Keithley 600B User Manual
CONTENTS
SPECIFICATIONS
MODEL 600B
SPECIFICATIONS
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.
7
0872R
MODEL 6008 ELECTROMETER
SECTION 1.
GENERAL DESCRIPTION
GENERAL DESCRIPTION
uremenfs with a minimum of adjustment. Zero drift with
rime is less than 2 m” per day.
zero offset due to
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.
b.
fast wnrm UD is an inherent characteristic ok
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.
d.
‘the ,“O-hour life ai rhe batteries enables us-
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.
1
FIGURE 1.
Fro”,. Panel cantro13.
GENERA‘ DESCRIPTION
MODEL 6008
TABLE l-l.
Front Panel Canerols
Functional oescripeian
Paraeraph
Sets the paramet~~r to be measured:
VOLTS, AMPERES,
?&S or COULOMBS.
2-2
MULTIPLIER Switch
(SlOS)
sees rix? full-scale meter sensitivity.
When used with AMPERES, OHMS or COULOMBS
the setting should be multiplied by ehe
RANGE setring.
2-2
METER Switch
(5106)
Controls parer co instrument. Also selects
the meter polarity and center scale.
2-2
ZERO Control
FINE (R133)
2-2
ZERO CHECK Switch
(5102)
FEEDBACK SWFtCh
(5103)
INPUT(.JlOZ)
2-2
2-2
2-2
TABLE 1-2.
Rear Panel Controls and Terminals
ZERO Control
COARSE (slo::
lV-lMA CAl Canerol
(R179)
Adjusement for recorder output.
2-7
Barrier strip cunnecrion (J104)
Xl
Unity gain output.
2-S
OHMS GUARD
output low Con".?cflo*.
2-7
A Connect link to OHMS GUARD when using 1V o"QmF.
2-7
B
Output high connection.
2-7
GND Chassis ground (input low).
2-7
MODEL 6000 ELECTROMETER
OPEKATION
SWTION 2.
OPERATION
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.
Excessive Leakage reduces the accuracy “i
reading irom nigh imoedance sources.
coaxi cabies
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.
NOTE
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
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
- 4uch as Teflon - may produce random 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
available
it
is advantage-
ous CO connect ehe Model 6008 to the circuit only when
a reading is being made.
In ~“me cases, rhe offsee
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-
smoere, there
may be no decoy of the terminal voltage when ehe Elrc-
trometer is left connected across the copacicor’s fer-
“i”8iS.
XOTE
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 ilul-
ciplier 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.
show the batferies checked by each
POSiCi”“. Ii rhe reading for any baccery is below
one-i,alf full scale, replace the indicated baetery.
TABLE 4.
Nultiolier Switch Positions far Checking Conditions
of SatCaries.
SaeCeev Checked
10 BA103 di DA104
3
SAlOl 6. k4102
1 Ml05
b. Set the controls as follows:
ZERO CHECK nutcon
Range Swirch
EUICI~L~~~ Switch
FEEDBACK Switch
METER Switch
LOCK
VOLTS
1
NORMAL
POWER OFF.
.c.
Turn the METER Switch to CENTER ZERO. Within
ten seconds, ehe meter needle should come co the ce”-
0872R
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.
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. 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.
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
2-2.
Set the concrois as foliows:
ZERO CHECK Sutton
LOCK
Range Switch VOLTS
multiplier Switch
LO
FEEDBACK Switch
NORMAL
METER Switch
CENTER ZERO
connece the ““know” source co the INPUT Recepeacle
and unlock the ZERO CHECK Buteon. Set the METER
Switch to + or -, as necessary. Increase the sensi-
tivity with the Multiplier Switch. Recheck the zero
setting after increasing the sensitivity.
Low Impedance Measurements. TO decrease the
in;& resistance frnm
1OL4
nh”w +Pe *II,- nnn.y CWifCh
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
d. To measure ~~“rces more than 10 volts, “se the
Model 6102A 1O:l Divider Probe or the 6103.4 1OOO:l
Divider Probe.
