Tektronix 601 Instruction Manual

MODEL 601 ELECTROMETER

CONTENTS

TABLE OF CONTENTS

Section

1. GENERAL DESCRIPTION .
l-l. General . . .
1-2.
1-3.

Features .

Specifications ,
l-4. Applications . .
1-5.
1-6.

2. OPERATION . . . . .

2-l.

Accessories . .
Equipment Shipped

. . .

Front Panel Controls

and Terminals . . . .

2-2.

Rear Panel Controls

and Terminals . . .

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

Input Connections . . .
Preliminary Procedures
Voltage Measurements .

Off Ground Voltage

Measurements . . . .

2-7.
2-8.
2-9.
2-10.
2-11.

Current Measurements .
Resistance Measurements
Charge Measurements . .

Recorder Outputs . . . . . . 17

Unity Gain Output . . .

3. APPLICATIONS . . . . . . . . . .

3-l.

General . . . : . . . . , .

3-2. current source , . . . . .

3-3. Static Charge Measurements
3-4.
3-5.

Capacitance Measurements .

current Integrator . . . .

3-6. Potentiometric Voltage

Measurements . . . . , .

3-7.

Measuring Diode

Characteristics . . . . ,

3-8.

4.

CIRCUIT DESCRIPTION . . . , .

Peak-Reading Voltmeter . .

4-l. General . . . . . . .

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

5.

SERVICING . . . . . . . . .

Voltmeter Opiration , .

Voltmeter Circuit . . .
Ammeter Operation . . .
Ohmmeter Operation . .
Coulombmeter Operation

5-l. General . . . . . . . .

5-2. Servicing Schedule .
5-3.

Parts Replacement , . ,

Page

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2

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5

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5

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27

28
29

31
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Section

5-4. Troubleshooting . . . .

5-5.

Procedures to Guide

Troubleshooting . . . .

6. CALIBRATION . . . . . . .

6-l.
6-2.
6-3.
6-4.

General . . , . . . . . . .

Calibration Schedule . . .

Grid Current Check . . . . .

DC Amplifier Balance

Adjustment . . . . . . . .

6-5. High-Megohm Resistor

Verification . . . . . . .

6-6. Meter Zero Calibration . .

6-J.

6-8.

7.

ACCESSORIES . . . . . . . .

J-l.
J-2.
J-3.

Accuracy Check . . . , , . .

Drift Check . . . . . . . .

Model 6011 Input Cable . .
Model 1531 Gripping Probe .
Model 6301 Guarded Probe . .

7-4. Model 6012 Triaxial-to-

Coaxial Adapter . . .

7-5. Model 6102A Voltage Divider

Probe , , . . , . , . . .

7-6. Model 6103A Voltage Divider

Probe , . . . . . , . .

J-7.

Model 6104 Test Shield . .

7-8. Model 6105 Resistivity

Adapter . . . . . . . . .~

7-9.

Models 2501 and 2503 Static

Detector Probes , . . . .

J-10.

Rack Mounting . . . , . . .

J-11. Model 6013 pH Electrode

Adapter . . . . . . . .

J-12.

MQdel

370

Recorder . . . . .

\

8.

REPLACEABLE PARTS . . . . . . .

8-1.
8-2.

Replaceable Parts List . . .

How to Order Parts . . . .

Model 601 Replaceable

parts List . . . . . . . ,

Schematic Diagram 194283 .

,*

Change Notice . . . . . . . . .last page

* Yellow Change Notice sheet is included

only for instrument modifications
affecting the instruction manual.

Page

31
31
35

35
35
35

36
36

36
37
38

43
43
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43

43
44
44

44
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46
47

4,8

51
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51

52
58

0667R

i

GENERAL DESCRIPTION

MODEL 601 ELECTROMETER

-

XGURE 1.

ii

Keithley Instruments Model 601 Electrometer.

9666

MODEL 601 ELECTROMETER

GENERAL DESCRIPTION

SBCTION 1.

l-l. GENEXAL.

a. The Keithley Model 601 Electrometer is a versatile battery operated instrument which
measures wide ranges of dc voltages, currents, resistances and charges.
refined dc vacuum tube voltmeter that uses an electrometer tube input to provide greater

than 1014 ohm input resistance.

VTVMs, but Lt can also make many more measurements without loading circuits.

The Electrometer has nine volta e ranges from 0.001 volt full scale to 10 volts,

b.
twenty-eight current ranges from 10'
resistance ranges from 100 ohms full scale to 1013 ohms,

10-12 coulomb full scare to 10-6 coulomb.

The Model 601 offers complete line isolation and excellent off-ground measuring capa-

bi;ity. Up to 1500 volts may be applied between the input low terminal and the case, and

safe operation is
guarding of the high terminal.

The Model 601 employs matched electrometer input tubes followed by three differen-

d.
tial transistor amplifier stages and a transistor output stage.
tive feedback is used for stability and accuracy.

assured

with the case grounded. A three-terminal input allows complete

The Model 601 has all the capabilities of conventional

GENERAL DESCRIPTION

It is a highly

l$

ampere full scale to 0.3 ampere, twenty-three linear

and thirteen charge ranges from

A large amount of nega-

l-2.

hour period after warm-up. During the 2-hour warm-up, zero drift is no more than 2 milli­volts after the first hour.

+l volt or fl milliampere for full-scale meter deflection.

25% with 1.4-kilohm recorders. The unity-gain amplifier output is equal to the input
voltage within 50 ppm or 100 inicrovolts, exclusive of zero drift.

&he current is determined by measuring the voltage drop across a resistor shunting the

oxput, or the fast method in which negative feedback is applied through the shunt resis-

tor.
greatly increases the response speed on the low-current ranges.

interruptions for-recharging.

corder output is used.

the panel meter,

FEATURES.
Voltmeter accuracy is *l% of full scale, exclusive of noise and drift.

a.

Zero drift of the Model 601 is 200 microvolts per hour maximum averaged over any 24-

b.

Two amplifier outputs are available. A switch on the rear panel allows either

c.

The-current output is variable

Current measurements can be made by one of two methods: the normal method in which

d.

The former method minimizes noise. The latter method reduces the input drop and

e. The lOOO-hour life of the batteries enables "sage in Long-term experiments without

Battery life is maintained even when the l-milliampere re-

For further convenience, battery condition is readily checked on

056JR

1

GENERAL DESCRIPTION

1-3. SPECIFICATIONS.

AS A VOLTMETER:

MODEL 601 ELECTROMETER

RANGE:

ACCURACY:

ZERO DRIFT:
any subsequent 24-hour period,

METER NOISE:

INPUT IMPEDANCE:

.OOl volt full scale to 10 volts in nine lx and 3x ranges.

~1% of full scale on all ranges exclusive of noise and drift.

After l-hour warm-up no more than 2 millivolts in the second hour, and in

the average drift will not exceed 200 microvolts per hour.

Cl0 microvolts maximum with input shorted on most sensitive range.

Greater than 1014 ohms shunted by 20 picofarads. Input resistance may

also be selected in decade steps from 10
AS AN AMMETER:
RANGE:
ACCURACY:

Multiplier Switch setting;
METER NOISE:

GRID CURRENT:

LO-14 ampere full scale to 0.3 ampere in twenty-eight lx and 3x ranges.

*z% of full scale on 0.3 to lo-11 ampere ranges using the smallest available

24% of full scale on 3 x lo-12 to lo-14 ampere ranges.

Less

than i3 x 10'15 ampere.

Less than 2 x LO-l4 ampere.

AS AN OHMMETER:

to

1011 ohms.

RANGE:
ACCUR4CY:

plier Switch setting:

100 ohms full scale to 1013 ohms in twenty-three linear lx and 3x ranges.

23% of full scale on 100 to 108 ohm ran 8 es using the largest available Multi-

;t5% of full scale on 3 x 10 to 1013 ohm ranges.
AS A COULOMBMETER:
RANGE:

ACCURACY:

LO-12 coulomb full scale to lo-6 coulomb in thirteen lx and 3x ranges.

i5% of full scale on all ranges. Drift due to grid current does not exceed

2 x lo-14 coulomb per second.
AS AN AMPLIFIER:
INPUT IMPEDANCE: Greater than 1014 ohms shunted by 20 picofarads. Input resistance may

also be selected in decade steps from 10 to 1011 ohms.

OUTPUTS: Unity-gain output and either voltage or current recorder output.
UNITY-GAIN OUTPUT:

clusive of zero drift.

At dc, output is equal to input within 50 ppm or 100 microvolts, ex-

Up to 0.1 milliampere may be drawn. Output polarity is same as

input polarity

0366R

MODEL 601 ELECTROMETER

GENERAL DESCRIPTION

VOLTAGE RECORDER. OUTPUT:

+l volt for full-scale input. Internal resistance is 910 ohms.

Output polarity is opposite input polarity.

Gain:

0.1, 0.33,

Frequency Response (Within 3 db):

etc.

to 1000.

dc to 100 cps at a gain of 1000, rising to 50 kc st

a gain of 3.3, decreasing to 1 kc at a gain of 0.1.

Noise:

Less than 2% rms of full scale at a gain of 1000, decreasing to less than 0.5%

at gains below 10.

CURRENT RECORDER OUTPUT:

il milliampere for full-scale input, variable +5% with 1400-ohm

recorders.
GENERAL:
ISOLATION:

Input low to case: greater than 1010 ohms shunted by 0.0015 microfarad. I*-

put low may be floated up to k1500 volts with respect to case.
POLARITY:

Meter switch selects left-zero (positive or negative) or center-zero scales.

Meter switch does not reverse polarity of outputs.

CONNECTORS: Input:

Teflon-insulated triaxial Dage 33050-l. Lo: binding post. Voltage

or current output: Amphenol 80-PC2F. Unity gain output, case ground: binding posts.
BATTERY CHECK:
BATTERIES:

E42N or HG42R).
DIMENSIONS, WEIGHT:

Condition of all batteries may be checked with front panel controls.

Four 2N6 (or 246, VS305 or NEDA 1602); three TR286 (or E286); two RM42R (or

1000 hours battery life.

10-l/2 inches high x 6-5/b inches wide x 10 inches deep; net weight,

14 pounds.

ACCESSORIES SUPPLIED:

Model 6011 Input Cable; mating output connector.

l-4. APPLICATIONS.

Voltmeter applications include directly measuring potentials across pH electrodes,

a.

piezoelectric crystals, capacitors,

electro-chemical cells and biological membranes.

The Model 601 is also useful as a null detector with potentiometers or bridges in high im-

pedance applications.

As a picoammeter the Model 601 can br used with photomultiplier tubes, flame and

b.

beta ray ionization detectors,

lithium ion drift detectors and gas chromatographs.

It is

also useful in nuclear studies , plasma physics and vacuum research.

c. As an ohmmeter the Electrometer is ideal for measuring insulation resistance and
resistor voltage coefficients.
since the Model 601 low terminal can be isolated from case ground.

It is useful for measuring "in circuit" resistances,

Volume and surface re-

sistivities can be measured with the Model 601 and the Model 6105 Resistivity Adapter.

d.

0366R

In addition to measuring charge directly

other coulombmeter uses are measuring

3

GENERAL DESCRIPTION

MODEL 601 ELECTROMETER

charge current over a period and obtaining integral curves of time varying currents. The
Electrometer can also be used as a charge amplifier to measure piezoelectric crystal out­puts.

l-5.

ACCESSORIES.

(Also see Section 7).

a. Model 6011 Input Cable has 30 inches of low noise triaxFa1 cable with mating triax-

ial input connector and three alligator clips.

Model 6013 pH Electrode Adapter has a Z-foot cable and triaxial connector and accepts

b.

Leed

& Northrop and Beckman pH electrode connectors.

The Adapter allows accurate and con-

venient pH potential measurements with the Model 601.

c. Model 6301 is a high impedance guarded probe with a 3-foot connecting triaxial
cable that allows measurements to be made more conveniently.
lation resistance of over 1014 ohms.

Using the Probe does not effect any Model 601

The Model 6301 has an insu-

specifications.

Model 1531 is a gripping probe with a 3-foot connecting triaxial cable. The Model

d.
1531 has an insulation resistance of over lOlo ohms.

e. Model 4005 Rack Mounting Kit adapts the Model 601 to rack mounting 10-l/2 inches

high x 19 inches wide.

The Kit can accommodate two Model 601's side-by-side by using an

additional cover.

Model 6012 Triaxial-to-Coaxial Adapter permits using the Model 601 with all Keithley

f.
electrometer accessories having uhf type coaxial connectors. These include the Models
6102A, 6103A, 6104, 6105, 2501 and 2503:

using the Adapter,

the Model 601 should not be floated.

Since circuit low and case ground are connected

Models 6102A and 6103A voltage divider probes, described in Section 7, facilitate

g.

measurements and extend the voltage range to 10 kilovolts.

Model 6104 Test Shield is suitable for resistance measurements with either 2 or

h.

3-terminal guarded connections,

as well as voltage and current tests.

i. Model 6105 Resistivity Adapter is a guarded test fixture for measuring volume and
surface resistivities of materials when used with the Model 601 and the Keithley Model
240A High Voltage Supply.

Models 2501 and 2503 Static Detector Probes are capacitive voltage dividers with a

j.
10,OOO:l ratio, when used with the Probe 3/8 inch from the charged surface.

k. Model 370 Recorder is uniquely compatible with the Model 601 as well as other

Keithley microvoltmeters, electrometers and picoammeters.

The recorder is a high quality

economical instrument that maximizes the performance of the Model 601, and many other

Keithley instruments, even in the most critical applications.

l-6.

with all components in place.

EQUIPMENT SHIPPED. The Model 601 Electrometer is factory calibrated and shipped

The shipping carton also contains the Instruction Manual,

'Model 6011 Input Cable and mating output plug.

4

0667R

MODEL 601 ELECTROMETER

OPERATION

SECTION 2.

2-l. FRONT PANEL CONTROLS AND TERMINALS (See Figure 2)

Range Switch.

a.

divided into a VOLTS position, 11 AMPERES ranges,

ranges.
for all ranges is the Range Switch setting times the Multiplier Switch setting. The 10 or
3 of the top meter scale corresponds to the full-scale deflection for the range selected;
for example,

b.
dc amplifier and sets the full-scale voltage range when the Range Switch is set to VOLTS.
The Multiplier Switch may also be used to multiply the AMPERES (3x maximum setting above

10a3), OHMS and COULOMBS ranges on the Range Switch.
the range used.

c.
position allows checking of the battery condition with the Multiplier Switch. POWER OFF
shuts off the instrument. OFF disconnects only the meter during recorder operation.
+ and - positions determine the polarity of the meter.
for center zero operation (lower meter scale).

A line above the dial skirt indicates the range used. Full-scale sensitivity

on the l-volt range, the needle is at 10 for a l-volt input.

Multiplier Switch.

METER Switch.

The Range Switch selects the measuring mode and the range. It is

The Multiplier Switch determines the voltage sensitivity of the

The Switch has six positions:

OPERATION

eight OHMS ranges and four COULOMBS

A line above the dial skirt indicates

the spring-returned BATTERY CHECK

The

CENTER ZERO sets the instrument

ZERO Controls. Two ZERO Controls are

d.

on the front panel:

knob) and a lo-turn FINE potentiometer

(center knob). These allow precise meter

zeroing.

ZERO CHECK Button. Depressing the

e.

Button effectively removes all input signal

from the instrument by shunting the input

and amplifier through 10 megohms. This
allows meter zeroing on any range. The
Button is locked in the zero check position

when the line is horizontal.

