Model 600A
Electrometer
Instruction Manual
Contains Operating and Servicing Information
WARRANTY
Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from
date of shipment.
Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries, diskettes, and documentation.
During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.
To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio. You
will be given prompt assistance and return instructions. Send the product, vansportation prepaid, to the indicated service facility.
Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance
of the original warranty period, or at least 90 days.
LIMITATION OF WARRANTY
This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse
of any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leakage, or problems arising from normal wear or failure to fallow instructions.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN
ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.
NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS
OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.
Safety Precautions
The following safety precautions should be observed before using
this product and any associated instrumentation. Although some instruments and accessories would normally be used with “on-hazardous voltages, there are situations where hazardous conditions
may be present.
This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury. Read the operating information
carefully before using the product.
The types of product users are:
Responsible body is the individual or group responsible for the use
and maintenance of equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and for en-
suring that operators are adequately trained.
Operators use the product for its intended function. They must be
trained in electrical safety procedures and proper use of the instmment. They mut be protected from electric shock and contact with
hazardous Iive circuits.
Maintenance personnel perform routine procedures on the product
to keep it operating, for example, setting the line voltage or replacing consumable materials. Maintenance procedures are described in
the manual. The procedures explicitly state if the operator may perform them. Otherwise, they should be performed only by service
personnel.
Service personnel are trained to work on live circuits, and perform
safe installations and repairs of products. Only properly trained service personnel may perform installation and service procedures.
Users of this product must be protected from electric shock at all
times. The responsible body must ensue that users are prevented
access and/or insulated from every connection point. In some cases,
connections must be exposed to potential human contact. Product
users in these circumstances must be trained to protect themselves
from the risk of electric shock. If the circuit is capable of operating
at or above 1000 volts, no conductive part of the circuit may be
exposed.
As described in the International Electrotechnical Commission
(IEC) Standard IEC 664, digital multimeter measuring circuits
(e.g., Keithley Models 175A, 199,2000,2001,2002, and 2010) are
Installation Category II. All other instruments’ signal terminals are
Installation C&gory I and must not be connected to mains.
Do not connect switchjng cards directly to unlimited power circuits.
They are intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When co”-
netting sources to switching cards, install protective devices to limit fault current and voltage to the card.
Before operating an instrument, make sure the line cord is connect-
ed to a properly grounded power receptacle. Inspect the connecting
cables, test leads. and jumpers for possible wear, cracks, or breaks
before each use.
For maximum safety, do not touch the product, test cables, or any
other instruments while power is applied to the circuit under test.
ALWAYS remove power from the entire test system and discharge
any capacitors before: connecting or disconnecting cables or jump-
ers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.
Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks 01 test fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS, 42.4V
peak, or 60VDC are present. A good safety practice is to expect
that hazardous voltage is present in any ““known circuit before
measuring.
Do not touch any object that could provide a current path to the
common side of the circuit under test or power line (earth) ground.
Always make measurements with dry hands while standing on a
dry. insulated surface capable of withstanding the voltage being
measured.
The instrument and accessories must be used in accordance with its
specifications and operating instructions or the safety of the equipment may be impaired.
The WARNING heading in a manual explains dangers that might
result in personal injury or death. Always read the associated information very carefully before performing the indicated procedure.
Do not exceed the maximum signal levels of the instruments and accessories, as defined in the specifications and operating information, and as shown on the instrument or test fixture panels, or
switching card.
When fuses arc used in a product, replace with same type and rating
for continued protection against fire hazard.
Chassis connections must only be used as shield connections for
measuring circuits, NOT as safety earth ground connections.
IF you are using a test fixture, keep the lid closed while power is ap
plied to the device under test. Safe operation requires the use of a
lid interlock.
Ifa@
wire recommended in the user documentation.
Then
fer to the operating instructions located in the manual.
Then
sure IO00 volts or more, including the combined effect of normal
and common mode voltages. Use standard safety precautions to
screw is present, connect it to safety eanh ground using the
symbol on an instrument indicates that the user should re-
symbol on an instrument shows that it can source or mea-
avoid personal contact with these voltages.
The CAUTION heading in a manual explains hazards that could
damage the instrument. Such damage may invalidate the warranty.
Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and
all test cables.
To maintain protection from electric shock and fire, replacement
components in mains circuits. including the power transformer, test
leads, and input jacks, must be purchased from Keithley Instruments. Standard fuses, with applicable national safety approvals,
may be used if the rating and type are the same. Other components
that are not safety related may be purchased From other suppliers as
long as they are equivalent to the original component. (Note that selected pans should be purchased only through Keithley Instruments
to maintain a.ccuracy and functionality of the product.) IF you are
unsure about the applicability of a replacement component, call a
Keithley Instruments office for information.
To clean an instrument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
cleaner directly to the instrument 01 allow liquids to enter or spill
on the instrument. Products that consist of a circuit board with no
case or chassis (e.g., data acquisition board For installation into a
computer) should never require cleaning if handled according to instructions. If the board becomes contaminated and operation is affected, the board should be returned to the factory for proper
cleaning/servicing.
Rev. ?.I99
MODEL 6OOA ELEKX'ROMFt73R
TABLE OF CONTEmTs
Title
section I.
Section II. - Specifications
- Introduction. ........................
....................... 2-1
Section III. - Operation .........................
Controls andTerminals
A.
Preparing the Instrment for Operation
B.
Measuring Voltage. .........................
C.
.......................
D. Measuring Current. .........................
E. MeasuringOhms ...........................
BatteryCheck. ...........................
F.
G. Using Extenal Indicators.
Misce.Ll.aneous Applications
R.
Zero Center Operation.
I.
Section IV.
Voltmeter ..............................
A.
- Circuit Discussion
.....................
..................... 3-5
.......................
..................... 4-l
B. Ammeter.. .............................
C. Ohmmeter ..............................
Section V.
- Accessories .........................
Section VI. -Maintenance. ........................
Pa3
1-l
3-1
3-l
............... 3-2
3-2
3-2
3-3
3-4
3-5
3-6
4-l
4-2
4-3
5-l
6-1
section VII.
