Keithley 1793 User manual

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KEITH LEY
INSTRUCTION MANUAL
Model 1793/6423
IEEE Standard 488 Output
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Keithley Instruments, Inc.
28775 Aurora Road/Cleveland, Ohio 44139/(216] 248-0400/Telex: 98-5469
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WARRANTY
We warrant each of our products to be free from defects in material
and workmanship. Our obligation under this warranty is to repair
or replace any instrument or part thereof which, within a year after
shipment, proves defective upon examination. We will pay local
domestic surface freight costs.
To exercise this warranty, write or call your local Keithley repre
sentative, or contact Keithley headquarters in Cleveland, Ohio.
You will be given prompt assistance and shipping instructions.
REPAIRS AND
CALIBRATION
Keithley Instruments maintains a complete repair and calibration
service as well as a standards laboratory in Cleveland, Ohio.
A Keithley service faciiity at our Munich, Germany office is
available for our customers throughout Europe. Service in the
United Kingdom can be handled at our office in Reading. Addition
ally, Keithley representatives in most countries maintain service
and calibration facilities.
To insure prompt repair or recalibration service, please contact
your local field representative or Keithley headquarters directly
before returning the instrument. Estimates for repairs, normal
recalibrations and calibrations traceable to the National Bureau of
Standards are available upon request.
KEITHLEY
Keithley Instruments, lnc./28775 Aurora Road/Cleveland, Ohio 44139/U.S.A./[phone]/Telex: 98-5469
Keithley Instruments GmbH/Heiglhofstrasse 5/D-8000 Munchen 70/WEST GERMANY/1089) 714-40-65/Telex: 521 21 60
Keithley Instruments, Ltd./I, Boulton Road/GB-Reading, Berkshire RG2 ONL/GREAT BRITAIN/(0734) 86 12 87/Telex: 847047
Keithley Instruments SARL/2 Bis, Rue Ldon Blum/B.P. 60/91121 Palaiseau Cedex/FRANCE/(6) 011.51.55/Telex: 600933F
Keithley Instruments B.V./Leidsestraatweg 149/Postbus 1190 /NL-Woerden/NETHERLANDS/103480) 13 643/Telex: 40 311
Keithley Instruments SA/Filiale DUbendorf/Kriesbachstr. 4/CH-8600 Dubendorf/SWITZERLAND/01 821 94 44/Telex: 57 536
Keithley Instruments Handels-Gesellschaft m.b.H./DOblinger Hauptstr. 32/A-1190 Wien /AUSTRIA/0222 314 289/Telex: 13 45 00

INSTRUCTION I^IMUAL
MODEL 1793/64;^3
IEEE STANDARD 488 OUTPUT
COPYRIGHT 1979 KEITHLEY INSTRUMENTS, INC.
THIRD PRINTING, l^RCH 1981, CLEVELAND, OHIO U.S.A.
DOCUMENT NO. 30535, REV. 8

CONTENTS
SECTION
PAGE
1. GENERAL INFORMATION
1-1. INTRODUCTION
1-3. COMPATIBILITY
1-6. WARRANTY INFORMATION
1-8. CHANGE NOTICES
1-10. SAFETY SYMBOLS
1-12. SPECIFICATIONS
2. INITIAL PREPARATION
2-1. INTRODUCTION
2-3. UNPACKING AND INSPECTION
2-5. MODEL 1793 INSTALLATION
2-7. MODEL 6423 INSTALLATION
2-9. MODEL 1793/6423 OUTPUT CONNECTOR
3. OPERATION
3-1. INTRODUCTION
3-3. OPERATING INSTRUCTIONS
4. THEORY OF OPERATION
4-1. INTRODUCTION
4-4. POWER SUPPLY
4-6. PARALLEL TO SERIAL CONVERSION
4-12. SERIAL TO PARALLEL CONVERSION
4-14. BUS OPERATION
4-16. ADDRESS ACCEPTANCE
4-18. DATA SENDING
5. MAINTENANCE
5-1. INTRODUCTION
5-3. TEST POINT DATA
5-5. 1793/6423 VERIFICATION PROCEDURE
5-7. ADDRESSABLE MODE VERIFICATION
5-8. TALK ONLY MODE VERIFICATION
5-9. SPECIAL HANDLING OF STATIC SENSITIVE DEVICES
6. REPLACEABLE PARTS
6-1. GENERAL
6-3. ORDERING INFORMATION
6-5. SCHEMATIC
6-7. COMPONENT LAYOUTS
1-1
1-1
1-1
1-1
1-1
1-1
1-1
2-1
2-1
2-1
2-1
2-2
2-2
3-1
3-1
3-1
4-1
4-1
4-1
4-1
4-1
4-1
4-1
4-3
5-1
5-1
5-1
5-1
5-1
5-1
5-2
6-1
6-1
6-1
6-1
6-1
ILLUSTRATIONS
Figure 2-1.
Figure 2-2.
Figure 3-1.
Figure 4-1.
Figure 4-2.
Figure 5-1.
Installation of Model 1793,
Installation of Model 6423,
Switch 502
1793/6423 Flow Diagram. . .
Timing Diagram
Isolated Serial Data. .. ,
PAGE
2-3
2-4
3-2
4-2
4-3
5-1
11

