Tektronix 725 Instruction Manual
INSTRUCTION
MANUAL
Programmable Current Source
Model
.-
725
WARRANTY
We warrant each of our products to be free from defects
and workmanship. Our obligation under this warranty is to repair
or replace any instrument
shipment, proves defective upon examination. We will pay local
domestic surface freight costs.
To
exercise this warranty, write
sentative, or contact Keithley headquarters
You will be given prompt assistance and shipping instructions.
or
part thereof which, within a year after
or
call your local Keithley repre-
in
Cleveland, Ohio.
in
material
REPAIRS AND
CALI BRATI
Keithley Instruments maintains a complete repair and calibration
service as well as a standards laboratory in Cleveland, Ohio.
A
Keithley service facility at our Munich, Germany office is
available for our customers throughout Europe. Service
United Kingdom can be handled at our office
in
ally, Keithley representatives
and calibration facilities.
most countries maintain service
ON
in
in
Reading. Addition-
the
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
The measurement engineers.
Keithley Instruments, Inc., 28775 Aurora Road, Cleveland, Ohio 441
European Headquarters:
United Kingdom:
France:
Heiglhofstrasse
1 Boulton Road, Reading, Berkshire. (0734) 861287
44 Rue Anatole France, F-91121 Palaiseau (01) 014-22-06
5,
0-8000
Munchen 70 West Germany,
39.
(089)
(21
7144065
6)
248-0400
INSTRUCTION MANUAL
Model
Cur
rent
725
Sou
rce
COPYRIGHT 1978, KEITHLEY INSTRUMENTS, INC.
FIRST PRINTING, APRIL 1978, CLEVELANDy OHIO U. S. A.
DOCUMENT NO. 29631, REVISION CODE AA
INSTRUCTION
Programmable Current Source
MANUAL
Model
WARN I NG
If
current is programmed to 0 and unit is in operate, a COMPLIANCE VOLTAGE up to
125
volts may be present at the output terminals. For maximum operator safety the Model
Current Source should always be set to
The
unit should also be set to STANDBY prior to changing range or polarity. This
ensure that no transient currents
will
STANDBY
mode when no current output
be generated.
WARN
I
NG
is
needed.
will
725
725
This instrument is not approved
National Electrical Code, Classes
for
use in “hazardous locations” as defined in the
1,
11,
and
Ill.
Class’l: Those locations in which flammable gases or vapors are or may be present in
the air in quantities sufficient to produce explosive or ignitable mixtures.
Class
11:
Those locations that are hazardous because of the presence
of
combustible
dust.
Class
Ill:
Those locations that are hazardous because of the presence of easily ignitable
fibers or flyings.
~
INSTRUCTION MANUAL
Programmable Current Source
725
Model
Sect
ion
CONTENTS
Page
CONTENTS
ILLUSTRATIONS
1.
GENERAL DESCRIPTION
1-1.
1-2.
1-3.
2.
OPERATION
2-1.
2-2.
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
3.
CIRCUIT DESCRIPTION
3-1.
3-2.
.
3-3.
3-4.
4.
ACCESSORIES.......................
r
4-1.
5.
MAINTENANCE
5-1.
5-2.
5-3.
5-4.
5-5.
6.
CALIBRATION
6-1.
6-2.
6-3.
7.
REPLACEABLE PARTS
7-1.
7-2.
7-3.
7-4.
7-5.
7-6.
....................
...............
.............................
GENERAL
WARRANTY INFORMATION
CHANGE
NOTICE
.........................
..................................
GENERAL
CONTROLS
I
NDI
CATORS
CONNECTIONS..............................
REMOTE
MEASUREMENT CONSIDERATIONS
PRELIMINARY
OPERATING CHARACTERISTICS
GENERAL.,
THEORY
CIRCUITRY
SWITCHING
................................
PROGRAMMING
AND CONTROL
......................
PROCEDURES
.......................
..............................
OF
OPERATION
...............................
..........
GENERAL
.................................
GENERAL
SERVICING
PARTS REPLACEMENT
CALIBRATION
TROUBLESHOOTING
SCHEDULE
..........................
..............................
.................................