Voltage-Resistance Diagram
- Replaceable Parts List.
....................... 7-3
Schematic Diagram. ...........................
rChangeNot.ice .............................
.................. 7-l
7-5
La&Page
?+l'he yellow Change Notice sheet is included only if the instrument contains mod-
ifications which affect the
0962~
instruction
manual.
i
MODEL 6OOdELFcl'RGhfg!FgB
INTFDIUCTION
SECTION I - INTRODUCTION
The Keithley Model 600A Electrometer is an ultra-high impedance voltmeter
with full-scale ranges of 0.01, 0.03, 0.10, 0.30, 1.0, 3.0 and 10 volts.
The maximum input resistance is greater than 10lh ohms; in addition, the
input resistance may be varied in decade steps from one ohm to 1011 ohms
by means of the shunt resistors built into the instrument. Thus, the
600A is not ,only appropriate for measurement in high-impedance circuits,
but also can be used where a high input impedance would merely introduce
unwanted pickup.
The 6OOA may be used as a direct-reading ammeter from 3 amperes to lo-l3
ampere full scale.
and 10x scales.
This &decade range is covered in overlapping 3x
Two current measuring methods are available to the user
of the 6OOA. Normally, current is determined by measuring the voltage
g,"",;"';"t"~ ;,33
input of the voltmeter through the current measuring resistor.
istor shunted from input to ground. Alternately, on
ampere ranges, negative feedback can be applied to the
This
largely eliminates the input drop and increases measuring speed, particularly on the,more sensitive ranges.
The 600A measures 10K to 1012 ohms full scale wit P a two-terminal input.
With a guarded input, its range is extended to 10 3 ohms. Unlike conventional ohmmeters, information is presented on the
linear scales
used
for current and voltage readings.
As a dc preamplifier, the 600A has gains of 0.1, 0.3, 1, 3, 10, 30 and
100.
The continuing stability of the gain is assured bv a feedback
factor in excess of 100 on any range.
The output is minus 1 volt, open circuit, with an internal resistance
of
17K.
Thus, the outputmay be used for driving oscilloscopes or
pen recorder amplifiers, or the output may be shunted down to provide
lo- or SO-mv outputs for servo-rebalance recorders.
NOTE
When the Model 600A is shipped from the factory, an angle
bracket (Keithley Part No. 13766A) sapports the printed
circuit board (PC-29).
rear panel with a #I6 x S/16 sheet metal screw.
The bracket is fastened to the
The bracket
and screw may be removed after the Model 600A is received.
WHEN SHIPPING THE INSTRUMENT TO ANOTHER DESTINATION, RE-
PLACE THE BRACKET TO FIRMLY SUPPORT THE PRIBTED CIRCUIT BOARD.
D704R
1-l
INTROlWCl'ION
MODEL 6OOA ELECTROMETER
1-2
MODEL 600A ELECTROMETER
& A VOLTMETER:
SPECIFICATIONS
SECTION II - SPECIFICATIONS
RANGE:
ACCURACY:
ZERO DRIFT:
INPUT IMPEDANCE:
0.01 volt full scale to 10 volts in seven lx and 3x ranges.
'r2% of full scale on all ranges exclusive of drift.
Less than 2 millivolts per hour after l-hour warm-up.
Greater than 1014
ohms shunted by 30 picofarads.
be selected in decade steps from 1 ohm to 101~ ohms.
& & AMMETER:
RANGE: LO-l3
ACCURACY:
MLJLTIPLIER Switch setting;
GRID CURRENT:
ampere full scale to 3 amperes in twenty-eight lx and 3x ranges.
23% of full scale on 3-ampere to lo-lo
+5% cf full scale on 3 x 10
ampef~lr::g;;~13 ampere ranges.
Less than ~5 x LO-l4 ampere.
fi & OHMMETER:
RANGE:
LO4 ohms full scale to 1013
ACCURACY:
23% of full scale on lo4
ohms in nineteen linear lx and 3x ranges.
to 1010 ohm ranges, using largest available MULTIPLIER
Switch setting; ?5% of full scale on 3 x 10~' to 1013 ohm ranges.
Input resistance may
using smallest available
& & AMPLIFIER:
GAIN:
FREQUENCY RESPONSE (Within 3 db):
0.1, 0.3, etc., to 100.
dc to 100 cps at a gain of 100, rising to 1.5 kc at a
gain of 0.1.
NOISE:
INPUT IMPEDANCE:
Less than 3% peak-to-peak of full scale.
Greater than 1014 ohms shunted by 30 picofarads.
be selected in decade steps from 1 ohm to 1011 ohms.
OUTPUT:
+-1 volt for full-scale input. Internal resistance is 17 kilohms.
ity is opposite input polarity.
GENERAL:
POLARITY:
METER Switch selects left-zero (positive or negative) or center-zero scales.
Output polarity is not reversed.
CONNECTORS: Input:
uhf type; ground binding post.
Input resistance may
Output polar-
output: Amphenol 80-PC~F.
0565R
2-1
SPECIFICATIONS MODEL 600A ELECTROMETER
BATTERIES:
minimum battery life.
DIMBNSIONS, WEIGHT:
weight, ?-l/2 pounds.
ACCESSORIES SUPPLIED: Mating input and output connectors; binding post adapter,
Two 413 (30 volts), four El46 (8.4 volts), two RM42R (1.34 volts). 500 hours
10-l/4 inches high x 6-l/2 inches wide x 6-l/2 inches deep; net
2-2 0565R
MODEL600AEIJX!TROMETER
O.PEFWION
SEc!PION
comIs Am -m
A.
Controls and Terminals: The
III - OPEMTION
input connector is a UHF type receptacle.
An accessory binding post which plugs into the center of the con-
nector is furnished,.
A ground binding post is mounted on the panel
above the input connector.
