCESSORIES

MODEL 630 POTENTIOMETRIC ELECTROMETER

two pawl-type fasteners at the rear. Store the top cover with handles, feet and tilt-bail
for future use.

6-3.

PLACING IN RACK.

the rack.

It is recommended, however,

The Model 630, once converted for rack mounting, easily fits into

that a blower be used in the rack enclosure in

which the Model 630 is mounted. The instrument specifications state a 0.002% per "C tem-

perature coefficient. A temperature rise of 5 W (9 OF) will cause a 0.01% error.

Item

(See Fig. 22)

1 Cover Assembly
2

Cover Assembly, Bottom (Supplied with

Model 630)

3

Angle, Rack

4 SCYCeW)

(Supplied with Model 630)

5

Front Panel (Supplied with Model 630)

Description

Slot Head, lo-32 UNC-2 x l/4

Keithley
Part No. Quantity

14623B 1

14590B 1
14624B

---­__--

2

4

1

I

Parts List for Model 4000 Rack Mounting Kit.

~@COVER ASSEMBLY

4

P

TABLE 7.

SCREW

OVER ASSEMBLY

FIGURE 22. Exploded

'Table 7 for parts.

View

for Rack Mounting with Model 4000 Kit.

Refer to

1265

MODEL 630 POTENTIOMETRIC ELECTROMETER

ACCESSORIES

FIGURE 23. Model 6013 pH Electrode Adapter Connected to pH Electrodes,

shown here with the Keithley Model 601 Electrometer,

6-5.

MODEL 370 RECORDER.

is used similarly with the Model630.

The Model 6013,

a. The Model 370 Recorder is uniquely compatible with the Model 630 as well as other

Keithley electrometers,

picoammeters and microvoltmeters.

The Recorder is a high quality

economical instrument that epitomizes the performance of the Model 630 and many other
Keithley instruments, even in the most critical applications.
with the Model 630 to

record

over the Model 630's entire range.

The Model 370 can be used

b. The Model 630 has the output necessary to drive the Recorder directly (1 volt, 1

milliampere), thus eliminating the need for a preamplifier.

The Model 370 floats f500
volts off ground, enabling the Model 630 to be used to its specified off-ground voltage.
The Recorder is specially shielded to avoid pickup of extraneous signals. The response

1067R

37

ACCESSORIES MODEL 630 POTENTIOMXTRIC ELECTROMETER

time of the Model 370 Recorder is 0.5 second; linearity is *l% of full scale. Ten chart
speeds - from 3/4 inch per hour to 12 inches per minute - are selectable with front panel
controls. The 6-inch chart has a rectilinear presentation. The Model 370 Recorder has a
self-priming inking system. Chart paper and ink refills are easy to install.

C. The Model 370 is ‘very easy to use with the Model 630.

Just connect the Model 630’s
OUTPUT Receptacle to the Model 370 with the furnished 3701 Input Cable and adjust an
easily accessible control for full-scale recorder deflection.

38

1067R

MODEL 630 POTENTIOMETER ELECTROMETER REPLACEABLE PARTS

SECTION 7. REPLACEABLE PARTS

7-l.

Model 630 and its accessories.

cription, a suggested manufacturer,
Number.

the manufacturers listed in the "Mfg.

REPLACEABLE PARTS LIST. The Replaceable Parts List describes the components of the

The List gives the circuit designation, the part des-

the manufacturer's part number and the Keithley Part

The last column indicates the figure picturing the part. The name and address of

Code" column are in Table 9.

7-2. HOW TO ORDER PARTS.

For parts orders,

a.

Part Number,

the circuit designation and a description of the part. All structual parts

include the instrument's model and serial number, the Keithley

and those parts coded for Keithley manufacture (80164) must be ordered through Keithley
Instruments, Inc. or its representative.
able Parts List,

Order parts through your nearest Keithley representative or the Sales Service Depart-

b.

completely describe the part, its function and its location.

