Keithley 485 Service manual
Model 485
Autoranging Picoammeter
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, transportation 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 WARRAN-IY
This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse of
any product or pwt. 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 follow instructions.
THIS WARRANTY IS IN LlBU 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 KBITHLEY 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
Keithley Instruments, Inc. - 28775 Aurora Road *Cleveland, OH 44139~216-248-0400 -Fax: 216-248-6168 * http://www.keithley.com
Model 485 Autoranging Picoammeter
Instruction Manual
0 1984, Keithley Instruments, Inc.
Test Instrumentation Group
All rights reserved.
Cleveland, Ohio, U.S.A.
January 1990, Sixth Printing
Document Number: 485-901-01 Rev. F
SPECIFICATIONS
ACCURACY I1 YEAR,
lW28~C
RANGE
2nA
20
200
RESOLUTION
“A 1 PA
“A 10 pA
O.lpA
2 PA 100 PA
20
!A 1 nA
200
,‘A 10 “A
2mA
,NP”T VOLTAGE BURDEN: Less than 200&V.
RANQING: Manual or autoranging.
AUTORANGING TIME: Average 250ms per range.
SmLlNG TIME AT DISPLAY: Less than 1 second to within 2 co”nts on
fixed range.
CONVERSION PERIOD: 300,“s.
TEMPERATURE COEFFICIENT 10°-160C B 26°-50”C,: f10.1 x BP-
plicable sccuracy specification) per OC.
MAwMUM COMMON MODE VOLTAGE: 30V rms. DC to 60Hz sine
100 “A
* l%rdg + countslt
0.4 + 4
0.4 + 1
0.2 + 1
0.15 + 1
0.1 + 1
0.1 +1
0.1 +1
WWB.
ANALOG OUTPUT:
Output Voltage: + IV = - 10000 co”ntf.. mept + 1OOmV = - 10000
mints 0” 2nn range.
OUtput tIea,*tance: 10000.
REL: Pushbutton allows zeroing of an range readings. Allows relative
readings to be made with respect to baseline value. Front panel ~nnuncistor
indicates REL mode.
DATA STORE and MINIMAX: 100 reading storage capacity: records data
at one of six selectable rates from 3 readings/second to 1 reading/hour, or
by manual triggering. Also detects and stores maximum and minimum
readings comin”““sIY while in the data store mode.
LOG: Displays logarithm (base 101 of the absolute value of the measured C”F
rent Iexamples: -3.000 = *ImA; -6.301 = +O.$Al.
IEEE-488 BUS IMPLEMENTATION (Option 48631
MULTILINE COMMANDS: DCL, SDC, GET, GTL, “NT. UNL. SPE. SPD.
UNILINE COMMANDS: IFC, REN EO,. SRC. ATN.
INTERFACE FUNCTIONS: SHl. AH,, T5. TEO. L4, LEO. SRI, RL2,
PPO. DCl, DTI, CO, El.
PROGRAMMABLE PARAMETERS: Zero Check. Range, REL. LOG, Trig-
ger, Calibration. EO,, SRO, Status. 0”tp”t Format. Terminator.
ANALOG REJECTION
RISE TIME RATIO
I10 .SO%, IS0 or EOHz, INPUTt
60ms
60iTlS
6rnS
3ms
3ms
lms
lms
GENERAL
DISPLAY: 4% digit LCD, 0.5” height: polarity. range and staf”s indication.
OVERRANGE INDICATION: “OL” displayed.
CONNECTORS:
Input: ENC.
Analog Output: Banana Jacks.
OPERATING ENVIRONMENT: 0-50.X. less than 70% R.H. up to 35’C:
linearly derate 3% R.H./OC up to 5OOC.
STORAGE ENVIRONMENT: -25O to +BO”C
POWER: lOF,-125V or 210.250V (switch selected,. go-llOV available.
SO-6OHr. 12 VA.
DIMENSIONS, WEIGHT: 65mm high Y 235mm wide x 275mm deep.
(3%” x 9%” x lO%“,.
Net Weight: 1 .Skg I4 Ibs.)