GENERAL
TEST EQUIPMENT
CALIBRATION PROCEDURES
GENERAL
ORDERING
FACTORY SERVICE
CROSS REFERENCE OF MANUFACTURERS
COMPONENT LAYOUTS
SCHEMATICS
INFORMATION
............................
..............................
.........................
...................
..............................
...
III
iv
1-1
1-1
1-1
1-1
2-1
2-
1
2-1
2-
1
2-2
2-6
2-8
2-9
2-11
3-
1
3-1
3-
1
3-1
3-3
4-1
4-
1
5-1
5-
1
5-1
5-
1
5-1
5-
1
6-1
6-
1
6-1
6-
1
7-1
7-
1
7-1
7-
1
7-1
7-
1
7-1
AA
iii
I
LLUSTRAT
I
ONS
INSTRUCTION
Programmable Current Source
MANUAL
Model
725
Figure
1-1
2-
1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
3-
1
4-
1
6-
1
6-2
6-3
6-4
7-
1
7-2
7-3
7-4
No.
Title
Model 725 Programmable Current Source . .
Model 725 Front Panel
Model 725 Rear Panel
Schematic
Triaxial Connector Schematic . . .
Resistive Load
Floating Supply .
Capac
Voltage Limit Characteristics .
Model 725 Block Diagram
Model 1004 Rack Mounting
Chassis - Top View
AccuracyCheck
Regulation Check
Current Model Vs. Voltage Mode Waveforms . . . . . .
Component Layout, PC-22%
Component Layout,
Schematic Diagram - Model 725 Amplifier
Schematic Diagram - Model 725 Power Supply
i
ti
ve Load
of
Output Connections
.....................
.
. . .
.
. . . . . . . .
Kit
PC-438
.
. . .
. . .
. .
.
. . . . . . . . . . . . . . . .
. .
. . . . .
.
.
.
. . . . .
. . .
.
. . . .
.
. .
. .
. .
.
. . . .
.
. . . .
. . . . . .
.
.
.
.
.
.
. . .
.
. .
. .
.
. . .
. . . .
. . . . . . .
. . . .
.
.....
. . . . . . .
.
.
.
.
.
. .
. .
.
Page
1-1
2-
1
2-2
2-3
2-3
2-10
2-1
1
2-12
2-12
3-
1
4-
1
6-0
6-5
6-6
6-6
7-10
7-1
1
7-12
7-13
INSTRUCTION
Programmable Current Source
Model
725
MANUAL
GENERAL
DESCRIPTION
r
1-1.
programmed by a
grammed by use of a Kepco
for the Model
1-2. WARRANTY INFORMATION. The warranty
manual.
1-3.
manual
GENERAL. The Model
725
CHANGE
will
The
A
read the associated CAUTION statements with regard to proper use and handling
the instrument. Damage to the instrument may occur
The
t
symbol indicates those areas on the instrument which are potential shock hazards.
Carefully read the associated
handling of the instrument. Serious personal injury may result
are ignored.
NOTICE. Improvements or changes to the instrument not incorporated into the
be explained on a Change Notice Sheet attached to the inside back cover.
symbol can be found in various places in this Instruction Manual. Carefully
symbol can be found in various places in the Instruction Manual. This
SECTION
725
is
BCD
code. The magnitude of the current (as a
SN-3
are given in Table
Digital-to-Analog Converter or equivalent. Specifications
1.
GENERAL DESCRIPTION.
a completely programmable current source. Ranges are
1-1.
is
stated on the inside front cover of the
IMPORTANT
WARNING
statements with regard to proper use and
%
of
full scale) is
if
these precautions are ignored.
if
these precautions
pro-
of
AA
FIGURE
1-1.
Model
725
Programmable Current Source.
1-1
GENERAL
DESCRIPTION
TABLE
Model 725 Programmable Current Source
SPECIFICATIONS
1-1.
INSTRUCTION
MANUAL
Programmable Current Source
Model
725
GENERAL:
OUTPUT:
DC
Voltage:
Resolution:
Polarity:
Float
Accu
Stab
Load
Line Regulation:
Overload Protection:
Nom. Settling Time:
(when used with Kepco Model SN-3)
Current:
i
ng:
acy
:
I
i
ty:
Regulation:
The Model
current under program control.