In ordering a part not listed in the Replace-

ment, Keithley Instruments, Inc.

amp
Cb

CbF
CbVar
CerD
Comp
compv

DCb

Carbon
Carbon Film
Carbon Variable
Ceramic Disc
Composition
Composition Variable

Deposited Carbon

M

m

Mfg.
Mil. No.

MY
n

P
Poly

mega (106)
milli (10-3)
Manufacturer
Military Type Number
Mylar

ohm
pica (lo-12)

Polystyrene

EAL
EMC
ETB
ETT

f
Fig.

k

1065

Electrolytic, Aluminum
Electrolytic, Metal Cased
Electrolytic, tubular
Electrolytic, tantalum

farad

Figure
kilo (103)

Table 8.

Abbreviations and Symbols.

Ref.

u.
v

Ew
WWVar

Reference
micro (10-6)
volt

watt

Wirewound
Wirewound Variable

39

REPLACiUBLE PARTS

MODEL 630 POTEX'TIOMKTRIC ELECTROMETER

m 630 VBLE PARTS LIST

(Refer to Schematic Diagram 18261E for circuit designations)

CAPACITORS

Circuit Mfg. Mfg. Keithley Fig.

Desig.

Value Rating Type Code Part No.

Part No. Ref.

Cl01
Cl02
Cl03
Cl04

Cl05

Cl06
Cl07
Cl08

Cl09
Cl10

Cl11
Cl12

22

pf

56 &f 6v

47

pf

56

uf

47

if

2 Pf

0.1 I.Lf
1500 pf
2O/fXI/lOO
.a1 IJ.f

.a05
.005

Cl13 0.1 pf
Cl14

2

IJ.f

Cl15 0.1 pf

Cl16 .Ol uf
Cl17
Cl18
Cl19
Cl20

Cl21
Cl22

100 ,lf

0.5

Ilf

100 Kf 10 v ETT 05397

4

Pf

0.25

1 Pf

IJf
pf

yf

500

”

500 v
6v
500

v

50

v

400

v

600 v

pf

300/250/250 v

400 v

400

”

400

v

400

v

50

v

400

v

600

v

10 v

400

v

250

v

400

v

25

v

Poly 71590 CPR-225 Cl38-22P
ETT 01295 5MC566BP006A4 C70-56M
Poly 71590 CPR-47J Cl38-47P
ETT 01295 5MC566BP006A4 C70-56M
Poly 71590 CPR-475

ETT 37942

MY

13050 OlOOSMlA

TC302

CerD 72982 ED-1500
EMC 37942 FP335A
Poly 12673

Poly
Poly

MY

12673
12673
13050

ETT 37942

MY

13050

22P
22P C134-.005M

22P
OlOOSMlA
TC302
OlOOSMlA

CerD 72982 ED-.01

Ett

MY

05397

13050

KlOOJlOS
SMlA

KlOOJlOS

ETB

MY

CerD 56289

14655

13050

BBR4-250
SMlA

5c13

Cl38-47P
C39-2M

C73-.lM
C22-1500P
ClOO-100-60-20
Cl35-.OlM

C134-.005M 15
C73-.lM
C39-2M 15
C73-.lM 15

C22-.OlM
C78-100M 15

C117-.5M

C78-100M 15

C27-4M
C73-.25M 15

C85-1M

15
17
15
17
15

15
15
15
15
15

15
15

15
15
15

13

c201
c202

C203

C204
C205

c301
C302
c303
c304
c305

C306
c307

40

1000 pf

.0068

100 pf
100 pf

0.47'pf

.05

p.f

20

pf

20

pf

.a01 pf

1 Pf

.05

uf

4

Pf

IJ.f

15
600

10 v

”

v

EAL
CerD 72982
ETT

10 " ETT

25

v

600

v

450

v

450

v

600

v

1000 "