ACCESSORIES AVAILABLE:
Model 1010:
Model ,017:
Model 1664:
Mods, 1758:
Model 4801:
Model 4603:
Model 4653:
Model 7006-3:
Model 7006-6:
Model 6573:
NORMAL MODE
7OdB
7OdB 350Vdc
65dB 350Vdc
6FdB 350Vdc
65dB 5O”dc
65dB 5OVdc
55dB
Single Rack Mounting Kit
Dual Rack Mounting Kit
Hard Shell Carrying Case
Rechargesble Battery Pack
Low Noise Input Cable (4ft.l. BNC to ONC
Low Noise Cable Kit
IEEE-486 Interface
IEEE-466 Digital Cable 13ft.b
IEEE-468 Digital Cable 16 ft.1
IEEE-488 Interface for IBM PC
MAXIMUM
CONTINUOUS
350”dC
5OVdc
Specifications subject to change without notice.
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
TABLE OF CONTENTS
SECTION l-GENERAL INFORMATION
Introduction.
Getting Started
Unpacking and Inspection
Specifications
Warranty Information.
Manual Addenda
Safety Symbols and Terms
Optional Accessories
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l-1
1-l
l-l
l-l
l-l
1-2
1-2
l-2
2.1
2.2
2.2.1
2.2.2
2.2.3
2.3
2.4
2.4.1
2.4.2
2.4.3
2.4.4
2.5
2.6
2.7
2.7.1
2.7.2
2.7.3
2.7.4
2.75
2.7.6
2.7.7
2.8
2.8.1
2.8.2
2.8.3
2.8.4
2.8.5
SECTION Z-BENCH OPERATION
introduction ...............................................................................
PreparationforUse
Line Power ..............................................................................
Battery Pack Power .......................................................................
BatteryCharging
TntBail ....................................................................................
Model 485 Familiarization
Display
FrontPanelControls
InputConnector ..........................................................................
AnalogOutputConnectors
Error Messages
EnvironmentalCondition .....................................................................
BasicBenchMeasurements
Power-Up ...............................................................................
Zero Check ..............................................................................
Current Measurements ....................................................................
RelativeMode
LOGMode ...............................................................................
Inverting Analog Output ...................................................................
MIN/MAXand 100 Point Data Store
MeasurementConsiderations
SourceResistance ........................................................................
SourceCapacitance
LeakageResistance .......................................................................
ZeroTimeStability
Groundingconsiderations
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2-l
2-l
2-l
2-l
2-l
2-1
2-l
2-l
2-2
2-2
2-2
2-2
2-3
2-3
2-4
2-4
2-4
2-4
2-5
2-5
2-6
2-6
2-6
2-7
2-8
2-8
2-8
2.9
2.9.1
2.9.2
2.9.3
2.9.4
2.9.5
3.1
3.2
i::
3.5
Applications
Op Amp Offset Current
FET Gate Leakage and Channel Current.
Insulation Leakage Currents and High Resistance.
Phototube, Photodiode and Beam Currents
Resistivity Tests
SECTION 3-PERFORMANCE VERIFICATION
Introduction ......................................
Environmental Conditions
Recommendrsd Test Equipment
Initial Conditrons
Verification Procedure
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3-l
3-l
,. 3-l
3-1
3-l
i
4.1
4.2
4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.5
4.6
4.7
5.1
5.2
5.3
5.4
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.5
5.6
5.6.1
5.62
5.63
5.6.4
5.6.5
5.7
5.8
5.9
TABLE OF CONTENTS (CONT.)
SECTION 4-THEORY OF OPERATION
Introduction ...............................................................................
Overall Functional Description. ................................................................
AnalogCircuitry ............................................................................
Current-to-Voltage Converter ...............................................................
Multiplexer ............................................................................
InputBufferAmplifier .....................................................................
-2VReferenceSource .....................................................................
AIDConverter.. ......................................................................... 4-3
Digital Circuitry .............................................................................
Microcomputer ...........................................................................
Address Decoding ........................................................................
PIA .....................................................................................
DisplayBoard.. ..........................................................................
Digital Calibration ...........................................................................
PowerSupply ..............................................................................