Range, polarity, operate/standby
and selection of compliance
are all directly programmable.
Magnitude is programmed by use of
a Kepco
Converter
IOOnA to
seven decade ranges.
Four digitally selectable comp-
liance limits are variable between
no compliance
constant current is maintained to
at least
0.1%
Programmable, posi tive or negative.
+I00
Less than IOppm
chanae in outout current oer volt
on tGe lpa to'
than 20ppm per volt on the
range.
i(0.6% of programmed value
of range).
During the first hour,
subsequent 8-hour periods:
i(0.02% of programmed value
0.01%
1
OOmA
i(O.l% of programmed value
0.03% of range)on the IOOnA range
t0.0055: of full range from no load
to full load on the 10pA through
IOOmA ranges. tO.O2%
range. ?0.2% on the IOOnA range.
i0.005% of
change in line voltage.
Voltage limited to compliance
voltage setting of polarity
selected. Automatic recovery.
30 milliseconds to within
final value.
725
provides constant PROGRAMMING:
limil
SN-3
Digital to Analog
or
equivalent.
IOOmA
full scale in
12
volts and
100
of
range.
volts off chassis maximum.
limit
volts.
of
lOOmA
90
volts. With
programmed, ISOLATION:
full range
or
1
OOnA
t
n
Less
0.1%
ranges
+
or
range) on the
ranges.
1pA
to POWER:
+
on
the IpA
full
range for
10%
0.1%
of
Functions:
Compatible Logic:
Logic Power:
ENVIRONMENT:
CONTROLS, INDICATORS:
CONNECTORS:
DIMENSIONS,
WEIGHT:
9
in. x
of
@
limit.
3,4
Range, polarity, selection
1
of
4
operate/standby are all directly programmable. Magnitude
is programmed
nal for
TTL or DTL. Maximum input
load,
operate/standby where driving
circuit must sink 60mA.
An
250mA TTL-compatible logic
supply is required.
1090hms; digital low to output
low.
20" to 30°C up to 50%
relative humidity.
Front panel ON/OFF switch.
operate, and compliance
Rear panel 15-pin D style
connector for digital input
Rear panel triaxial connector
for magnitude programming.
Front and rear panel output
mni tori ng,
35
Overall bench size
high x 225mm wide x 310mm
compliance limits, and
by
0-100%
10
TTL loads, except
external
Indicator lights for range,
(mating connector suppl ied).
triax connectors. Rear panel
banana jacks for compliance
105-125 or 210-250 volts
(switch selectable). 50-60Hz.
VA
maximum.
133mm
(5-
1
a 0-IOV sig-
of
full range.
5V
(t0.25V)
/4
in.) ha 1 f-rack.
155mm
deep. (6-l/4 in. x
12-1/4 in.). Net weight
kg. (7-1/2 Ibs.).
1-2
AA
INSTRUCTION
Programmable Current Source
Model
725
MANUAL
OPERATION
r
2-1. GENERAL. This section provides interface information and operating instructions
for the Model 725.
2-2. CONTROLS. The Model 725 is remotely programmable and as such,
only two switches.
TAGE selector switch (S201) is on the rear panel. These switches are shown in Figures
2-1 and 2-2 and functionally described in Table 2-1.
2-3.
725.
applied to the instrument. Nine
emitting diode type. Seven of the lamps (DS301-DS307) are dedicated to the current ranges,
with the lighted LED indicating the programmed range. The two remaining LED'S
and DS308) give indication of the operating modes of the instrument. When the
lamp is on, the instrument is in operating mode and current is supplied to the
connectors; when off, standby mode
voltage required to drive the programmed current through the load reaches the preset
compliance voltage
constant voltage mode.
INDICATORS.
A
neon lamp (DS201) is lighted when the line
The line
Ten front panel indicators provide the operating status of the Model
limit.
SECTION 2.
POWER
At
switch (S302) is on the front panel and the LINE VOL-
of
the indicators are of the high efficiency light-
is
implied. The COMPLIANCE LIMIT lamp lights when the
this point, the 725 changes from constant current to
OPERATION.