600

v

250

v

CerD

MY

EMC 39742 FP144
EMC 56289

CerD 72982
MY

MY

ETB

56289

89B224

ED-680
05397 KlOOJlOS
05397 KlOOJlOS

56289

5Cll
56289 6PS-S50

TVL2762

ED-.001

13050

56289
14655

Z400VB
6Ps-~50 C62-.05M

BBR4-250

C93-1000M
C22-.0068M
C78-100M
C78-100M
C85-.47M

C62-.05M
C36-20M
C36-40-20M
C22-.OOlM

C14-1M

C27-4M

18
18
18
18
18

14
19
19
19
19

19
19

1067R

MODEL 630 POTENTIOMETRIC ELECTROMETER

CAPACITORS (Cont'd)

REPLACEABLE PARTS

Circuit
Desig.

C308
c309
c310

c311

C312

Circuit
Desig.

DlOl
D102
D103
D104
D105

D106 Silicon 1~645 01295 RF-14 15
D107 Si.licon 1~645 01295 RF-14 15
D108 Silicon lN645 01295 RF-14 15
D109 Silicon lN645 01295 RF-14 15

Value

50 pf

.0047 pf
.0022 pf

.05 pf
.47 pf

TYPO
Silicon

Silicon
Silicon
Silicon
Silicon

Rating

6v
600 v
1000 v

600 v
600 v

TYPO

EMC
CerD
CerD

MY
MY

Number

1~645
lN645
lN645
lN645
LN645

Mfg. Mfg.

Code Part No.
56289 TEllOO

72982 ED-.0047
56289 5GAD22

56289 6PS-S50

14655 W6P47

Mfg.

Code

01295 RF-14 14
01295 RF-14 14
01295 RF-14 14
01295 RF-14 15
01295 RF-14 15

Keithley
Part NO.

C17-50M 19
C22-.0047M 19
C72-.0022M 19

C62-.05M 19
ClOl-.47M

Keithley

Part No.

Fig.
Ref.

14

Fig.
Ref.

D201 Silicon MR1031B 04713 RF-30 18

D202 Silicon MR1031B 04713 RF-30 18
D203 Silicon MRlO31B 04713 RF-30 18
D204 Silicon MR1031B 04713 RF-30 18
D205 ZellfXL- LN713 12954 DZ-14 18

D206 Silicon lN645 01295 RF-14 18
D207 ZeW2-Z DZ40731A 12954 DZ-13

D208 Silicon lN3256 02735 RF-22 18
D209 Silicon lN645 01295 RF-14 18
D210 Silicon lN645 01295 RF-14 18

D211 Silicon LN3256 02735 RF-22 18

D301 Silicon lN2378 08520 RF-25 19
D302 ZE9lC!r - 80164 DZ-24 13

D303 Silicon lN3256 02735 RF-22 19

D304

Silicon

lN3256 02735 RF-22

18

1067R

41

REPLACEABLE PARTS

MODEL 630 POTENTIOME'l'RIC ELKTROME'TER

MISCF.LLANEOUS PARTS

Circuit
Desig.

BlOl

DSLOl

DS301
DS302
DS303
DS304
DS305

DS306

E301
E302 Light Modulator 80164

F201

Battery, 1.35 v (Mfg. No. F&f-1W) 09569
Battery Holder (Mfg. No. 2101)

Neon Lamp (Mfg. No. NE-81) 08804 PL-6

Neon Lamp
Neon timp
Neon Glow Lamp (Mfg. No. Ale)
Neon Glow Lamp (Mfg. No. AlC)
Neon Glow Lamp (Mfg. No. AlC)

Neon Glow Lamp (Mfg. No. Ale)

Light Modulator 80164

Fuse, slow blow, 2 amp (Mfg. No. 313002)

Description

Mfg. Keithley

Code

94139 BH-15

80164 1512

80164 1516
08804
08804
08804

08804

75915 FU-25

Part No.
DA-15

PIr31
PL-31
PL-31

PL-31

1514

1516

Fig.
Ref.

14

15

13
13
13

13

19

19

18

F301 (117 v)
F301 (234 v)

JlOL

5102

5103

no4

5105

JlO6
5107
5108

5201

ML01

Fuse, slow blow, 1 amp (Mfg. Type MDL)
Fuse, slow blow, 0.5 amp (Mfg. No. 312.500)
Fuse Holder (Mfg. No. 342012)

Receptacle,

Mating connector for JLOL

Binding Post, M (Mfg. No. DF31BC)
Binding Post, HI (Mfg. No. DF3LGC)

Plug, bnc, mate of 5105 (Mil. No. UG-88/U)
Receptacle, bnc, mate of J104 (Mil. No.
UG-1094/U)

Banana Jack, HI (Mfg. No. 108-745-l)
Banana Jack, LO (Mfg. No. 108-745-2)
Connector, mate of 5201 (Mfg. No.
00-5002-013-103-002)

Connector, mate of 5108 (Mfg. No.
02-013-013-5200)

Shorting Link (Mfg. No. 938-L)

Meter

special triaxial INPUT

71400
75915
75915

80164
80164
58474
58474

95712
95712
74970

74970
73690

73690
24655
80164

FU-10
FU-6
FH-3

cs-140
BP-8B

BP-%

cs-44
cs-15
BJ-3

BJ-4
cs-155

CS-156
BP-6

ME-38

3

3

2

2
2

3
3

13

P301

42

Cord set, 6 feet (Mfg. No. 4638-13) 93656

co-5

3

1067~

MODEL 630 POTENTIOMETRIC ELECTROMETER

MISCELLANEOUS PARTS (Cont'd)

REPLACEABLE PARTS

Circuit

Desig. Description

Rotary Switch less components, NULL 80164

Knob Assembly, Null Switch 80164
s102
SLO3

s104

--_

s301

5302
5303

s304

---

5305

---

--­S306

---

--­S3O,-ir"

-

Toggle Switch, DETECTOR INPUT 80164

Rotary Switch Less comwnents. COARSE ZERO

ZERO knob Assembly, METER ZERo

Rotary Switch less components, RANGE 80164

Rotary Switch with components, RANGE
Knob Assembly, Range Switch
Rotary Switch Less components, POLARITY 80164 SW-119

Rotary Switch with components, POLARITY
Knob Assembly, Polarity Switch

Slide Switch, 117-234
Rotary Switch with components, Readout

Dial Assembly, O-4 Readout

Rotary Switch less components, Readout
Rotary Switch with components, Readout
Dial Assembly, O-9 Readout

Rotary Switch less components, Readout
Rotary Switch with components, Readout
Dial Assembly, O-9 Readout

Rotary Switch less components, Readout 80164
Rotary Switch with components, Readout
Dial Assembly, O-9 Readout

Rotary Switch less components, Readout
Dial Assembly, O-LO Readout

Mfg.

Code

80164
80164

80164
80164 14838~

80164 19161A
80164
80164 SW-151

80164 18355~
80164

80164
80164 17080B
80164 14828A

80164
80164
80164 14828A

80164
80164 148288
80164 SW-127

80164 14829A

Keithley
Part No. Ref.

SW-162
148388

SW-197
SW-220

15LLOA
SW-163

19376B

14838A

14827A

SW-118

SW-118

170810

SW-118

19160B

Fig.

2

2
3

2

2

3
2

2

2

2

2

T201
T202

VCLOL

Circuit

Desig. Value Rating

RlOl RlOl 1010 n 1010 n 5%, 5%, 1 1 w w CbF CbF 77764 77764 BBFW BBFW RL25-1010 RL25-1010 16 16
R102 R102 16.67 IQ 16.67 IQ l%, l%, 1 1 w w DCb DCb 91637 91637 DC-L DC-L R13-16.67M R13-16.67M 16 16

gtNNomina.1 value, factory set,
YecOn instruments with 11-step switch.

R381 is used instead.

10671~

Power Transformer
Inverter Transformer

Vibrating Capacitor

80164
80164 TR-80

80164

RESISTORS

Mfg. Mfg.