Front Panel iontrols:
RANGE switch,
the meter.
the AMPERES position, a shunt resistor whose
located
in the center of the front panel under
This control selects VOLTS, OHMS, or AMF'ERES. On
value is
the reciprocal of the designated range may bs used to decrease the
innut resistance as well as to measure current.
MULTIPLBR switch, located in the center of the front panel
directly under the meter, determines the voltage sensitivity
of the dc amplifier, and sets the voltage range when the
RANGE is set on VOLTS.? On OHMS or AMPERES, the setting of
this knob multiplied by the OHMS or AMPERES setting gives the
full scale meter reading.
Rear
ZERO control, located at the left under the meter, is used to
set the meter to sero.
METER-BATTERY switch, at the right under
instrument on, determines meter polarity
the meter, turns the
or zero center opera-
tion, and tests the batteries.
ZERO CBECK switch, located at the bottom
input terminal through one megohm, while
right, shorts the
the amplifier input
is shorted.
Panel Controls:
OUTPUT connector for external recorders.
NORMAL-FAST.
FAST position,
around the shunt resistor.
This control is locked in NORMAL position. In
current measurements are made with feedback
On OBMS, the FAST position is used
when the INPUT GUARD terminal is used.
INPUT GUARD.
With the NORMAL - FAST switch on FAST, the low
impedance end of the test sample is returned to this terminal
when it is desired to measure the resistance of a guarded
sample.
COARSE ZERO.
If the amplifier is quite badly unbalanced, the
COARSE ZERO switch is used to bring the front panel ZERO con-
trol in range.
ZERO CENTER When meter cannot be centered with ZERO control it
may be brought within range with this control.
og6m
3-l
OPERATION
PREPARING THE INSTRUMENT FOR OPERATION
B.
(1) Set controls as follows:
MULTIPLIER: 10
RANGE SWITCH: VOLTS
ZERO CHECK WITCH: Locked
INPUT TERMINAL: Shield with cap
(2) Turn the bigTER switch to meter +. The instrument should come
to eero in approximately 5 seconds.
(3)
Rotate the MULTIPLIER switch toward the high sensitivity end,
adjusting ZERO as required.
with the front panel ZERO control, use COARSE ZERO control on rear
panel to bring the instrument within
If
it is impossible to eero
range
of the ZERO control.
the meter
(II) Connect leads as required for measurement.
If high impedance is
involved, the input should be shielded using a coaxial connection or
shielded enclosure.
various accessories
for the Model 600A may
The
be used.
If the impedance,is low@elow about lOlo ohms) and leads can be kept
short, the binding
post
adapter furnished with the instrument may be
used.
The Keithley Model 6101A Shielded Test Lead will suffice for mDst
measurements.
C.
b@XURING VOLTACE
Place RANGE switch at VOLTS.
Turn MLTIPLIW. switch to expected
sensitivity and check meter zero.
Release ZERO check, and read.
If the sensitivity of the instrument is increased, recheck the
zero reading.
D.
MKXXlRING CURRENT
(1) NORMAL method (3 amperes to lo-l3 amperes full scale)
Turn RANGE switch to desired AMPERES range. Make sure the switch at the
rear of the instrument is on the NORMAL position.
to the input,
the RANGE switch and MULTIPLIEJt.
Full scale sensitivity is the product of the settings of
Check aero with the ZERO CHECK switch
Connect current source
and then read the unknown current.~ The full scale voltage drop is the
setting of the MULTIPLIER switch.
3-2
0962R
MODEL 6COA EIJXlTROMETER OPERA!CION
(2) FAST method (low7 to lo-l3 amperes full scale).
Proceed as above except with the FAST-NORMAL switch at FAST. The inout
drop is now negligible and the inout circuit time constant is reduced
at least 100 times.
Observe the following cautions:
(a) Use only the ZERO CHECK switch to check zero.
Do not short the input.
(b) The low side of the output is no longer at ground.
Therefore, a recorder attached to the output must
not be grounded to the Model 6COA.
(c) Do not use this method for the measurement of
capacitor leakage.
E. -----
MEASURING OHMS
(1) NORMAL method
(10K
to lo11 ohms full scale).
Turn RANGE switch to desired OHNS range. Make sure that NORMAL-FAST
switch is in the NORMAL position.
Connect resistance sample to be measured only after ZERO CHECK switch
has been locked. The test voltage at full scale is the setting of the
MULTIPLIER switch.
Before reading OHMS, turn RANGE switch to the approximate range of the unknown resistance. By manipulating the NULTIPLIER and the RANGE switch, the sample can be tested at a number of test
potentials, if desired.
This two terminal method is the simplest-and will wcrk quite satis.factorily up to about 1011 ohms. At resistances greater than 1011 ohms,
it is desirable to employ a GUARD connection both to speed up the response of the instrument and to nullify the error of leakage across
the electrometer input insulation.
(2) GUARDED method (10" to lo13 ohms full scale).
Proceed as with the two terminal method with the exception that the
sample is connected between the INPUT terminal and the GUARD terminal
on the rear panel.
The FAST-NORMAL'switch must be set at FAST.
(3) EXTERNAL VOLTAGE method,
Any external voltage may be used. The unknowo is connected between
the test potential and the INPUT terminal of the electrometer. The
current is then measured, using the NORMAL or FAST method, and the
resistance calculated.
og62R
3-3
MODEL ~OOAELEC!J!ROME!~ER
Proceed as follows:
(a) Lock the ZERO CHECK Switch.
(b) Connect unknown between INPUT terminal and source of po-
tential. A switch should be connected in the hiph voltage line
so that when the sample is disconnected from the potential, the
low impedance end of the sample is grounded.
(c) FAST-NORMAL switch should be at NORMAL.
(d) Apply potential to sample before unlocking ZERO
CHECK.
Start the RANGE switch at low current sensitivities and
advance the sensitivity until a reading is obtained.
If the potential applied is at least 100 times the ammeter drop (the
setting of the MULTIPLIER switch), the resistance is equal to:
POTENTIAL APPLUD
CURRENT READING
If the potential applied is not large compared to the ammeter drop,
the resistance is equal to:
POTENTIAL APPLIED - INPUT DROP (VOLTS)
CURRENT READING
le) If it is possible to operate
the input drop need not be considered in the
F.
