Tektronix 600B Instruction Manual

CONTENTS

SPECIFICATIONS

MODEL 600B

SPECIFICATIONS

7

CONNECTORS: Input: Teflon4nrulared UHF Type. Out-

puo: &wrier srrip.

BATTERIES: Four 2N6 (or 246. VS305. NEDA 1602,; one

RM.IW. 700waur lxmerv life

DIMENSIONS. WEIGHT: 10~1/4” high x S-112” wide x

6-l/2” deep: net weight. 7.114 poundo.

ACCESSORIES SUPPLIED: Mating input connector.

0872R

MODEL 6008 ELECTROMETER

GENERAL DESCRIPTION

SECTION 1.

GENERAL DESCRIPTION

uremenfs with a minimum of adjustment. Zero drift with

rime is less than 2 m” per day.

temperature change is less than 200 microwits per %.
after a ,O-minute warm-up. This offset, however. can
easily be compensated for with the front-panel zero
controls.

fast wnrm UD is an inherent characteristic ok

b.

this Electrometer. It can be used well wiehin 30
minutes of a cold scare on the mose sensitive range
and nlmosc immediately on less sensitive ranges.

‘the ,“O-hour life ai rhe batteries enables us-

d.

age in long-term experiments xiehauc interruptions

<or replacement. Baeeery life is maintained even wiwn
the i-milliampere recorder output is used. Fur rilr­ther convenience. battery condition is readily check-

ed on the panel meter.

zero offset due to

FIGURE 1.

1

Fro”,. Panel cantro13.

GENERA‘ DESCRIPTION

MODEL 6008

TABLE l-l.

Front Panel Canerols

MULTIPLIER Switch

(SlOS)

METER Switch

(5106)

ZERO Control

FINE (R133)

ZERO CHECK Switch

(5102)

FEEDBACK SWFtCh

(5103)

INPUT(.JlOZ)

Functional oescripeian
Sets the paramet~~r to be measured:

VOLTS, AMPERES,

?&S or COULOMBS.

sees rix? full-scale meter sensitivity.
When used with AMPERES, OHMS or COULOMBS

the setting should be multiplied by ehe

RANGE setring.
Controls parer co instrument. Also selects

the meter polarity and center scale.

TABLE 1-2.

Rear Panel Controls and Terminals

Paraeraph

2-2

2-2

2-2

2-2

2-2

2-2

2-2

ZERO Control

COARSE (slo::

lV-lMA CAl Canerol

Adjusement for recorder output.

(R179)

Barrier strip cunnecrion (J104)

Xl

OHMS GUARD

Unity gain output.
output low Con".?cflo*.

A Connect link to OHMS GUARD when using 1V o"QmF.

B

Output high connection.

GND Chassis ground (input low).

2-7

2-S
2-7
2-7
2-7
2-7

MODEL 6000 ELECTROMETER

OPEKATION

SWTION 2.

2-1.

INPUT CONNECTIONS. The Model 6008 INPUT Recep-

cacle is a Teflon-insulated UHF connector. A shield

cap is provided. The ground posr, below ehe Recep-

tacle, is conneceed co chassis ground.

a. The accessories described in Sectton 5 are de­signed co increase rhe accuracy and convenience of
input connecfions. Use them eo gain rhe maximum c=p­ability of rhe Model 6008.

c. Use hixh resisronce. low-loss marerials - such

as ‘Teflon , recommended,, polpe~hylene or oolpsqrene

- for insulation. Insuinci”” leakage resiseance of
test fixtures and Leads shouid be several orders of

magnitude higher than rhe internal resistance of the

SOUrCe.
reading irom nigh imoedance sources.

used should be II io” noise type whici, employ a graph-

ite or ocher conducrive coacinq berrreen the dieiectric

.Ind ehe surrounding shield or=id, An+2nol-Sorg Elec-

tronics core., ?,icr”do~, I:::. , _..” “_...r.-.. ..LL5 aLIu

lz-lble co. make socisixcory types.

Excessive Leakage reduces the accuracy “i

coaxi cabies

NOTE

OPERATION

used and a binding post adapeer may be used. however,
keep the leads short.

f. When the Model 6008 is used on the most sensi-

tive current range with the FEEDBACK Switch =e FAST,
Borne insulators
dom signals which show up as erratic meter deflections.
InsulaCion used in the Model 6008 is carefully seiec-

ted LO minimize these spurious signals.

g. If a well shielded chamber and a well made high

impedance transfer switch is
ous CO connect ehe Model 6008 to the circuit only when
a reading is being made.
current can charge the external CASE circuifry. ilne
e::ample of this occurs when measuring a capacitor’5

leakage resistance by observing the decay of the ter-

minal voltage. If rhe leakage c~rre”:~is less than

the offset current (Less thnn 2 :< LO-

may be no decoy of the terminal voltage when ehe Elrc-

trometer is left connected across the copacicor’s fer-

“i”8iS.