Type

On instruments with continuous front panel switch,

Code

Part No. Part No.

TR-67

vc-1 15

Keithley

13
18

Fig.
Ref.

43

REPLACEABLE PARTS

MODEL 630 POTEN'PIOMETRIC ELECTROMETER

RESISTORS (Cont'd)

Circuit
Desig.

R103
R104
R105

Rl06
RI.07
Rl08
R109
RllO

Rlll
R112

R113
R114
R115

R116
Rl17
R118
R119
R120

Value

1010 n
109 R
109 12
10 kil
10 kn

10 kn
10 kn

10 kn
10 kn
10 kn

10 kn
10 kn

10 ka

4.7 kn
100 kn

Rating

Mfg.

TYPO

DCb

Mfg.

Code Part NO. Part No. Ref.

00327 NllA Rl2-2M
CbVar 80294 3068S-l-105 RP40-1M
Comp

01121

EB Rl-1M 16

DCb 00327 NllA

Keithley

Fig.

16

15

R125-1010 16
Comp 75042 GBT R37-109 16
camp 75042 GBT R37-109

16
DCb 00327 NllA Rl2-1OK 16
DCb 00327 NllA RlZ-1OK 16

DCb

00327

NllA Rl2-1OK
DCb 00327 NllA R12-10K
DCb 00327 NllA R12-10K
DCb 00327 NllA RlZ-101~

16
16
16
16

DCb 00327 NllA RlZ-10K 16
DCb 00327 NllA RlZ-10K

DCb 00327 NllA R12-10K
DCb 00327
DCb 00327
Comp

01121 EB Rl-100K

NllA RlZ-10K

NllA R12-4.7K

16
16
16

13

R121
R122
Rl23
RI24
Rl25

R126
RI.27
R128
11129

R130
R131

R132
RI.33
I1134
Iu35

111.36

R~L37
1~138
R139
R140

8. 2 1c;i
10 ko

8. 2 k:!
109 i?

109 0
1 MC:

15 I<;:

4.7 M?

4.7 MC

333 k:

1. I<<?

166. 7 k::

333 ki!
1 M\i
15 lc

4.7 BY

4. 7 I(:~'
470 k

4,7 I<

4.7 M

Comp

01121

EB

Rl-8.2K

17
ww var 12697 62~~ RP42-1OK
Comp

01121
Comp 75042 G:BT
Comp

Comp

75042 GBT R37-10g 16

01121 EB Rl-1M

EB

Rl-8.2K 17
R37-109

15

16
Comp 01121 EB Rl-15K 16
Comp 01121
camp

01121 EB Rl-4.7M

DCb 00327

CompV 71450

DCb 00327
DCb 00327 NllA

EB Rl-4.7M 16

16

NllA RlZ-333K

70

RP31-11~

NllA R12-166.7IZ

Rl2-333K

16

16

16

16

Comp 01121 EB Rl-1M 16
Camp

Comp 01121 EB

DCb 00327

DCb 00327 NllA
DCb 00327

DCb 00327

01121 EB Rl-151~ 16

Rl-4.7M

16

NllA Rl2-4.7K 17

RlZ-470K

17

NllA R12-4711 17

NllA R12-4.7M

16

2

0166R

MODEL 630 POTLWTIOMETRIC ELECTROMETER

RESISTORS (Cont'd)

REPLAC1hBLI‘: PARTS

Circuit
Desig. Value Rating

R141
R142
R143
R144
R145

R146

100 kn lO%, l/2 w
820 ci lO%, l/2 w Comp
330 kn lO%, l/Z w Comp

4.7 MO
15 kn

1.5 kn

lO%, l/2 w Comp 01121 EB
lO%, 2 w

lO%, l/2 w
R147 10 kn l%, l/2 w
R148

10 R l%, l/2 w
R149 100 n l%, l/2 w
R150 1.11 kn

R151 200 n
R152

2.5 kn l%, l/2 w
R153 10 kn
R154
R155

R156
R157
R158

8.06 kQ

2&l

10 kn
1 kil
10 hl

l%, l/2 w
l%, l/2 w
l%, l/2 w

l%, l/S w MtF

20%, .2 w
lO%, l/2 w

20%, .2 w
lO%, l/2 w

Mfg. Mfg.