POWER
switch
is
equipped with
is
on and line power
(DSlOl
OPERATE
OUTPUT
is
AA
5202
DS2Ol
FIGURE
2-1. Model 725 Front Panel.
DS101
DS308 J102
2-1
OPERATION
INSTRUCTION
Programmable Current Source
MANUAL
Model
725
J701
FIGURE
2-2. Model 725 Rear Panel.
SiOl
F2OI
P201
~
~-
2-4. CONNECTIONS. The input and output connections are described below and shown in
Figures 2-1 and 2-2. These connections are also listed in Table 2-1. The output connec-
tions are also shown schematically in Figure 2-3.
a. Output Connectors. The front and rear panel triaxial OUTPUT connectors (J102,
Jl03) are wired in parallel.
is high, the inner shield is low and the outer shield is chassis ground.
connectors are shown schematically in Figure 2-4. The OUTPUT connection can be made
By
definition, the inner conductor of the triax connector
The triax
to
either the front panel connector or the rear panel connector. The unused OUTPUT connector should have a cover (two
CAP-18
are supplied) installed to provide protection against
electrical shock and dust accumulation. The cover also provides electrical shielding.
Output connections should be made using low-noise triaxial cable. For custom length
cables, Keithley Part
connector
is
available by ordering Keithley Part
No.
SC-22 low-noise triaxial cable should be used.
110.
CS-141.
A
mating
WARFJ I NG
\
%
When the Model 725
is
float
connectors even though the
The actual voltage present
ng, high voltage may be present at the OUTPUT
nstrument
s
dependent on the customer supplied voltage
is
in standby (non-operate mode).
source, up to 100 volts.
Low
b.
and Ground Terminals. Two
identified as LOW (J202) and
1.
The LOW terminal (Black) is
connectors.
2-2
GROUND
binding posts are located
J201).
nternal
y
connected
to
the low
on
the rear panel and
of
the two OUTPUT
.-
AA
INSTRUCTION
Programmable Current Source
Model
725
MANUAL
OPERATION
GROUND
r
I
I
I
L
LOW
I
--
J202
LOW
MODEL
-@-
I0
I----
LOW
HIGH
725
HIGH
/
/
JlO3
J102
OUTPUT
1
I
I
I
OUTPUT
CHASS
s
FIGURE
2-3.
[
CHASS
GROUND
Schematic
HIGH
Low
I
S
*--,
'\
,'m
1
,
of
Output Connections,
',
,.
I
NNER
CONDUCTOR
<
INNER
SH I ELD
AA
FIGURE
2-4.
Triaxial Connector Schematic.
2-3
OPERATION
2. The
provided for connecting LOW to chassis ground. mfloatinqtions, the 1 ink
gust be removed.
to minimize noise pickup.
C.
COMPLICANCE MONITOR Terminals, Two banana jacks (Black, Red) are located on the
rear panel and permit monitoring
1.
GROUIJD
--
The black terminal (Jl06) is connected to LOW of the OUTPUT connectors.
terminal (Green) is connected to chassis ground.
For other applications, leave the shorting link in, where possible,
of
the compliance voltage.
INSTRUCTION
Programmable Current Source
A
shorting link
MANUAL
725
Model
is
---.
=
is
full
2. The red terminal (Jl05) is connected to an internally buffered voltage, which
approximately at the same voltage as OUTPUT
d. knaloq Input. The
rear panel. The analog input must be a positive voltage
scale current). The analog voltage must be floating (not referenced to any other signal
or chassis ground).
source. This cable should be kept
and to improve transient response.
Keithley Part No.
(Keithley
Do not short
A
damage the Model 725.
e. Program Connector. Programming and control connections to the Model 725 are made
through a 15-pin
and
its
also see the discussion on Remote Programming and Control (paragraph 2-5).
f.
1.
with third-wire earth grounded receptacles. Prior to connecting P201 to line power,
verify that the line voltage selector switch
voltage level,
Part
accessories are supplied with the Model 725. See Table 2-2 for pin identification,
Line Power Cord and Fuse.
The Model
CS-141.
No. 29449B). Also, see Magnitude Programming, paragraph 2-5f.