FEEDBACK Switch, The FAST and NORMAL

f.

positions of the Switch determine the feed­back connections within the instrument.
With the Switch at FAST, current measure-

ments are made with the range resistors in

the feedback network;

input voltage drops and faster response
speeds. The FAST position is also used for
coulomb measurements, and~to increase re-

sponse speed.

the range resistors shunt the input.

INPUT Receptacle. The INPUT Recepta-

g.

cle is a Teflon-insulated triaxial type
connector.

When the Switch is in NORMAL,

Its center terminal is the cir-

a MEDIUM Switch (outer

this results in lower

FIGURE 2. Model 601 Front Panel Controls
and Terminals.
to Replaceable Parts List and the Schematic
Diagram.

Circuit designations refer

0666R

5

OPERATION MODEL 601 ELECTROMETER

cuit high; the inner shield is circuit low

(circuit ground);

ground.
provided.
Receptacle,

(See Figure 4.) A shield cap is

The LO Terminal, below the

is connected to circuit low;

the outer shield is case

it is connected to case ground only if the
shorting link on the rear panel is connect­ed.

2-2.

REAR PANEL CONTROLS AND TERMINALS

(See Figure 3).

COARSE ZERO SWITCH. The COARSE ZERO

a.

Switch has 11 positions to extend the zero­ing capability of the front panel ZERO Con­trols.

OUTPUT Switch.

d.

The Switch is a two­position slide switch for the output. In
the 1 MA position,

the instrument will
drive l-milliampere recorders. In the 1 V
position, the output is 1 volt for full­scale meter deflection. Source resistance
is approximately 1090 ohms.

C. 1 MA CAL Control. The Control varies
the output from 0.95 to 1.05 milliampere
for 1400-ohm recorders, so the recorder
scale will correspond with the Electrometer
meter.

OUTPUT Receptacle. A 2-terminal microphone-type receptacle provides 1 volt or 1 mil-

d.

liampere for full-scale meter deflection.

Switch is at NORMAL.

Neither terminal is at ground when the FEEDBACK Switch is at FAST.

Pin No. 2 is at circuit low when the FEEDBACK

Both terminals.are isolated from case ground.

‘LtiUKli 3.

Model

and Terminals.

bUL Kear hnel COntrols

Xl OUTPUT and OHMS GUARD Terminals. The potential between the Xl OUTPUT Terminal

e.

and the OHMS GUARD Terminal (circuit low when the FEEDBACK Switch is in NORMAL) is equal
to the input voltage with 0.005% linearity or 100 microvolts.

When the FEEDBACK Switch

is at FAST, the Xl OUTPUT Terminal is at circuit low and the OHMS GUARD Terminal is float­ing.

LO Terminal.

f.

A black terminal allows connection to the input low connection. Con-

necting the LO and CASE GROUND Terminals puts both at case ground.

CASE GROUND Terminal.

g.
of the Model 601 and the outside shell of the input connector.

A blue termitial is connected directly to the outside cabinet

It is connected to nothing

else within the instrument.

NOTE

If the Model 601 will be stored for a long period, remove batteries.

Also, make

sure the METER Switch is at POWER OFF when the instrument is not being used.

6

0666R

MODEL 601 ELECTROMETER

OPERATION

7

heavy wire with red clip cover

TABLE 1.

Lead

Input (circuit) high center
thin wire with black clip cover
thin wire with blue clip cover

Input (circuit) low Inner shield

Case Ground Outer shield

Color Coding of Alligator Clips for Model 6011 Input Cable.

Circuit JlOl Terminal

2-3. INPUT CONNECTIONS.

The accessories described in Section 7 are designed to increase the accuracy and

a.

convenience of input connections.

Use them to gain the maximum capability of the Model

601.
b.

tions.

The Mo4el 6011 Input Cable,

Table 1 contains the color coding of the alligator clips.

supplied with the instrument, facilitates input connec-

The high terminal is
shielded by the inner braid of the triaxial cable up to the miniature alligator clip. If
the unshielded clip causes pick up from near-by electric fields, remove it and connect

the shielded lead directly to the source.

NOTE

Techniques and applications are thoroughly discussed in the brochure, Electro­meter Measurements, by Joseph F. Keithley.
ments, Inc.,

or its representatives.

It is available from Keithley Instru-

Carefully shield the input connection and the source being measured, since power

C.
line frequencies are well within the pass band of the Electrometer.
is thorough,

any alteration in the electrostatic field near the input circuitry will cause

Unless the shiefding

definite meter disturbances.

Use high resistance, low-loss materials - such as Teflon (recommended), polyethy-

d.

lene or polystyrene - for insulation.

The insulation leakage resistance of test fixtures

and leads should be several orders magnitude higher than the internal resistance of the

SOlL?ZCe.

Excessive leakage reduces the accuracy of readings from high impedance sources.

Triaxial or coaxial cables used should be a low-noise type which employ a graphite or

other conductive coating between the dielectric and the surrounding shield braid.

Amphen­ol-Borg Electronics Corporation, Microdot, Inc., and Simplex Wire and Cable Company make
satisfactory types. Using the supplied Model 6011 Input Cable is j simple way to insure
good input connections,

NOTE

Clean, dry connections and cables are very important to maintain the value of all
insulation materials. Even the best insulation can be compromised by dust, dirt,

solder flux, films of oil or water vapor. A good cleaning agent is methyl alcohol,

which dissolves most common dirt without chemically attacking the insulation. Wash

salt solutions with distilled water before using the cleaning agent.

Any change in the capacitance of the measuring circuit to low will cause extraneous

e.

disturbances.

cables to prevent their movement.

sinusoidal signal,

Make the measuring setup as rigid as possible, and tie down connecting

A continuous vibration may appear at the output as a

and other precautions may be necessary to isolate the instrument and

0666R

7

OPERATION MODEL 601 ELECTROMETER

the connecting cable from the vibration.

For low impedance measurements -

f.

below 108 ohms or above 10m8 ampere - un-

shielded leads may be used.
the leads short.

However, keep

When measuring currents LO-l4

g.

or less with the FEEDBACK Switch at FAST,
sOme insulators
produce random signals which show up as
erratic meter deflections. Insulation

used in the Model 601 is carefully selected

to minimize these signals.

h.

It is usual,ly better to connect the

Model 601 to the circuit only when a reading

is being made.

rent can charge the external test circuitry.

One example of this occurs when measuring a

capacitor's

the decay of the terminal voltage. If the leakage current is less than the grid current,
there may be no decay.of the terminal voltage when the Electrometer is left connected

across the capacitor's terminals.

Keep the shielded cap on the INPUT Receptacle when the Electrometer is not in
a circuit.

The Model 6012 Triaxial to Coaxial Adapter enables using coaxial cables and acces-

i.

sories with the Model 601 by adapting the triaxial INPUT connector to the uhf coaxial type.

- such as Teflon - may

In some cases, the grid cur-

leakage

resistance

ampere

by observing

L

FIGURE 4. Model 601 Triaxial Incut Receo
tac1e.
input high;
or input low;

ground.

NOTE

The center terminal is circuit 0;

the inner shield is circuit

the outer shield is case

NOTE

The Adapter connects circuit low to case ground.
when using the Adapter.
as the input low.

2-4.

the METER Switch to the BATTERY CHECK po­sition.

through the .OOl to 0.1 positions, and ob­serve the meter readings.
read one-half of full scale or mwre for each

Multiplier Switch position. Table 2 shows

the batteries checked by position.
reading for any battery is below half

scale,
teries may cause the Model 601 to drift more

than normal for at least 72 hours due to
change in battery terminal voltage.

8

PRELIMINARY PROCEDURES.
Check battery condition by setting

a.

Rotate the Multiplier Switch

replace all batt'eries.

The instrument chassis will be at the same potential

The meter should

If the

Note new bat-

Do not float the Model 601

Multiplier position

I

.OOl
.003
.Ol

.03

0.1 R208 h 732n9

TABLE 2. Multiplier Switch Positions for
Checking Condition of Batteries

Battery Checked

B201 & B202
B203
B204 & B205
B206 & B207

0766R

I

MODEL 601 ELECTROMETER

Set the controls as follows:

b.

OPERATION

METER Switch

Range Switch

Multiplier Switch

FEEDBACK Switch NORMAL
ZERO CHECK Button

Turn the METER Switch to CENTER ZERO.

c.
come to the center zero position.
ZERO Controls.

After a few moments increase the voltage sensitivity by advancing the Multiplier

d.

Normally,

Switch to .3, .l, etc.

After long periods of storage or after a" overload,

e.
sively.

The electrometer tubes are shock mounted; however,

there is no need to use the COARSE ZERO Switch.

Continue zeroing with the FINE ZERO Control.

meter may cause a zero offset.

though,

can occur for several hours.

If the Model 601 has been stored for some time, the grid current will exceed the
specification when first used

---I

one or two hours of use.
tube; the instrument is not faulty.

POWER OFF

VOLTS

1

LOCK

the

meter needle should

If not,

Within ten seconds,

adjust to meter zero with the MEDIUM and FINE

the Model 601 may drift exces-

a severe jolt to the Electro-

This is corrected with the Zero Controls.

Drifting,

NUTE

then decrease to below the specified amount after

This is a" inherent characteristic of the electrometer

Although the grid current of the Electrometer is much below that found in conven-

f.

tional voltmeters,

grid current charging the input capacitance,

the input is open.

Follow the particular procedures in paragraph 2-5 to 2-9 for measuring voltage, cur-

g.

rent,

resistance and charge.

voltage, current,

set to IV if the output is notconnected

----­effect.

When the output is connected to a load,

it can be observed on the meter.

A small voltage results from the

and the Electrometer appears to drift when

Use the ZERO CHECK Button to discharge the build-up.

When using Multiplier Switch settings of 10, 3 and 1 in the

resistance and charge measuring modes,

---

to a load.

this effect is not present.

make sure the Output Switch is

---

Otherwise,

the meter shows a loading

--

-----

NOTE

Using the center zero scales decreases accuracy 0.5% because Lhe scale spa" is

shorter.

2-5. VOLTAGE MEASUREMENTS.

The Model 601 can be used to measure voltages several ways.

a.

1. In the normal method - FEEDBACK Switch at NORMAL - the unknown voltage is co"-

netted to the INPUT Receptacle.

To reduce the slowing effects of input capacity, use the fast method to measure

2.

Input impedance is iO-l4 ohms, 20 pf.

the voltage. A guarded circuit is possible this way.

3.

if desired.

0667R

To measure Low impedance sources,

the Model 601 input resistance can be decreased

9

OPERATION

Accessory probes extend the Model 601's range to 10 kilovolts.

4, .

NOTE

Locking the ZERO CHECK Switch places 10 megohms acro.ss input high and low, which
may temporarily cause instability in some types of high impedance sources.

Normal Method Voltage Measurements.

b.

MODEL 601 ELECTROMETER

Follow the instructions of paragraph Z-4..

1.
METER Switch

Range Switch VOLTS
Multiplier Switch
FEEDBACK Switch

ZERO CHECK Button

Connect the unknown voltage to the INPUT Receptacle; unlock the ZERO CHECK Button.

2.
Set the METER Switch to + or -, as necessary.
Switch.

3.
C. Fast Method Voltage Measurements.

capacity and allows guarded voltage measurements.

1.

Recheck zero setting after increasing sensitivity.

For off-ground measurements, see paragraph 2-6.

This method reduces the slowing effects of input

Follow the instructions of paragraph Z-4,.

METER Switch

Range Switch
Multiplier Switch 10
FEEDBACK Switch

ZERO CHECK LOCK

CENTER ZERO

10

NORMAL

LOCK

CENTER ZERO
VOLTS

FAST

Set the controls as follows:

Increase sensitivity with the Multiplier

Set the controls as follows:

2. Connect CASE GROUND Terminal to OHMS GUARD Terminal, using the shorting link.
Connect the unknown voltage t.o the high (center) terminal of the INPUT Receptacle

3.

and to the CASE GROUND Terminal on the rear panel. Use the LO Terminal as a guard be-

tween circuit high and low.

or -, as necessary.

ting after increasing sensitivity.

To make off ground voltage measurements, see paragraph 2-6.

4..

d. Low Impedance Measurements.
one of the AMPERES ranges. The input resistance is now the reciprocal of the current
range.
the 10s7 AMPERES range.
Operating procedures are the same as subparagraph b.

Model 601 will not run off scale as easily in the presence of excessive ac fields. This

occurs only when the input is left open.

10

For instance,

Increase sensitivity with the Multiplier Switch. Recheck zero set-

to obtain a" input resistance of 107 ohms, set the Range Switch to

Set the full-scale voltage range with the Multiplier Switch.

Unlock the ZERO CHECK Button. Set the METER Switch to +

To decrease input resistance, set the Range Switch to

At lower input resistances, the

0567R

MODEL 601 ELECTROMETER

OPERATION

To measure sources more than 10 volts, use one of two divider probes.

e.

The Model
6102A 1O:l Divider Probe extends the Model 601's range to 100 volts; overall accuracy is
?3% and input resistance is lOLo ohms.

The Model 6103A 1OOO:l Divider Probe extends the

Model 601's range to 10 kilovolts; overall accuracy is f5% and input resistance is 1012

ohms.

Follow the same operating procedures with the dividers as in subparagraph b. The
Model 6012 Triaxial-to-Coaxial Adapter must be used with the Models 6102A and 6103A
Divider Probes. Note, however, using the Adapter connects circuit low to case ground; do
not float the Electrometer. The full-scale voltage range is the divider ratio times the
Multiplier Switch setting.

Operating the Model 601 nwre than 1500 volts off ground may permanently damage
the instrument. Isolation between circuit low and ground may break down some­where Fn the circuit, putting the case at an off-ground potential. Since these
breakdowns are very difficult to locate, it might not be possible to float the
instrument safely again.

2-6. OFF GROUND VOLTAGE MEASUREMENTS.

a. The Model 601 can measure an unknown voltage whose low is up to 1500 volts off
ground while its own case is at ground. This allows safe operation of the Electrometer.
Its operation is the same as given in paragraph 2-5, except for input connections and
some added cautions.

These differ, depending upon the FEEDBACK Switch setting.

FEEDBACK Switch set to NORMAL. Disconnect the shorting link between the LO and

1.

CASE GROUND Terminals on the rear panel. Make sure the Model 601 case is securely con-

nected to an earth ground,

volts dff ground.

Connect the unknown voltage directly to the INPUT Receptacle.

and that the low of the unknown voltage is less than 1500

Opel-~

ate the Model 601 as described for normal method voltage measurements.

FEEDBACK Switch set to FAST. Do not use the shorting link.

2.

601 case is securely connected to an earth ground,

tage is less than 1500 volts off ground.

Ground the outer shield of the INPUT Receptacle.

and that the low of the unknown vol-

Make sure the Model

Connect the high of the unknown voltage to the canter terminal of the INPUT Receptacle.
Connect the low to the GUARD Terminal. Use the inner shield of the INPUT Receptacle as

a guard. Operate the Model 601 as described for fast method voltage measurements.

NOTE

When the Model 601 is off ground, make sure the shell of a mating plug to the

OUTPUT Receptacle is not connected to either pin in the Receptacle.

If the Model 6012 Adapter is used, do not float the Model 601. The Adapter connects

b.

the input low to the case ground,

so that the Model 601 chassis and controls are at the

same potential as the Low of the unknown source.

NOTE

Use only an insulated blade screwdriver to adjust the COARSE ZERO Switch and 1 MA

CAL Cdntrol when floating the Model 601.

circuit low to case ground,

creating a shock hazard and damaging the external cir-

An ordinary screwdriver could short the

cuitry.