BATTERY CHECK
Turn METER-BATTERY switch to Bl, B2, etc.
on
FAST micro-microanmreter..
calculation.
All batteries should read
half scale or higher on the meter.
Bl, B3, Bh, and B5 are tested directly.
series on position B2.
Since the battery drains are nearly iden-
B2a and B2b are tested in
tical in B2a and B2b, both should be changed when the series arrange-
ment reads low.
B6 and B7 are not tested because they are operated under virtually
shelf-life conditions.
They may be replaced yearly as preventive
maintenance or may be tested at any time by removing the case and
measuring with a voltmeter.
They should be replaced if.they test
less than eight volts.
3-4
OPERA!l!ION
G.
USING EXTKRNAL INDICATORS
The output of the Model 6CGA may be used to drive servo rebalance
recorders as well as hish impedance devices such as oscilloscopes
and pen drive amplifiers.
(1) For use with servo rebalance recorders;
The output circuit consists of a 16.67K resistor through
which 60 microamperes flow for full scale deflection of
the .panel meter,
Shorting the output does not affect the
meter reading of the Model 6OOA, but low impedances placed
across the output terminals lower the terminal voltage
for full scale deflection.
Thus, if it is desired that
the output voltage for full scale be 10 millivolts, a
168 ohm resistor should be connected across the output
terminals.
If a full scale of 50 millivolts is.required,
878 ohms should be used.
(2) For use with oscilloscopes and pen recorder amplifiers,
the output is minus one volt for full scale meter deflection
on any range.
The frequency response is dc to 100 cycles on the 10 millivolt range rising to 1 kc on the 10 volt range.
amolitude which can be delivered bv the amplifier is approxi-
.
mately 2 volts peak to peak.
"
The maximum
H.
MISCELLANEOUS APPLICATIONS
CURRENT INTEGRATOR:
The Model 6OOA may be used
as an integrator for small
currents such as cyclotron
and mass spectrometer beam
currents, since it is basically an operational amplifier with electrometer input
when the FAST-NORMAL switch
at the rear is placed in the
FAST position.
To integrate current, connect a polystyrene capacitor
of suitable value between
the GUARD terminal and the
input.
The RANGE switch
is set at VOLTS so that there is no resistance placed across the,capacity.
Then if Fig. 600-l is consulted,
it can be seen that the standard resis-
tor has been replaced by a capacitor and the 600A is now an integrator.
The full scale charge on the capacitor in coulombs is simply the product
of the capacitor value chosen (in farads) and the setting of the MULTIPLIER
Cg62R
3-5
switch (in volts).
If it is desired that a time ccnstant be introduced
into the integrating circuit the appropriate shunt resistor may be
selected by the function switch.
Practically, it is suggested that the capacitor be enclosed in a grounded can. The connection to the GUARD terminal may be made by a simple un-
shielded lead.
means of a coaxial connection to one side of a Wee" adapter.
The connection to the input terminal should be made by
The cur-
rent input is made to.the other side of the %eeu.
The following procedure is suggested: Depress the ZERO
CHECK
switch,
thus removing the charge from the capacitor and shorting the input.
Zero if necessary.
Release the ZERO CHECK switch. If the integration
is to take place over a long period of time it is suggested that the
instrument be used cx the one volt range or higher so that zero drift
and grid current will not be factors.
CURRENT SOURCE:
a constant current to any device placed across its input terminals.
When measuring ohms, the instrument is designed to supply
The
magnitude of the current is equal to the reciprocal of the designation on
the OHMS segment of the RANGE switch. Therefore the instrument may be
used as a current source for calibration of other instruments if desired.
Depress ZERO CHECK and turn RANGE switch to OHMS.
The current that is
supplied on each range is the reciprocal,of the OHMS setting, and is not
affected by the setting of the MULTIPLIER switch. However, for the cur-
,rent to be accurate, the amplifier should be in balance.
It will be
sufficient to balance the amplifier on the .l volt range of the MJLTI-
PLIER Switch.
STATIC CHARGE MEASUREMKNTS: The instrument is zeroed and the RANGE
switch ulaced on VOLTS.
3 or lO*volts full scale.
The voltage sensitivity is perhaps placed at
The charged object is then brought near the
uncovered, unshielded input connector of the 600A. Depending on the dis-
tance between the charge and the instrument a voltage will be induced on
the input terminal and can be read on the panel meter. The instrument
zero should be checked frequently since accumulation of charge due to the
electrometer tube grid current will cause a slow drift of input voltage.
Connecting a capacitor across the input reduces the drift due to grid
current and also the sensitivity to charge.
An electrode connected to
the INPUT terminal which increases the capacitance between the INPUT
terminal and the charged object will increase the sensitivity to charges.
I.
ZERO CENTER OPKRATION
In some applications, such as null indication or in measuring volt-
ages of either polarity near zero,
it may be desirable to use the ZERO
CENTER position on the bWl'ER-BATTERY switch. Onthis position, operation is just the same as for left-zero (normal), except that for zero
input voltage or current, the meter pointer is at center scale.
The ZERO CENTER control
On
the rear panel is used to set the meter
pointer to zero for zero center operation. It should require only
infrequent attention.
3-6
0962R
MODEL 6008 ELECTRCME!I!EB
SECTION IV - CIRCFIT DISCUSSION
CIRXJlT DISCUSSION
The basic element of the Model 6OOA is a highly accurate, stable dc
voltmeter with a full scale se
put impedance greater than 10 ohms shunted by 30 micro-microfarads.
sitivity of 10 millivolts and an in-
1C
Amperes and ohms are measured by the use of resistance standards.
The various connections necessary for ampere and ohms measurements
will be discussed following the detailed description of the amplifier.
A. VOLTMETER
Refer to DR1201hC at the rear of the manual.
The amplifier proper con-
sists of Vl, V2, and V3.
