Keithley 7158 User manual

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Model 7158 low Current
Scanner Card
Instruction Manual
Contains Operating and Servicing Information
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Model 7158 Low Current Scanner Card
Instruction Manual
0 1987, Keithley Instruments, Inc.
Test Instrumentation Group
All rights reserved.
Cleveland, Ohio, U.S.A.
June 1990, Second Printing
Document Number: 7158-901-01 Rev. B
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SAFETY PRECAUTIONS
The following safety precautions should be observed before using this
product and any associated instrumentation. Although 6ome 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 us-
ing the product.
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. A good safety practice is to expect that hazardous voltage is
present in any unknown circuit before measuring.
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 we.
For maximum safety, do not touch the product, test cables, or any other
instruments while power is applied to the circuit under test. ALWAYS re-
move power from the entire test system and discharge any capacitors be-
fore: connecting or disconnecting cables or jumpers, installing or
removing switching cards, or making internal changes, such as installing
or removing jumpers.
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.
Do not exceed the maximum signal levels of the instruments and awes-
series, as defined in the specifications and operating information, and as
shown on the instrument or test fixture rear panel, or switching card.
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 main. When connecting sources to switch-
ing cards, install protective devices to limit fault current and voltage to
the card.
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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 measur-
ing 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 on the test fixture, connect it to safety earth
ground using #18 AWG or larger wire.
The f symbol on an instrument or accessory indicates that 1OOOVor
more may be present on the terminals. Refer to the product manual for de-
tailed operating information.
Instrumentation and accessories should not be connected to humans
Maintenance should be performed by qualified service personnel. Before
performing any maintenance, disconnect the line cord and all test cables.
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SPECIFICATIONS
MODEL 7158 LOW CURRENT SCANNER CARD
CHANNBLS PER CARD: 10
CONTACT CONFIGURATION: Single pole. When a channel is open, sign81 HI is con-
nected to signal LO. Signal LO is common for ail 10 channels and aulput.
CONNIXTOR TYPE; BNC
RELAY DRIVE CURRENT: lOOmA per card typical.
MAXIMUM SIGNAL LEVEL; lOOmA, 3OV, peak (resistive load)
368 BANDWImHz lM& typical.
CONTACT LIFE: 10’ closures (cold switching); 10’ closures (at maximum signal level)
CONTACT RESISTANCE: <Xl to rated life
CONTACT POTBNTIALr <20,&V
ACTUATION TIME: <Ims, exclusive of mainframe
OPPSET CURReNT: <10’“A (<3 x 10-laA typical)
COMMON MODR VOLTAGE: 3OV peak
GENRRAL
ENVIRONMENT,
Operating: 8’ to 50°C, up to 35’C at 70% RH
storage: -2.5” to 65°C
DIMENSIONS, WEIGHI! 32mm high x 114mm wide x 272mm long (1%” x 4%” x
10%“). Net weight 0.5gkg (20.5 oz.)
ACCBSSORY SUPPLIED; Model 4801 Low Noise Cable
ACCBSSORY AVAILABLG; Model 4804 t&x female to BNC male adapter
Specifications subject to change without notice.
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TABLE OF CONTENTS
SECTION 1 - GENERAL INFORMATION
1.1
1.2
1.3
1.4
I.5
I.6
Introduction. ........................................ 1
warrant\~ Information ................................ 1
Manual.Addenda .................................... 2
Safety Symbols and Terms ........................... 2
Unpackmg and lnspectlon ............................ 2
Specifications ........................................ 3
SECTION 2 - OPERATION
2.1 Introduction ......................................... 5
2.2 Safety Precautions ................................... 5
2.2.1 High Impedance Considerations .................... 5
2.2.2 Static Precautions .................................. 6
2.3 Connections and Cabling ............................. 6
2.4 Installation and Removal ............................. 8
2.5 Operation .......................................... 10
2.5.1 Scanner Control of the Channels ................... 11
2.52 Operation Notes .................................. 18
2.6 Applications. ....................................... 18
SECTION 3 - SERVICING INFORMATION
3.I
3.2
3.3
3.4
3.5
3.6
Introduction ........................................ 25
Handling and Cleaning ............................. 25
Relay Replacement .................................. 26
Recommended Test Equipment ....................... W
Offset Current Test ................................. W
Contact Resistance Test .............................. 29
SECTION 4 - REPLACEABLE PARTS
