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Model 7708 40-Channel Differential Multiplexer
with Automatic CJC
User's Guide
PA-744 Rev. C / 8-03
A GREATER MEASURE OF CONFIDENCE
Safety Precautions
The following safety precautions should be observed before using Operators of this product must be protected from electric shock at
this product and any associated instrumentation. Although some in- all times. The responsible body must ensure that operators are pre-
struments and accessories would normally be used with non-haz- vented access and/or insulated from every connection point. In
ardous voltages, there are situations where hazardous conditions some cases, connections must be exposed to potential human con-
may be present. tact. Product operators in these circumstances must be trained to
This product is intended for use by qualified personnel who recog- protect themselves from the risk of electric shock. If the circuit is
nize shock hazards and are familiar with the safety precautions re- capable of operating at or above 1000 volts, no conductive part of
quired to avoid possible injury. Read and follow all installation, the circuit may be exposed.
operation, and maintenance information carefully before using the Do not connect switching cards directly to unlimited power circuits.
product. Refer to the manual for complete product specifications. They are intended to be used with impedance limited sources.
If the product is used in a manner not specified, the protection pro- NEVER connect switching cards directly to AC mains. When con-
vided by the product may be impaired. necting sources to switching cards, install protective devices to lim-
it fault current and voltage to the card.
The types of product users are:
Before operating an instrument, make sure the line cord is connect-
Responsible body is the individual or group responsible for the use
ed to a properly grounded power receptacle. Inspect the connecting
and maintenance of equipment, for ensuring that the equipment is
cables, test leads, and jumpers for possible wear, cracks, or breaks
operated within its specifications and operating limits, and for en-
before each use.
suring that operators are adequately trained.
When installing equipment where access to the main power cord is
Operators use the product for its intended function. They must be
restricted, such as rack mounting, a separate main input power dis-
trained in electrical safety procedures and proper use of the instru-
connect device must be provided, in close proximity to the equip-
ment. They must be protected from electric shock and contact with
ment and within easy reach of the operator.
hazardous live circuits.
For maximum safety, do not touch the product, test cables, or any
Maintenance personnel perform routine procedures on the product
other instruments while power is applied to the circuit under test.
to keep it operating properly, for example, setting the line voltage
ALWAYS remove power from the entire test system and discharge
or replacing consumable materials. Maintenance procedures are de-
any capacitors before: connecting or disconnecting cables or jump-
scribed in the manual. The procedures explicitly state if the operator
ers, installing or removing switching cards, or making internal
may perform them. Otherwise, they should be performed only by
changes, such as installing or removing jumpers.
service personnel.
Service personnel are trained to work on live circuits, and perform Do not touch any object that could provide a current path to the com-
safe installations and repairs of products. Only properly trained ser- mon side of the circuit under test or power line (earth) ground. Always
vice personnel may perform installation and service procedures. make measurements with dry hands while standing on a dry, insulated
surface capable of withstanding the voltage being measured.
Keithley products are designed for use with electrical signals that
are rated Measurement Category I and Measurement Category II, as The instrument and accessories must be used in accordance with its
described in the International Electrotechnical Commission (IEC) specifications and operating instructions or the safety of the equip-
Standard IEC 60664. Most measurement, control, and data I/O sig- ment may be impaired.
nals are Measurement Category I and must not be directly connect- Do not exceed the maximum signal levels of the instruments and ac-
ed to mains voltage or to voltage sources with high transient over- cessories, as defined in the specifications and operating informa-
voltages. Measurement Category II connections require protection tion, and as shown on the instrument or test fixture panels, or
for high transient over-voltages often associated with local AC switching card.
mains connections. Assume all measurement, control, and data I/O
When fuses are used in a product, replace with same type and rating
connections are for connection to Category I sources unless other-
for continued protection against fire hazard.
wise marked or described in the Manual.
Chassis connections must only be used as shield connections for
Exercise extreme caution when a shock hazard is present. Lethal
measuring circuits, NOT as safety earth ground connections.
voltage may be present on cable connector jacks or test fixtures. The
American National Standards Institute (ANSI) states that a shock If you are using a test fixture, keep the lid closed while power is ap-
hazard exists when voltage levels greater than 30V RMS, 42.4V plied to the device under test. Safe operation requires the use of a
peak, or 60VDC are present. A good safety practice is to expect lid interlock.
that hazardous voltage is present in any unknown circuit before
measuring. 5/03
If a screw is present, connect it to safety earth ground using the To maintain protection from electric shock and fire, replacement
wire recommended in the user documentation. components in mains circuits, including the power transformer, test
leads, and input jacks, must be purchased from Keithley Instru-
The ! symbol on an instrument indicates that the user should re- ments. Standard fuses, with applicable national safety approvals,
fer to the operating instructions located in the manual. 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
The symbol on an instrument shows that it can source or mea- long as they are equivalent to the original component. (Note that se-
sure 1000 volts or more, including the combined effect of normal lected parts should be purchased only through Keithley Instruments
and common mode voltages. Use standard safety precautions to to maintain accuracy and functionality of the product.) If you are
avoid personal contact with these voltages. unsure about the applicability of a replacement component, call a
Keithley Instruments office for information.
The symbol indicates a connection terminal to the equipment
frame. To clean an instrument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
The WARNING heading in a manual explains dangers that might cleaner directly to the instrument or allow liquids to enter or spill
result in personal injury or death. Always read the associated infor- on the instrument. Products that consist of a circuit board with no
mation very carefully before performing the indicated procedure. case or chassis (e.g., data acquisition board for installation into a
The CAUTION heading in a manual explains hazards that could computer) should never require cleaning if handled according to in-
damage the instrument. Such damage may invalidate the warranty. structions. If the board becomes contaminated and operation is af-
fected, the board should be returned to the factory for proper
Instrumentation and accessories shall not be connected to humans.
cleaning/servicing.
Before performing any maintenance, disconnect the line cord and
all test cables.
Model 7708
Keithley Instruments, Inc.
40-Channel Differential Multiplexer with Automatic CJC
28775 Aurora Road
Cleveland, Ohio 44139
User's Guide
(440) 248-0400
Fax: (440) 248-6168
www.keithley.com
Introduction
The Model 7708 is a 40-channel differential multiplexer card with the following features: