Keithley 248 Service manual
Model 248 High Voltage Supply
Instruction Manual
A GREATER MEASURE OF CONFIDENCE
W ARRANTY
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 Cle veland, Ohio. Y ou
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.
LIMIT A TION OF W ARRANTY
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 follow 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 PR OPERTY .
Keithley Instruments, Inc. • 28775 Aurora Road • Cleveland, OH 44139 • 440-248-0400 • Fax: 440-248-6168 • http://www.keithley.com
CHINA: Keithley Instruments China • Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-62022886 • Fax: 8610-62022892
FRANCE: Keithley Instruments SARL • BP 60 • 3 Allée des Garays • 91122 Palaiseau Cédex • 33-1-60-11-51-55 • Fax: 33-1-60-11-77-26
GERMANY: Keithley Instruments GmbH • Landsberger Strasse 65 • D-82110 Germering, Munich • 49-89-8493070 • Fax: 49-89-84930759
GREAT BRITAIN: Keithley Instruments, Ltd. • The Minster • 58 Portman Road • Reading, Berkshire, England RG3 1EA • 44-1189-596469 • Fax: 44-1189-575666
ITALY: Keithley Instruments SRL • Viale S. Gimignano 38 • 20146 Milano • 39-2-48303008 • Fax: 39-2-48302274
NETHERLANDS: Keithley Instruments BV • Avelingen West 49 • 4202 MS Gorinchem • 31-(0)183-635333 • Fax: 31-(0)183-630821
SWITZERLAND: Keithley Instruments SA • Kriesbachstrasse 4 • 8600 Dübendorf • 41-1-8219444 • Fax: 41-1-8203081
TAIWAN: Keithley Instruments Taiwan • 1FL., 85 Po Ai Street • Hsinchu, Taiwan • 886-3-572-9077 • Fax: 886-3-572-9031
Model 248 High Voltage Supply
Instruction Manual
©1995, Keithley Instruments, Inc.
All rights reserved.
Cleveland, Ohio, U.S.A.
Second Printing, February 1999
Document Number: 248-901-01 Rev. B
Manual Print History
The print history shown below lists the printing dates of all Revisions and Addenda created for this manual. The Revision
Level letter increases alphabetically as the manual undergoes subsequent updates. Addenda, which are released between Revisions, contain important change information that the user should incorporate immediately into the manual. Addenda are numbered sequentially. When a new Revision is created, all Addenda associated with the previous Revision of the manual are
incorporated into the new Revision of the manual. Each new Revision includes a revised copy of this print history page.
Revision A (Document Number 248-901-01)..................................................................................December 1995
Addendum A (Document Number 248-901-02)................................................................................ February 1996
Addendum A (Document Number 248-901-03)........................................................................................July 1997
Revision B (Document Number 248-901-01)....................................................................................February 1999
All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Other brand and product names are trademarks or registered trademarks of their respective holders.
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 non-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 ensuring 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 instrument. They must be protected from electric shock and contact with
hazardous live 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 ensure 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,
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 Category I and must not be connected to mains.
Do not connect switching 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 connecting 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 connected 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 jumpers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.
no conductive part of the circuit may be
Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or 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.
pect that hazardous voltage is present in any unknown circuit before measuring.
A good safety practice is to ex-
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.
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 are 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 applied to the device under test. Safe operation requires the use of a
lid interlock.
If a screw is present, connect it to safety earth ground using the
wire recommended in the user documentation.
!
The symbol on an instrument indicates that the user should refer to the operating instructions located in the manual.
The symbol on an instrument shows that it can source or measure 1000 volts or more, including the combined effect of normal
and common mode voltages. Use standard safety precautions to
avoid personal contact with these voltages.
The
WARNING heading in a manual explains dangers that might
result in personal injury or death. Alw ays read the associated infor mation very carefully before performing the indicated procedure.
CAUTION heading in a manual explains hazards that could
The
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 parts should be purchased only through Keithley Instruments
to maintain accuracy 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 the 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 or allow liquids to enter or spill
on the instrument.
Rev. 1/99
248 High Voltage Supply
VOLTAGE RANGE:0 to ±5000V DC
Output Maximum
Voltage Output Current Conditions
0 to ± 5000 V DC 5.000 mA DC NO FILTER
0 to ± 3000 V DC 5.000 mA DC FILTER 1
0 to ± 5000 V DC 3.000 mA DC FILTER 2
VOLTAGE SET ACCURACY: ±(0.01% of setting + 0.05% of range).
