Keithley 487, 486 User Manual

Model 486

PICOAMMETER

Model 487

PlCOAMMETER/SOURCE

QUICK REFERENCE GUIDE

INTRODUCTION

This quick reference guide contains descriptions of vari­ous features and information concerning the operation of
the Model 4861487.

~21990, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Document Number: 486-903-01 Rev. A

1

Asyst ts a registered trademark of Asyst Software technologies.

Hewtett-Packard Is a registered trademark of Hewlett-Packard

Company.

IBM and AT are registered trademarks and PC/XT is a trademark
of International Business Machines, I~C.
PC&488 is a registered trademark of Capital Equipment Cow
ration.

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TABLE OF CONTENTS

SAFETY WARNINGS

ERROR MESSAGES ......................... 7

CURRENT MEASUREMENTS

VOLTAGE SOURCE (Model 487) .............. 14

V/l OHMS MEASUREMENTS (Model 487)

MENU .................................... 21

FRONT PANEL TRIGGERING ................. 22

EXTERNAL TRIGGERING .................... 24

DATA STORE OPERATION .................. 26

ANALOG OUTPUT .......................... 27

TALK-ONLY

IEEE-488 PROGRAMMING .................. .29

Device-dependent Commands ................. 29

Display Intensity ........................ 29

Reading Source ........................ 29

Zero Check and Correct .................. 29

Display
V/lOhms
Data Format

Hit Control ............................ 31

Self-Test
EOI and Bus Hold-off

Default Conditions or Calibration ...........

SRQ

Data Store ............................ 32

Operate

Filters ................................ 33

Interval ............................... 33

Range................................3 3

Integration

...............................

.............................

...............................

.........................

..................

...........................

...........................

..............................

...................

..............................

............................

.......

19

28

..3 0
..3 0

39
31

.31

32

..3 2

33

34

5
8

3

Trigger ...............................

Status.. ..............................

Voltage Source (487)

Delay ................................

Execute ............................

Terminator ..........................

Relative ..............................

Data Formats
SRQ Mask and Serial Poll Byte
StatusWords

..............................

............................

....................

................

i: l

35

..3 5

35 a

..3 5

36
36
40

..4 1

a

a

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SAFETY WARNINGS

The following precautions should be observed before us-

ing Model 488/487. Refer to main manual for detailed

safety information and complete operating instructions.

The Model 48W487 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 instruction manual carefully before

using the instrument.

Before operating the instrument, make sure the line cord

is connected to a properly grounded power receptacle.

Exercise extreme caution when a shock hazard is pre-

sent. Lethal voltages may be present on the test fixture or

the Model 487 output jacks. The American National Stan-

dards 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

hazardous voltage is present in any unknown circuit

before measuring.

Inspect the connecting cables, test leads, and jumpers

for possible wear, cracks, or breaks before each use.

5

For maximum safety, do not touch the Model 487 con­nections, test fixture, test cables or connections to any
other instruments while power is applied to the circuit un­der test. Turn off all power and discharge all capacitors
before connecting or disconnecting cables or jumpers.
Also, keep the test fixture lid closed while power is ap­plied to the device under test. Safe operation requires the
use of the lid interlock.

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.

Do not exceed the maximum signal levels of the instru­ment, as shown on the rear panel and as defined in the

specifications and operation section of the instruction

manual.

Connect the chassis of the test fixture to safety earth
ground using #I 8 AWG or larger wire.

Instrumentation and accessories should not be con-

nected to humans.

Maintenance should only be performed by qualified serv­ice personnel. Before performing any maintenance, dis­connect the line cord and all test cables from the instru­ment.

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ERROR MESSAGES

Table 1. Error Messages

Message

NO DEFLTS
UNCAL
ROM ERROR

RAM ERROR
TRG OVERUN

CAL VALUE
CAL ERROR

CAL LOCK

CAL ZCHK
INTERLOCK

Description

Checksum error in default condi­tion during power-up.
Checksum error in calibration
during power-up
Failed ROM self-test.
Failed RAM self-test.
Trigger overrun; instrument trig­gered while still processing a pre­vious trigger.
Calibration value conflicts with
the currently selected range.
Calibration value not within allow­able limits.
Sent calibration command with
calibration switch (CAL LOCK)
disabled.