4.1
4.2
4.3
4.4
4.5
introduction ........................................ 33
Parts Lists ......................................... 33
Ordering Information ............................... 33
Factory Service ..................................... 35
Component Layout and Schematic Diagram ........... 35
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LIST OF TABLES
SECTION 2 - OPERATION
2-l
2-2
2-3
Example Channel Assignments in 2-P& Mode. 12
Example Channel Assignments in l-Pole Mode 13
Example Channel Assignments in Matrix (O-Pole)
Mode 14
2-4 Scanner Control of Model 7158 4-Pole Mode 15
2-5 Scanner Control of Model 7l58 2-Pole Mode 15
2-6 Scanner Control of Model 7l58 l-Pole Mode. 16
2-7 Scanner Control of Model 7158 Matrix (O-Pole) Mode. 17
SECTION 3 - SERVICING INFORMATION
3-l Recommended Test Equipment, 27
SECTION 4 - REPLACEABLE PARTS
4-l Model 7l58 Electrical Parts. 34
4-2 Model 7158 Mechanical Parts 35
iii/iv
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LIST OF ILLUSTRATIONS
SECTION 2 - OPERATION
2-l Multi-Card Connection. 7
2-2 Installing Card in Model 705, 9
2-3 Installing Card in Model 706.. 10
2-4 Model 7l58 Simplified Schematic, 11
2-5 Capacitor Leakage Schematic 20
2-6 Capacitor Leakage Instrument Setu x ““” ., 21
2-7 Measuring Leakages with One Car 23
SECTION 3 - SERVICING INFORMATION
3-l Offset Current 28
3-2 Coax Pigtail Preparation. 30
3-3 Contact Resistance 31
SECTION 4 - REPLACEABLE PARTS
4-l Model 7l58 Component Layout 36
4-2 Model 7l58 Schematic Diagram 37
v/vi
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SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION
The Model 7l58 Low Current Scanner Card has ten channels of paired
single-pole single-throw (SET), normally open (NO) relays. The card
will switch any one of ten signals to one output, or switch one signal
to any one of ten outputs.
Signal HI is connected to signal LO (analog ground) when the scanner
mainframe channel is open, and to output HI when the channel is clos-
ed. Signal LO is common to all ten channels and the output. An addi-
tional relay isolates all circuitry on the card from the output when no
channel is closed.
Features of the scanner card include:
l Low offset current error (<IpA specified, <30fA typical)
l Switching of AC or DC signals up to lOOmA.
l BNC input and output connectors.
l Two outputs for daisy-chaining of Model 7158 cards.
l Configurable for low current or low voltage switching.
The Model 7l58 is field-installable in the Models 705 and 706 scanner
mainframes.
1.2 WARRANTY INFORMATION
Warranty information is stated on the inside front cover of this manual.
If there is a need for service, contact the Keithley representative or
authorized repair facility in your area. Check the back cover for ad-
dresses. The service form supplied at the end of the manual should
be used to provide the service facility with information concerning any
difficulty.
1
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1.3 MANUAL ADDENDA
Product improvements or changes to this manual will be explained on
an addendum included with the manual. It is recommended that this
information be incorporated immediately into the appropriate ptaces
in the manual.
If an additional instruction manual is required, order the manual
package (Keithley Part Number 7158-901-00). The manual package in-
cludes an instruction manual and all pertinent addenda.
1.4 SAFETY SYMBOLS AND TERMS
The symbol A on the card denotes that the user should refer to the
operating instructions.
The WARNING used in this manual explains dangers that could result
in personal injury or death.
The CAUTION used in this manual explains hazards that could damage
the card.
1.5 UNPACKING AND INSPECTION
The Model 7158was inspected both electrically and mechanically before
shipment. Upon receiving the Model 7l58, unpack all items from the
shippin carton and check for any obvious damage that may have oc-
curred 6:urmg transit. Report any damage to the shipping agent. Re-
tain and use the original packaging materials in case reshipment is
necessary. The following items are shipped with every Model 7158:
Model 7158 Low Current Scanner Card
Model 7l58 Instruction Manual
Model 4801 Low Noise Coax Cable (48 in., supplied accessory)
2
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The following item is an optional accessory:
Model 4804 Triax (F) to BNC (M) Adapter
1.6 SPECIFICATIONS
Detailed specifications of the Model 7158 precede the Table of Contents
of this manual.
314
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SECTION 2
OPERATION
2.1 INTRODUCTION
This section contains an operation overview, safety information, con-
nections and cabling information, an installation procedure, operating
instructions, and an application for the card.
2.2 SAFETY PRECAUTIONS
WARNING
Maintain inputs and outputs withln 30V peak of earth
ground. lMn off all power and discharge stored energy in
external cimultry before making or breaklng connections.