VL is a cathode follower
which drives the amplifier
at the same instantaneous
potential as the input
signal. In other words the
neutral or ground terminal
of the amplifier is not
grounded to the chassis out
is attached to the output
cathode follower.
600-2 shows this diagram-
The amplifier A
FIOURE BOO- 2
atically.
is driven by the cathode
follower.
Fig.
Input dividers are neither stable nor accurate at high impedance. Consequently the Model 600A will accept 10 volts without the use of input
dividers, preserving the high input impedance and accuracy of the amplifier. Accessory probes are available for extending the voltage range at
reduced input resistance and accuracy.
Since the amplifier proper is driven by the cathode follower, the plus
and minus 30 volt batteries for the cathode follower are referred to
input ground while the battery supplies for the amplifier are referred
to amplifier ground which is "floating". In subsequent discussion,
reference will be made to the amplifier ground as "floating ground" and
to cathode follower ground as "output ground".
The amplifier input consists of two balanced 5886 electrometer tubes.
The filaments are operated in parallel from battery Bl. The control
grid of Vl, the active electrometer tube, is protected by R2, a 109 ohm
resistor, bypassed for high frequencies by C2. The control grid cf 712,
the 'tdummy" tube, is returned through a variable voltage to floating
ground.
This variable supply is made up from B2a, B2b, R15 (ZERO on the
front panel) and Rll, ~28, R29;R30, R31, R32 on SW-& (COARSE ZERO on
rear panel).
og62R 4-1
CIRCUDl! DISCUSSION M3DEL 6OOAELBXF0ME!!PE2
The ZERO ccntrcls function by adjusting the dc voltage of the dummy
electrometer tube grid.
The voltmeter sensitivity is determined by the resistor placed in
series with the meter, R33 through R39. Meter current passing
through Rh2 develops the constant one volt output for any ranse.
C3 and R6 serve to stabilize the feedback loop against oscillation.
AMMETER
B.
Grid current of the input
electrometer tube fixes the
minimum current that may be
measured. The Model 600A
grid current will us~&lly
be less than 2 x lo-
OUTPUT
amperes. On low current
ranges, the grid current
will be apuarent and may be
balanced out with ZERO con-
CHASSIS GROUND
Y
trol or subtracted from the
final reading.
PIQURE’ 600- 3
(1) Shunt Resistor Method (NORMAL)
In the normal operating connection as shown in Fig. 600-3, current is
measured by placing a resistor across the input terminals and measuring
the voltage drop.
Currents from 3 amperes to lo-13 amperes may be
measured by this method since the range switch selects resistors ranging
from one ohm to 1011 ohms
in
decade steps.
The voltage drop is selected
by the MULTIPLW switch; the setting is the input voltage drop for full-
scale meter deflection.
(2) Feedback Method (FAST)
In the voltmeter discussion above, floating ground has been driven by
the cathode follower and output ground has been connected to the low
impedance side of the input conne&or. In the FAST connection, shown
in Fig. 600-1, the amplifier ground is connected to the low impedance
side of the input; the cathode follower ground floats, and
negative
feedback is applied through the shunt resistor.
In the Model 6OOA, it is possible to use this connection with currents
of 0.1 microamperes or less.
To change the connection, remove the lock
from NORMAL-FAST switch at the bottom of the rear panel and change it to
the FAST position.
The advantages of this connection are:
(a) The effect of input capacity is largely neutralized, that
is, the time constant of the input and cable capacity and the
shunt resistor used will be decreased at least 100 times as
4-2
0962R
MODEL6GOAEUXXF0~
CIRCUIT DISCUSSION
compared to the NORMAL connection,
correspcnding to a loo-fold
increase in response speed.
(b) The input drop will be reduced~ about 100 times.
If Fig. 600-l is again consulted, it will be seen that this connecticn
converts the 600A into an operational amplifier with a resistor from
the output to the input. Therefore, the following cautions apply:
(a) The input cannot be shorted since this will remove the feed-
back.
(b)
The internal impedance of the current source being measured
should not be less than about one-tenth of the value of the feed-
back resistor used for measurement.
(c) This connection should not be used for measuring the leakage
current of capacitors since the connection of the capacitor to the
input causes the circuit to be transformed into a differentiator
with the resultant extreme sensitivity to very small voltage tran-
sients. For this measurement the NORMAL should be used.
(d) Do not attempt to use the FAST connection for currents exceed-
ing 0.1 microamperes.
OHMMETER
C.
(1) Two Terminal Xethod
The Model:600A employs a
linear scale to provide a
megohmmeter of high accuracy. The linear ohms scale
is achieved by supplying a
constant current to the
sample and measuring the
voltage drop across it.
The method is shown in
Fig. 600-h.
(2) Ohms measurement using
CIOURE 600-4
GUARD terminal:
There are two disadvantages
with the method just out-
lined:
(a) When measuring resistanoes greater than 1011 ohms, input capa-
city causes the meter reading to be annoyingly slow.
(b) If it is desired to use large voltages across the sample, this
same voltage will appear across the input insulation of the electrometer and the input insulation will contribute error to the reading
because of the current also flowing in it.
Og62R
4-3
CIRCUl!C DISCUSSION
MODEL 6OOAEIBXFiOMgTER
For these reasons a second connection for measuring ohms is provided.
RX
The switch at the rear of
the instrument is moved
from N0FW.L to FAST and
the resistance sample is
connected to the GUARD
terminal.
shows the arrangement.
Now, as with measuring
amperes with the FAST
method, the amplifier
ground is attached to the
input ground and the cathode-follower ground is
floating.
FIQURE 600-8
that feedback is applied
through the unknown re-
sistance to reduce the
slowing effect of instrument input capacity.
Also, since the potential
across the input terminal is small, the leakage error is
(3)
Use of External Voltage Supply
With the constant current
t
method of measuring resistante, the voltage across the
unknown may not be arbitrarily selected, and the
time of measuring capacitor
leakage tends to be long,
since constant-current
charging is slower than the
exponential charge available
EXTERNAL
VOLTAQE
t
with an RC circuit.