Model 1758 Battery Option ...................................................................
SECTION 5-MAINTENANCE
Introduction ...............................................................................
Top Cover Removal/Installation ...............................................................
Battery Pack (Model 1758) Installation
Front Panel Calibration ......................................................................
Recommended Calibration Equipment.
CalibrationJumper ........................................................................
Environmental Conditions ..................................................................
Calibration Procedure. .....................................................................
CalibrationStorage ........................................................................
Calibration Over IEEE-488 Bus .................................................................
Troubleshooting ............................................................................
Recommended Test Equipment .............................................................
Self Diagnostic Program ...................................................................
Power Supply and Battery Pack (Model 1758) Checks
A/D Converter and Display .................................................................
SignalConditioning .......................................................................
Input Amplifier NJ105) Balancing ..............................................................
LineFuseReplacement ......................................................................
Special Handling of Static Sensitive Devices.,
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4-2
...........................................
4-l
4-l
4-l
4-1
4-2
4-3
4-4
4-4
4-4
4-4
4-4
4-4
4-4
4-4
5-I
5-l
5-l
5-l
5-1
5-2
6-2
5-2
5-2
5-3
5-3
5-3
5-3
5-6
5-6
5-7
5-7
5-7
5-8
6.1
if
6.4
6.5
SECTION B-REPLACEMENT PARTS
Introduction ...............................................................................
ReplaceableParts ...........................................................................
Ordering Information ........................................................................
FactorySen/ice .............................................................................
Component Location Drawings and Schematic Diagrams
ii
..........................................
6-l
6-l
6-l
6-l
6-l
LIST OF ILLUSTRATIONS
2-1
2-2
2-3
2-4
2-5
2-6
2-7
Z-8
2-9
2-10
3-l
4-l
4-2
4-3
4-4
4-5
5-I
5-2
6-l
6-2
6-3
6-4
6-5
6-6
6-7
6-8
Model485FrontPanel ....................................................................... 2-2
Model 465 Inverting Analog Output
Simplified Model for Input Signal Conditioning
Test Fixture Guarding ....................................................................... 2-8
LeakageTestSetUpUsingModel6104 ........................................................ 2-8
Op Amp Input Offset Currents Measurement
F5T Gate Leakageand Channel Currents Measurement.
Insulation Leakage Currents end High Resistances Measurement .................................... 2-9
Set Up to Measure Photomultiplier, Photodiode end Beam Currents .............................. ,, 2-9
ResistivityTestSetUp
Shielded Test Fixture ........................................................................ 3-2
Simplified Block Diagram ..................................................................... 4-l
Current-to-Voltage Converter
Simplified Schematic of the Multiplexer
Simplified Schematic of the Input Buffer Amplifier
AIDConverter
Segmentldentification
JumperLocations ...........................................................................
Model485MiscelianeousParts
Display Assembly
Mother Board, Component Location Drawing. Dwg. No. 485-100
Mother Board, Schematic Diagram, Dwg. No. 485-106., .......................................... 6-9
Display Board, Component Location Drawing, Dwg. No. 485.110 ................................... E-13
Display Board, Schematic Diagram, Dwg. No. 485-116
Model 1758 Battery Peck, Component Location Drawing, Dwg. No. 1758-100 ......................... 615
Model 1758 Battery Peck, Schematic Diagram, Dwg. No. 1768-106 ................................. 6.16
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2-7
2-8
2-9
Z-IO
4-2
4-2
4-2
4-3
5-4
5-7
6-2
6-3
6-7
6-14
iii
LIST OF TABLES
2-1
2-2
2-3
3-1
3-2
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
6-1
6-2
83
8-4
Error Messages.. ..........................................
Range, Accuracy and hlaximum Allowable Inputs
Equivalent Input Resistance With Zero Check Enabled
Recommended Test Equipment ..............................
RangeAccuracy ...........................................
Range Calibration ..........................................
Recommended Troubleshooting Equipment
TroubleshootingModes .....................................
Power Supply Checks and Battery Pack (Model 1758) Checks
A/DConverterChecks ......................................
DisplayBoardChecks ......................................