VOLTAGE DISPLAY ACCURACY: Voltage Set Accuracy ±1V, typical (±2V, max.).
VOLTAGE RESOLUTION: 1V (set and display).
VOLTAGE RESETTABILITY: 1V.
VOLTAGE LIMIT RANGE: 0 to 100% of full scale.
VOLTAGE REGULATION
Line: 0.001% for ±10% line voltage change.
Load: 0.005% for 100% load change, typical.
OUTPUT RIPPLE (10Hz–100kHz)
0.002% of full scale, Vrms, max. NO FILTER
1.0mV rms @ 1kV FILTER 1 or FILTER 2
2.0mV rms @ 3kV FILTER 1 or FILTER 2
3.0mV rms @ 5kV FILTER 2
CURRENT CURRENT LIMIT
VOLTAGE AND TRIP RANGE FILTER
0 V to 1.5 kV 0.4 mA to 5.25 mA NO FILTER or FILTER 1
1.5 kV to 5.0 kV 0.5 mA to 5.25 mA NO FILTER or FILTER 1
CURRENT LIMIT ACCURACY: 0.01% + 2.5µA.
CURRENT RESOLUTION: 1µA.
CURRENT DISPLAY ACCURACY: Current Set Accuracy ±1µA, typ. (±2µA, max.).
STABILITY: ±0.02% per hour typical for ambient temperature within 2°C.
TEMPERATURE DRIFT: 50ppm/°C, 0° to 50°C, typical.
PROTECTION: Arc and short circuit protected; programmable voltage and current
limits and current trip.
SETTLING TIME:
From 0 to Programmed Voltage: To within 99.9% of final value within 3s.
Discharge Time from Programmed Voltage to Within 50V of Zero: Within 6s for
no load (faster with load, slower with filters on).
2
:
3
0.4 mA to 3.25 mA FILTER 2
0.5 mA to 3.25 mA FILTER 2
1
:
MONITOR OUTPUTS:
Output Scale: 0 to +10V for 0 to full range output regardless of polarity.
Current Rating: 10mA maximum.
Output Impedance: <1Ω.
Accuracy: ±0.2% of full scale.
Update Rate: 8Hz.
EXTERNAL VOLTAGE SET:
Input Scale: 0 to +10V for 0 to full range output regardless of polarity.
Input Impedance: 1MΩ.
Accuracy: ±0.2% of full scale.
Update Rate: 16Hz.
Output Slew Rate: <0.3s for 0 to full range under full load.
NOTES:
1
Polarity of output is set with a rear panel switch. The unit must be powered off and the output fully discharged before changing polarity.
2
Regulation specifications apply for greater than 25V DC (with full load) or 50V DC (with no
load). Below these values, the unit may not regulate correctly.
3
Peak to peak values are within five times the rms value.
GENERAL
DIMENSIONS: 89mm high × 206mm wide × 406mm deep (3.5 in × 8.1 in × 16 in).
WEIGHT: 3.7 kg (8 lbs).
INPUT POWER: 55 watts; 100, 120, 220, 240V AC ±10%, 50 or 60Hz.
OUTPUT HIGH VOLTAGE CONNECTOR: SHV male (Kings Type 1704-1 or equiva-
lent), on rear panel.
REMOTE INTERFACE: GPIB (IEEE-488.1).
WARRANTY: One year parts and labor on materials and workmanship.
WARM-UP TIME: 1 hour.
OPERATING ENVIRONMENT: 0°C to 50°C.
ACCESSORIES AVAILABLE
248-MHV High Voltage Female-to-Male Cable, 3m (10 ft)
248-SHV High Voltage Female-to-Female Cable, 3m (10 ft)
248-RMK-1 Single Fixed Rack Mount Kit: Mounts a single Model 248 in a standard
248-RMK-2 Dual Fixed Rack Mount Kit: Mounts two Model 248s side-by-side in a
19-inch rack.
standard 19-inch rack.
Specifications are subject to change without notice.