Keep the shield cao on the INPUT aeceofocle
when the ~leccromerer is nof in use.

3-2.

PRELMINARY PROCEDURES.

8. Check battery condition by holding the llETER
Swirch tn the S,,TTER,’ CHECK position. Turn the ilul­ciplier Switch eo 10, 3 end I pOsitiOns =nd observe
one meter readings. The meter shoutd read one-haii
of fllll ‘.-.!e or more in ench Nuleiplier switch ?“Si
tion.

Table f.
POSiCi”“. Ii rhe reading for any baccery is below
one-i,alf full scale, replace the indicated baetery.

- 4uch as Teflon - may produce ran-

available

it

is advantage-

In ~“me cases, rhe offsee

smoere, there

XOTE

show the batferies checked by each

Clean, dry connecrions and cables are very im­porcaoc to maincain the value oi 311 insularion
materials.

Even the besr insulation will be com-

promised by d”SC. cirrc. so,oer Tl”X, LilrnS of
oil or water vapor. A good cleaning agent is
methyl =lcohoi. which disolves most common dirr
wirhour chemic=lly acr=cking the insulation.
:,ir dry the cables or ~onnecei”“s after uashing
vith alcohoi or “se dry nirrogen if available.
Or, if available, Freon is an excellent cleaning
agent.

d. When working with a high impedance source any
change in shunt cnpaci~once of the input circuit will
cnuse disturbances in the reading.

Nake the messuring

sefup as rigid as possible, nnd eie down connecting
cables to prevent their ,!?A~iL%iii.. ;\ i~il.illY”Ub “LYLA-

tion may appear 8~ the outpur as a sinusoidal signnl,
=nd orher precaurions may Le necessary co isolace rhe,
insrrumenc and connecting cnble from the “ibra+zton.

e. For low impedsnce meesuremencs - below LOS

ohms or above LO-8 ampere - unshielded leads may be

0872R

TABLE 4.

Nultiolier Switch Positions far Checking Conditions
of SatCaries.

SaeCeev Checked

10 BA103 di DA104

3

1 Ml05

SAlOl 6. k4102

b. Set the controls as follows:

ZERO CHECK nutcon
Range Swirch
EUICI~L~~~ Switch
FEEDBACK Switch

METER Switch

Turn the METER Switch to CENTER ZERO. Within

.c.

LOCK
VOLTS

1

NORMAL
POWER OFF.

ten seconds, ehe meter needle should come co the ce”-

3

OPERATION

HODEL 6OOS ELECTROMETER

ter zero pasit.ion.

1f not. adjust the meter zero
with the front panel ZERO Control. Normally, there
is no need co “se the COARSE ZERO Switch.

d. After a

few moments increase

the voltage sensi­tivity by advancing the Multiplier Switch to .3, .1,
etc.

Continue zeroing with the ZERO Control.

e. After long periods of starage or after an over-

load, the Model 6008 nay drift excessively. The in-

put cransistars are insensitive to mechantcal shock;
however. B severe inpa overload may cause a zero
offset. This is corrected with the Zero Controls.
Drifting, though. can occur foe several hours.

f.

Although the offset current of the Electrom-

eter is much below that found in conventianal valt-

meters. it can be observed on the meter.

The c”rrent
charges ehe input caoacitance. and the Electrometer
appears to drift uhen the input is open.

Use the
ZERO CHECK S”tr~n co discharge the charge build-up.

Depressing the ZERO CHECK Button removes all signal
from the amolifier.

2-3.

“OLTXE \E‘\SUREEENTS.

a. The liodel 6~3011’s high input impedance allaws
circuit measurements wi’chaut causing circuit loading.
FOC law resistance in-circuit tests, the input resis-

tance can be lowerr<, 1,, -v,..:,.: ,,:, ‘k-t&p ~,i~c,b:,e,,is.

Range Switch to lo-’ AMPERES range.

Set the full-

scale voltage range with the ~“lci~lier Switch. Op­eraeing procedures are the same as subparagraph b
above.

d. To measure ~~“rces more than 10 volts, “se the
Model 6102A 1O:l Divider Probe or the 6103.4 1OOO:l
Divider Probe.