Due to these facts, it may
be desirable to use an ex-
ternal voltage supply and
FIQURE 600-6
measure the leakage current
on the AHPERES scale (NORMAL
operation).
Fig. 600-5
The result is
reduced.
.
The unknown is connected between the input terminal of the electrometer
and the source of voltage. This is shosn in Fig. 600-6. If the applied
voltage is large compared to the voltage drop across the electrometer
(so that the voltage across the sample is substantially the applied voltage) the resistance is simply equal to the voltage applied divided by the
current measured. If the voltage drop is an appreciable fraction of the
applied voltage, the resistance equals the voltage applied minus the input
4-4
0962R
MODEL 6oOA ELXC!CBOMEZER
CIRCUIT DISCUSSION
drop divided by the current measured. It will be rarely necessary
to correct for the input drop of the electrometer due to the excellent voltaRe sensitivity of the Model
600~.
It is advisable to use the NOW micro-microammeter connection
for the measurement of leakage resistance of capacitors in this
manner, since instability is likely to occur using the FAST connection.
However, in cases where the capacity shunted across the
sample is small, it will be possible to realize a considerable
increase in speed of response by utilizing the FAST connection.
Some precautions are recommended when testing capacitors. Be sure
that capacitors have discharged before removing from test circuit.
With the ZERO CHECK switch depressed,the input is shorted to
ground through 1 megohm, providing a discharge path for the cana-
citor. The reading: time may be shortened if the capacitor is allowed to charge through a low impedance position on the AMPERES
switch before the appropriate measuring resistor is inserted in
the circuit.
It should be further noted that capacitor measurement is likely
to be a slow process in any case due to the fact that it may take
considerable time for the molecular orientation of the dielectric
to take place at the testing potential. It may take minutes or
even hours in some cases to achieve a stable reading.
4-5
AccEssoRm
SECTION V - ACCESSORIES
MODEL 6lOl.A Sl-IIEZOEIC TEZ LEAlk
The Model 6101A Lead consists of an input connector, 3 feet of
low noise cable and a shielded probe head. Its purpose is to
allow convenient connection to the electrometer input.
MODEL 61OZA - 1O:l VOLWGE-DIVIDER PIiOBE:
The Model 6102A divider probe is intended for general purpose
measurements where an extension of the upper voltage range of
the 600A is desired. The division ratio is 1O:l correct to 1%
and the probe input resistance is lOlo ohms.
supplied with a mating connector and 3 feet of cable.
MODEL 600~ ELET'ROEEim
The probe is
MODEL 6103A Y 1ooO:1VOL!IWE-DIVIDEB PFiOBE:
The Model 6103A probe is intended for very high voltage measure-
ments at high impedance. The division rat& is 1OOO:l correct
to 3% and the probe input resistance is 10
is supplied with a mating connector and 3 feet of cable.
MODEL 61OL TEST SHIELD:
The Model 61Oh Test Shield is intended for use in making measurements wherein complete shielding of the component under test is
required. External terminals are provided for either grounded
tests, or a test requiring an external voltage source.
ohms. The probe
5-l
MODEL 6OOA ELWPFtOMfZ!CEZ
MAIN'lWANCE
SECTION VI - UACATNTENANCE
No periodic maintenance is required other than checking the batteries
as provided for by the front panel control.
The method of performing
these checks is outlined in Section III-E.
The calibration of the voltmeter is set by R41 located on the horisontal chassis carrying Bl, B3 Bh and B5. This is set at the factory
and should not require adjustment. If recalibration is performed, an
accurate voltage
source should be used.
A.
Trouble Shooting
The circuit is completely described in Section IV. Study of that
section will facilitate any trouble shooting.
The most usual trouble encountered is that on the most sensitive voltage range, with the input shorted, it is not possible to bring the
meter pointer to zero. However before assuming that the instrument is
at fault make sure that resetting the COARSE ZERO control at the rear
of the instrument will not oring the instrument back into balance.
If this does not work it will
cover to gain access to all circuitry.
be
necessary to remove the instrument
The instrument cover is removed by unscrewing the three screws on both sides of the instrument
and lifting the cover upward.
With the cover removed, follow this
procedure:
Short floating ground to output ground to remove the negative feed-
back.
This is most conveniently accomplished by shorting the two
ends of the FAST-NORMAL switch on the rear panel. In this condi-
tion the instrument will become very sensitive and, in operating
the zero control, the meter will be very difficult to hold on
scale.
However, t&indication that the circuit is operating
satisfactorily is that it is possible to swing the voltage through
the'correct operating point as indiczited on the voltage-resistance
diagram.
Now with the MULTIPLIER switch at .Ol volts, proceed to check the
operating points of the tube electrodes.
Regardless of the condition of the amplifier balance, the filament
or cathode, and screen potentials should be reasonably close to
the values on the circuit diagram. The
plate
and grid potentials
will depend on the settine of the ZERO control, However if it is
possible to swing the voltage through the correct value it may be
assumed that the stage is working.
Proceed in this manner until
the point is found where the voltage cannot be swung through the
value marked on the diagram.
easy to find the fault.
First check the tube involved and then
At this point it will
be
relatively
check the components.
og6m
6-1
.MAINlXNANCE
Miscellaneous troubles:
MODEL 6OOA ELEC!TRom
tube
tube
Cause
Remedy
-----
Replace Vl and V2
with matched set
Replace batterv
Reulace Vl and V2
with matched set
See section above
Trouble
--
Excessive erid
current
Excessive drift
Excessive micro-
phonics
Tnstrument does
not zero.
The proper method of inserting electrometer tubes is shown in the voltage-resistance diagram.
where the leads emerge, with the fingers.
Defective electrometer
Battery failing
Defective electrcmeter
See section above
When inserting do not touch the glass base,
6-2
0962R
MODEL 600A ELECTROMETER REPLACEABLE PARTS
SECTION 7. REPLACEABLE PARTS
7-1.