SBG 10/25/00
Table of Contents
1 General Information
1.1 Introduction..........................................................................................................................................................1-1
1.2 Features................................................................................................................................................................1-1
1.3 Warranty information...........................................................................................................................................1-1
1.4 Manual addenda...................................................................................................................................................1-1
1.5 Safety symbols and terms ....................................................................................................................................1-1
1.6 Specifications.......................................................................................................................................................1-2
1.7 Unpacking and inspection....................................................................................................................................1-2
1.7.1 Inspection for damage................................................................................................................................1-2
1.7.2 Shipment contents......................................................................................................................................1-2
1.7.3 Instruction manual......................................................................................................................................1-2
1.8 Optional accessories.............................................................................................................................................1-2
1.8.1 Connecting cables ......................................................................................................................................1-2
1.8.2 Rack mount kits .........................................................................................................................................1-2
2 Operation
2.1 Introduction..........................................................................................................................................................2-1
2.2 Safety precautions................................................................................................................................................ 2-1
2.3 Preparation for use ...............................................................................................................................................2-1
2.3.1 Line voltage selection ................................................................................................................................2-1
2.3.2 Line fuse.....................................................................................................................................................2-2
2.3.3 Line cord ....................................................................................................................................................2-2
2.3.4 Connection to the other instruments ..........................................................................................................2-2
2.4 Front panel summary ...........................................................................................................................................2-2
2.5 Rear panel summary.............................................................................................................................................2-4
2.6 Guide to operation................................................................................................................................................2-6
2.6.1 Setting the output voltage ..........................................................................................................................2-6
2.6.2 Setting the voltage limit.............................................................................................................................2-7
2.6.3 Setting the current limit..............................................................................................................................2-7
2.6.4 Setting the current trip................................................................................................................................2-7
2.6.5 Primary trip ................................................................................................................................................2-7
2.6.6 Reset mode.................................................................................................................................................2-7
2.6.7 Store and recall...........................................................................................................................................2-7
2.6.8 Output filter................................................................................................................................................2-8
2.6.9 Error and status messages ..........................................................................................................................2-8
2.6.10 Analog programming and monitor.............................................................................................................2-9
2.6.11 Default setup.............................................................................................................................................. 2-9
i
3 IEEE-488 Programming
3.1 Introduction.......................................................................................................................................................... 3-1
3.2 Bus connections................................................................................................................................................... 3-1
3.3 Primary address ................................................................................................................................................... 3-1
3.4 Command syntax................................................................................................................................................. 3-1
3.4.1 Multiple commands................................................................................................................................... 3-1
3.4.2 Command buffer........................................................................................................................................ 3-1
3.4.3 Command queries...................................................................................................................................... 3-1
3.4.4 Command examples................................................................................................................................... 3-2
3.5 Detailed command description............................................................................................................................ 3-2
3.5.1 Output control commands.......................................................................................................................... 3-3
3.5.2 Setting control commands ......................................................................................................................... 3-3
3.5.3 Interface control commands ...................................................................................................................... 3-4
3.5.4 Status reporting commands........................................................................................................................ 3-4
3.6 Status reporting.................................................................................................................................................... 3-4
3.6.1 Status byte register..................................................................................................................................... 3-5
3.6.2 Standard event status register .................................................................................................................... 3-5
3.7 GPIB error messages ........................................................................................................................................... 3-7
3.7.1 Err6 (Syntax Error over GPIB).................................................................................................................. 3-7
3.7.2 Err7 (Illegal Parameter entered over GPIB).............................................................................................. 3-7
3.7.3 Err8 (GPIB output queue full)................................................................................................................... 3-7
3.8 Program examples ............................................................................................................................................... 3-7
3.8.1 Computer hardware requirements.............................................................................................................. 3-7
3.8.2 Computer software requirements............................................................................................................... 3-7
3.8.3 General program instructions .................................................................................................................... 3-7
3.8.4 Program example 1, QBasic...................................................................................................................... 3-8
3.8.5 Program example 2, Turbo C..................................................................................................................... 3-9
4 Performance V erification
4.1 Introduction.......................................................................................................................................................... 4-1
4.2 Environmental conditions.................................................................................................................................... 4-1
4.3 Warm-up period................................................................................................................................................... 4-1
4.4 Recommended test equipment............................................................................................................................. 4-1
4.5 Verification procedures ....................................................................................................................................... 4-2
4.5.1 DC voltage accuracy.................................................................................................................................. 4-2
4.5.2 DC current accuracy.................................................................................................................................. 4-3