MODEL 1793/6423
GENERAL INFORMATION
SECTION 1. GENERAL INFORMATION
1-1. INTRODUCTION.
1-2. The Model 1793/6423 is an IEEE Standard
488-1978 Bus Interface option that provides the
logic and control functions necessary to interface
the Keithley Models 177, 179 and 179-20A Digital
Multimeters, the Model 480 Picoammeter, and the
Model 642 Electrometer. It may be either field or
factory installed. The combination of the Model
1793/6423 and its host DMM, Picoammeter or Elec
trometer can operate in either the TALK ONLY or
ADDRESSABLE mode, as determined by the setting of an
internal switch. In the TALK ONLY mode, it can send
data to an IEEE compatible listener at one of seven
switch selectable rates, from 2.5 readings/second to
1 reading/hour. In the ADDRESSABLE mode, readings
may be triggered or non-triggered, depending on
whether its odd or even address is received from the
IEEE controller. The internal switch settings
determine the reading rate for the TALK ONLY mode,
and its address when in the ADDRESSABLE mode. The
Model 1793/6423 provides an output of 4-1/2 digit
ASCII data, sign, and overrange.
1-3. COMPATIBILITY.
1-4. The Model 1793 is compatible with the
following Keithley instruments:
a) Model 177 DMM Serial Number 16500 and above.
b) Models 179 and 179-2GA DMM Serial Number 24000
and above.
c) Model 480 Picoammeter Serial Number 12000 and
above. NOTE: The first 3-1/2 digits of the output
are the same as the 480 display.
1-5. The Model 6423 is compatible with the Model
642 Electrometer Serial Number 53402 and above.
1-6. WARRANTY INFORMATION.
1-7. The Warranty is given on the inside front
cover of this Instruction Manual. If there is a
need to exercise the warranty, contact the Keithley
Representative in your area to determine the proper
action to be taken. Keithley maintains service
facilities in the United Kingdom and West Germany,
as well as in the United States. Check the inside
front cover of this Manual for addresses.
1-8. CHANGE NOTICES.
1-9. Improvements or changes to the equipment which
occur after printing of the Instruction Manual will
be explained on a Change Notice sheet attached to
the inside back cover.
1-10. SAFETY SYMBOLS.
1-11. Safety symbols used in this manual are as
follows:
A
IMPORTANT
The /' \ symbol may be found in various places
in this manual. Carefully read the associated
CAUTION statements with regard to proper use and
handling of the equipment. Damage to the equip
ment may occur if these precautions are ignored.
\
This ^ symbol may be found in various places
in this manual. This symbol indicates those
areas on the equipment which are potential shock
hazards. Carefully read the associated WARNING
statements with regard to proper use and
handling of the equipment. Serious personal
injury may result if these precautions are
i gnored.
1-12. SPECIFICATIONS.
1-13. Detailed specifications for the Model 1793/
6423 are listed in Table 1-2. These specifications
are defined as the performance standards or limits
against which the Model 1793/6423 is tested. Table
1-1 lists general operating characteristics of the
Model 1793/6423. These characteristics are not
specifications, but are typical operating charac
teristics or constraints which are included as
additional information for the user.
TABLE 1-1
General Operating Characteristics
1. The 1793/6423 digital output low (pins 12 and 18
thru 24 on J501) is intended to be connected to a
ground point within 30VRMS of earth ground.
2. Common mode input to the meter shall not exceed
lO^V'Hz to guarantee valid data output.
3. 488 BUS outputs are open collector with Power
Up/Power Down protection (No invalid information
transmitted to the BUS).
4. Maximum transfer rate for one entire reading
(after being addressed) is 1msec.
1-1