Model 600A. The List gives the circuit designation, the part description, a suggested
manufacturer, the manufacturer's part number and the Keithley Part Number.
address of the manufacturers listed in the "Mfg. Code" column are contained in Table 2.
7-2. HOW TO ORDER PARTS.
Part Number, the circuit designation and a description of the part.
and those parts coded for Keithley manufacture (80164) must be ordered from Keithley
Instruments, Inc. In ordering a part not listed in the Replaceable Parts List, completely
describe the part, its function and its location.
Keithley
amp
CbVar
CerD
Comp
REPLACEABLE PARTS LIST.
a. For parts orders,
Order parts through your nearest Keithley distributor or the Sales Service Department,
b.
Instruments,
ampere
Carbon Variable
Ceramic, Disc
Composition
include the instrument's model and serial number, the Keithley
Inc.
The Replaceable Parts List describes the components of the
The name and
All structural parts
Mil No. Military Type Number
n
P
ohm
pica (lo-12)
DCb
f
k
M or meg mega (106) or megohms
m
Mfg.
Deposited Carbon
farad v volt
kilo (103)
milli (10-3) WWVar Wirewound Variable
Manufacturer
TABLE 1.
v
Var
w watt
ww Wirewound
Abbreviations and Symbols.
micro (10-6)
Variable
1164R
7-l
REPLACEABLE PARTS MODEL 600A ELECTROMETER
@DEL 600A REPLACEABLE PARTS LIST
(Refer to Schematic Diagram DR12014C for circuit designations.)
BATTERIES
Circuit
Desig.
Bl
B2a
B2b
B3
B4
B5
B6
B7
Description
1.34 v mercury
8.4 v mercury
0.4 v mercury
1.34 v mercury
30 v dry cell
30 v dry cell
8.4 v mercury
0.4 v mercury
Circuit
Desig. Value
Cl01 100 pf
Cl02 100 pf
Cl03 0.02 uf
Cl04 0.02 uf
Mfg.
Code
37942
61637
61637
37942
61637
61637
61637
61637
Mfg.
Part No. Part No.
RM42R BA-10
E146X BA-9
E146X BA-9
FM42R BA-10
413 BA-5
413 BA-5
EL46X BA-9
EL46X
Keithley
BA-9
CAPACITORS
Keithley
Rating
Type
Mfg.
Mfg.
Code Part No. Part No.
1000 " CerD 72982 831XSRlOlK c22-LOOP
1000 " CerD 72982 831XSRlOLK c22-LOOP
1000 " CerD 72982 84125V203P C22-.02M
1000 " CerD 72982
84125V203P C22-.02M
MISCELLANEOUS PARTS
Circuit
Desig. Description
JlOL
Receptacle, uhf, Input, Mil. No. SO-239A (Mfg.
No. 6804)
---
Dust Cap for 5101, n, Mil. No. MX-913/U (Mfg.
No. 7901)
Plug, uhf, Mate for Input, Mil. No. 49190 (Mfg.
No. 83-822)
Reducing Adapter, uhf, for CS-64 and CS-49, Mil.
No. UG-175/U (Mfg. No. 83-185)
5102
Binding Post, Black, G (Mfg. No. DF2LBC)
5103 Receptacle, Microphone, Output (Mfg. No. 80-PC2F)
-_-
Plug, Microphone, Mate for Output (Mfg. No. 80-MC%)
5104 Binding Post, Red, INPUT GUARD (Mfg. No. DF21RC)
Ml01 Meter
SlOl
---
---
Rotary Switch less components, Range 80164
Rotary Switch with components, Range
Knob Assembly, Range Switch
Mfg.
Code
91737
91737
02660
02660
58474
02660
02660
Keithley
Part No.
CS-64
CAP-4
cs-49
CS-36
BP-11B
CS-32
cs-33
58474 BP-11R
80164 ME-16
SW-63
80164 L2326B
80164 153678
7-2
0765R
MODEL 600A ELECTROMETER
REPLACEABLE PARTS
MISCELLANEOUS PARTS (Cont'd)
Circuit
Desig.
s102
s103
s104
--SLOS
---
--S106
---
---
---
Circuit
Desig.
Description
Push Button, ZERO CEFXK
Slide Switch, NORMAL-FAST (Mfg. No. G326)
Rotary Switch less components, COARSE ZERO
Rotary Switch with components, Coarse Zero
Rotary Switch less components, MULTIPLIER
Rotary Switch with components, Multiplier
Knob Assembly, Multiplier Switch
Rotary Switch Less components, METER-BATTERY
Rotary Switch with components, Meter-Battery
Knob Assembly, Meter-Battery Switch
Knob Assembly, ZERO Control
RESISTORS
Mfg.
Value Rating
Type
Code
Mfg.
Keithley
Code Part No.
80164
14376A
79727 SW-45
80164 SW-51
80164 12094B
80164 SW-47
80164 12093B
80164
L5384A
80164 SW-62
80164 12092B
80164
148388
80164 15110A
Mfg.
Part No.
Keithley
Part No.
RlOl
R102
R103
R104
RL05
RL06
R107
R108
R109
RllO
18-l
LO9 R
Not Used
Not Used
LO Ml
a33 !ul
10 m
312 kn
Not Used
220 kG
RLll 450 kG
R112
Rl13
RL14
3.4 kG l%, 1 w
9 'm
lkn
Rll5 10 kG
R116
R117
R118
R119
R120
R121
R122
R123
;,":i n
n
109 n 1%
100 m
10 N-l
1M
LOO kQ
10 kn
lO%, l/2 w
20%, l/2 w
l%, 1 w
lO%, l/2 w
l%, 1 w
L%, l/2 w
l%, l/2 w
l%, L/2 w
l%, l/2 w
l%, L/2 w
3%, 5 w
1%
1%
l%, 2 w
l%, 1 w
l%, l/2 w
l%, l/2 w
l%, l/2 w
* Nominal value, factory set.