The Model 6102A extends the Model
6OOB’s
range to 100 volts; averall accuracy is *&%
and Input resistance is 1010 ohms.
The Node1 6103
extends the Model 6008’s range to 10 kilovolts’ overall accuracy is r6% and input resistance is 10
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 in-
put. 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 inpue 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.
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-
4
0872B
MODEL 6000 ELECTROMETER OPERATION
FIGURE 4.
Error Due to hmeter Reeisfmce.
Current SOUPCSS may be considered a voltage (E) in series with 3
resistance (a).
the current with the ammeter short circuited is I = E/R.
!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.
1.
The rull-scale curre”c range is the Range
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.
The input voltage drop is the Meyer reading times
the Multiplier Switch serFin!.
::mT.
On the iaw current ranges, baiance out ihe
oifset current vitb the Zero Controls or
suberacr ehe value from the reading. To
find the amount of offset current, cap the
INPUT Receptacle and read the meter.
d. Fast
Eleehod (ranges
below 10-j ampere).
1.
Fallow the inseructions of paragraph Z-1.
see the conerois as follows:
ZERO CHECK Sutton
Range Switch
,Hultiplier Switch
FEEDBACK Switch
METER Switch
LOCK
lo-” AXPERES
1
FAST
CENTER ZERO.
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.
DO not set the Range Switch to 1O-5 AHP-
ERRS or higher.
Check zero with the ZERO
CHECK
Button.
Da nor short the input because this will
remove the
feedback
from the circuit.
“LlhSR
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
zero seabiliev.
3. !$ich the fast method, the input drop is re-
duced and the response speed is
increased
at ieasc
100 times. iiowever,
follow rhese cautions:
a\ The internal impedance ai the unknown cur-
rent should not be less than .I ai the value oi
ihe Lardmck resistor wing "sea.
Otherwise,
~iir
full 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.
b) The OHMS GUARD Terminal of the Barrier Strip
Cmnector is “a longer connected to case ground.
Therefore. do “at use a grounded recorder.
.is an
alternate. use the unity-gain output (paragraph
2-8).
C)
Use,‘with caution,
the fast mechod to meas-
ure capacitor leakages.
A very stable voltage
supply must
be used.
Connecting a capacitor fo
the inpue
changes the circuit to a differenciacor,
resulting in extreme sensitivity to very small
voltage transients and a” increase in meter noise.
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 cur-
rent 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.
II.
The Xodel 6000 can meas”re resistance by tw
merhads.
1. In the constant current methad, the Electrometer measures the voltage drop across the unknown
sample as a knno;.r.,
_^__._...
_“...,-..... i..Zi’i;lCi L:u”,r &‘“ugiL
it.
The voltage drop is proportional to the resis-
tance Of the snmple.
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.
b) Above lOi
ohms the fast method is preferred. 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.
2.
In the preceding merhod, the voltage across
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.
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
XZTER Switch
LOCK
1011 OHMS
1
NORMAL
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.
II s c
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.
The
test current is the reciprocal of the OHMS Range
setting.
NOTE
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
1012 OHMS
Multiplier Switch
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.
Unlock the ZERO
CHECK
Button.
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.
2.
Set the FEEDBACK Switch to NORHAL.
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 pa-
tential 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.
U.
I!: the ?oce”ri;il mp1ieu is less than 100
rimes the inmr droo. the resistance is equal to
rhe difference between the aoplied potential and
the input drop, 211 :I,, -~’ ‘,., ,.a ..,.,. :
FICUIW b.
:!easuring ~es~srnnce oy tne VoLcmecer-
,‘mmecer Xethod.
;s:>:::;; rrc:: : I::.:::: “I:‘--? “,
is applied to the unknown resistance sample, I<,. The
Xodel 6008
measures
the current through R,. from
wi,ich the resistance is calculated.
Switch S connects
the low end of R, ea ground when na potential is
appiied.
7.
If the current is read by the face method,
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
b.
For recording with the Node1 6008, use the
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. Interface 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
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