6OOB’s

range to 100 volts; averall accuracy is *&%
and Input resistance is 1010 ohms.
extends the Model 6008’s range to 10 kilovolts’ over­all accuracy is r6% and input resistance is 10

The Model 6102A extends the Model

The Node1 6103

12

ohms,
Follow the same Operating procedures with the divid­ers as in subparagraph b. The riall-scale voltage

range is the divider ratio times the MultipLier Switch

setting.

2-4.

CURRENT MEASUREMENTS.

a. The Model 6008 can measure currents three ways.

1. In the normal method - used on any range ­the current is determined by measuring the voltage
drop across a resistor shunring che’amplifier in­put. This method is useful when lower noise is more
important than faster response speeds or if some
damping is needed.

2. In the fasr method - far “se anly below the
10-Z ampere range - the shunt resistor is between.
the amplifier ““ep”t and input in the feedback loop.

This circuit largely neutralizes the effect af in-

pue capaciey and greatly increases the response
speed. Also, the inpue voltage drop is reduced to
less than One millivolt on any range.

3. For galvanometric current measurements, the
Model 6006 acts as B null indicator between a very
cccurate current source and the “nknawn current

SO”CCe.

Make all voltage meas”rement~ with the FEED-

BACK Switch & in the NORMAL posieion.

b. High Impedance Eleasurements ( LO14 ohms, ‘0

picofarads), Follow the instr”ctions of paragraph

Set the concrois as foliows:

2-2.

ZERO CHECK Sutton

LOCK

Range Switch VOLTS
multiplier Switch
FEEDBACK Switch
METER Switch

connece the ““know” source co the INPUT Recepeacle

LO
NORMAL
CENTER ZERO

and unlock the ZERO CHECK Buteon. Set the METER
Switch to + or -, as necessary. Increase the sensi­tivity with the Multiplier Switch. Recheck the zero
setting after increasing the sensitivity.

Low Impedance Measurements. TO decrease the

in;& resistance frnm

nh”w +Pe *II,- nnn.y CWifCh

1OL4

to one of the AMPERES ranges. The input resistance
is now the reciprocal of the current range. For in­stance, to obtain an inpur resistance of 10’ ohms -

which is normal for convantional “T”Ms - set the

4

b. Rise time varies primarily with the current
range, the input capacity and the method used. With
ehe FEEDBACK Switch in ehe FAST oosition. the rise
time on ehe ?ast sensitive range is less than 2.5

seconds and on the lo-6 ampere range is less than 3
milliseconds. Given a choice. it is beteer ta place
the Electrometer near to the current source than to

the data reading instrument. Transmitting the input

signal through long caaxial cables slightly decreases

the respanse speed and significantly increases noise

due to the cable capacitance.

c. Normal Methad (0.3 to lo-l3 ampere ranges)

1. hollow rhe instructions

of

paragraph 2-2

Set the controls as follows:

ZERO CHECK Sutton
Range Switch

Multiplier Switch

FEEDBACK Switch

METER Switch

LOCK
10-l AMPERES

1
NORMAL
CENTER ZERO.

Connece the unknown source to ehe INPUT Receptacle
and unlock the ZERO CHECK Sutton. Set the METER
Switch to + or -, as necessary. Increase the sen-

0872B

MODEL 6000 ELECTROMETER OPERATION

FIGURE 4.

Error Due to hmeter Reeisfmce.

resistance (a).

the current with the ammeter short circuited is I = E/R.

Current SOUPCSS may be considered a voltage (E) in series with 3

!4ith the short circuit removed, the
effective ineue resisrance of the ammeter (Ri”) is in series with the source resistance (R). The current in
the complete circuit is reduced and Imere= =

E/(R i Ri”). If the effective srmneter input resistance is small

camparea to 2. :,,ter ,., I a”d the error introduced by circuir loading is negligible.

sensicivic:: k.ith the d.inge sw~cch and the Wiclpiier
Svitcn.

31, not set c.i:e !luitiplier jwiwh higher

than 3 for Lange Switch settings LO-3 and above.

Check zero xieh the ZERO CHECK Sutton.

2.

The full-scale current range is the Range
Switch setting times the ~lultiplier jwirch secti”g.
When selecting ehe ?luleiplier Switch setting, re-

member mail seer,ings permit lwer currene 'iour'ce

resistance. 2nd Larger settings improve insceumene

The rull-scale curre”c range is the Range

1.

zero seabiliev.

Switch setting times ~i:e !iulriplier Switch setting.
use the smallese >lulti=lier Switch setting possible
to obeain the best accuracy.

The input resistor

varies with the Range Switch setting. from 10 ohms
at 10-l .u!PERES CO iUi! ohms for lo-11 AHPERES.