OffsetJumparSetUp ......................................
Static Sensitive Devices ....................................
Mother Boerd, Parts List ....................................
Display Board, Parts List ....................................
Model 1758 Battery Pack, Parts List ...........................
Model485SperePartsList ..................................
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2-3
2-3
2-4
3-l
3-2
5-3
5-3
5-5
6-6
6-6
5-7
5-7
5-8
6-4
6-13
6-15
6-17
iv
SAFETY PRECAUTIONS
The following safety precautions should be observed before operating the Model 485.
This instrument is intended for use by qualified personnel who recognize shock hazards and are familiar
with the safety precautions required to avoid possible injury. Read over the manual carefully before
operating this instrument.
Exercise extreme caution when a shock hazard is present at the instrument’s input. The American
National Standards Institute (ANSI) states that a shock hazard exists when voltage levels greater than
30V rms or 42.4V peak are present. A good safety practice is to expect that a hazardous voltage
is present in any unknown circuit before measuring.
Do not exceed 30V rms between the input connector shell and earth ground.
Inspect the test leads for possible weer, cracks or breaks before each use. If any defects are found,
replace with test leads that have the same measure of safety as those supplied with the instrument.
For optimum safety do not touch the test leads or the instrument while power is applied to the circuit
under test. Turn the power off and discharge all capacitors, before connecting or disconnecting the instrument.
Do not touch any object which 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.
Do not exceed the instrument’s maximum allowable input as defined in the specifications and operation
section.
Safe operation and good measurement practice dictates use of an external resistor when necessary to
limit input currents to less than 3mA.
Model 485 Addendum
me following idormation is supplied as a supplement to tfi manual k order to prmide the user
with the latest tiprovements. It is recommended that vefication tio~tion k added to Section 3
of the Model 485 Instiction Manual and c&bration tifomatimr be added to Section 5.
~is addendum contatis complete procedures for vefi@g and cahhatig the Model 485 ustig the
WltMq Model 2& Cdibmtor/Somce. Complete sepmate pmcedmes a pmtided for @otig di@ti
calibration horn either the hont panel or over the IEEE+8 bus. Dgitd ctibration over the bus is
automated ustig a BASIC pro~am mn @ the W 85 computer.
PA-2w Rev. A / 149
PERFORMANCE VERIFICATION USING
MODEL 263 ~LIBRATOR/SOURCE
Use of the Model 263 to verify ac~aq specifications of
the Model 485 stip~ies the prored~ by etiating the
need for user desi~ed _nt somces. The quipment
fisted h Table >1 of the manual is not needed.
Idetiy performance verification shotid be perfomed
when the tis~ent k first received to emm that no
daage or chmge h calibration has ocmed dtig ship
ment. It may&O be perfomed when fi~ent acwa~
is swpe~ Orfo~w~ c~bration. E perfmrnance on any
of the rmges ia outside the specified tits, ctibrate the
titiment.
NOTE
Mthe
~ent does not meti spedicatiom md
is stfl under warrmty ~ess thm Q months stice
date of shipment), con~d your ~lMey mpmsentative Orthe factory b detetie the atimr to &
t&en.
2. Tm on the Models 485 and 263, and allow them to
wm up for one hour. The Model ~ may be operated
from either ~ie power or battery pack power, as long
as the batteq pack has been fu~y charged..
Veficatirur Prncedw
Weed as fo~ows to verify the accuraq of the Model 485:
1. On the Model 485, press ZERO CHECK and select the
M rmge.
2. With an open input, adjust the ZERO pot for .0000 *1
cmrnt on the display.
3. Comect the Model 263 to the Model 485 as shown in
Fi~e 1. Make sue the cdlbrator is in standby.
4. Relesae ZERO CHECK on the Model 485.
5. Using the AMPS (adive) c~nt source, program the
Model 263 to output 1.90~nA and verify that the
reading is within the Itits h Table 1,
6. Using Table 1 as a guide, check the rest of the current
ranges by applying the a~ropriate current and verifying that the reatig is within the allowable limits.