06668

II

OPERATION

MODEL 601 ELECTROMETER

-------------

r

1

r----------‘--

R

I

I

EE

I

I
I
I

I
I

I
I

I

FIGURE 5.
sarias with a resistance (R).

ammeter is attached to measure the current,

Annneter Circuit Loading. Current sources may be considered a voltage (E) in

The current with no annneter attached is I=E/R. When an

the effective input resistance of the ammeter

Rin is in series with the source resistance (R).

less and Imeter = E/(R + Rtn).
pared to R, Imeter+

2-7.

CURRENT MEASUREMENTS.

- I and the error introduced by circuit loading is negligible.

If the effective ammeter input resistance is small com-

a. The Model 601 can measure currants three ways.

Rin

I meter

The current in the complete circuit is

In the normal method - used on any range - the currant is determined by measur-

1.

ing the voltage drop across a resistor shunting the amplifier input.

This method is

useful when lower noise is more important than faster response speeds or if some damp-

ing is needed.

In the fast method

2.

tor is between the amplifier output and input in the feedback loop.

- for use only below the 10V5

ampere range

- the shunt resis-

This circuit
largely neutralizes the effect of input capacity and greatly increases the response
speed.

Also, the input voltage drop is reduced to a maximum of one millivolt on any

range.

For galvanometric current measurements, the Model 601 acts as a null indicator

3.

between a very accurate current source and the unknown current source.

Its off ground

operating capability makes it ideal for this application since the reference source and
unknown may both have a common grounded terminal.

b. Rise tima varies primarily with the current range, the input capacity and the method

used.

On most ranges, the rise time in the fast mode is less than one second with 50
picofarads across the input. Even with much larger shunt capacities, the negative feed­back maintains a short rise time. Given a choice, it is better to placg the Electrometer
nearer to the current source than to the data reading instrument.

Transmitting the input
signal through long cables greatly decreases the response speed and increases noise due
to the cable capacitance.

To measure from a source with both terminals off ground in either method, remove

C.

the link between the LO and CASE GROUND Terminals on the rear panel.

Connect the unknown

current to the INPUT .Receptacle. The source must be less than *1500 volts off ground

(see paragraph 2-6).

12

0766R

MODEL 601 ELECTROMETER

Normal Method (0.3 to lo-l4 ampere ranges).

d.

OPERATION

Follow the instructions of paragraph 2-4.

1.
METER Switch

Range Switch

Multiplier Switch

FEEDBACK Switch

ZERO CHECK Button

Connect the unknown current to the INPUT Receptacle and unlock the ZERO CHECK Button.
Set the METER Switch to + or -, as necessary.
Switch and the Multiplier Switch.
Range Switch settings 10m3 and above.

Full-scale current range is the settings of the Range Switch times the Multiplier

2.
Switch.
drop and obtain the best accuracy.

ting, from 10 ohms at 10-l AMPERES to loll ohms for lo-11 AMPERES.
is the percentage of full scale that the meter reads times the Multiplier Switch setting.

On the low current ranges, balance cut the grid current with the Zero Controls

or subtract the value from the reading.
cap the INPUT Receptacle and read the meter.

Use the smallest Multiplier Switch setting possible to minimize input voltage

Do not set the Multiplier Switch higher than 3 for

Check zero with the ZERO CHECK Button.

The input Fesistor varies with the Range Switch set-

NOTE

To find the aawunt of grid current,

Set the controls as follows:

CENTER ZERO

10-l AMPERES
1

NORMAL

LOCK

Increase the sensitivity with the Range

Input voltage drop

Fast Method (ranges below lOa ampere).

e.

Follow the instructions of paragraph 2-4.

1.
METER Switch CENTER ZERO

Range Switch

Multiplier Switch

FEEDBACK Switch
ZERO CHECK Button

Connect the unknown source to the INPUT Receptacle and unlock the ZERO CHECK Button.

Set the METER Switch to + or -, as necessary.
Range Switch and the Multiplier Switch. Do not set the Range Switch to 10e5 AMPERES or
higher. Check zero with the ZERO CHECK Button.

NOTE

Use only the ZERO CHECK Button to check zero for the fast method.

the input, because this will remove the feedback from the circuit.

The full-scale current range is the Range Switch setting times the Multiplier

2.
Switch setting. When selecting the Multiplier Switch setting, remember small settings
permit lower current source resistance, and larger settings improve instrument zero
stability. Check the caution in subparagraph 3a below.

Set the controls as follows:

10-6

AMPERES

1
FAST
LOCK

Increase the sensitivity with the

Do not short

066711

13

OPERATION

With the fast method, the input drop is reduced and the response speed is in-

3.

creased at least 100 times.

The

4

internal impedance of the unknown current scnxce should not be less than

However, follow these precautions:

MODEL 601 ELECTROMETER

0.1 of the value of the feedback resistor being used. otherwise, adequate feedback
voltage cannot be developed at the input,

and zero instability results. The feedback

resistor value is the reciprocal of the AMPERES range of the Range Switch.

voltage drop across the current source should be at least 100 times the voltage drop

acrOsS the Model 601.

b) The low side (Pin No. 2) of the OUTPUT Receptacle is no longer connected to the

low side of the INPUT Receptacle.

to be electrically connected,

low side of the current source.

Therefore, do not allow the low side of a recorder

such as through the ground lead of a power cord, to the

Another alternative is “sing the unity-gain output.

(See paragraph Z-11.)

c) Do not use the fast method to measure capacitance unless “sing a very stable vol-

tage supply.

to;,

.

resulting in extreme sensitivity to very small voltage transients.

Connecting a capacitor to the input changes the circuit to a differentia-

I

Galvanometric Method.

f.

Also, the

Operate the Model 601 as a pico-

1.

ammeter in the fast method of operation.
Use an accurate reference current source

to buck out the unknown current source.

Connect as shown in Figure 6.

2. Set the METER Switch to CENTER

ZERO and “se the higher current ranges.

Adjust the buckout current to indicate

null on the Model 601. Increase the
Electrometer’s sensitivity as needed.

When the Model 601 is as close to null

as possible, the known reference cur­rent source equals the unknown source

* the Model 601 current readings.

FIGURE 6. Measuring Current by the Galvan­ometric Method. Use an accurate reference

current source to buck Out the unknown cur­rent source, I,.
current ranges,

The Model 601, on its

serves as a null detector.

Use a uhf-tee fitting and Model 6012 Adapter

at the Model 601 input.

Connect the Elec­trometer to the two sources with coaxial
cable. Select cable carefully for very low

2-S. RESISTANCE MEASUREMENTS.

a. The Model 601 can measure resistan-

currents (see paragraph Z-3). For off

ground measurements,

“se triaxial cable and

connectors, grounding the outer shield.

ces by three methods.

1. In the normal or two-terminal method (ammeter-voltmeter), the Electrometer measures

the voltage drop across the unknown sample as a known, constant current flows through

it.

The voltage drop is proportional to the resistance of the sample.

This method is

the simplest for the 100 to loLL ohm ranges.

2. Above 10L1 ohms or to prevent leakage,

the guarded method is better.

It results

in faster response speeds and also nullifies leakage errors acress the Electrometer in-

Put I

since the potential acress the input terminal is small.

In the preceding methods,

3.

set. In some cases,

as in measuring capacitor leakage,

the voltage across the sample cannot be arbitrarily

these methods involve much more

,a

14

06678

MODEL 601 ELECTROMETER

OPERATION

time than if a larger voltage could be applied.

Model 601 is used as a fast picoammeter.

The unknown resistance sample is connected to

In the external voltage method the

an external known voltage source and the current through the sample is measured.
the normal or fast method may be used.

The resistance is calculated from the readings.

NOTE

Discharge any capacitor before removing it from the circuit.

Depressing the
ZERO CHECK Button shorts the input through a lo-megohm resistor, providing a
discharge path.

Normal Method (100 to 10" ohm ranges).

b.

Follow the instructions of paragraph 2-4.

1.
METER Switch

Range Switch
Multiplier Switch
FEEDBACK Switch
ZERO CHECK Button

Connect the resistance sample to the INPUT Receptacle.

Set the controls as follows:

+

105 OHMS
1

NORMAL

LOCK

Unlock the ZERO CHECK Button.

Check zero with only the ZERO CHECK Button.

Either

NOTE

Do not open circuit the Electrometer on the OHMS ranges; the input will develop

up to 10 volts due to its constant current characteristic.

Keep the input

shorted or the ZERO CHECK Button locked.

The full-scale ohms range is the Range Switch setting times the Multiplier Switch

2.

setting. Use the largest Multiplier Switch setting possible to obtain the best accuracy.

Before making a final reading, manipulate the Multiplier and Range Switches, so

3.

the sample is tested at a number of test potentials.

The applied test voltage is the

percentage of full scale that the meter reads times the Multiplier Switch setting.

4. When the test current is applied, high termipal of the INPUT Receptacle is negative.
NOTE

Shield the input if the resistance sample exceeds LO8 ohms.

c. Guarded Method (to 1014 ohm ranges).

1. Follow the instructions of paragraph 2-4. Set the controls as follows:
METER Switch

Range Switch
Multiplier Switch
FEEDBACK Switch

ZERO CHECK Button

loll

1
FAST
LOCK

OHMS

0667R

15

OPERATION MODEL 601 ELECTROMETER

Connect the low impedance side of the resistance sample to the Model 601 GUARD Terminal,

and the high impedance side to the center terminal of the INPUT Receptacle.
ZERO CHECK Button.

Read the resistance as outlined for the normal method, subparagraph b.

2.

Unlock the

The low terminal of the INPUT Receptacle is now a driven guard.

3.

to minimize the slowing effects of capacity between high and low and errors due to leak-

age resistance between high and low.

The Model 6011 Input Cable,

4.

means of making guarded resistance measurements.

CASE GROUND and GUARD Terminals on the rear panel. This allows the CASE GROUND or blue
test lead terminal to be connected to the low impedance side ‘of the unknown resistance.
The inner shield or the black test clip is the GUARD Terminal.

d. External Voltage Method (to 1017 ohms).

1. Turn the ZERO CHECK Switch to LOCK.
of the INPUT Receptacle and the power supply.
high voltage line to ground the low impedance end of the sample when it is disconneCtad

from the potential.

the Power Supply must be floating,

minals and connect the CASE GROUND Terminal to an earth ground.

2. Set the FEEDBACK Switch to NORMAL.

ies can arise for resistance samples less than 0.1 the value of the feedback resistor.

3.

Apply a potential to the sample before releasing the ZERO CHECK Button.

Range Switch to .3 AMPERES and increase sensitivity until a reading is obtained.

Before disconnecting,

supplied with the Model 601, provides a convenient

Connect the shorting link between the

Connect the sample between the High Terminal

(See Figure 7,.) Put a switch in the

make sure to lock the ZERO CHECK Button. If

remove the link between the CASE GROUND and LO Ter-

Usually this method is best, since instabilit-

It may be used

Set the

4. If the potential applied is at

least 100 times the full-scale input

drop (Multiplier Switch setting), the
resistance is equal to the applied poten-

tial divided by the current reading.

high voltage sensitivity of the Model 601,

therefore, permits external.voltages of

0.1 volt or more to be used.
If the potential applied is less

5.

&han 100 times the input drop, the resis-

tance is equal to the difference between
the applied potential and the input drop,
all divided by the current reading.

6. If.the current is read by the fast

method,

it need not be included in the calcula­tion.
sample is large,
capacitor leakage measurements, the fast

method increases response speed and this

connection is recommended.

the input drop is so slight that

If the capacity shunted across the

such as encountered in

The

I

,I r-

FIGURE 7. Measuring Resistance by the Ex-

ternal Voltage Method.
known source, V, is applied to the unknown
resistance sample, R,.
sures the current through s, from which
the resistance is calculated.
grounds R when no potential is applied.

Note in a eve i2 figure the power supply is

floating.

I -

A potential from a
The Model 601 mea-

601

Switch S

I

1

16

MODEL 601 ELECTROMETER

2-9. CHARGE MEASUREMENTS.

OPERATION

a. Follow the instructions of paragraph 2-4,.

Set the controls as follows:

METER Switch CENTER ZERO
Range Switch 10-7 COULOMBS
Multiplier Switch .Ol
FEEDBACK Switch FAST
ZERO CHECK Button LOCK

Unlock the ZERO CHECK Button and then connect the unknown source to the INPUT Receptacle.

If the Electrometer reads off scale, increase the Multiplier Switch setting.

If the sen-

sitivity is not enough, decrease the Multiplier Switch setting until the reading is on

scale.

Changing the Multiplier Switch setting does not affect the transfer of charge

from the unknown source to the instrument. If increasing sensitivity with the Multiplier
Switch does not bring the reading on scale, increase sensitivity with the Range Switch
and repeat the above steps.

The full-scale charge range is the Range Switch setting times the Multiplier Switch

b.

setting.

Grid current contributes 2 x 10-14. coulomb per second maximum.

NOTE

Because of the instrument's RC time constant,

internal capacitance on the LOS7

coulomb

wait 20 seconds after discharginlg

range before making another measurement.

On the 10-S coulomb range, wait at least two seconds.

2-10.

omy, versatility and performance.

1% linearity. It can float up to l 500 volts off ground.

RECORDER OUTPUTS.

a. For recording

with

the Model 601, "se the Keithley Model 370 Recorder for ease, econ-

The Model 370 is a pen recorder with 10 chart speeds and

The Model 370's input cable has a

connector which mates directly with the OUTPUT Connector on the Model 601; this avoids

interface problems often encountered between a measuring instrument and a recorder. The

Model 601 OUTPUT, when set to IMA Position,

will drive the 370; no preamplifier is needed.

b. Other recorders, oscilloscopes and similar instruments can be used with the Model

601.

The Model 601 has two variable outputs, fl volt and *l milliampere, to amplify sig­nals within l/2% for recorders, oscilloscopes and similar instruments. These can be used
on all ranges of the Model 601.

NOTE

.

The Model 601 may be used with the FEEDBACK Switch in FAST position with other

instruments. However, make sure there is no common ground between low terminals
of the Electrometer and the other instrument.

c. l-Volt output.

Receptacle. Pin no.

Connect oscilloscopes and pen recorder amplifiers to the OUTPUT

1 is the negative terminal and pin no. 2 is grounded when the FEED­BACK Switch is set to NORMAL. Set the OUTPUT Switch to 1 V. The Model 601 output is now
*l volt for full-scale meter deflection on any range. Internal resistance is 910 ohms.

The frequency response (*3 db) is dc to 200 cps at a gain of 1000, rising to 50 kc at a

gain of 3.3, and decreasing to 1 kc at a gain of 0.1.
scale at a gain of 1000,

decreasing to 0.5% at gains below 10. The METER Switch does not

Noise is less than 2% rms of full

reverse the output polarity.

0667R

17

OPERATION

NOTE

Neither terminal of the OUTPUT
Receptacle should be at case

ground potential if the instru-

ment is used off ground.

sure the shell of any mating
plug is not connected to either
terminal in the Receptacle. The
shorting link should not be con­nected between LO and CASE GROUND.

Use a recorder with an input iso-

lated from ground when making off

ground measurements.

Make

MODEL 601 ELECTROMETER

L

M^rl.c.l

Lx”UrL

601

output

(Tlcl?I z

1 kR

>

t

Recorder

l-Milliampere Output. Connect 1-mil- b

d.

liampere instruments to the OUTPUT Recept- FIGURE 8.
acle. Pin no. 1 Fs the negative terminal.
Set the OUTPUT Switch to 1 MA. The output

is approximately 1 milliampere for full-

scale meter deflection on any range. For
exact output, adjust the meter on the .003­volt range with the FINE ZERO Control for

full-scale deflection.
scale.
Switch does not reverse the output polarity.
the COARSE ZERO Switch and the 1 MA CAL Control.

e.