Comp
Comp
DCb
Comp
DCb
DCb
DCb
DCb
DCb
DCI,
DCb
WWVar
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
01121 EB
75042
91637
BTS
DC-1
01121 EB
91637 DC-1
79727 CFE-15
79727
79727
91637
79727
CFE-15
CFE-15
DC-l
CFE-15
79727 CFE-15
73138
A
63060 Rx-1
63060 Rx-1
63060 Rx-1
91637
91637
79727
DC-2
DC-1
CFE-15
79727 CFE-15
79727 CFE-15
Rl-1M
R37-109
R13-10M
Rl-33K
R13-10M
R12-312K
R12-220K
R12-450K
R13-3.4K
R12-9K
R12-LK
RP4-10K
R20-loll
R20-1010
R20-10g
R14-100M
R13-10M
R12-LM
R12-100K
R12-10K
0765R
7-3
REPLACEABLE PARTS
MODEL 600A ELECTROMETER
RESISTORS (Cont'd)
Circuit
Desig.
R124 1 kn
R125 100 n
R126 10 R
R127
(1)
R128 450 kc?
RL29 8.6 kn
R130 8.6 kn
R131 8.6 krl
R132 8.6 ko
R133 166.7 k~
R134 50 kn
R135 16.7 k~
R136 5 kn
RL37 1.667 k~
RL38 500 n
RL39 166.7 n
(2)
R140
Value
ln
*20 n
*lo ksl
9kn
Rating
l%, l/2 w
l%, LO w
l%, 10 w
l%, 10 w
.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%, 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
Mfg. Mfg.
'We
ww
ww
ww
ww
DCb 79727 CFE-15
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
DCb
Code Part No. Part No.
79727 CFE-15 R12-LK
91637 RSE-10 R34-100
91637 RSE-LO R34-10
91637 RSE-10 R34-1
01686 7070
79727 CFE-15 R12-8.6K
79727 CFE-15 R12-8.6K
79727
79727
79727
79727
79727
79727
79727
79727
79727
79727
79727
CFE-15
CFE-15 R12-8.6K
CFE-15
CFE-15
CFE-15
CFE-15
CFE-15
CFE-15
CFE-15
CFE-15
CFE-15
Keithley
R92-20
RL2-450K
Rl2-8.6K
RL2-166.7K
R12-50K
R12-16.7K
RL2-SK
~12-1.667~
R12-500
Rl2-166.7
Rl2-10K
RL2-9K
R141 10 kn
RL42 16.67 kn
R143 47 kcl
R144 600 ko
R145 47 ko
R146 1.14 m
R147 Not Used
R148 250 kn
R149 900 k.0
R150 1.14 &
Circuit
Desig.
VlOl 5886 80164 EV-5886-2
v102 5886 80164 EV-5886-2
v103 6418 81453 EV-6418
v104 6418 81453 EV-6418
9~ Nominal value, factory set.
(1) If used, this resistor is in parallel with R127.
(2) If used, this resistor is in parallel with R139.
lO%, 2 w
l%, l/2 w
l%, l/2 w
l%, L/2 w
l%, l/2 w
l%, l/2 w
20%, L/4 w
l%, L/2 w
L%, L/2 w
Number
WWVar
DCb
Deb
DCb
DCb
DCb CFE-15
CbVar
DCb
DCb
VACUDM TUBES
71450
79727
79727
79727
79727
79727
71450
79727
79727
Mfg.
Code Part No.
WP
CFE-15 R12-16.67K
CFE-15 RLZ-47K
CFE-15
CFE-15 R12-47K
RQll-130
CFE-15 R12-900K
CFE-15
RP9-1OK
R12-600K
R12-1.14M
RP2-250K
R12-1.14M
Keithley
7-4
0765R
MODEL 600A ELECTROMETER
REPLACEABLE PARTS
11121 Allen-Bradley Corp.
Milwaukee, Wis.
12660 Amphenol-Borg Electronics Corp.
Broadview, Chicago, Illinois
37942 Mallory, P. R., and Co., Inc.
Indianapolis, Ind.
$4655 Ohmite Mfg. Co.
Skokie, Ill.
58474 Superior Electric Co., The
Bristol, Corm.
61637 Union Carbide Corp.
New York, N. Y.
63060 Victoreen Instrument Co.
Cleveland, Ohio
71450 CTS Corp.
Elkhart, Ind.
TABLE 2.
Code List of Suggested Manufacturers.
Manufacturers, Cataloging Handbook H4-1.)
72982 Erie Technological Products, Inc.
Erie, Pa.
75042 International Resistance Co.
Philadelphia, Pa.
79727 Continental-Wirt Electronics Corp.
Philadelphia, Pa.
80164 Keithley Instruments, Inc.
Cleveland, Ohio
81453 Raytheon Co.
Industrial Components Div.
Industrial Tube Operation
Newton, Mass.
91637 Dale Electronics, Inc.
Columbus, Nebr.
91737 Gremar Mfg. Co., Inc.
Wakefield, Mass.
(Based on Federal Supply Code for
1164R
7-5
1 DR
12124
-A
1 VOLTS
OHMS
170K
1OM
17ou
INF.
IN,‘=.
IOM
I N F.
170K
foM
170K
A EC0 IGO-cu.
J EC.0 \S\b RR
.c EC0 1670
9-X-C
L7*WWl
3*20*&
L
PROPERPl OF KE~THLEY INSTRUMCN~~. INC
NOT TO SE USED OR REPRODUCED EXCEPT
AS AUTHORIZED B” THE COMPANY.
THE ABOVE VOLTAGE AND RESISTANCE READINGS
WERE TAKEN WITH CONTROLS SET A5 FOLLOWS;
MULTIPLIER ON IO
METER SWITCH
ON METER +
!ZCINGE SWITCH ON
VOLTS
FWV
ZERO CHECK LOCKED
OUTPUT Al ZERO
FAST -NORMAL SWITCH IN
NORMAL POSITION
REslSTANCES ARE APPROXIblATE
REGDINCS
TAKEN
WITH VTVM
CLEVELAND. OHIO
TO GROUND,
CONFIDENTIAL
-
‘---7---~---,-~.-
L--_--L
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