Etimenti Condltiom
M measurements shodd be made at m mbient
temperature b~een M“ md 28°C (&” to 82°~ with a
relatiw humidity less thm 70°h.
Irritid
Conditimra
Before perfofig the verification procedure, m&e sure
the Models 485 md 263 meet the fo~owtig conditiom:
1 E the tis~ents have been subjed b tempmams
blow M°C (&°F) Orabom 28°C (82°F), dow sufficient
tie for the titruments to reach temperahs tithti
the rmge. GenerWy, it tskes one hour to stabtie m
irrs~ent that is M“C (MOF)outside of the specfied
range.
Table 1. Range Accumcy
263 Output
(AMPS)
1.90M0 A
19.0000 M
190.WO A
1.90000 PA
19.0000 ~A
190.000 @
1.9oooofl
*Includes Model 263 error.
Allowable Reading*
(M”C -28°C)
1.8933 to
B.936 to
M9.69 to
1.8976
28.986
to
to
E9.86 to
1.8986 to
1.9067
19.064
190.31
1.9024
19.014
lW.14
1.9014
MODEL 4W BNC TO TRIW ADAPTER
MODEL 263
Rgum 1. Model 485 Verification Connections
\
MODEL 485
.
CALIBRATION USING MODEL 263
CALIBRATOWSOURCE
me fo~oting pua~aphs ptide detded pmcedwes for
c~bratig the Model 485 Picommeter using the Model
263 Wbrator/Some. M but one of the cfibratimr adjmtienta ~e digiti md ~ & done km the ~nt pmel
m over the ~EE~ bus.
TOc~brate the tis~ent bm the tint pmel, pefiom
the fo~otig pmedures, muitig pma~aph ‘TEEE=
BW Cfibration”. TO ctibate the Model 485 over the
=4 bus, pdom the foflwtig pmedmes, ornitig
pmagaph ‘Tmnt ~el Mbration”.
Environmental Conditions
C~bration shmdd be pefiomed under labrato~ ccm&tiom hatig m -bient tempera~ of 23 +l°C md a
relative hufidity of less tha 70%. With both the Model
485 and 263 on, dow them to wam up for one hem. K
either ina~ent has ken subjected to mtieme temperatim or hufidity, dow at least one ad~tiond how for
the titiment to stabike before be@tig the ctibration procedw.
NWE
Cfibration can be stopped at ay tie md ody
those ranges out of spwificatimr need be cdbra~d.
Calibmtion Stomge Enable
The Model 485 mmt be in cfibratimr storage enable to
stem cfihation comtita h NVRAM. E the instiment
k not placed h ti mode, subsequent ctibration W be
lost when the ~
~g steps tO enable cab~mtiOn stOrage.
1. Mthe Model 485 is presently rm, * it off.
2. We holtig k the S~/CLR button, - the ina~ment back on.
3. When the “CA~ message is displayed, mle=e the
~/CLR button. The ina~ent ti ~ to the rmrmd diapl~ mode md the stotig of cdibratimr cons~ts is now enabled.
at k bd off. @fiOm the fOflw-
Required Equipment
The fo~-g item (one of each) me necess~ ti ctihate
the Model ~:
1. WitMq Model 263 Cti&ator/Some.
2. Trim to Tri= Cable (suppfied with 263)
3. kiW~ Model W Mde BNC to Pemde Tfi Adapter.
N~: The fo~owtig ad~tiond item@ be nwces~
if c~bration is to be petioned over the ~E4 bus.
4. KiMey Model 4853 EEE48 Intetiace tisti~ed h the
Model 485.
5. ~ 85 Computer eqtipped tik ~ 82937 GP~ kterface md 1/0 ROM.
6. KltMey Model 7008 ~E cable.
Front Panel Calibmtion
Petiom the foE- steps to dbrate the Model& tim
the front pmek .
1. On the Model 485, depress ZERO C~CK and select
the M rmge.
2. With m open tiput, adjust the Z~O pot for.~ AI
count on the display.
N~E
H
Q104, U105, RIU, Rl14 or RIB hwe been replaced, the pico-der may not zero. See paa&aph 5.7 h the Model& btition Manual fur
the pmcedti to bdmce the tiput amp~er.