See Figure 8. Set the OUTPUT Switch to 1 MA.

for full-scale recorder deflection. Operation is the same as for current outputs.

f. When the FEEDBACK Switch is in the NORMAL position,
terminal is grounded to the LO Terminal.
using oscilloscopes and recorders with the Model 601 set for normal operation.
position, however,
common ground between the recorder or.oscilloscops and the Model 601 LO Terminal, or use
the unity-gain output.

2-11.
device to minimize circuit loading errors or for convenient connections to a recorder

when the FEEDBACK Switch is in FAST position.

Check the recorder and meter zero and repeat adjustment if necessary.

For servo rebalance recorders, use a divider across the Model 601 OUTPUT Receptacle.

neither side is grounded. If this is used,

UNITY GAIN OUTPUT. The unity-gain amplifier can be used as an impedance matching

Then adjust the 1 MA CAL Control until the recorder reads full

Therefore,

601 Output for Driving 50 and lOO-Millivolt

Recorders. Use 1% resistors in the divid-

ers for 50-millivolt recorders, resistor R
is 5Ofi; for 100-millivolt, R is 1OOQ.

Use only an insulated screwdriver to adjust

Use the 1 MA CAL Control to trim the output

no difficulty will be experienced

Divider Circuits Across Model

The METER

the negative side of the output

In FAST

make sure there is no

.

a. The unity-gain output is equal to the input within 50 ppm or 100 microvolts when
the load resistance is 100 kilohms or better below 10 volts.
between a lOlo ohm source, for example,
tance,

overall accuracy better than 0.025% can be achieved.

1. Connect the voltmeter to the Xl OUTPUT and GUARD Terminals as shown in Figure 6,

The GUARD Terminal is connected to LO Terminal with the FEEDBACK Switch in NORMAL.

imum output amplitude is 10 volts peak-to-peak.

2. Adjust the Model 601 Zero Controls to obtain a zero-voltage reading on the in-

strument using the unity-gain output.

and a 0.01% voltmeter with a 1-megohm input resls-

Make sure the latter's sensitivity is high enuugh

By placing the Model 601

Max-

MODEL 601 ELECTROMETER

OPERATION

FIGURE 9.

601 is used between a high-resistance source, V,,
accuracy without causing circuit loading.

Measuring Potential of High Resistance Source with 0.025% Accuracy. The Model

and a 0.01% voltmeter to obtain high

The digital voltmeter or, as above, the

Keithley Model 662 Differential Voltmeter connects to the Model 601 unity-gain terminals.

for a precise zero adjustment.

This adjustment is necessary because a slight zero shift

may occur when the Model 601 is changed from the O.l-volt range or lower to a range

above 0.1 volt.

The shift, caused by a gain-reducing network switched in by the ampli-

fier on the l-volt and higher ranges, is too slight to be read on the meter, but it can

cause an error in accurate measurements using the unity-gain output.

When the FEEDBACK Switch is in FAST position,

b.

the unity-gain terminals permit more

convenient connections to recorders without special precautions. In this mode, the Xl

OUTPUT Terminal is grounded and the GUARD Terminal delivers a full-scale output equal to

the Multiplier Switch setting times the input signal.

0866R

19

MODEL 601 ELECTROMETER

APPLICATIONS

SECTION 3.

3-1.

tility of the Model 601 is such that it is almost a complete dc laboratory in itself. Some
particular applications are considered.
niques to increase the usefulness of the Model 601.

3-2. CURRENT SOURCE.
ranges as long as the input voltage drop is less than the Multiplier Switch setting.

low these procedures:

+ or -.

on the Range Switch.
Receptacle.)

affect the maximum input voltage drop,

For accurate output current, check the meter zero on the .Ol-volt range.

3-3. STATIC CHARGE MEASUREMENTS.
can readily make qualitative or quantitative measurements.

GENERAL.

Set the FEEDBACK Switch to NORMAL, the Range Switch to OHMS and the METER Switch to

a.

The current supplied at the INPUT Receptacle is the reciprocal of the OHMS Setting

b.

c. The Multiplier Switch does not affect the current at the INPUT Receptacle.

This Section discusses ways of using the Model 601 Electrometer.

The Model 601 can be used as a r4,% current source on all the current

(For example, lo9 OHMS indicates 10-g ampere current at the INPUT

which is equal to the Multiplier Switch setting.

Electrometers are very sensitive to static charges and

APPLICATIONS

The versa-

The purpose of these is to suggest uses and tech-

FOl-

It does

Zero the Model 601; set the FEEDBACK Switch to NORMAL and the Range Switch to VOLTS

a.

(10 volts full scale). Bring the charged object near the uncovered, unshielded INPUT
Receptacle.

will be induced on the input terminals which can be read on the meter.

quently,
a slow drift of the input voltage.

Connecting a capacitor across the input reduces the drift due to grid current and

b.
also the sensitivity to charge. Therefore, with the FEEDBACK Switch in NORMAL, set the
Range Switch to COULOMBS position.

farads is equal to the COULOMBS Range.
3-4.. CAPACITANCE MEASUREMENTS.

to 100 microfarads.

measures the charge.

a. Charge the capacitor as follows:

1.

Depending upon the distance between the charge and the instrument, a voltage

Check zero fre-

since accumulation of charge due to the electrometer tube grid current will cause

The capacitor value connected across the input in

The Model 601 can measure capacitance from 500 picofarads

The Electrometer charges the capacitor to a known potential and then

The resulting capacitance is easily figured.

Set the Model 601 front panel controls to:

METER Switch

Range Switch VOLTS

Multiplier Switch

FEEDBACK Switch NORMAL
ZERO CHECK Button LOCK

+

.OOl to 10

Connect the unknown capacitor to the INPUT Receptacle. unlock the ZERO CHECK

2.

Button and charge the capacitor to a known voltage by setting the Range Switch to the

0667R

21

APPLICATIONS

MODEL 601 ELECTROMETER

OHMS ranges.
voltage (percentage of full scale that the meter reads times the Multiplier Switch set-

ting) across the capacitor at any given time.

Charge the capacitor to a convenient voltage, such as 0.1, 1, etc. Charge large

3.
capacitors to a lower voltage than that used for low-value capacitors.
control the charging rate:
voltage across the capacitor reaches the desired value.

When the capacitor reaches the desired value, quickly set the Range Switch to the

4.

VOLTS position.

venient, disconnect the capacitor first and then set the Range Switch to VOLTS.

Measure the charge on the capacitor following the instructions in paragraph 2-R.

b.

The value of the unknown capacitance is the stored charge divided by the initial

c.

voltage:

3-5.

Figure 10 shows the circuit.

Output voltage, V,ut, is

CURRENT INTEGRATOR.

As the capacitor charges,

start with the lower ranges and increase the setting as the

Disconnect the capacitor from the INPUT Receptacle.

c (farads) = Q (coulo"bs)

The Model 601 works as an integrator for time-varying currents.

Set the Range Switch to COULOMBS.

the meter will advance up scale to show the

The OHMS ranges

Or, if more con-

v (volts)

Use the unity-gain output.

"o,t = i$

where C is the coulomb range setting in farads.

3-6. POTENTIOMETRIC VOLTAGE MEASUREMENTS. The floating capability, high input impedance,
l-millivolt sensitivity and low zero drift make the Model 601 useful as a null detector
in potentiometric voltage measurements.
loading of the source voltage, on or off null, can be tolerated.

with the center zero scale, following the procedures in paragraph 2-6. When the Model 601

is at null - no meter deflection - the voltage from the known source equals the unknown

voltage.

3-7.

3-7.
teristics in one simple step without using any other equipment.

teristics in one simple step without using any other equipment,
Figure 12. Figure 12.

MEASURING DIODE CHARACTERISTICS. The Model 601 can accurately measure diode charac-

MEASURING DIODE CHARACTERISTICS. The Model 601 can accurately measure diode charac-

The measurements are made on the OHMS ranges, selecting constant currents down The measurements are made on the OHMS ranges, selecting constant currents down

a-Lr Ix br

1

The circuit shown in Figure 11 is useful when no

601 601

i dt

I

Make the measurements

The circuit is shown in

The circuit is shown in

~%RD o *

-L

-L

I

.

FIGURE 10. FIGURE 10.

tegrator. tegrator. A square wave from a current source, I,, A square wave from a current source, I,, is applied to the Model 601 input. is applied to the Model 601 input.

Using the COULOMBS ranges, Using the COULOMBS ranges, the output through the unity-gain terminals is shown. the output through the unity-gain terminals is shown.
22

Current Integrator. Current Integrator. The diagram shows the Model 601 acting as a current in- The diagram shows the Model 601 acting as a current in-

I

0667R

MODEL 601 ELECTROMETER

. .

t t

q ’ q ’

601 601

APPLICATIONS

, ,

Voltage Supply Voltage Supply

+ - + -

FIGURE 11.
buck out the potential from the unknown source, V,. The Model 601 on the voltage ranges
and center-zero scales acts as a null detector.

to 10-11

acteristic curve can then be plotted in volts and amperes or in volts and ohms.
rent polarity is positive out of the center terminal of the INPUT Receptacle.

voltage from the positive meter scale.

3-8.
Set the Range Switch to the COULOMBS ranges and apply the input voltage to the INPUT Re­ceptacle through an external diode.
sistance (Ri) and diode leakage resistance (Rd) are high and if the time constant of the
RC combination is high compared to the period of the signal, the capacitor will charge to
the peak value of the applied ac voltage minus the small drop across the diode.
601 input resistance on the VOLTS or COULOMBS ranges is 1014 ohms or greater, and may there­fore be neglected compared to the leakage resistance of most diodes.
selected "sine the COULOMBS ranges with the FEEDBACK Switch in the NORMAL position.

'PEAK-READING VOLTMETER.

farads is eaual to the COULOMBS-ranee sett

Potentiometric Voltage Measurements. An accurate voltage supply is used to

ampere in decade steps and reading the voltage drop across the diode.

Read the

The Model 601 easily converts to a peak-reading voltmeter,

In the circuit shown in Figure 13, if the input re-

The capacitor (C) is

:in

g

0

0

"I

JlOl
Input

t
I

I
I

I
I
I

Amplifier

and Meter

Ri

The char-

The cur-

The Model

C in

i+ItiUKE IL. measurmg umae knaraccer~scv2s
with Model 601. Use the OHMS ranges of the

Electrometer.

0966R

F

IGURE 13.
Reading Voltmeter.
The diode is external tc the voltmeter. C

is the capacitor selected with the Range
Switch; Ri is the Model 601 input resis­tance.

Diagram of Model 601 as Peak-

Use the COULOMBS ranges.

23

APPLICATIONS

MODEL 601 ELECTROMETER

IGURE 14.

matograph.

Measuring Output of Gas Chro­The Model bOL is usetul as a

_ _-.

_ .

sensitive current detector in a gas chro­matograph.

Floating the Electrometer per­mits grounding the polarizing power source
and flame column.

IGURE 15.

Monitoring Anode of Photomul­tiplier. The Model 601 permits monitoring
the anode current of a photomultiplier where
both the cathode and power supply must be
grounded.

With its case grounded, all Model

601 front panel controls are also at ground.

24

0666R

MODEL 601 ELECTROMETER

CIRCUIT DESCRIPTION

SECTION 4. CIRCUIT DESCRIPTION

4-l. GENERAL.
ter with a full-scale sensitivity of 1 millivolt and an input impedance of 1014 ohms shun­ted by 2.0 picofarads.

are selected to make measurements over a total of 73 voltage, current, resistance and

charge ranges. Current and resistance are measured using precision resistance standards,

from lo-ohm wirewound resistors to 1011

is measured using close tolerance polystyrene film capacitor standards.

4-2. VOLTMETER OPERATION.

The voltmeter amplifier has matched electrometer input tubes followed by three dif-

a.

ferential transistor stages and a transistor output stage.
feedback is used for stability and accuracy.

for the voltmeter mode of operation.

When there is no input signal and the zero is set,

b.

loop of Figure 16 equals that in the lower loop (ib): i, = ib. With an input signal, the

circuit reacts as follows:

When a positive voltage, +ei, is applied to the input, the amplifier drives the

1.

base of transistor 0202 less negative, and current i,

drop through the Multiplier Switch resistor, R,,,.

therefore, it keeps the voltage drop,
input voltage.

The Keithley Model 601 is basically an extremely stable Linear dc voltme-

By using the front panel controls,

ohm glass-sealed high meoghm resistors. Charge

Figure 16 shows the simplified circuit

At equilibrium this drop equals ei;

e,, across the amplifier to a fraction of the

shunt resistors and capacitors

A large amount of negative

the current (ia) in the upper

is decreased causing a voltage

Amplifier [

>

t

101 ei

1

I

FIGURE lb. Simplified Circuit of Model 601 in Voltmeter Mode.

to schematic diagram. ei is the input voltage;

fier. Rm is the resistor for a given Multiplier Switch setting. ec, is the voltage drop
across R,,,. 5105 is the unity-gain terminal; J106, ohms guard terminal.
stantaneous currents within the loops.

.

t

ea

i

Floating Ground

Output Ground

Circuit designations refer

ea is the voltage drop across the ampli-

ia and ib are in-

Ground references correspond to schematic diagram.

0667R

25

CIRCUIT DESCRIPTION

When a negative voltage, -ei, is applied to the input, the amplifier drives the

2.

MODEL 601 ELECTROMETER

base of transistor 0202 more negative, and i, is increased. The current in the lower

loop,

ib, becomes greater than i,, producing a voltage drop, eo, across R,,,. The drop

is sufficient to null the negative input voltage, ei, again keeping the voltage drop

across the amplifier to a fraction of the input voltage.

The voltage drop

3.

imately lo5

The output stage,

C.

on the 0.001 to 0.3-volt ranges.

the,same potential as the input signal.

~CYXISS

the amplifier is e, = ei/(ktl); k is the loop gain, approx-

transistors Q202 and Q203, drives the amplifier common at nearly

Using this circuit,

the input can accept voltages

up to fl0 volts without input dividers. This maintains high input impedance and eliminates

instabilities which can occur with high resistance dividers.

4,-3. VOLTMETER CIRCUIT.

Two balanced electrometer tubes are used for the amplifier input. Their filaments

a.

are operated in parallel from batteries B201 and B202.

the control grid of VlOl,

overloads.

Capacitors Cl01 and Cl11 are high-frequency bypasses. The control grid of

the active electrometer tube, from excessive grid current due to

Resistors RlOl and R114 protect

~102 is returned to amplifier common (floating ground).

NOTE

Refer to Schematic Diagram 194.283 for circuit designations.

b. Depressing the ZERO CHECK Button, S102, connects the junction of resistors RlOl and

Rll4, to circuit low. .This removes all signal from the grid of VlOl, and the input imped­ance is reduced to 10 megohms.

An emitter follower stage,

c.

transistors 0101 and Q102, matches the relatively high
output impedance of the electrometer tube to the low input impedance of the differential
amplifier stage formed by transistors 9103 and QlO4,.

differential amplifier stage, transistors Q105 and Q106.

This latter stage drives a second

Transistor Q106 drives the com-

plimentary pair output stage, transistors Q202 and Q203.

d. The zero balance controls adjust the dc voltages of the electrometer tube screen
grids. ,The screen grids of VlOl and V102 are returned, in effect, to the emitters of
transistors ~101 and QlO2 through the COARSE and MEDIUM ZERO Switches, S103 and S104.
emitter voltage of QlOl and Q102 can very,

resulting in a negative feedback loop for sig-

The

nals in phase at the electrometer tubes through the QlOl and Ql02 emitter circuit back to

the VlOl and V102 screen grids.
tial and tube operating points.