4.5.3 Load regulation.......................................................................................................................................... 4-5
4.5.4 Output voltage ripple................................................................................................................................. 4-5
5 Servicing
5.1 Introduction.......................................................................................................................................................... 5-1
5.2 Troubleshooting................................................................................................................................................... 5-1
5.2.1 Line power................................................................................................................................................. 5-1
5.2.2 Power-on reset........................................................................................................................................... 5-1
5.2.3 Stuck keys.................................................................................................................................................. 5-1
5.2.4 Output problems ........................................................................................................................................ 5-1
5.2.5 No high voltage.......................................................................................................................................... 5-2
5.2.6 Repeated trips ............................................................................................................................................ 5-2
5.2.7 Rear panel voltage set mode...................................................................................................................... 5-2
ii
5.2.8 Front panel test...........................................................................................................................................5-2
5.3 Calibration............................................................................................................................................................5-2
5.4 Circuit description................................................................................................................................................5-2
5.4.1 Component locations..................................................................................................................................5-2
5.4.2 Voltage control...........................................................................................................................................5-2
5.4.3 Pre-regulator and high-frequency inverter.................................................................................................5-3
5.4.4 Limits and trips ..........................................................................................................................................5-3
5.4.5 A/Ds and D/As...........................................................................................................................................5-4
5.4.6 Microprocessor control ..............................................................................................................................5-4
5.4.7 GPIB and front panel interface ..................................................................................................................5-4
5.4.8 Low voltage power supplies ......................................................................................................................5-4
5.4.9 Front panel .................................................................................................................................................5-5
5.4.10 High voltage section...................................................................................................................................5-5
5.5 Disassembly .........................................................................................................................................................5-5
5.5.1 Cover removal............................................................................................................................................5-5
5.5.2 Front panel and display board removal......................................................................................................5-5
5.5.3 Main circuit board removal........................................................................................................................5-6
5.5.4 High-voltage module removal ...................................................................................................................5-6
5.5.5 Miscellaneous parts removal......................................................................................................................5-6
5.5.6 Reassembly ................................................................................................................................................5-6
6 Replaceable Parts
6.1 Introduction..........................................................................................................................................................6-1
6.2 Parts list................................................................................................................................................................6-1
6.3 Ordering information ...........................................................................................................................................6-1
6.4 Factory service.....................................................................................................................................................6-1
iii
List of Illustrations
2 Operation
Figure 2-1 Model 248 front panel..................................................................................................................................2-2
Figure 2-2 Model 248 rear panel ...................................................................................................................................2-4
Figure 2-3 Typical high voltage connections ................................................................................................................2-5
Figure 2-4 Voltage monitor, current monitor connections ............................................................................................2-6
Figure 2-5 Voltage set, current monitor connections.....................................................................................................2-6
3 IEEE-488 Programming
Figure 3-1 Status model.................................................................................................................................................3-5
4 Performance V erification
Figure 4-1 Connections for DC voltage accuracy tests .................................................................................................4-2
Figure 4-2 Connections for DC current accuracy tests.................................................................................................. 4-4
Figure 4-3 Connections for load regulation tests...........................................................................................................4-6
Figure 4-4 Connections for output voltage ripple tests..................................................................................................4-6
5 Servicing
Figure 5-1 Model 248 exploded view............................................................................................................................5-6
v
List of Tables
2 Operation
Table 2-1 Filter limits...................................................................................................................................................2-8
Table 2-2 Error messages.............................................................................................................................................2-8
Table 2-3 Status messages............................................................................................................................................2-9
Table 2-4 Analog monitor examples............................................................................................................................2-9
Table 2-5 Analog input voltage examples....................................................................................................................2-9
Table 2-6 Current monitor examples............................................................................................................................2-9
Table 2-7 Default setup ................................................................................................................................................2-9
3 IEEE-488 Programming
Table 3-1 Command summary.....................................................................................................................................3-2
Table 3-2 Status byte....................................................................................................................................................3-6
Table 3-3 Standard event status register.......................................................................................................................3-6
4 Performance V erification
Table 4-1 Recommended verification test equipment..................................................................................................4-1
Table 4-2 DC voltage accuracy summary ....................................................................................................................4-3
Table 4-3 DC current accuracy summary.....................................................................................................................4-4
5 Servicing
Table 5-1 Output problems and repair information......................................................................................................5-1
vii
1
General Information
1.1 Introduction
The Model 248 High Voltage Supply , designed for use in the
laboratory or for test applications, features reversible polarity, excellent regulation, and low output voltage ripple. The
digital displays provide accurate readings of voltage and current, and digital entry of current and voltage values allow
easy, precise setting of output values. Output voltage can be
set from the front panel, via a remote analog voltage, or over
the standard IEEE-488 interface. Voltage and current signals
are also available for remote monitoring.
1.2 Features
Key Model 248 features include:
• High voltage operation — The unit can source voltages
up to a maximum of 5kV.
• 25W power capability — The Model 248 can source
currents up to 5mA at 5kV.
• Ease of use — Digital displays and data input simplify
voltage and current voltage setting.
• Programmable voltage limit — Voltage limit can be
preset to assure safe operation.