3. Comect the output of the Model 263 ~hatur/Sowe
to the tiput of the Model 485 as show h Fi~ 2.
M*e sue the ctibrator is h standby.
4. On the Model 485, press the R~ arrd ~G pwhbuttmrs stidtanemrsly md hold k unti the message
“CAH is &played. Release the buttons. The tit is
now h the c~bration mode m kdicated by the “~~
annunciator.
5. Release Z~O HCK on the Model 485.
6. Pro&mn the Model 263 to output .m nA. Use the
AMPS (active) -ent some.
7. The Model& maybe displaying a smfl offset (=1
count). TOcmcel this offset, press ML rm the Model
485 to zem the display.
8. Pro~a the Model 263 to output 1.900W nA.
9. Adjust the display of the Model 485 to read l.~
uatig the S~/CLR md RCL httons. The STO/CLR
button hcrements the displayed reading and the R~
button demments the displayed reatig.
MODEL 4W BNC TO TRl~ ADAPTER ~
MODEL 263
MODEL 485
Rgum 2. Model 485 Catibmtion Connections
10. Ustig Table 2 as a guide, repeat the basic pmcedme the ~E48 bus ustig the Model 263 C~brator/Sowe.
oufltied h steps 5 thmuxh 9 to ctibrate the rest of the
-ent range; of the M;del 485.
11. TOatom A:bration comtmta md ~t the ctibration
mode, simti~eously press the ~ md LOG buttom
UM the message “Stofl is &played. E titead the
message “ouf’ is displayed, then ctihation storage 2. Make sue the =488 adtiess of the Model 2@ is set
was not embled md cahbatimr crmstits W be lost
when the Model N is tied off.
Table 2. Model 485 Range Calibtion
263 titput
Cumnt
1.90000 d
485 Readtig
19.0000A
190.000 A
Lm &
19.0000@
190.000 @
1.9W d
IEEE-488 Bus Calibmtion
1. Comect the Models 263 md 485 to the GP~ titefiace
of the HP 85 computm. The Model 485 mti have a
Modd &53 ~488 htefiace tistied.
to 8 md the adhss of the Model 4853 is set to 22.
3. Enter the c~iration pm~m tito the HP 85 computer.
4. TO‘dbmte the titiment, stiply press the R~ key
on the computi. The -m wfl prompt for the Only marmd adjustimt md then automatically cdbrate
d the mmnt rmges of the Model 485.
5. The pm-@ prompt for storage of the c~tiation
constita me 330). ~ ptides the user the opportity to stop at this petit to avoid pemment cAha-
tiOn. me Ctibation con~ts WM ~ lost when the
Model 485 is tied off.
6. Stomge of c~bmtion comtits is pefimed mrhe 350
of the pmga md is tidcated by the “Stofl message
on the Model 485. H btead the message “out” k
displayed, c~iratiorr storage was not enabled md
c~bmtion com~ts w~ be lost when the Model &
is ~ed off,
Z After c~bration is completed, it is mcomended that
you somce a mnt fmm the Model 263 to each rmge
at k h~ scale b verify acwacy.
Pdom the fofltig steps to dbrate the Model 485 mr
10 CLEAR 722 @ CLEfiR
NAIT 1020
22
32
OUTPUT 722 ; “CIRIX”
42 BEEP @ DISP
50 DIsP
S0 DISP “IF DISPLAY WILL NOT ZERO, PRO- CEEO TO P6RAGRAPH 5.7 IN THE 48 SMANUAL.