This connection stabilizes the electrometer plate poten­Also, for signals arriving at the VlOl control grid, the

gain of the first stage will be much greater than spurious signals.

e. The voltage drop across the Multiplier Switch resistors, R162 through R170, deter-

mines the voltmeter sensitivity.

Applying a full-scale signal to the input causes a 1.1

milliampere current to flow through the meter circuit and the selected Multiplier Switch

resistor producing a full-scale meter deflection.

26

0567R

MODEL 601 ELECTROMETER

CIRCUIT DESCRIPTION

Input

JlOl

Amplifier

18~ .Z

T

I

1

I

I

Output Gnd

] 1 NORMAL

[GURE 17.

schematic diagram.

resistor selected by the Range Switch, SlOl.
ences correspond to ,schematic.

The recorder output is derived from the current flow from transistor Q203 through

f.
the Multiplier Switch resistor. With the Output Switch, 5108, on lV, *l volt for full­scale deflection is obtained at the output connector, JlO3, by i-l.1 milliamperes flowing
through resistor R173. With SLOB at 1 MA, resistors Rl71 and R172 are connected across
JlO3, allowing fl milliampere to pass through an external load. With an external load of

1400 ohms the current may be varied by *5% by the IMA Cal Control, potentiometer R172.

Block Diagram of Model 601 as a Pi&xxxrmeter.

R,,, is the resistor for a given Multiplier Switch setting.

Floating Gnd

Circuit designations refer to

Rs

is

the

SlO5 is the FEEDBACK Switch. Ground refer-

NOTE

The "normal" and "fast" referred to below are only the positions, of the FEEDBACK

Switch. "Normal method" Fs when the Switch is set to NORMAL: "fast method" is

when the Switch is set to FAST.

4-4,. AMMETER OPERATION.

Normal Method.

a.

NORMAL position),

(See Figure 17.)

meter is calibrated to read the current in amperes for the appropriate range.

b. Fast Method.

position), the Model 601 functions as an annneter with negative feedback.
amplifier output is divided by the Multiplier Switch resistors, Rl62 to R170, and fed back
to the amplifier input through a feedback resistor selected with the Range Switch. (See

Figure 17.) Amplifier low (floating ground) is connected to the low impedance side of the

input,
minimizing the effects of input capacity;
millivolt.

0667R

and the output ground is floating. This method increases the response speed by

1n the normal method of current measurements (FEEDBACK Switch in
one of the Range Switch resistors, R102 through Rll2, shunts the input.
The Model 601 then measures the voltage drop across the resistor.

1n the fast method of current measurements (FEEDBACK Switch in FAST

The differential

it also reduces the input drop to less than 1

The

27

CIRCUIT DESCRIPTION

MODEL 601 ELECTROMETER

= E/RE! 1,

18~ I=

4

18~ =

2

+

T

m
lit

FIGURE 18.
designations refer to schematic diagram. Rm is the resistor for a given Multiplier Switch

setting.
graph 4,-5); Rs is the range resistor selected with the Range Switch.
correspond to the schematic.

Block Diagram of Model 601 for Normal Method of Measuring Resistance.

Rx

is the unknown resistance being measured; E is the voltage source (see para-

Ground references

Cira

4-5.

NORMAL position),
Figure,lB.
Rx. The source is obtained from battery B203 through the resistor divider network, R201

through R203.
voltage
stage through Rs, the range resistor. Rs is one of the resistors, R102 through R112.

Since feedback to the amplifier low (floating groun&) keeps the base of transistor Q203
at nearly the same potential as the collector, the current, I, through Q and R, is con­stant. I is equal to E/R,, regardless of the value of s, as long as the voltage drop
across G does not exceed the Multiplier Switch setting.

source regardless of the input. The Model 601 can then measure the voltage drop across
Rx and indicate the resistance value on its calibrated meter.,

in FAST position and the sample resistance connected between the input terminal, X01, and

the OHMS GUARD terminal, JlO6),

19.
reduces the slowing effect of the instrument's input capacity.
also reduced, since the potential across the input terminal is small.
amplifier low (floating ground) is connected to the low terminal of the INPUT Receptacle

and the output ground is floating.

OHMMETER OPERATION.

Normal Method.

a.

Rx is the unknown resistor. A voltage source, E, applies a potential across

E varies from 0.1 to 8.4 volts, depending upon the OHMS range used. The

source is connected between floating ground and the second differential amplifier

Guarded Method. In the guarded method of resistance measurements (FEEDBACK Switch

b.

The circuit is similar to the normal method, except for the feedback.

In'the normal method of resistance measurements (FEEDBACK Switch in

the Model 601 uses a constant-current, voltage-drop circuit. Refer

This circuit provides a true

feedback is applied through the sample. Refer to Figure

This circuit

Errors due to leakage are

In this mode,

The guard terminal is at output ground potential.

to

MODEL 601 ELECTROMETER CIRCUIT DESCRIPTION

I

l-Y--+!9

I i 1 / Am~lif~r / jt ~202

t

Gnd

Floating

18~ Z

T

FIGURE 19. B.lock Diagram of Model 601 for Guarded Method of Measuring Resistance.
designations refer to schematic diagram. Rm is the resistor for a given Multiplier Switch

setting. Rx is the unknown resistor being measured;

4-5); Rs is the range resistor selected with the Range Switch. J106 is the OHMS GUARD

terminal. Ground references correspond to the schematic.

4-6.
that used for an ammeter with the fast method. A negative feedback is applied around a
shunt capacitor, Cl07 to CllO, selected with the Range Switch.

places R, in Figure 17.

citor,

in the Normal or Fast method to measure charge,

COULOMBMETER OPERATION. The Model 601 circuit for measuring charge is similar to

The stored charge is proportional to the voltage across the capa-

which is measured by the Model 601 voltmeter circuits.

the same as to measure current.

E is the voltage source (see paragraph

The shunt capacitor re-

The Model 601 may be used

Cira

,t

0667R

29

SERVICING MODEL 601 ELECTROMETER

Instrument

Use

Keithley Instruments Model 153 Microvolt- General circuit checking
Ammeter; 10~~ to lOOOv, 200MR input resis-

tance, *l% accuracy; float *500x7 off ground

Keithley Instruments Model 24,l Regulated

Source to calibrate 1 to LO-volt ranges

High Voltage Supply; 0 to 1000 v, *0.05%
Keithley Instruments 260 Nanovolt Source;

Source to calibrate 1 mv to 1 v ranges

10-3 to 1 ", 10.25%

Keithley Instruments Model 6011 Input

Connecting cable for Models 601 and 260

Cable,; supplied with Model 601
Keithley Instruments Model 6012 Triaxial

to Coaxial UHF Adapter

Adapts the Model 601 for use with in-

struments and accessories with coaxial
connection?..

;I;:;;yyl;"st

ruments Model 261 Picoampere

to 10m4, ampere

Keithley Instruments Model 370 Recorder
Keithley Instruments Model 2611 Test

Source to calibrate current, resistance

and charge ranges
Monitor drift
Connecting cable for Models 601 and 261

Cable; Supplied with Model 261.
Keithley Instruments'Model 515 Megohm

Bridge
Keithley Instruments Model 662 Guarded

Differential Voltmeter; 100 WV to 500 v,
kO.Ol%

TABLE 3. Equipment Recommended for

Model

instruments or their equivalents.

Verify high-megohm resistors in Range

Switch
Calibrate Meter zero

601 Cal .Fbration

and

Troubleshooting.

30

0667~

MODEL 601 ELECTROMETER

SERVICING

SECTION 5.

5-1.

Model 601 Electrometer.

performance of the instrument.

5-2.

convenient battery check as described in paragraph 2-4. Except for battery replacement

the Model 601 requires no periodic maintenance beyond the normal care required of high-

quality electronic equipment.
should be checked approximately every six months for specified accuracy.

balance requires occasional adjustment; see paragraph 6-4.

5-3.

Electrometer.

meet the specifications

from Keithley Instruments, Inc. In normal use,

10,000 hours of operation.
could be used in an emergency, but the drift,
not be met.

GENERAL.

SERVICING SCHEDULE.

PARTS REPLACEMENT.
The Replaceable Parts List in Section 8 describes the electrical components of the

a.

The electrometer tubes, VlOl and V102, are specially matched and aged; order only

b.

Section 5 contains the maintenance and troubleshooting procedures for the

Follow these procedures as closely as possible to maintain the

Periodically check the condition of the batteries, using the

The value of the high-megohm resistors, RllO, Rlll, Rll2,

Replace components only as necessary.

They can be checked only by replacement.

SERVICING

The dc amplifier

Use only reliable replacements which

they should not need replacement before

Standard 5886 tubes

noise and grid current specifications may

NOTE

when replacing the electrometer tubes,

leads emerge.

Transistor pairs QlOl, Q102 and Q103, Q104 are matched for dc beta (hFE). Order

c.

only from Keithley Instruments, Inc.,

5-4.

ocz;r in the Model 601. Use the procedures outlinedtand use only specified replacement

parts. Table 3 lists equipment recommended for troubleshooting.
be readily located or repaired,

cated in the table do not clear up the trouble, find the difficulty through a circuit-by-

circuit check,

tion 4 to find the more critical components and to determine their function in the circuit.
The complete circuit schematic, 194283, is in Section 8.

5-5. PROCEDURES TO GUIDE TROUBLESHOOTING.

theOUTPUT Switch. This switch should not be in the IMA Position with no load.

are found satisfactory, use the following procedures to isolate the trouble.

TROUBLESHOOTING.
The procedures which follow give instructions for repairing troubles which might

Table 4 contains the more common troubles which might occur.

b.

If the instrument will not operate, check the condition of the batteries. Then check

a.

Increased leakage will result from any contamination.

or its representative; replace only as a pair.

contact Keithley Instruments, Inc., or its representative.

such as given in paragraph 5-5.

do not touch the glass base where the

If the trouble cannot

If the repairs indi-

Refer to the circuit description in Sec-

If these

0667R

31

SERVICING

MODEL 601 ELECTROMETER

Difficulty

Excessive Zero Drift.

Excessive grid current

Excessive microphonics.

cannot meter zero on any
range.

unable to zero meter on
most sensitive range

Meter will not zero on one
Multiplier Switch set- of Multiplier Switch. if faulty.
ting.

Electrometer tubes may be
defective

DC amplifier not balanced.

Batteries failing

Excessive humidity or de-

fective electrometer tube.
Instrument not used.
Defective electrometer tube Check VlOl and VlO2; re-

See paragraph 5-5.

Incorrect plate voltage on Check per paragraph 5-5.

electrometer tube.
Faulty reqistor for setting Check resistors; replace

Probable Cause

Check VlOl and VlO2; re-

place if faulty.
Check per paragraph 6-4,.
Replace batteries (para-

graph Z-4).
Check VlOl and V102; re-

place if faulty.
F&n for seven hours.

place if faulty.
See paragraph 5-5, d.

step 6.

Solution

10-10 to 10-14, ampere Defective high megohm resis- Check per paragraph 6-5.
current ranges are out of tars.
specifications.

TABLE 4,.

b.
voltages referenced to either floating ground or output ground; a properlj, operating
Electrometer will have these 'values *lo% if operating from fresh batteries;

settings for these values are the Range Switch at VOLTS, Multiplier Switch at 1, and the

meter zeroed.

c. At times,
COARSE ZERO Switch, S103 (Figure 3), to bring the Model 601 into balance. If this does
not work, continue to check the circuits.

1. Check the filaments of the electrometer tubes,

voltage drop across the filament dropping resistor, Rl15 (Figure 23).

are operating properly, the voltage will read +1.7 volts dc *lo%.

2.

the amplifier printed circuit board, ~~-115, for possible breaks.

Model 601 Troubleshooting.

The schematic diagram indicates all tube element voltages .and transistor terminal

Measurements are with the Model 153.

the meter will not zero on any range with the input shorted.

Inspect the leads from the shock-mounted input printed circui

See paragraph 5-3 for checking VlOl and V102.

The control

Adjust the

VlOl and V102, by measuring the

If both filaments

board, PC-111, to

32

0567R

MODEL 601 ELECTROMETER

Amplifier.

d.

To check the amplifier, disconnect the feedback loop by removing Batteries 8206,

1.

B207, B208 and 0209.

This allows each stage of the amplifier to be individually checked.

SERVICING

It also eliminates the possibility of applying excessive voltage to the electrometer
tube grids,

Connect the Model 153 between the plates of VlOl and V102 (Figure 23). Adjust the

2.

COARSE and MEDIUM ZERO Controls for null.

causing serious damage.

If a null cannot be reached, check VlOl, V102,

the COARSE and MEDIUM ZERO Control circuits (resistors R129 to R150), and transistors

QlOl and Ql02. Check the transistors by removing them and adjusting for null again.

If null is now reached,

replace the transistor pair with a new pair.

3. Check the next stage by connecting the Model 153 across the emitters of QlOl and
Q102 (Figure 25) and adjusting the COARSE and MEDIUM ZERO Controls for null. If null is
not reached,

check this stage and the base circuit of the next stage.

Check the base
circuit by removing transistors Q103 and QlO4 (Figure 25) and again adjusting for null.
If null is now reached,

Check the next stage by connecting the Model 153 across the collectors of QlO3 and

4,.

replace the transistor pair with

Q104, (Figure 25), and adjusting the COARSE and MEDIUM ZERO Controls for null.

a new pair.

If null
is not reached, check this stage and check for shorts in the base circuit of QlO5 and
Q106 (Figure 25).

Connect the Model 153 across the collectors of QlO5 and Q106. Adjust the FINE ZERO

5.

Control for null. If null is reached, the dc amplifier is operating correctly and the

trouble is in the output stage,

The feedback loop includes the multiplier resistors, R162 through R170, the recor-

6.

the feedback stage or in transistor Q201.

der output resistors, R173 on 1V position or R171 and R172 on 1 MA position, and the
meter.

An opening of any of these components prevents zeroing for only that particular

multiplier setting.

Troubleshoot the output stages,

7.
transistors Q202 and Q203, by making volt­age measurements with the Model 153 to

within *lo% of the specified schematic
value.

ii&g-1

FIGURE 20. Base Connections for Electrom-

eter Tube VlOl.

0667R

33

MODEL 601 ELECTROMETER

CALIBRATION

SECTION 6.

6-

1. GENERAL.
The following procedures are recommended for calibrating and adjusting the Model

a.

60

or if difficulty is encountered, contact Keithley Instruments, Inc., or its representa-

tives to arrange for factory calibration.

adjustment, high-megohm resistor verification,
calibration and accuracy check.

6-2.

meter tubes are functioning correctly.

months or when amplifier components are replaced.

six months.

Use the equipment recommended in Table 3.

1.

Procedures are covered for the following:

b.

CALIBRATION SCHEDULE.
Check grid current (paragraph 6-3) at regular intervals to make sure the electro-

a.

The dc amplifier balance adjustment (paragraph 6-4) is necessary about every six

b.

Verify the value of the high-megohm resistors (paragraph 6-5) approximately every

c.

CALIBRATION

If proper facilities are not available

grid current check, dc amplifier balance

calibration of t,he ohms ranges, meter zero

Calibrate the meter zero (paragraph 6-6) about once a year or when components are

d.

replaced.

e. Check the Model 601 (paragraph 6-7) once a year,

improper operation is suspected.

f. If the Model 601 is not within specifications after the calibrations and adjustments,

follow the troubleshooting procedures or contact Keithley Instruments, Inc., or its near-

est representative.
6-3.

petted.