TYPO

Code Part No. Part NO. Ref.

camp 01121 EB

01121 EB
01121

EB

Keithley Fig.

Rl-100K 16
Rl-820 16
Rl-330K 16
Rl-4.7M

C?imp

01121

IIB

camp 01121 EB
DCb 00327 NllA
DCb
DCb
DCb

DCb
DCb

DCb

compv

00327 NllA RI?-10 17
00327

NllA

00327 NllA R12-l.llK 17
00327 NllA

00327 NllA Rl2-2.5K 17
00327 NllA Rl2-1OK 17

07716

CEA

71450 70 RP31-2K 16

R3-15K
Rl-1.5K 16

R12-101~
R12-100 17

Rl2-200

R88-8.06K

Comp 01121 EB Rl-10K
compv
camp

71450

01121

70

EB

RP31-1K 16
Rl-1OK 16

16

16

17

17

15

16

R201
R202
R203
R204
R205

R206
R207
R208
R209
R210

R211
R212
R213
R214

R301
R302
R303
R304
R305

R306
R307

1 kn
10 ko

4.7 kn
470 n

2.2 kn

5.6 kn
56 ko,

50 kn

27 ks2
20 kn

35 kn
47 12

680 11

39 kC2

108 n
220 0

820 kQ

150 Ia

50 kn

1 Mrl
1MQ

lO%, 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
l%, l/2 w
lO%, l/2 w
lO%, 5 w

l%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w

20%, l/2 w
lO%, l/2 w
lO%, l/2 w
lO%, l/2 w
l%, 5 w

lO%, l/2 w
lO%, l/2 w

camp

01121

camp 01121
Camp
Comp
camp

01121

01121

01121 EB Rl-2.2K 18

EB
EB
EB Rl-4.7K
EB

Rl-1K 18
Rl-1OK 18

18

Rl-470

18

Comp 01121 EB Rl-5.6K 18
Comp

01121

EB

Rl-56K 18
DCb 00327 NllA RlZ-50K 18
Comp

01121

EB Rl-27K 18

wwvar 71450 AW RP34-20K 18
DCb

Comp
camp
Comp 01121

Comp
Comp 01121
Comp
Comp

m 91637

00327

01121
01121

75042

01121
01121

NllA R12-35K

EB Rl-47 18
EB
EB

Rl-680

Rl-39K 18

GBT R37-108
EB
EB

Rl-220

Rl-820K

EB Rl-150K
RS-5

R4A-50K
Comp 01121 EB Rl-1M

Comp

01121

EB Rl-1M

18
18

13

20
20
20
20

20
20

1067R

45

REPLACEABLE PARTS MODEL 630 POTENTIOMETRIC ELECTROMETER

RESISTORS (Cont'd)

Circuit

Desig.
R308

R309
R310

R311
R312
R313
R314
R315

R316
R317
R318
R319
R320

R321
R322
R323
R324
R325

Value

3.3 kiz
lM!z

470 n
470 m

2.7,

1Im
10 M!J.

680 k~
330 kil
270 kr2

2.2 l"G

5.6 kn
9<

K

1MCl
220 ksi
125 kn

Rating

lO%, 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
lO%, l/2 w

lO%, l/2 w
lO%, l/2 w

lO%, l/2 w
lO%, l/2 w
lO%, l/2 w

O.l%, 50 w

0.25%, 1 w
lO%, l/2 w
lO%, l/2 w

O.l%, 2 w

Mfg. Mfg.