Cannot calibrate picoammeter
with zero check enabled.
Tried to put V-Source of Model

487 in operate while an enabled

safety interlock switch is open.

CURRENT MEASUREMENTS

Current Ranges

SHIFT

q

The available current ranges of the Model 4861487 are
listed in Table 2.

Table 2. Current Ranges

v RANGE A

El 0

AUTO

RANGE

.

2nA

20nA

200nA

2c1A

20/.iA

2oopA

2mA

‘Higher voltages require current to be limited to 3mA.

2.19999nA

21.9999nA

219.999nA

2.19999pA

21.9999pA

219.999uA

2.19999inA

35OVdc
35OVdc
35OVdc
35OVdc

5OVdc
50Vdc
50Vdc

Autorange is enabled by pressing SHIFTand then AUTO

RANGE in that order.

To avoid possible damage to the instru­ment, do not apply more than 5OVdc to
the input when autorange is enabled
(unless an external series resistor to

limit current to 3mA is used).

CAUTION

Zero Check and Correct

ZERO

SHIFT

CHECK

q El

CORRECT

When zero check is enabled, the input amplifier is inter­nally disconnected from the input connector of the instru­ment. A 1 OOkG resistor shunts the input connector, and
the instrument displays the offset of the selected range.

When zero correction is performed, the offset is meas­ured and algebraically subtracted from every subsequent
reading (including zero checked readings).

Zero check is enabled by pressing ZERO CHECK.
Pressing ZERO CHECK a second time disables the fea­ture.

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When zero correction is performed, only the present

range is zero corrected. Before making measurements, it
is recommended that each current range be zero cor­rected.

To perform zero correction:

1. Enable zero check.

2. To perform zero correction, press SHIFT and then
CORRECT in that order.

Filters

SHIFT

cl

Filtering is used to stabilize noisy measurements. The
Model 486/487 has two available filters; a digital filter and
an analog filter. The digital filter bases the reading on the
weighted average of a number of measurement conver­sions. The analog filter is a simple RC filter whose time
constant varies with the selected range.

When the filter is enabled, the selected filter(s) (digital fil­ter, analog filter or both) will be used.

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To check or change the filter selection:

Press SHIFT and then FILTER SELECT in that or­der. One of the following messages will be dis­played to indicate the currently selected filter(s):

FILTER DIGITAL
FILTER ANALOG
FILTER DIG+AN

To select a different filter, use the rotary knob or the

4 and b keys to display the desired filter selection.

Enter the displayed filter selection by pressing
SHIFT and then FILTER SELECT.

(Digital filter selected)
(Analog filter selected)
(Both digital and analog

filters selected)

Rel

REL

0

q

The rel (relative) feature serves as a means of baseline
suppression by allowing a stored offset value to be sub­tracted from subsequent readings. When rel is enabled,
the instrument takes the currently displayed reading as a
baseline value. All subsequent readings represent the
difference between the applied signal level and the
stored baseline.

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A baseline can be established for both current and VII
ohm measurements and is “remembered” by both func­tions.

Rel is enabled by pressing the REL key. Pressing REL a

second time disables the feature.

Making Current Measurements

To make current measurements:

1. Select a current range that is appropriate for the ex­pected measurement or enable autorange (press
SHIFT and then AUTO RANGE).

2. Enable zero check and, if the display is not zeroed,
perform zero correction by pressing SHIFT and
then CORRECT.

3. Connect the current to be measured to the input of
the Model 486/487 (see Figures 1 and 2).

4. Disable zero check and read the measured current
on the display of the Model 486/487.

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Input Connector

Max Overload

2nA - 2pA Range; 35OVdc

2OpA - 2mA Range;

50 Vdc

Chassis Gmund

Fiaure 1. Triax InDut Connector (3-Lua)

Model 486

Figure 2. Picoammeter Connections

VOLTAGE SOURCE

(Model 487)

The voltage source may float. However,

CAUTION

neither V-Source terminal may ever be
more than 500V above chassis.

V-SOURCE OUTPUT

500V MAX TO ,& OR.+

I HI

LO 1

5oov
MAX

Figure 3. Model 487 V-Source Output Terminals

Table 3. Model 487 V-Source

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