DC Amplifier Balance R204
Meter Center Zero Calibration
Meter Calibration

GRID CURRENT CHECK. Check grid'current whenever excessive noise or drift is sus-

To read the grid current of the Model 601,

METER Switch
Multiplier Switch
Range Switch
ZERO CHECK Button Unlocked
FEEDBACK Switch

Circuit

Control Designation

R211
R220

+

FAST

after the other adjustments, or if

set the front panel controls to:

.Ol

lo-l1 AMPERES

Fig.

Ref. Paragraph

23 6-4
24 6-6
24

Refer to

6-6

TABiE 5. Model 601 internal Controls.
picturing the location and the paragraph describing the adjustment.

0567R

The Table lists all internal controls, the figure

35

CALIBRATION

MODEL 601 ELECTROMFIER

Cap the INPUT Receptacle.

2 x

10-14

ampere.

(This is less than 20% of full scale.)

battery condition and the electrometer tube, VlOl.

for a long time,

allow it to run for 7 hours before checking the grid current.

The grid current indicated on the meter should be less than

If this is exceeded, check the

If the instrument has not been used

6-4,. DC AMPLIFIER BALANCE ADJUSTMENT. Gradual aging of components may require an occa­sional adjustment of the amplifier balance. Also readjust the DC AMP BAL potentiometer,

R204., if amplifier components are replaced.

Set the front panel controls to:

a.

METER Switch
Multiplier Switch

Range Switch
ZERO CHECK Button

FEEDBACK Switch

CENTER ZERO

0.1
VOLTS

LOCK

NORMAL

Zero the meter on the O.l-volt range.

Connect the Model 153 across the collectors of transistors QlO5 and Q106 (this is

b.

across the ends of resistors R152 and R153, Figure 25). Make the connections from the

component side of the printed circuit board.

c. Adjust the DC AMP BAL potentiometer,

Float the Modal 153 low terminal.

R204 (Figure 23), until the meter shows a null.

6-5.

HIGH-MEGOHM RESISTOR VERIFICATION.

a. About every six months, it is necessary to check the value of the high-megohm re-

sistors, RllO to R112, on the Range Switch.

The instrument should be within its rated
accuracy for two or three years from the time it leaves the factory. After this, some
of the resistors may drift out of tolerance and should be replaced. Faulty high-megohm
resistors will affect the‘ accuracies of measurements for the 10Tg to lo-11 AMPERES and the

108 to 1012 OHMS settings of the Range Switch.

To check these resistors,

ac:;racy up to 1011 ohms.

An accurate megohm bridge, such as the Keithley Instruments

it is necessary to use a bridge capable of better than 1%

Model 515 Megohm Bridge which is accurate to 0.25% for these ranges, is therefore neces-

sary.

If such equipment is not available,

two procedures are recommended

to

check out

the resistors:

Return the complete instrument to the factory for resistor calibration.

1.
Replace the high-megohm resistors periodically with a certified set from Keithley

2.

Instruments to assure absolute calibration accuracy.

6-6.

METER ZERO CALIBRATION. Check meter zero whenever components are replaced or other

adjustments are made.

Turn the METER Switch to METER OFF. Set the mechanical Zero Meter adjustment for

a.

'zero meter reading (top-scale zero).

Turn the Model 601 on.

b.

lo-volt range.

INPUT Receptacle.

meter reading.

36

Zero the meter on the .OOl-volt range.

Set the Multiplier Switch to 10;

Adjust the METER CAL potentiometer,

Then switch to the

apply 10 volts t0.05% to the Model 601

R220 (Figure 24), for full scale

0667R

MODEL 601 ELECTROMETER

c.

Set the center zero by first zeroing the meter on the .OOl-volt range. Then switch

to the l-volt range.

Set the METER Switch to CENTER ZERO and adjust the CENTER ZERO CAL

potentiometer, ~211 (Figure 24),

CALIBRATION

for exact center-scale meter zero.

6-7.

ACCURACY CHECK.

a. Checking the accuracy is the quickest way to spot faulty Model 601 operation. Per-

form the check about once a year, if components are replaced,

or if other adjustments are

made. If accuracy is verified over all ranges, the Model 601 should be able to meet all

specifications.

b.

Voltage.
lo-volt range.
601 should indicate the input voltage to *l% of full scale.
the 3-volt range.
for accuracy of -f-l% of full scale.

If the accuracy must be checked often, check the stability.

Connect the Model 601 to the Model 241.

Increase the input voltage in l-volt steps from 0 to 10 volts.

First, set the Model 601 for the

The Model

Perform rhe same operation in

Connect the Model 601 to the Model 260. Check the other voltage ranges

Make sure the OUTPUT Switch is in the 1 V position for

the 1, 3 and 10 volt ranges (see paragraph 2-4,g).

c.

Current. Connect the Model 601 to the Model 261 with the Model 2611.

full-scale accuracy of all current positions on the Range Switch.

ampere ranges,

current to *2% of full scale from .3 to 10-S ampere ranges,

to lo-l1 ampere ranges.

output is 10.25%.

d.

Ohms.
more are low, replace them.
not affect the current ranges.

set the FEEDBACK Switch to FAST.

The Model 601 should indicate the input

f&% of full scale from the 10-g

For the ranges above low4 ampere,

construct a current source whose

Set the Model 601 FEEDBACK Switch to NORMAL when calibrating these ranges.

Check batteries B203, ~204 and B205 according to paragraph 2-4.

A low battery can put all the ohms ranges out of tolerance and

Otherwise, all the ohms ranges will be within specifica-

For the 10-5 to lo-11

Check the

If one or

tions if the current ranges are within specifications.

e.

Coulombs.

1.

Calibrate the 10-7 through lo-10

Range Switch

Setting

Time Current

Applied

(seconds)

coulomb ranges using a variable time cur-

rent source.

Set the Model 601 FEEDBACK

Switch to NORMAL and the MULTIPLIER Switch

to 1. Connect the Model 261 to the Model

601 INPUT Receptacle. Set the Model 261

for 10-10

ampere output.

Apply the cur-

rent to the Model 601 for the time noted

in Table 6 for each range.

This procedure

10-7 COULOMBS
10-S COULOMBS
10-g COULOMBS
10-10 COULOMBS

TABLE 6.

Data for Calibrating

100 9315%
100 63*5%
100

5

uses the time constant circuit to check

the range capacitor accuracy.
trometer is being used here as a volt-

The Elec-

Input Current Zero to

meter. Range Switch to Model 601

Setting

(ampere)

2. To check the Model 601 as a charge
amplifier,
and the Multiplier Switch to 3.

set the FEEDBACK Switch to FAST

Use Model

261 to provide an input current. With the

Range Switch set to the COULOMBS ranges
given in Table 7,

input current.

apply the corresponding

Use a stop watch or an

oscilloscope to time the rise to full-

scale deflection.

10-7

COULOMBS

10-S COULOMBS

10-g

COULOMBS

10-10
ABLE 7.

he Table gives the input current needed to

COULOMBS

Coulomb Ranges Accuracy Check.

. I

check the rise time for each coulomb range.

10-S 30

10-g 30
10-10 30
10-11 30

Meter

Reading

63*5%

100*5%

Coulomb

Ranges.

Rise Time,
Full Scale

(seconds)

0667R

37

CALIBRATION MODEL 601 ELECTROMETER

6-8.

a.

DRIFT CHECK.

Set the front panel controls to:

Refer to the accuracy check before performing the drift check.

METER Switch

+

Multiplier Switch .03

Range Switch

VOLTS

ZERO CHECK Button LOCK

FEEDBACK Switch NORMAL

Set the Output Switch on the back panel to 1 MA.

b. Connect the Model 601 OUTPUT Receptacle to the Model 370 Recorder.

to 1 volt.

c. Make the drift run for at least 24, hours.

Make sure the Model 601 chassis cover is attached with at least two screws.

The zero drift specification is 200 micro-

Set the recorder

volts per hour maximum averaged over any 24-hour period after warm-up; during two-hour

warm-up, no more than 2 millivolts after the first hour (Refer to Figure 21).

If the instrument does not meet the zero drift specification, check the batteries.

d.

If the batteries are satisfactory and the instrument still does not meet the zero drift

specifications, change the electrometer tubes.

NOTE

If new batteries have been installed, the Model 601 drift specification will be
exceeded for at least the first 72 hours. hit is recommended that new batteries

be used for 120 hours before making a drift run.

FIGURE 21. Typical Drift Chart for Model 601.

The drift run shows the stability of the
Electrometer over a 24.-hour period. After a l-hour warm-up,
millivolts in the second hour.

In any subsequent 24-hour period, the average drift will

not exceed 200 microvolts per hour.

the drift is no more than 2

38

0567~

MODEL 601 ELECTROMETER

CALIBRATION

FIGURE 22.

components,

Side View of Model 601 Chassis.
printed circuits and switches is shown.

cuit designations.

Front panel faces right.

Figure 23 shows the opposite side.

CR162

NlXJ)

Location of

Refer to the Parts List for cir-

0866

39

CALIBRATION

MODEL 601 ELECTROMETER

FIGURE 23.

Side View of Model 601 Chassis.
components, printed circuits and switches is shown.
designations.

Figure 22 shows the opposite side.

40

Front panel faces left.

Refer to Parts List for circuit

Location of

0866

MODEL 601 ELECTROMETER

CALIBRATION

FIGURE 24.
Circuit PC-114.

0866

Component Locations on Printed

FIGURE 25.
Circuit PC-115.

Component Locations on Printed

R‘,C K,?(l

41

CALIBRATION

FIGURE 26. Component Locations on Range

Switch SlOl. For other components see

Figures 27 and 28.

FIGURE 27.

Switch 5101.

For other components see

FFgures 26 and 28.

MODEL 601 ELECTROMETER

42

FIGURE 28. Component Locations on Range Switch SlOl.
ponents see Figures 26 and 27.

For other com-

0866

MODEL 601 ELECTROMETER

ACCESSORIES

SECTION 7.

7-l. MODEL 6011 INPUT CABLE (Figure 29).

triaxial cable with a mating plug (Keithley Part CS-141), which connect directly to the

Model 601 INPUT Receptacle. Three alligator clips are on separate leads for three-termin-

al connections.
nished with each Model 601.

7-2.

foot triaxial cable. Its insulation resistance is lOlo ohms. The gripping feature is
useful for attaching the probe at a single point for repeated measurements.
terminated by a special triaxial type plug (Keithley Part CS-141).
rectly into the Model 601 INPUT Receptacle. Do not use the Probe for measurements that
are more than 500 volts off ground.

I

MODEL 1531 GRIPPING PROBE (Figure 30). The Model 1531 has a gripping probe and 3-

Refer to Table 1

Page

7 for color coding.

ACCESSORIES

The Model 6011 Cable has 30 inches~of low-noise

One Model 6011 Cable is fur-

The cable is

The plug connects di-

1.

FIGURE 29.

Input Cable.

Keithley Instruments Model 601

IGURE 30. Keithley Instruments Model 153

Gripping Probe.

7-3.

lead. Insulation resistance is more than 1014 ohms. It consists of a probe and 3 feet
of low-noise cable, terminated by a special triaxial type plug (Keithley Part CS-141).
The plug connects directly into the Model 601 INPUT Receptacle.

lows point-by-point guarded measurements.

7-4. MODEL 6012 TRIAXIAL-TO-COAXIAL ADAPTER (Figure 32). The Model 6012 permits using the

Model 601 with all Keithley electrometer accessories having uhf type connectors.

graphs 7-5 through 7-9 describe these accessories. One end of the Adapter is equivalent
to a Keithley CS-141 plug and the other is a uhf-type connector.

FIGURE 31. Keithley Instruments Model 6301
Guarded Probe.

MODEL 6301 GUARDED PROBE (Figure 31). The Model 6301 is a guarded probe and shielded

Using the Model 6301 al-

Para-

--

FIGURE 32. Keithley Instruments Model 6012
Triaxial-to-Coaxial Adapter.

0666

43

ACCESSORIES

MODEL 601 ELECTROMETER

NOTE

Do not make off-ground measurements with the Model 601 Electrometer when using

the Model 6012 Adapter.

The Adapter connects case ground and circuit low, de-

feating the Model 601 three-terminal input circuit. The chassis would be at

the same off-ground potential as the voltage being measured.

7-5.

MODEL 6102A VOLTAGE DIVIDER PROBE (Figure 33).

divider with an input resistance of 10" ohms.

100 volts with an accuracy of 3%.

axial cable.

terminated with a uhf plug.

to the Model 601 INPUT Receptacle.

The Probe is furnished with 30 inches of low-noise co-

Use the Model 6012 Adapter to connect the Probe

Instructions for using the Probe with the Electrome-

. . “.-^ I.. ..^r”“r.,..l, 7-5

FIGURE 33.

6102A 1O:l Voltage Divider Probe.

7-6.

MODEL 6103A VOLTAGE DIVIDER PROBE (Figure 34).
divider with an input resistance of 1012 ohms.
10 kilovolts with an accuracy of 5%.
coaxial cable,
Probe to the Model 601 INPUT Receptacle.
trometer are in paragraph 2-5.

Keithley Instruments Model

terminated with a uhf plug.

The Probe is,furnished with 30 inches of low-noise

Use the Model 6012 Adapter to connect the

Instructions for using the Probe with the Elec-

The Model 6102A is a 1O:l voltage

It can be used with the Model 601 up to

FIGURE 34.

Keithley Instruments Model

6103A 1OOO:l Voltage Divider Probe.

The Model 6103A is a 1OOO:l voltage

It can be used with the Model 601 up to

7-7.

MODEL 6104 TEST SHIELD.

a. The Model 6104 facilitates resistance

measurements with either 2-terminal or 3-

terminal guarded connections, as well as
voltage and current tests.

2-Terminal Operation.

b.

Connect the high impedance side of

1.

the test sample to the Model 6104 INPUT

Terminal.

Connect the low impedance side
to either black jack marked GROUND, which­ever is more convenient.

Lock the enclosure and connect the

2.

Model 6104 bnc receptacle to the Model

601 INPUT Receptacle, using the Model
6012 Adapter.

Use a short coaxial cable.
Operate the Model 601 as described in
Section 2.

44

.

: ____________ ------_---- ---------,
I

t:

T

I
I
I

mi

1

----------------- YL-- ------------ 1

FIGURE 35.

Diagram of Model 6104 Circuit.

0

0

I
,
I

I
1
I

0666

MODEL 601 ELECTROMETER

C. 3-Terminal Operation.

ACCESSORIES

1. For guarded measurements,

make the connections as above with some additional steps.

2. Connect the Model 6104 black external plug to the Model 601 OHMS GUARD Terminal.
Connect either Terminal marked EXTERNAL SOURCE to the test sample at its high im-

3.

pedance side.

Connect an external voltage supply to the banana plugs on the side of the Model

4.
6104, positive to red and negative to black.
thlev Model 240A High Voltage Supply) to the desired voltage.

Lock the enclosure and connect the Model 6104 to the Electrometer.

Set the external source (such as the Kei-

Operate the Electrometer

as explained in Seciion 2

FIGURE 36.
Test Shield.

7-S.

MODEL 6105 RESISTIVITY ADAPTER.
The Model 6105 is a guarded test fixture for measuring resistivities of materials

a.
in conjunction with the Model 601 and the Model 240A High Voltage Supply.
system direct1

ities up to 10
ting and Materials.
tact with uniform pressure.
inch thick.

Keithley Instruments Model 61

FIGURE 37. Keithley Instruments Model 611
Resistivity Adapter.