70 OISP
80 DISP ,’PRESS ‘CONT’ KEY ON THE HP 85 TOCONTINUE. “
90 P6USE
100 CLEAR @ BEEP
110 DISP “CONNECT ?G3 OIJTPUT TO 485 INPUT (SEE FICURE 2) ~ ~
120 DIS?
130 OISP “PRESS ‘CONT’ TO CONTINUE. “
140 PAUSE
152 06Th 1, .0000000019,2,.000000019,3, .00000019,4, .0000019,5,.000019,6, .00019,7,
160 CLEAR
170 CLEAR 708
180 OUTPUT 708 ; “F1R4UI . gE-gx,
190 OUTPUT 722 ; “COX,,
200 FOR 1=4 TO 10
210 REAO J
~ZO OUTPUT 722 ~ ,,R,, ;J; ,,x, ! 485; ~e~ect ~ange,
230 OUTPUT 708 ; R; I; ,X< ! 265; select range.
240 OUTPUT 708 ; “Z101X” ! 263; output zero amp5.
2S0 WAIT 3000
260 OUTPUT 722 ; “ZIXS’ ! 485; enable REL to
270 REAO J@ WAIT 2000
~sO OUTp UT 708 ; ,,zOx,, ! ~E~;
290 Wfl IT 2000
300 OUTPUT 722 ; “V’’; J; “X,” ! 485; send calibration value.
310 OUTPUT 722 ; “ZOX” ! 485; disable REL.
320 NEXT I
330 BEEP @ OISP “TO STORE C6L CONSTANTS, PRESS ‘CONT’ . “
340 PAUSE
‘AOJUST ‘ZERO’ POT ON 495 FOR
! 485; set to 2nA range and enable ZERO CHECK.
.0000 +/-1 COUNT. “
! 263; program for 1.9nA.
! 4S5; disable ZERO CHECK.
cancel Of
source programmed outpu
5et .
350 OUTPUT 722 ; ‘“LOX,’ ! 485; store cal constants.
560 CLEhR @ BEEP
370 DISP “CfiLIBRATION COMPLETE”
380 END
485 CALIBRATION PROGRAM
MODEL 485 AUTORANGING PICOAMMETER
vi
Features:
l 4% Digit LCD Display
l Fast Autoranging
l Bench or Portable
l Digital Calibration
l 100 Point Data Store
l O.lpA Sensitivity
l Analog Output
l LOG/Relative Functions
l Min/Max Reading Hold
Options:
l Model 1758 Rechargeable Battery Pack
l Model 4853 IEEE-488 Interface
SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION
This instruction manual contains the necessary information
for operating and maintaining the Model 485 Autoranging
Picoammeter and the Model 1758 Rechargeable Battery
Pack. The information is divided into the following sections:
1. Section 1 contains general information and provides
guidelines for using this manual. Important safety information is also presented here.
2. Section 2 contains detailed operation information for the
Model 485.
3. Section 3 contains the information needed to verify the
accuracy of the Model 485. Performance verification can
be done upon receipt of the unit or whenever the basic accuracy is in question.
4. For the more technically oriented, information on theory
of operation, maintenance and servicing is contained in
Section 4 through 6.
NOTE
The Model 4853 IEEE-488 interface comes supplied with its own instruction manual.
1.2 GElTlNG STARTED
Perform the following steps in sequence to acquaint yourself
quickly and safely with the basic operation of the Model 485.
1.
Verify that the Model 485 was not damaged in transit, as
explained in paragraph 1.3.
2.
Carefully read the safety precautions and warnings found
preceding this section and the first two sections (General
Information and Bench Operation) of this manual.
Referring to paragraph 2.2.1 (Line Power) set the line
3.
voltage switch and plug the power cord into a properly
grounded cutlet. If the optional battery pack is installed
the charge circuitry will be activated.
4.
Acquaint yourself with the controls and display of the
Model 485 as follows:
A. Turn on the Model 485 by pressing in the ON/OFF
pushbutton. All the zeroes will be displayed briefly.
B. Select autoranging by pressing in the AUTO pushbut-
ton. The nA and AUTO annunciators will be displayed.
Pressing any of the other range pushbuttons will put
the Model 485 in manual ranging as indicated by the
absence of the AUTO annunicator.
C. Engage the ZERO CHECK pushbutton and note that
the ZERO CHECK annunciator turns on. Release the
ZERO CHECK button.
D. Select LOG by pressing the LOG pushbutton. The
LOG annunciator will turn on. Press the LOG button
again to take the Model 485 cut of the LOG measurement mode.
E. REL (relative) can be used in the linear measurement
mode or the logarithm measurement mode. The
stored REL level will be subtracted from all subsequent
measurements. Press the REL pushbutton and note
that the REL annunciator turns on.