TYPO

camp
Comp
camp

camp
Comp
camp

Comp

camp

Comp
Comp
Comp
Comp
Comp

ww

Code

01121
01121 EB
01121

01121

01121
01121
01121
01121

01121
01121
01121
01121
01121

91637

ww 01686

Comp 01121
Comp '01121

ww 80164

Keithley

Part NO. Part No.
EB

Rl-3.3K
Rl-1M

EB
EB

EB
EB
EB

EB
EB

EB
EB
EB
EB

RH-50

T2
EB
EB

Rl-470
Rl-470K

Rl-1M
Rl-4.7K
Rl-1M
Rl-1OM

Rl-680K
Rl-330K
Rl-270K
Rl-2.2M
Rl-5.6K

R73-';
Rl30-9~

Rl-1M
Rl-220K

(1)

Fig.

Ref.

20
20
20

20
20
20
20
20

20

20

20
20
20

20
20
20
20
20

R326
R327
R328
R329
R330

R331
R332
R333
R334
R335

R336
R337
R338
R339
R340

68 kfi
68 k.Q
250 ka
1 kn

32.33 kn
180 kn

1 kn

2.563 Ici2
1 kn

250.9 n

O.l%, 2 w

lO%, 5 w

O.l%, l/4 w

0.25%, 50 w

0.25%, 50 w
lO%, l/2 w

lO%, l/2 w

O.l%, 2 w

lO%, 5 w

O.l%, l/2 w

lO%, l/2 w
lO%, 5 w

O.l%, l/2 w

lO%, 5 w

O.l%, ll2 w

ww 80164
wwvar

71450
ww 80164
ww
ww

Comp

80164
80164

01121

Comp 01121

ww 80164
WWVar 71450
ww 80164

Comp 01121

wwvar 71450
ww

80164
wwvar 71450
ww 80164

AW

EB
EB

AW

EB

AW

(1)

RP3-200

(1)
19102A

19102A

Rl-68K
ill-68K

(3)

RP3-1K

(3)

Rl-180K
RP3-1K

(3)

KP3-1K

(3)

R341

to R346

40 kn

O.OZ%, 1 w

ww 80164

(4)

f:Nominal value, factory set.

(1) R325, R326 and R328 comprise a matched set Keithley Part No. 15436A.
(2) See paragraph 4-6.
(3) R333, R335, R338 and R340 comprise a matched set, Keithley Part No. 154328.
(4) Part of Assembly with 5303, Keithley Part No. 18355B.

14
20
20
20
20

20

20

20

20

20
20

13

46

MODEL 630 POTENTIOMETRIC ELECTROMETER

REPLACEABLE PARTS

Circuit
De&g. Value Rating

R347

to R357

to R368

8 kn

1.6 ksl

.02%, 5 w

O.l%, 1 w

R369

to R379

R3809W

to R389

R381""
R390

320 R

O.l%, 112 w

64 n O.l%, l/2 w

750 n
1 kn

lO%, 4 w
lO%, l/2 w

Circuit

Desig.

Number

Mfg.

TYPO

ww

Code Part No. Part No. Ref.

80164

ww 80164

ww 01686

ww 01686

wwvar 12697

Comp 01121

TRANSISTORS

Mfg.

Code

MTg.

7044

7044

58~

EB

Keithley

Part No.

Kcithley

(5)

(6)

R67-320

R67-64

RP49-750

Rl-1K

Fig.

13

13

13

13

2

14

Fig.
Ref.

4201

Q202

Q203
Q204

Q205

Q206
4207
4208

2N1381 01295
2Nll83 02735
2N1535 04713
2N1381 01295

Al380 73445
A1380 73445

2N1183 02735
2N1183 02735

Circuit

Des&. Number
VlOOl

v1002

v1003

v3001
V3002
v3003

v3004
v3005

EF86 73445
EF86 73445
6U8 81454

7025 73445
7025 73445
7025 73445
6CM6 00011

OG3 73445

VACUUM TUBES

Mfg.

Code

TG-8
TG-11
TG-7

TG-8
TG-32

TG-32
TG-11
TG-11

Keithley

18
18

13

18
18

18
18
18

Fig.

Part No. Ref.
EV-EF86

E!V-EF86
BV-6U8

EV-7025
EV-7025
EV-7025

EV-6~~6
EV-OG3

15
15
15

19
19
19
19
19

""On instruments with the discontinuous front panel dial, R380 has a nominal value, factbry

and Ii381 replaces the rest of the string.

set,

(5) Part of Assembly with S304.
(6) Part of Assembly with S305.

1067R

47

REPLACEABLE PARTS MODEL 630 POTENTIOMETRIC ELECTROMETER

MODEL 6302 REPLACEABLE PARTS LIST

Keithley

Description

Part No.

Alligator clip

Insulated Banana Plug

Test Lead Cable 48" long

00011 Sylvania Electric Products, Inc.

Buffalo Operations of Sylvania
Electronic Systems

Buffalo, N. Y.

00327 Welwyn International, Inc.

Cleveland, Ohio

01121 Allen-Bradley Corp.

Milwaukee, Wis.

01295 Texas Instruments, Inc.

Semiconductor-Components Division

Dallas, Texas

01686 RCL Electronics, Inc.

Riverside, N. J.

02735 Radio Corp. of America

Commercial Receiving Tube and
Semiconductor Division
Somerville, N. J.

AC-1

BG-5
SC-20

09569 Mallory Battery Co. of Canada Ltd,

Toronto, Ontario
Canada

12673 Wesco Division

of Atlee Corp.
Greenfield, Mass.

12954 Dickson Electronics Corp.

Scottsdale, Ariz.

13050 Potter co.

Wesson, Mass.

14655 Cornell-Dubilier Electric Corp.

Newark, N. J.

24655 General Radio Co.

West Concord, Mass.

37942 Mallory, P. R., and Co., Inc.

Indianapolis, Ind.

04713 Motorola, Inc.

Semiconductor Products Division
Phoenix, Arizona

05397 Union Carbide Corp.

Linde Division

Kemet

Dept.

Cleveland, Ohio

08520

Electronic Devices, Inc.

North Ridgeville, Ohio

08804 Lamp Metals and Components

Department G. E. Co.
Cleveland, Ohio

'TABLE 9. (Sheet 1).

Code List of Suggested Manufacturers.

Code Tar Manufacturers, Cataloging Handbook H4-1.)

48

56289 Sprague Electric Co.

North Adams, Mass.

58474 Superior Electric Co., The

Bristol, Corm.

71400 Bussmann Mfg. Div. of

McGraw-Edison Co.

St. Louis, MO.

71450 CTS Corp.

Elkhart Ind.

71590 Centralab Division of

Globe-Union, Inc.
Milwaukee, Wis.

(Based on Federal Supply

0166R

MODEL 630 POTENTIOMETRIC ELECTROMETER

REPLACEABLE PARTS

2982 Erie Technological Products, Inc.

Erie, Pa.

3445

3690 Elco Resistor Company

4970 Johnson, E. F., Co.

5042 International Resistance Co.

5915

7764

TABLE 9 (Sheet 2). Code List of Suggested Manufacturers. (Based on Federal Supply
Code for Manufacturers, Cataloging Handbook H4-1).

Amperex Electronic Co. Division of
North American Philips Co., Inc.
Hicksville, N. Y.

New York, N. Y.

Waseca, Minn.

Philadelphia, Pa.
Littelfuse, Inc.

Des Plaines, 111.
Resistance Products Co.

Harrisburg, Pa.

80164 Keithley Instruments, Inc.

Cleveland, Ohio

81454 Reade Mfg. Co.

Jersey City, N. J.

91637 Dale Electronics, Inc.

Columbus, Nebr.

93656 Electric Cord Co.

Caldwell, N. J.

94139 Keystone Electronics Co.

Newark, N. J.

95712 Dage Electric Co., Inc.

Franklin, Ind.

0166R

49

ii-­c--