1. The maximum signal level is lOOmA peak (30V compliance).
2. Make sure the scanner mainframes are grounded through an earth
grounded receptacle before operation.
3. Inspect all connections for wear and defects such as cracks and ex-
posed wires.
2.2.1 High Impedance Considerations
Because of the high impedance circuits on the card, be careful when
handling it to avoid contamination from such foreign materials as body
oils. Such contamination can substantially lower leakage resistance,
degrading performance.
Handle the card only by the edges. If you remove the relay covers, be
careful not to touch board surfaces or exposed parts.
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To avoid dirt build-up over a period of time, operate the scanner and
scanner card only in a clean environment. If contamination is suspected,
the card should be carefully cleaned using the procedure given in
paragraph 3.2.
2.2.2 Static Precautions
The card’s IC chips are static-sensitive and can be damaged by static
discharge, rendering the card partially or completely inoperative. For
that reason, be careful not to touch exposed areas of the circuit board
if static is thought to be a problem,
CAUTION
Static discharge to exposed circuits can damage the card
and might invalidate the warranty.
2.3 CONNECTIONS AND CABLING
Signal input and output connections are made with BNC connectors
on the card. The locations for each channel input and the outputs are
indicated on the relay covers. The two output connectors permit multi-
ple Model 7158cards to be connected together. For example, a 20.channel
scanner system can be connected as shown in Figure 2-l.
In addition to card-to-card connections, the Model 4801 low noise cable
can be used for scanner-to-scanner connections when daisy-chaining
up to five scanner mainframes.
CAUTIONCAUTION
Keithley’s Model 7058 low current scanner card has trlaxKelthley’s Model 7058 low current scanner card has trlax
connectors, Be careful not to interchange trlax and BNCconnectors, Be careful not to interchange trlax and BNC
connectors to avold damaging them.connectors to avold damaging them.
Caps are provided for all connectors. Unused connectors should be cap-
ped to prevent contamination of the insulators, which could degrade
performance.
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The supplied low noise coax cable has a conductive lubricant (graphite)
to minimize the error current caused by friction between cable insulators
and conductors. This becomes a consideration when measuring cur-
rent levels in the picoamp range. Since cable flexing due to vibration
and cable expansion and contraction due to temperature fluctuation
cause friction, the signal cables should be fastened to a rigid surface
and not subject to temperature changes. (The temperature changes nor-
mally experienced in laboratory environments are not a problem).
Figure 2-1. Multi-Card Connection
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2.4 INSTALLATION AND REMOVAL
The procedures to install the Model 7l58 in the Model 705 or 706 Scan-
ners are similar except for the card orientation. See Figure 2-2 for a
Model 705 and Figure 2-3 for a Model 706.
WARNING
Turn off the scanner mainframe and disconnect the power
cord before installing or removing scanner cards.
CAUTION
Leave the Model 7158 In Its anti-static bag until ready for
cabling snd installing to avoid possible static damage.
Once the card is cabled, insert it card edge first into the scanner main-
frame by aligning it with the grooves in the appropriate slot. Make sure
it is proper1 seated into the mainframe connector. Push the locking
tabs forwar 1( to the center of the card to lock it in.
To remove a card, first turn off the mainframe and all other equipment
connected to the card. Unfasten the locking tabs on the card by pull-
ing the tabs outward. Grasp the end of the card and carefully pull it
out of the mainframe.
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I J
Figure 2-2. Installing Card in Model 705
9
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Figure 2-3. lnstalllng Card In Model 706
2.5 OPERATION
As shown in Figure 24 for current switching, each channel on the
Model 7158has a pair of single-pole single-thmw (SKI), normally open
(NO) relays. ‘Ihe relay pair switches signal HI between signal IQ (analog
ground) and output HI. Signal LO (outside shell of the BNC) is com-
mon to all channels and outputs in the system.
An additional relay isolates all circuitry on the card from the outputs
when no channel is closed. That is, the isolation relay is open when
all channels are open, and it is closed when any channel is closed,
10
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The card is designed for scanning current sources: when a channel is
not selected, a current path is maintained through its signal HI to LO
relay. This protects sensitive devices under test from spikes when
switching an ammeter in and out of each circuit.
The Model 7158can also be configured for voltage switching (schematic
shown in Figure 2-48). This configuration is made possible by remov-
ing the socketed driver chips (Ul and U2) for the channel HI to LO
relay coils. (These chips are static sensitive. See paragraph 3.2 for handl-
ing precautions)
A. Current Swltchlng
6 8. Voltage Switching - -
Flgure 2-4. Model 7166 Slmpllfled Schematic
11
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