F. To activate the 100 point DATA STORE with
MinIMax, press end hold in the STO/CLR pushbut-
ton. When the reading rate r = 0 is displayed let go of
the button. The ST0 annunciator will turn on. Press
the RCL pushbutton and the last data point will be
displayed briefly followed by the reading (data). Other
date points can be displayed by holding in the RCL
button. Turn off the DATA STORE by pressing the
STO/CLR pushbutton again.
5. When you are comfortable with the controls of the Model
485, go on and make the desired measurements using
Section 2, Bench Operation as a guide.
1.3 INSPECTION
The Model 485 Bench Picoammeter was carefully inspected,
both mechanically and electrically, before shipment. Upon
receiving the Model 485, check for any obvious signs of
physical damage that might have occurred during shipment.
Report the damage to the shipping agent immediately. Retain
the original packing materials in case reshipment becomes
necessary. The following items are included with every Model
485 order:
l Model 485 Autoranging Picoammeter
l Model 485 Instruction Manual
l Additional accessories as ordered.
If an additional instruction manual is required, order then
manual package (Keithley Part Number 486-901-00). The
manual package includes an instruction manual and all pertinent addenda.
1.4 SPECIFICATIONS
Detailed Model 485 specifications may be found immediately
preceding the table of contents of this manual.
1.5 WARRANTY INFORMATION
Warranty information may be found on the inside back cover
of this manual. Should it be necessary to exercise the warran-
ty, contact your Keithley representative or the factory to
determine the correct course of action. Keithley Instruments
maintains service facilities in the United States, West Germany, Great Britain, France, the Netherlands, Switzerland
1-l
and Austria. Information concerning the application, cperaticn or service of your instrument may be directed fc the ap-
plications engineer at any of these locations. Check the inside
front cover of this manual for addresses.
Model 1684 Hard Shell Carrying Case-Hard vinyl case,
IOOmm x 300mm x 350mm (4 x 13 x 14 inches) has a fit-
ted foam insert with room for the Model 485, instruction
manual end small accessories.
1.6 MANUAL ADDENDA
Information concerning improvements or changes to the in-
strument which occur after the printing of this manual will be
found on an addendum sheet included with this manual. Be
sure to review these changes before attempting to operate or
service the instrument.
1.7 SAFETY SYMBOLS AND TERMS
The following safety symbols and terms are used in this
manual or found on the Model 485.
The symbol
should refer to the operating instructions in this manual.
The WARNING heading in this manuel explains dangers that
could result in personal injury or death.
The CAUTION heading in this manual explains hazards that
could damage the instrument.
1.8 OPTIONAL ACCESSORIES
The following accessories can be used with the Model 485.
Model 1010 Single Reck Mounting Kit-Use to mount
one Model 485 in e standard 5% x 19” rack.
on the instrument indicates that the user
A
Model 1768 Rechargaable Battery Pack-Provides six
hours minimum operation from full charge, recharges within
10 hours end is field installable.
Model 4801 Input Cable-A low noise coaxial cable four
feet (1.2m) in length with a male BNC connector on each
end.
Model 4803 Low Noise Cable Kit-Consists of 50 feet
(15.2m) of low noise coaxial cable, 10 male BNC connectors,
and five female chassis mount BNC connectors.
Model 4863 IEEE-486 Interface-Field installable prcgram-
mable option provides isolated data output. Switchselectable talk only or addressable modes. Mounts within and
powered by the Model 485.
Model 7008 IEEE-488 Digital Cable-Useful for ccnnecting the Model 4853 to the IEEE-488 bus. The Model 7008-3 is
0.9m 13 ft) in length and has a standard IEEE-488 connector
at each end. The Model 7008-6 is 1.8m (6 ft) in length.
Modal 8673 IEEE-486 Interface for IBM PC-Field in-
stallable programmable option provides data output for the
IBM PC. Mounts within and powered by the IBM PC.
Model 1017 Dual Reck Mounting Kit-Use to mount two
Model 486’s in a standard 5% x 18” rack.
l-2
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