3. !$ich the fast method, the input drop is re-

duced and the response speed is

100 times. iiowever,

follow rhese cautions:

increased

at ieasc

The input voltage drop is the Meyer reading times

the Multiplier Switch serFin!.

a\ The internal impedance ai the unknown cur-

rent should not be less than .I ai the value oi

::mT.

ihe Lardmck resistor wing "sea.

Otherwise,

full feedbacK voltage cannot be developed at the

On the iaw current ranges, baiance out ihe

oifset current vitb the Zero Controls or
suberacr ehe value from the reading. To

input, and zero instability results.
resistor value is the reciprocal of the AMPERES
range of the Range Switch.

The feedback

find the amount of offset current, cap the
INPUT Receptacle and read the meter.

b) The OHMS GUARD Terminal of the Barrier Strip

Cmnector is “a longer connected to case ground.

d. Fast

Eleehod (ranges

below 10-j ampere).

Therefore. do “at use a grounded recorder.

.is an

alternate. use the unity-gain output (paragraph

Fallow the inseructions of paragraph Z-1.

1.

2-8).

see the conerois as follows:

the fast mechod to meas-

A very stable voltage

Connecting a capacitor fo

ZERO CHECK Sutton
Range Switch
,Hultiplier Switch
FEEDBACK Switch
METER Switch

LOCK

lo-” AXPERES

1
FAST
CENTER ZERO.

Use,‘with caution,

C)

ure capacitor leakages.
supply must

the inpue

be used.

changes the circuit to a differenciacor,
resulting in extreme sensitivity to very small
voltage transients and a” increase in meter noise.

~iir

Connect the unknown source to the

INPUT

Receptacle

and ““lock the ZE:.’ ?LF.Y p:,?+-- =.- tL* ‘!--‘”
Switch to t or -, as necessary.

increase the se”­sitivity with chc I;ar,ge Sw,,ci~ a”- ~lir kurLIpiier
Switch.

ERRS or higher.
Button.
remove the

DO not set the Range Switch to 1O-5 AHP-

Check zero with the ZERO

Da nor short the input because this will

feedback

from the circuit.

“LlhSR

CHECK

e.

Galvanometric Method.

1.

Operate the Model 6008 as a picaammeter in

the tast method.

use an accurare reference current

source s,,ch as the Keithley Model 261 to buck out

the unknown current source.

connect as shown Fn

Figure 5.

5

OPERATION

MODEL 6008 ELECTROMETER

2. Set the METER Switch to CENTER ZERO and “se
the higher current rangas. Adjust the buckout cur­rent to indicate null on the Model 6006.

Increase

the Electrometer sensitivity as needed. When the

Node1 6008 is as close to null aa possible, the un­known current is equal to the algebraic sum of the
H.adel 261 setting and the Model 6008 current read-

ine

Method. Cse an Llccur3te reference currene source CO

buck 0”~ ehe unknown c”rrenf s~“rce. The Eladel 6008,
on its current ranges. ierves as a null detector.
“se a UHF-tee ittlng at the Xodel 6008 input,

con­nect the Elecz:Jmeter to the two s~“rces with CO.%­ial cable. Select cable carefully for very low cur­rents (see parngrapil ‘-1).

2-5.

KLSISTANCE XEASUFGXZNTS.
The Xodel 6000 can meas”re resistance by tw

II.

merhads.

1. In the constant current methad, the Electrom­eter measures the voltage drop across the unknown
sample as a knno;.r.,

The voltage drop is proportional to the resis-

it.
tance Of the snmple.

_^__._...

_“...,-..... i..Zi’i;lCi L:u”,r &‘“ugiL

In this method the Model 6008

can be used in one af ~0 different modes: normal

or fast.

a) The normal wj:r is trcommended for “se from

1 kilohm to 1011 ohms.

NOTE

Discharge any capacitor completely befare

removing it from the circuit.

Depressing
the ZERO CHECK Sutton shorts the input
through a IO-megohm resistor, providing a

discharge path.

b. Xormal constant Current Method (recommended f,ar

“se from 1 kilahm to 1011 ohms).

1. Set the controls as follows:
ZERO CHECK Butfo”

Range Switch

Multiplier Switch

FEEDBACK Switch

LOCK
1011 OHMS
1

NORMAL

XZTER Switch

Unlock the ZERO CHECK Button.

Check zero only wit!:

the ZERO CHECK Button.

NOTE

Do not open circuit the Electrameter 0” the
OHMS ranges; the input will develao “o f~

10 volts due to its consrant current charac­teristic. Keep the input shorted or the

ZERO CHECK Sutfon Locked.