GENERAL INFORMATION
MODEL 1793/6423
TABLE 1-2
Specifications, Model 1793/6423 IEEE-488 Output
OUTPUT:
DATA FORMAT:
4-1/2 digit ASCII data, sign, and overrange.
.XXXXX. ^CR LF,
'
Sign
(Plus implied)
Displ ay
Termi nator
T
OVERRANGE OUTPUT: ASCII "OVER" in place of "XXXXX"
LOGIC LEVELS: Meets all IEEE Std. 488-1978 specifications.
MODES OF OPERATION: (Selected by internal switches)
TALK ONLY: Allows user to connect meter to an IEEE-compatible
listener. Data outputted at seven switch
selectable rates from 2.5 rdgs/sec to 1 rdg/hr.
ADDRESSABLE: Allows user to connect meter to an IEEE-compatible
controller. Address selected by internal switches.
Non-Triggered addresses are even from 0 to 28.
Triggered address is non-triggered address +1.
NON-TRIGGER: Upon receiving its non-trigger address, outputs the
displayed reading
TRIGGER: Upon receiving its trigger address, initiates a
single A-D conversion and outputs the reading 400
msec later.
ISOLATION: Digital outputs isolated from input circuitry
(lO^^n, 40pF typ).
ENVIRONMENT:
OUTPUT CONNECTOR:
INSTALLATION:
Model 1793 Operate: 0 to 55°C, 0 to 80% RH.
Storage: -25 to +70°C.
Model 6423 Operate: 20 to 30°C, 0 to 70% RH.
Storage: -25 to +55°C.
24-pin IEEE-488 standard connector.
Field installable, mounts within and powered from
meter. Adds 0.6kg (1.3 lbs), 10 watts.
Model 1793 Precludes 1788, 1792 installation.
Model 6423 Precludes 6422, 6428 installation.
ACCESSORIES AVAILABLE: 1.8m (6 ft.) IEEE Cable Keithley Model 7008.
1-2

MODEL 1793/6423
INITIAL PREPARATION
SECTION 2. INITIAL PREPARATION.
2-1. INTRODUCTION.
2-2. This section provides information for incoming
inspection, preparation for use, and installation of
the Model 1793/6423.
2-3. UNPACKING AND INSPECTION.
2-4. The Model 1793/6423 was carefully inspected,
both mechanically and electrically before shipment.
Upon receiving your IEEE output option, unpack all
items from the shipping container and check for any
obvious damage which may have occured during
transit. Report any damages to the shipping agent.
Retain and use the original packaging materials if
reshipment is required. The following items
(Keithley Part No. in parentheses) are shipped with
all orders of your option:
a. Model 1793
1) PC-524 Assembly (30370D)
2) Shield Assembly (30I07C)
3) Replacement Top Cover (30409C)
4) A copy of this Instruction Manual
5) Separate Optional Cable (Model 7008), as
ordered.
b. Model 6423
1) PC-524 Assembly (30494D)
2) Shield Assembly (30133B)
3) Back Panel Assembly (30496A)
4) A copy of this Instruction Manual
5) Separate Optional Cable (Model 7008), as
ordered.
2-5. MODEL 1793 INSTALLATION.
2-6. The Model 1793 is installed internally in the
Model 177, 179, I79-20A or 480 and is powered by its
own line operated power supply. Installation of the
Model 1793 precludes use of the Model 1788 Battery
Pack and 1792 BCD Output. Refer to Figure 2-1 and
install the Model 1793 as follows:
\
WARNING
Disconnect the line cord before removing
the case cover.
a. Turn off power and disconnect line cord.
b. Turn the DMM bottom side up and loosen the
four screws in the bottom cover.
c. Hold the top and bottom covers together to
prevent their separation and turn the DMM over to
the normal position.
d. Lift off the top cover and the calibration
shield if installed. Remove the Model 1788 Battery
Pack or Model 1792 BCD Option if installed. The
four plastic spacers must remain in place on the
upright studs projecting through the main printed
circuit board.
NOTE
Do not discard the calibration shield.
This shield must be installed during
calibration, as described in the
Instruction Manual for your instrument.
e. If the Model 1788 was removed, set the LINE/
BAT switch on the main printed circuit board to the
LINE position.
f. Set the Line Voltage Switch (S50I) on the 1793
to the proper voltage (IIOV or 230V).
g. The 1793 is powered by the AC line. Discon
nect J1003 from its mating receptacle on the instru
ment's mother board (J1005 on the Model 480), and
reconnect to P1003A on the 1793. Connect J1003B of
the 1793 to P1003 on the instrument's mother board
(PI005 on the Model 480).
2-1