The complete

measures volume resistivities up to 3 x 10lg ohm-cm and surface resistiv-

KS

ohms,

in accordance with the procedures of the American Society for Tes-

The shielded Model 6105 is a means for maintaining good sample con-

The Adapter holds samples up to 4 inches in diameter and .25

Maximum excitation voltage is 1000 volts.

b. The Model 6105 Instruction Manual explains the operating procedures for the system,

using the Model 240A and an Electrometer.

The Model 601 can also be used with the Model 6105 alone.

a :&stant current source (paragraph 3-2)

with the FEEDBACK Switch in FAST position.

Operate the Model 601 as

Con-

nect the OHMS GUARD Terminal on the rear panel to the center terminal of the Model 6105

0666

45

ACCESSORIES

MODEL 601 ELECTROMETER

FIGURE 38.
Static Detector Probe.

Power Receptacle.
rent from the Model 601 is the reciprocal of the OHMS setting of the Range Switch; the

voltage is the Multiplier Switch setting times the meter reading.

7-9.

from the charged surface. Measurements are accurate within 10%.
of a 3-inch diameter head and 10 feet of cable. Connect the Probe to the Model 601 INPUT
Receptacle using the Model 6012 Adapter.

eter and it connects directly into the Electronieter

without any cable.

7-10.

the instrument to rack mounting to the stand&d EIA 19-inch width.

instrument case.

The feet and tilt bail can be removed without removing the bottom cover assembly.

the rear feet first.
front feet and tilt bail and replace the shield.

MODELS 2501 AND 2503 STATIC DETECTOR PROBES.

a. The Model 2501 is a 10,OOO:l capacitive divider when used with the head 3/8 inch

b. The Model 2503 i+ similar to the Model 2501. However, its head is l/2 inch in diam-

RACK MOUNTING (See Figure 40).

a. The Model 601 is shipped for bench use.

b. To convert the instrument, remoye the two,screws at the bottom of each side of the

Keithley Instruments Model 2501

Other operating procedures are as for the 3-instrument system. The cx-

Lift off the top cover assembly with the handles; save the four screws.

Then, remove the shield in the front of the instrument, remove the

FIGURE 39. Keithley Instruments Model 250

Static Detector Probe.

The Model 2501 consists

- with the Model 6012 Adapter L

The Model 4005 Rack Mounting Kit converts

Remove

I

Item

(See Fig. 40) Description

I

3

1

I

46

2 -- Mounting Filler Cover Screw, Assembly No. Panel Panel 10 -

TABLE 8. Parts List for Keithley Model 4005 Rack Mounting Kit.

Keithlev
Part No.

3/8, HSS 19396B 19397B 20018B ---

Quantity

12 1 1 1

0667R

MODEL 601 ELECTROMETER

3

0

0

0

0

ACCESSORIES

3

FIGURE 40 .

list.

c. Insert the top cover assembly (1)

screws previously removed. Attach the mounting panel (2) to the rack with four #lo screws
and kep nuts. Fasten the Model 601 to the mounting panel with four #lO screws. Fasten
the filler panel (3) to the opening in the mounting panel with four i/l0 screws and kep
nuts.

If two Model 601 Electrometers are to be rack mounted side-by-side, another top

d.
cover assembly (Keithley Part 19525B) is used instead of item 1 in Figure 40.
panel (3) is not used.

mensions are 10-l/2 inciles high x 6-5/8 inches wide ‘& 10 inches deep.

7-11. MODEL 6013 pH ELECTRODE ADAPTER.

a. The Model 6013 is designed to allow accurate and convenient pH potential measure-

ments with the Model 601 Electrometer. It accepts Leeds & Northrop(L&N), Coleman and

Beckman (B-C) pH electrode connectors.
guarded to insure that the accuracy of the Model 601 is affected in no way.

Exploded View of Model 4005 Rack Mounting Kit.

in place and fasten to the chassis with the four

This Kit will also hold any two Keithley models whose bench di-

The Adapter uses Teflon insulation and’is fully

Refer to Table 7 for parts

The filler

b. The top of the Model 6013 contains two sets of connectors, one of which accepts an

old type L6d\I electrode, while the other accepts either a new type La or the B-C electrode.
Connect the electrodes to the proper set.
Model 601 INPUT Receptacle.

Set the Adapter’s switch for 601.

C.
Set the Range Switch to VOLTS. Use the appropriate range for the Multiplier Switch.

0667R

Connect the Adapter cable directly into the

Set the Model 601 WTER Switch to CENTER ZERO,

47

MODEL 601 ELECTROMETER

NOTE

To check zero on the Electrometer, use only the ZERO CHECK Button on the Model

6013 pH Electrode Adapter.

d. For guarded measurements, connect the GUARD Terminal on the Adapter to the Model

601 OHMS GUARD Terminal.

r--------L- "",

I

.

I

4

I
I

Shield

4

>

>

Do not use the ZERO CHECK Button on the Electrometer.

-

Model 6013

I

Zero Check

Guard

---- ---e--B
f

+

I

<

<

(

Ref.

FIGURE 41.

7-12. MODEL 370 RECORDER.

a. The Model 370 Recorder is uniquely compatible with the Model 601 as well as other

Keithley electrometers, microvoltmeters and picoammeters.

economical instrument that maximizes the performance of the Model 601, and many other
Keithley instruments, even in,the most critical applications. The Model 370 can be used
with the Model 601 to record voltage, resistance,

entire range.

b.

The Model 601 has the output necessary to drive the Recorder directly (1 volt, 1

milliampere),

volts off ground.
The response time of the Model 370 Recorder is 0.5 second; linearity is *l% of full scale.
Ten chart speeds -

front panel, controls.

corder has a self-priming inking system.

>

Block Diagram of Model 6013 in use with the Model 601.

The Recorder is's high quality

currents and charge over the Model 601's

thus eliminating the need for a pre-amplifier.

The Recorder is specially shielded to avoid pickup of extraneous signals.

from 3/4, inch per hour to 12 inches per minute - are selectable with

The 6-inch chart has a rectilinear presentation. The Model 370 Re-

Chart paper and ink refills are easy to install.

The Model 370 floats *500

<

C.

The Model 370 is very easy to use with the Model 601.

necting the two units,

accessible control for full-scale recorder deflection.

Cable mates with the output connector on the Model 601.

setting the Mpdel 601 Output Switch to 1MA and adjusting an easily

All that is necessary is con-

The furnished Model 3701 Input

MODEL 601 ELECTROMETER

ACCESSORIES

:GURE 4,2. Maximum Recording Convenience is Obtained Using the Keithley Model 370,
specially Designed for use with Keithley Electrometers and Other Instruments.

The Model

'0 can be directly connected to the Model 601 output with the Recorder's accessory cable.

Response time, floating capability and other specifications of the Model 370 Recorder are

compatible with those of the Model 601 Electrometer.

0567

49

MODEL 601 ELECTROMETER REPLACEABLE PARTS

SECTION 8. REPLACEABLE PARTS

8-1.

REPLACEABLE PARTS LIST.
the Model 601.
manufacturer,

The List gives the circuit designation, the part description, a suggested

the manufacturer's part number and the Keithley Part Number.

The Replaceable Parts List describes the components of

The last column

indicates the figure picturing the part. The name and address of the manufacturers listed
in the "Mfg.

a-2.

HOW TO ORDER PARTS,

For parts orders,

a.

Part Number,

Code" column are in Table 10.

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

the circuit designation and a description of the part.

All structual parts
and those parts coded for Keithley manufacture (80164) must be ordered through Keithley
Instruments, Inc. or its representatives.
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 Replaceable

ment, Keithley Instruments, Inc.

amp
CerD

Comp
DCb

EdllpWX
Ceramic, disc

Composition
Deposited Carbon

NO.
n

P
Poly Polystyrene

Number

ohm
pica (LO-l*)

ETB
f

Fig.
GCb

I<

M or meg
Mfg.

MtF
MY

Electrolytic, tubular

Ref. Reference
req'd

farad

Figure

P

Glass enclosed carbon v
kilo (103) w

ww

mega (106) or megohms

wwvar<
Manufacturer
Metal Film
Mylar

TABLE 9.

Abbreviations and Symbols.

required
micro (10-6)
volt
watt

Wirewound
Wirewound Variable

0567R

51

REPLACEABLE PARTS

(Refer to Schematic Diagram 194283 for circuit designations.)

MODEL 601 ELECTROMETER

MODEL 601 REPLACEABLE PARTS LIST

BATTERIES

Circuit
Desia.

B201
B202

B203
B204
B205

B206
B207
B208
B209

Description

1.35v mercury

1.35~ mercury

8.4~ mercury

8.4~ mercury

8.4~ mercury

9v zinc carbon
9v zinc carbon

9v zinc carbon
9v zinc carbon

Circuit

Desig.

Value Rating

Cl01 22 pf 600 v

Cl02 125 iJ.f

Cl03

.OOl pf 500 "
Cl04 150 pf
Cl05 150 pf

15 "

500 "
500 "

Mfg.
Code Part No. Part No.

72665 RM42R
72665 PxM42R

72665 TR-286
72665 TR-286
72665 TR-286

09823 2N6
09823 2N6
09823 2N6
09823 2N6

CAPACITORS

Mfg. Mfg.

Type

Code

CerD 72982
ETB 73445
Poly 71590
POlY. 71590
Poly 71590

Mfg.

Keithley

BA-10
BA-10
BA-18
BA-18
BA-18

BA-17
BA-17
BA-17
BA-17

Keithley

Part No.

ED-22

Part No.

c22-22P
C462 C3-125M
CPR-1000J
CPR-150J
CPR-150.J

Cl38-.OOlM

C138-15OP

C138-15OP

Fig.
Ref.

22, 23
22, 23
22, 23
22, 23
22, 23

22, 23
22, 23
22, 23
22, 23

Fig.
Ref.

28
22
28
28
28

Cl06 5 Pf
Cl07 0.1 I.rf

Cl08 .Ol IJ.f
Cl09

.OOl pf

Cl10 100 pf
Cl11 22 pf

Cl12 0.1 pf
Cl13 680 pf
Cl14 0.1 IJ.f
Cl15 .02 IJ.f

cl16

.0011J.f

200 v
200 v
200 "
200 v
500 "

600 v

50 v

600 v

50 v

600 v
600 v

Circuit
Desig. Description

----

----

----

----

Battery holder, 2 req'd
Battery holder, 3 req'd

Battery holder, 4 req'd

Battery retain clips, 6

Poly 14167
Poly a4171
Poly 84171
Poly 84171
Poly 71590

CerD 72982

MY 84411

CerD 72982

MY 84411

CerD 72982
CerD 72982

MISCELLANEOUS PARTS

Mfg.

Code

80164
80164

80164

req'd 80164

E1013-1

c31-5P
2PJ-104G C108-.lM
2PJ-103G ClOB-.OlM
2PJ-102G Cl08-.OOlM
2PJ-1OlG ClO8-1OOP

ED-27

c22-22P
601 PE C41-.lM
ED-680

C22-680P
601 PE C41-.1M
ED-.02

C22-.02M
ED-.001 C22-.OOlM

KeithZey

BH-20
BH-21

BH-6
BH-22

26
27
27
27
27

23
25
25
22
24

22

Fig.

--­_--

---

---

52

0667~

MODEL 601 ELECTROMETER

REPLACEABLE PARTS

MISCELLANEOUS PARTS (Con't)

Circuit
Desig.

Description

D201 Silicon diode (Number 1~645)
D202 Silicon diode (Number 1~645)
D203 Silicon diode (Number lN645)

3101

-___

JlO2

Receptacle, triaxial, INPUT (Mfg. No. 33050-l)
Plug, triaxial, mate of JlOl (Mfg. No. 30197-l)

Binding Post, LO (Mfg. No. DF21B) 58474

5103 Receptacle, Microphone, OUTPUT (Mfg. No. 80-PC2F)

-___

JlO4
5105
5106
5107

Ml01

(F) Plug, Microphone, mate of 5103 (Mfg. No. 80-MC2M) 02660

Binding Post, CASE GROUND(Mfg. No. DFZLGRN)
Binding Post, XL OUTPUT (Mfg. No. DF2LR)
Binding Post, GUARD (Mfg. No. DF2LBLU) 58474
Binding Post, LO (Mfg. No. DF21B)

Meter 80164 ME-53A

SlOl Rotary Switch Less components, Range

--_-

-___

Rotary Switch with components, Range 80164 19257B

Dial Assembly, Range

Mfg. Keithley

Code

Part No.

Fig.
Ref.

01295 w-14 24
01295 RF-14 24
01295 RF-14

95712
95712

cs-181

cs-141
BPLL-B

02660 CS-32

cs-33

58474
58474

BPlL-GRN
BPll-R
BPLl-BLU

50474

BPLL-B

24

22, 2
___

22, 2
23, 3

---

22, 3
22, 3
22, 3
22, 3

22

80164 SW-204 22, 2

_-_

80164 L7033A

__-

s102

--_-

Push Button, ZERO CHECK
Knob Assembly, Zero Check

s103 Rotary Switch less components, COARSE ZERO

----

Rotary Switch with components, Coarse Zero

s104 Rotary Switch less components, MEDIUM ZERO

----

s105
Slob

--_-

----

5107

____

sloa

-_-_

Rotary Switch with components, Medium Zero 80164 1926LB

Slide Switch, FEEDBACK

Rotary Switch less components, Multiplier
Rotary Switch with components, Multiplier
Dial Assembly, Multiplier 80164 19223A

Rotary Switch, METER
Knob Assembly, Meter 80164 14825A

Slide Switch, OUTPUT 80164 SW-45 23, 3
Knob Assembly, Fine Zero Control

(F) Furnished Accessory

80164

80164

80164
80164

L4376A 23, 2

18038A
SW-166

19283B

_-_

22, 3

___

80164 SW-209 22, 2

__-

80164

19089A

80164 SW-205
80164

L9263B

23, 2
22, 2

---

---

80164

SW-206 23, 2

---

80164 L6995A

---

0667R

53

REPLACEABLE PARTS

MODEL 601 ELECTROMETER

RESISTORS

Circuit

Desig.

RlOl
R102
R103
Rl04
R105

Rl06
Rl07
Rl08

R109

RllO
Rlll

R112
R113
R114
R115

R116
Rl17

Value

10 m
10 n
100 n
1 kn

10 kn
100 ksl

1m-l
10 m
100 l"n
109 n

1010 n
1011 n
800 kn l%, l/2 w
10 m

10 kn

2.2

kn

150 kn

Rating

lO%, l/2 w

TYPE

Comp 01121
l%, 10 w Liw
l%, 10 w biw
l%, 1/2 w
l%, l/2 w

l%, l/2 w
l%, l/2 w
lO%, 1 w DCb 91637 DC-1

e

l/,, 2 w

DCb

DCb 79727 CFE-15 R12-10K

DCb 79727 CFE-15
DCb

DCb 91637 D-2

t3-O%, l/R w GCb
t3-0%, l/R w GCb 63060

t3-0%, l/R w GCb

DCb 79727 CFE-15 R12-800K
lO%, l/2 w Comp
l%, l/2 w

DCb
lO%, l/2 w Comp 01121

l%, l/2 w

DCb 79727 CFE-15
R118 150 kn l%, II2 w MtF
R119
Rl20

10 kn

1.2 kQ

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

wwvar

W

Mfg.

Mfg.

Keithley

Code Part No. Part No.

EB Rl-1OM 28
91637
91637

RS-10 R34-10 27, 28

RS-10 R34-100 27, 28
79727 CFE-15 R12-1K

R12-100K

79727

CFE-15

R12-1M
R13-10M 28
R14-100M

63060

63060
01121

Rx-1

Rx-1

R20-109
R20-1010

RX-1 R20-1011

EB

Rl-1OM

79727 CFE-15 R12-10K

EB Rl-2.2K

R12-150K

07716

12697
79727

CEC

62~~ RP42-10K
CFE-15

R94-150K

R12-1.2K

Fig.
Ref.