2. The full-scale ohms range is the Hultiplier
Switch setting times the Range Switch setting.
the smallest Range Switch se:cing possible to ob­tain the best accuracy.

3. Before making a final :eading, manipulate ti:e

X~ltiplier and Range Switches. so the sample is

tested at a number of test potentials.

The applier.
test voltage is the percentage ai full scale that
the meter reads times the-X”iti?lier Switch seccin;.

4. When the test current is applied, the high
terminal of the INPUT Receptacle is positive.
test current is the reciprocal of the OHMS Range
setting.

NOTE

II s c

The

b) Above lOi

ohms the fast method is prefer-

red. It results in faster respanse speed and

also nullifies leakage across the Electrometer

input, since the pacential acr‘oss the input ter-

minal is small.

In the preceding merhod, the voltage across

2.

the sample cannot be arbritrarily see. I” some
cases. as in measuring capacieor leakage, this re­sults in excessively long testing time.

In the
voltmeter-anrmerer method the Moiri COGa is “sad as
a picoammeter. The unknown resistance sample is
connected to an external known voltaee 80”rce and
ehe current through the sample is measured.

Eith­er the normal or fast method may be used. The re­sistance is calculated from the readings.

Shield the inpue if the resistance sample
exceeds lOa ohms.

c. Fast Canstant C”rrent(C”ardedi Method (recom-

mended for “se from 1011 to 1013 ohms).

1. Follow the instructions of paragraph 2-2

set the controls as fallows:

ZERO CHECK Button LOCK
Range Switch

Multiplier Switch

1012 OHMS

1
FEEDBACK Switch ?AST
METER Switch

c

Connect the high impedance side of the resistance

sample to the INPUT Receptacle and the low impedance

side t” the OHMS GUARD Terminal.

CHECK

Button.

Unlock the ZERO

MODEL 6008 ELF.CTRO”ETER

OPERATION

2.

Read the resistance as in subparagraph b2

above.
d. voltmeter-amecer Method (to 1016 ohms).

1.

Turn

the ZERO CHECK Switch to LOCK. Connect
sample between INPUT receptacle and pawer supply.
(see Figure 6). Put a switch in the high voltage
line to ground low impedance end af the sample when

it is disconnected from the potential.

Set the FEEDBACK Switch to NORHAL.

2.

lJeilallp
this method is best, since inStabilities can arise
for resistance samples less than 0.1 the value of
the feedback resistor.

3. TO make e meaetiremenc. scare with switch S
3s shown in Figure 6 and make sure the ZERO CHECK
Sutton is set to LOCK. set switch S to apply e pa­tential t~cross the samoie far a known period of

rime. ~!:en uniock rhe ZERO CHECK Gutcon and take
the reading.

$9~ eke !<a,ge Switch ea 10-l A:NPE?.ES

and increase sensitivity until .I reading is obtained.

If the current is read by the face method,

7.

the input drop Is so slight that it need not be in-

cluded in the calculation.

If the capacity shunted
acreee the sample is large, such as encountered in
capacitor leakage measurements. the faster methad

increases response speed and thFs cannectian is rec­annended. Xate. however. Lhat power supply transi­ente will be magnified.

2-6. CHARGE KSASUREMENTS

a. Follaw ehe instructiww of paragraph 2-2. see

the controls as follows:

ZERO CHECK Button
Range Switch
>lultFolier Switch
FEEDBACK sviech
XETER Switch

LOCK
10-7 CO”LOPBS

.Ol

FAST

CENTER ZERO

I!: the ?oce”ri;il mp1ieu is less than 100

U.
rimes the inmr droo. the resistance is equal to
rhe difference between the aoplied potential and
the input drop, 211 :I,, -~’ ‘,., ,.a ..,.,. :

FICUIW b.

,‘mmecer Xethod.

:!easuring ~es~srnnce oy tne VoLcmecer-

;s:>:::;; rrc:: : I::.:::: “I:‘--? “,

is applied to the unknown resistance sample, I<,. The
Xodel 6008
wi,ich the resistance is calculated.

measures

the current through R,. from

Switch S connects

the low end of R, ea ground when na potential is

appiied.

For recording with the Node1 6008, use the

b.

Xeiehley ?lodel 370 Recorder for ease. economy, versa-

eility and performance. The Model 370 is a pen re­corder with LO chart speeds and 1% linearity. Inter-

face pnblems ofren encountered between a measuring
inscrumenc and a recorder ore avoided using the Node1

~> 7n

\‘- preempiifier is needed.

:;0 special wiring

is required. when using the Node1 370 make sure the

Recorder’s sensitivity conrrol is set t0 maximum

(completely clackwise).

oR72R

7