INITIAL PREPARATION
MODEL 1793/6423
h. Connect P1008 to its mating recepticle on the
printed circuit board (J1002 on the Model 480 and
J1008 on the Models 177, 179, a 179-20A).
j. Install the Model 1793 in the instrument so
that it rests on the plastic spacers. The ground
clip must make contact with the upper side of the
shield on the Model 1793.
k. Set up the DIP switch, S502, for the proper
mode of operation and timing/address as explained in
the Operating Instructions (paragraph 3-3).
1. Install the top cover that was shipped with
the Model 1793. This cover has a hole to accom
modate the connector of the Model 1793.
m. Save all removed parts for reinstallation in
the event that the 1793 is to be removed at a later
date.
2-7. MODEL 6423 INSTALLATION.
2-8. The Model 6423 is installed internally in the
Model 642 Electrometer mainframe and is powered by
its own line operated power supply. Installation of
the Model 6423 precludes use of the Model 6422 BCD
Output and the Model 6428 Battery Adapter. Refer to
Figure 2-2 and install the Model 6423 as follows:
X
WARNING
Disconnect the line cord before removing
the case cover.
a. Turn off power and disconnect the line cord.
b. Remove the four attaching screws and remove
the top cover.
c. Remove and replace the back panel plate with
the plate that is furnished with the Model 6423.
(Remove the Model 6422 or 6428 if installed.)
d. Remove the front four attaching screws from
the mother board and replace them with the metal
spacers, as shown in Figure 2-2. These spacers may
fit snugly and require use of a wrench to install
them. Take care not to cross thread or tighten them
too tight.
e. Connect P10G8 to J1013 on the mother board.
After making the connection, place the printed cir
cuit board outside of the Model 642 so that there is
no strain on the cable and the board will be out of
the way during installation of the shield and
spacers in the following steps.
f. Place the shield on the spacers and attach
with the four screws, as shown. The printed circuit
board will not fit properly unless the shield is in
stalled with the nut plates on the bottom side and
with the hole pattern positioned as illustrated.
g. Install the four spacers into the shield.
h. Place the printed circuit board on the spacers
(component side down) and attach it with four
screws.
i. Attach the output connector (J501) to the back
panel plate using two No. 6 hex head bolts and two
No. 6 kep nuts (see Component Layout 30494D - page
6- ).
j. Disconnect the AC power line at the mother
board of the 642 (J/P 1006) and reconnect to P1003A
of the 6423. Connect J1003B of the 6423 to P1006 of
the 642.
k. Set the Line Voltage Switch (S501) on the
6423 to the proper line voltage (llOV or 230V).
1. Set up the DIP switch, S502, for the proper
mode of operation and timing/address as explained in
the Operating Instructions (paragraph 3-3).
m. Reinstall the case top cover.
n. Save all removed parts for reinstallation in
the event that the 6423 is to be removed at a later
date.
2-9. MODEL 1793/6423 OUTPUT CONNECTOR.
2-10. The Model 1793/6423 uses a 24-pin connector
(J501) which will interface with IEEE-488 1978 con
nector.
2-11. An optional cable accessory is available for
interfacing the 1793/6423 with external equipment.
The Model 7008 is a 1.8m (6 ft.) IEEE Cable.
2-2

MODEL 1793/6423
INITIAL PREPARATION
P1003A
PLASTIC SPACER
(4 PLACES)
LINE VOLTAGE SWITCH
(S501)
P1008
I GROUND CLIP
J1008
DMM CASE
FIGURE 2-1. Installation of Model 1793
2-3

INITIAL PREPARATION
MODEL 1793/6423
MODIFIED PC-524
(30494D)
_i
STANDOFF (8) f
SHIELD
PIOOB/
J1013
a
642
MAINFRAME
FIGURE 2-2. Installation of Model 6423.
2-4