• Programmable current limits — Current limit and trip
point can be preset to prevent possible equipment damage.
• Output filter — Reduces output ripple and noise.
• Monitor outputs — Provide 0 -10V signals that can be
used to monitor the output voltage and current.
• External voltage control — Allows the voltage source
output value to be controlled with a 0 -10V input signal.
• Standard IEEE-488 interface — Allows the instrument
to be controlled over the IEEE-488 bus.
1.3 W arranty information
Warranty information is located on the inside front cover of
this instruction manual. Should your Model 248 require warranty service, contact your Keithley representative or an authorized repair facility in your area for further information.
When returning the unit for repair, be sure to fill out and include the service form at the back of this manual in order to
provide the repair facility with the necessary information.
1.4 Manual addenda
Any improvements or changes concerning the unit or manual
will be explained on an addendum. Addenda are provided in
a page replacement format. Simply replace the obsolete pages with the new pages where indicated.
1.5 Safety symbols and terms
The following symbols and terms may be found on an instrument or used in this manual.
The symbol indicates that 1000V or more may be
present on the terminals.
!
The symbol on equipment indicates that you should
refer to the operating instructions located in the instruction
manual.
The WARNING heading used in this manual explains dangers that might result in personal injury or death. Always
read the associated information very carefully before performing the indicated procedure.
1-1
General Information
The CAUTION heading used in this manual explains hazards that could damage the unit. Such damage may invalidate
the warranty.
1.6 Specifications
Detailed Model 248 specifications are located at the front of
this manual.
1.7 Unpacking and inspection
1.7.1 Inspection for damage
Upon receiving the Model 248, carefully unpack the unit,
and inspect for any obvious signs of physical damage that
might have occurred during shipment. Notify the shipping
agent of any damage immediately.
1.7.2 Shipment contents
The following items are included with every Model 248 order:
• Model 248 High Voltage Supply
• Model 248 Instruction Manual
• Additional accessories as ordered
1.7.3 Instruction manual
If an additional Model 248 Instruction Manual is required,
order the manual package, Keithley part number 248-901-
00. The manual package includes an instruction manual and
any pertinent addenda.
1.8 Optional accessories
The following optional accessories are av ailable for use with
the Model 248.
1.8.1 Connecting cables
Model 248-SHV : SHV -to-SHV high v oltage cable, 10 feet in
length.
Model 248-MHV: SHV-to-MHV high voltage cable, 10 feet
in length.
1.8.2 Rack mount kits
Model 248-RMK-1: Mounts a single Model 248 in a stan-
dard 19-inch rack.
Model 248-RMK-2: Mounts two Model 248s side-by-side in
a standard 19-inch rack.
1-2
2
Operation
2.1 Introduction
This section contains detailed information on operating the
Model 248 from the front panel. For IEEE-488 bus programming information, refer to Section 3.
2.2 Safety precautions
Be sure to observe the safety precautions below before operating the Model 248.
WARNING
The Model 248 is capable of sourcing
hazardous high voltages that can cause
personal injury or death due to electric
shock. This unit should be used only by
qualified personnel who recognize the
dangers of high voltages.
Make certain that the source is turned
off and that high voltage is completely
discharged before removing the high
voltage cable. High voltage cables can
store charge if they are disconnected
from the supply while the high voltage is
on. The charge on the cable can cause
injury or damage even after the cable is
disconnected from the unit.
CAUTION
Do not change the high voltage polarity
unless the power is off. Doing so may
damage the unit.
2.3 Preparation for use
2.3.1 Line voltage selection
The Model 248 operates from a 100, 120, 220, or 240V nominal AC power source with a line frequency of 50 or 60 Hz.
Before connecting the power cord to a power source, verify
that the line voltage selector card, located in the rear panel
fuse holder, is set for the correct AC line voltage.
CAUTION
This instrument may be damaged if operated with the line voltage selector set
for the wrong AC line voltage, or if the
wrong fuse is installed.
Conversion to other AC input voltages requires a change in
the fuse holder voltage card position and fuse value.
WARNING
Disconnect the line cord before changing the line voltage setting or replacing
the fuse.
Disconnect the power cord, open the fuse holder cover door,
and rotate the fuse-pull lever to remov e the fuse. Remove the
small printed circuit board. Select the operating voltage by
orienting the printed circuit board to the desired position.
Press the circuit board firmly into its slot so that the desired
voltage is visible. Rotate the fuse-pull lever back into its nor mal position, and insert the correct fuse into the fuse holder.
See paragraph 2.3.2 for correct line fuse information.
2-1
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