28
28

28
28

26, 28
26

26
26
27
23
23

25
25
25
22, 2
22

R121
R122
Rl23
Rl24

150 kn l%, l/2 w MtF
15 kn

68

m

450 kn

R125 450 IQ
R126

Rl27

R128
R129
Rl30

R131
R132

Rl33

R134
Rl35

R136
R137
R138
R139
R140

100 kn
15 ksl

68 kn
15 kIl

2

ksl

2

kn

2

kn

2kQ
2kcl
2

kn

2

kn

2

kn

2

kn

2

kn

402 n

l%, l/2 w

DCb 79727 CFE-15 R12-15K
l%, l/2 w DCb
l%, l/2 w
l%, l/2 w

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

l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, 112 w

l%, k/2 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
l%, 112 w

DCb 79727 CFE-15 R12-450K
DCb 79727 CFE-15 R12-450K

Comp

DCb

DCb
DCb

DCb

DCb

DCb

DCb

DCb

DCb

DCb

DCb

DCb

DCb

DCb

07716

CEC R94-150K

79727 CFE-15

01121
79727

79727
79727

79727

79727

79727
79727
79727
79727

79727

79727
79727
79727
79727

EB Rl-100K
CFE-15 R12-15K
CFE-15
CFE-15 R12-15K 22
CFE-15 R12-2K 22

CFE-15 Rl2-2K 22
CFE-15
CFE-15 R12-2K
CFE-15 R12-2K 22
CFE-15 R12-2K 22

CFE-15 R12-2K
CFE-15 R12-2K
CFE-15
CFE-15 R12-2K
CFE-15 R12-402

R12-68K

R12-68K

R12-2K

R12-2K

25
25
25
25
25

25
25
25

22
22

22
22
22
22

22

54,

0667R

MODEL 601 ELECTROMETER

REPLACEABLE PARTS

RESISTORS (Con't)

circuit Mfg. Mfg.

Desig.

R141
Rl42
Rl43
R144
R145

R146
R147
R148
R149
R150

R151
R152
R153
R154
R155

R156
Rl57
R158
R159
Rl60

Value Rating

402 n
402 n
402 n
402 n
402 n

402 n
402 R
402 n
402 R

15 m

10 kn
80 kn
80

kn

1.5 kil

3.3 kn

3.3 kn
22 kQ

22

kn

30

kn

15 kn

l%, l/2 w

l%,

II2 w

l%,

l/2 w

l%,

l/2 w

l%, 112 w

l%,

l/2 w

l%,

II2 w

l%,

l/2 w

l%,

l/2 w

l%, l/2 w
lO%,

l%,

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

lO%,
lO%,

l%,

l/2 w

l%,

l/2 w

l%,

l/2 w

l%,

l/2 w

l/2 "

l/2 w
l/2 w

TYPO
DCb

DCb 79727 CFE-15 R12-402
DCb
DCb 79727
DCb 79727 CFE-15

DCL! 79727 CFE-15 R12-402
DCb 79727 CFE-15 R12-402
DCb 79727 CFE-15 R12-402
DCb 79727 CFE-15 RlZ-402
DCb 79727

camp 01121 EB
DCb
DCb 79727
camp 01121
Comp 01121

Comp 01121
DCb 79727 CFE-15 Rl2-22K
DCb 79727

DCb
DCb

Code Part No. Part No. Ref.

79727

79727

CFE-15

CFE-15
CFE-15

CFE-15

79727

CFE-15 R12-80K
CFE-15

EB Rl-1.5K
EB Rl-3.3K

EB

CFE-15
79727 CFE-15
79727

CFE-15 Rl2-15K

Keithley

Rl2-402
R12-402

Rl2-402
R12-402

Rl2-15K
Rl- 10K
RlZ-80K

Rl-3.3K

Rl2-22K
Rl2-30K

Fig.

22
22
22
22
22

22
22
22
22
22

25
25
25

-­__

25
__

__
__
__

R161
Rl62
R163
R164

R165
R166

R167
R168
R169
R170

R171
R172
R173
R174
Rl75

R176

R201
R202

R203
~204

R205

2.2

kfi

9.1 kc

2.73

kn

910 n

273 n

91 n

27.3 n

9.1 n

2.73 n

.Vl n

8.6

kn

20

kn
910 n
10 n

470 n

10 R

1 k0
9 kR

70

k0

10 kfl
180 kQ

l%,

l/2 w

0.5%, l/2 w

0.5%, II2 w

0.5%, II2 w

0.5%, l/2 w

0.5%, II2 w

0.5%, l/2 w

0.5%, l/4 w

0.5%, l/4 w

0.5%, l/4 w

l%,

l/2 w

lO%, 5 w

0.577, 112 w

lO%,
lO%,

II4 w
l/2 w

lO%, l/4 ”

l%,

II2 w
l%, l/2 w
I%, 112 w
lO%, 5 w

lO%, 112 w

DCb 79727
MtF 07716
MtF
MtF

07716 CBC R61-2.73K
07716

MtF 07716

MtF
MtF

07716

07716 CBC R61-27.3
ww 01686
ww 31686
ww

01686 T-2A R123-.91
DCb 79727

War 71450

MtF

camp
Comp

07716

01121

01121

Comp 01121

DCb 79727
DCb 79727

DCb 79727

WWvar 71450

camp

01121

CFE-15

Rl2-2.2K

CBC R61-9.1K

-_

22

22
CBC
CBC R61-273

CBC

R61-910

R61-91

22

22
22

22
T-2A R123-9.1
T-2A R123-2.73

22

22

22

CFE-15 R12-8.6K
AW RP34-20K

23
23, 3

CEC R61-910 23

CB

R76-10

EB Rl-470
CB

CFE-15

R76-10

RlZ-1K
CFE-15 RLZ-9K
CFE-15 RlZ-70K

-_
22

_-

24
24

24
AW RP3-1OK 23
EB

Rl-180K

24

0667~

55

REPLACEABLE PARTS

MODEL 601 ELECTROMETER

RESISTORS (Con't)

Circuit Mfg.

Desig.
R206

R207
R208
R209

R210
R211

R212
R213

R214

R215
R216

R217
R218
R219
R220

Value

820 n
820 n
39 kn
180 kn

1 kn

1 kn

180 kn

330 n

15 kn

120 kn
330 n

15 kn

120 kn

500 n

2

kn

Rating

lO%,

l/2 w

lO%, l/2 w

lO%, l/2 w

lO%,
l%,

l/2 w

l/2 w

lO%, 5 w

LO%, l/2 w

lO%,

lO%, l/2 w

lO%,
lO%,

lO%,
lO%,
l%,

l/2 w
l/2 w
l/2 w

l/2 w

l/2 w

l/2 w

lO%, 5 w

TYPO
Comp

Comp
Comp
Comp
DCb

WWVar

Camp
Comp
Comp

Camp

Comp

Comp
camp
DCb

WWVar

Code

01121 EB
01121 EB
01121 EB
01121 EB

79727 CFE-15

71450 AW
01121 EB
01121 EB
01121 EB

01121 EB

01121 EB
01121 EB

01121 EB

79727 CFE-15
71450 AW

TRANSISTORS

Circuit
Desig.

Number

Mfg.

Code

Mfg.

Keithley

Part No. Part No.

Rl-820 24
Rl-820 24
Rl-39K 24
Rl-180K 24
R12-1K 24

RP34.-1K 24

Rl-180K 24
Rl-330 24
Rl-15K 24

Rl-120K 24

Rl-330 24

Rl-15K 24
Rl-120K 24
R12-500 24
RP34-2K 24

Keithley
Part No.

Fig.

Ref.

Fig.
Ref.

QlOl
4102

Q103
4104
QlO5

Q106
Q201

Q202
Q203
4204
4205

4206

Circuit

DesFg .

VlOl

v102

A1380

A1380
A1380
A1380

S17638

S17638
Al380

2N1605
2N1381
S17638
S17638

517638

Number

5886
5886

80164 TG-32
80164 TG-32
80164 TG-32
80164 TG-32

07263 TG-33
07263 TG-33

73445 TG-32

93332 TG-22
01295 TG-8
07263 TG-33

07263 TG-33
07263 TG-33

VACUUM TUBES
Mfg.

Code

Keithley
Part No.

80164 ""EV-5886-3P

80164 **EV-5886-3P

25
25
25
25
25

25

24

24
24
24
24

24

Fig.

Ref.
23

23

** Replace VlOl and V102 as a pair.

56

06678

MODEL 601 ELECTROMETER

REPLACEABLE PARTS

01121 Allen-Bradley Corp.

Milwaukee, Wis.

01295 Texas Instruments Inc.

Semi Conductor-Components Division
Dallas, Texas

01686 RCL Electronics, Inc.

Riverside, N. J.

02660 Amphenol-Borg Electronics Corp.

Broadview, Chicago, Illinois

07263 Fairchild Camera & Instrument Corp.

Semiconductor Division

Mountain View, Cal.

07716 International Resistance Co.

Burlington, Iowa

09823 Burgess Battery Co.

Freeport, Ill.

12697 Clarostat Mfg. Co., Inc.

Dover, N. H.

71450 CTS Corp.

Elkhart, Ind.

71590 Centralab Division of

Globe-Union, Inc.

Milwaukee, Wis.

72665 Mallory Battery Co.

Cleveland, Ohio

72982 Erie Technological Products, Inc.

Erie, Pa.

73445 Amperex Electronic Co. Division o

North.American Philips Co., Inc.
Hicksville, N. Y.

79727 Continental-Wirt Electronics Corp

Philadelphia, Pa.

80164 Keithley Instruments, Inc.

Cleveland, Ohio

84171 Arco Electronics, Inc.

Great Neck, N. Y.

14167 Efcon, Inc.

Garden City, Long Island, N. Y. Ogallala, Nebr.

56289 Sprague Electric Co.

North Adams, Mass.

58474 Superior Electric Co., The

Bristol, Corm. Semiconductor Products Division

63060 Victoreen Instrument Co.

Cleveland, Ohio 95712 Dage Electric Co., Inc.

TABLE 10. Code List of Suggested Manufacturers.

facturers, Cataloging Handbook H4-1.)

84411 Good-All Electric Mfg. Co.

91637 gale Electronics, Inc.

Columbus, Nebr.

93332 Sylvania Electric Products, Inc.

Woburn, Mass.

Franklin, Ind.

(Based on Federal Supply Code for Manu-

0667R

57

CHANGE.NOTICE
January. 9, 1967
Page 53.

Change to the following:

Circuit
Desig.

.

Ml01

Description

Meter

MODEL 601 ELECTROMETER

Mfg.

Code

Keithley
Part No.

'%0164 ME-81

Fig.
Ref.

22

CHANGE NOTICE

August 29, 1967

Page 3.

ISOLATION:
microfarad.

Page 54.

Change the ISOLATION Specification to the following:

Circuit ground to chassis ground:

gr?ater than

9 ohms shunted by 0.0015

10

Circuit ground may be floated up to -1500 volts with respect to chassis ground.

Change to the following: ’

circuit Mfg. Mfg.

Desig.

Value Rating

R108 10 MQ

TYPO

l%, l/2 w DCb

Code

Part No. Part No. Ref.

79727 CFE-15 Rl2-1OM 28

MODEL 601 ELECTROMETER

Keithley

Fig.

CHANGE NOTICE

MODEL

‘$13

pH ELECTRODE ADAPTER

Pane 1. The second sentence in the first paragra~ph should be changed to:

One hole accepts either a Beckman and Coleman (B-C) or a new type~Lee,ds and

Northrup connector. The other hoie accepts an old type Leeds and Northrup connector.

.

MODEL 6013

pH ELECTRODE ADAPTER

1. GENERAL.
a. The Keithley Model 6013 pH Electrode Adapter is designed to allow accurate and con-

venient pH potential measurements w,ith both the Keithley Model 601 Electrometer and the
Keithley Model 630 PotentiometricElectrometer.

It accepts a Beckman and Coleman (B-C)

or a Leeds and Northrup (L&N) connector. The two terminals marked REF accept a banana

jack or a phone tip jack.

The Adapter uses Teflon insulat$on.on a1.J high impedance connections and is fully -~-

b.

guarded to insure that the accuracy~of ~the Model 60l.qr the Model 6.3~0 is affected in no ~_
way.
out shorting the pH electrodes.

The ZERO CHECK Button on the Model 6013 ,alLows checking zero on the Model 601 with-

The Adapter can float off ground with either the Model

' 601 or the Model 630.

2. USE WITH THE MODEL 601 ELECTROMETER.
a. To use the Model 6013 with the Model 601, set the Transfer Switch on the Model 6013

to the 601 position. Set both the ZERO CHECK Button on the Model 601 and the ZERO CHECK

Button on the Model 6013 to the LOCK Position. Place the FEEDBACK Switch on the Model 601

in

the FAST PosFtFon.

b. Connect the Adapter cable directly into the Model 601 INPUT Receptacle.

Connect the
TO GUARD Terminal on the Model 6013 to the OHMS GUARD Terminal on the rear panel of the
Model 601.

c. Open the ZERO CHECK Button on the Model 601.

Insert the pH electrodes into the

Model 6013.

d. To obtain a reading,

set the Model 601 METER Switch to CENTER ZERO.

Switch to VOLTS. Use the appropriate range for the Multiplier Switch.

CHECK Button on the Model 6013.

Read the voltage off the lower meter scale. To convert

Set the Range

Open the ZERO

the voltage to pH, refer to Figure 2.

NOTE

To check zero on the Model 601, use only the ZERO CHECK Button on the Model 6013.

Do not use the ZERO CHECK Button on the Model 601. The Button on the Model 6013,

is zign&d to disconnect the Hi electrode before shorting the Model 601 leads.
If the Model 601 ZERO CHECK Button is used to check zero, the electrodes will

be shorted and may be damaged.

e. The Adapter will float off ground with the Model 601.

3.

USE WITH THE MODEL 630 POTENTIOMETRIC ELECTROMETER.

. '_

.a. To use the Model 6013 with theMode 630, set the Transfer Switch.on the Model 6013

to the 630 position.

b. conrie.2t the .\&pter Cl512 d<rx.cly iFto the !~Lxl?L 630 INPU-I Kec~plx;,.

Connect the

TO <Xi) Tlr;iiixiL on the >Iodel 6013 to the CND Terminal on the front panel of the Model 630.

0966

L

To obtain a reading set the Model 630 NULL Switch to the VTVM Position., Switch the

c.

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

qtge off the meter.

To convert the voltage to pII, refer to Figure 2.

.

NOTE

:.

To check zero on the Model 630 use either the ZERO'CHECK Button on the Model

6013 or the DETECTOR INPUT Switch in the ZERO CK Position on the Model 630.

Both switches disconnect the source before shorting the leads to the'Mode1 630.

For floating measurements open the link between the LO and GND Terminals on the

d.

front panel of the Model 630.

The Model 6013 will float off ground with the Model 630.

NOTE

If the Adapter becomes contaminated, clean it with distilled water followed by

a thorough swabbing with pure methyl alcohol, $H30H.

This will-suffice for most

contaminants.

Read the volt-

.

Glq-+>

Shield4

Ref.

>

630 t--j 601

F IGURE 1. Model 6013 pH Electrode Adapter

Wiring Diagram,

east Mode)601

I ----I----

I

630

0966

SOI

38

SY
Str

L-

d

I

I

, /

I

I

I

I
I

I

-

r
I

/

----

,/

I
I

” Q 0 0

----2.

----