HIGH
"D"
725 is provided with a three-wire line cord and plug (P201) which mates
i.e.,
ANALOG
A
low noise triaxial cable should be used to connect to the voltage
When the Kepco
or LOW of Analog Input connector to chassis ground, as this may
type connector (JlO4) located on the rear panel. A mating connector
117V
INPUT triaxial connector
-
<
3
feet to minimize capacitive loading of the source
A
mating connector is available by ordering
position for
HIGH,
SN-3
CAUT
I
ON
105-125 volts and 234V position for 210-250 volts.
through a
is
purchased, a custom cable is supplied
(S201) is set
(J101)
from
to
47Kn
0
isolation resistor.
is located on the
to
10
volts.
correspond to the input
(1OV
T
2. The line fuse (F201) is a type
234V.
2-4
3AG,
slow blow. Use
1/4A
for
ll7V
and
1/8A
for
AA
INSTRUCTION
Programmable Current Source
Model
725
MANUAL
OPERATION
r
CONTROLS, INDICATORS
I
tem
FRONT
Li ne power lamp (DS201)
RANGE
STATUS Indicators
OUTPUT
REAR
PANEL
POWER
(DS30
(DSlOl
switch (S202)
I
nd i ca tors
1
-DS307)
,
DS308)
Connector (J 102)
PANEL
TABLE 2-1.
AND
CONNECTIONS.
Functional Description
Controls
Lights when line power
When a range
indicating programmed current range.
DSlOl
limit
voltage mode, rather than constant current mode when
1
ighted.
DS308 is lighted in operate mode. When off standby
mode
connector and HIGH to LOW shorted by 200R resistor.
Triaxial connector wired in parallel with
panel OUTPUT connector Jl03. Use J102 or Jl03.
See NOTE for Triaxial Connector signal definition.
1
ine power to 725.
is
applied by S202.
is
programmed, one of seven
indicates that the preset compliance voltage
has been reached - 725 operates in constant
is
implied, with no current supplied to OUTPIIT
is
lighted-
rear
Line VOLTAGE Switch (S201)
ANALOG INPUT (J101)
A
OUTPUT Connector (Jl03)
P L I
(F201)
AN
GROUND
C
E
MO
N
I
TO
R
LOW and
Connectors (J202, J701)
C.
OM
(J105, J 106)
FUSE
Must be set to correspond with the level of the input
1
ine voltage (117 or 234 volts).
-
Triaxial connector
paragraph
shield
Do not short HIGH or LOW
this may damage the 725.
Triaxial connector wired in parallel LJith front
panel OUTPUT connector J102. Use J102 or Jl03. See
NOTE
LOW (J202) is connected to LOW of OUTPUT connectors
J102 and
ground. The link (supplied) permits connecting LOW
to chassis ground.
Permits monitoring
is
connected to OUTPUT LOW and Jl05
internal ly biiffered voltage (=OUTPUT HIGH) through
47
KSd
Type
2.-5f.
is
LOW and outer shield
for triaxial connector signal definition.
JlO3.
isolation.
3AG,
Slow
Elow.
See Magnitude Programming,
Inner conductor
I
CAUT
Ground (J201)
of
the compliance voltage. JlO6
117V
ON
of
JlOl to chassis ground, as
(1/4A); 234V (1/8A)
is
HIGH, inner
is
Chassis ground.
is
connected to chassis
is
connected to an
AA
Power
Cord (P201)
Connects line power to instrument.
2-5
OPERATION
I
tern
TABLE 2-1. (CON'T)
Funct iona 1 Descri pt ion
INSTRUCTION
Programmable Current Source
MANUAL
Model
725
PROGRAM
2-5.
numericial code
range = 10-lA.
Driving circuit must be able to sink =3mA per line. The programmed range
by one
supplied unless the POLARITY line
an output current.
is
REMOTE
a. Range Programming. The range is programmed by supplying a
b. Polarity Control. The current source is set up such that a positive current
c. Operate Commaned. The operate line must be pulled low to enable the 725 to produce
shorted and a 200 ohm resistor connected across the output connector.
Connector (Jl04)
PROGRAMMING
is
equal to the range exponent of the range selected. Example:
(lomx
of
seven front panel range indicating LED'S.
AND
CONTROL.
where x is the range code). See Table 2-2 for pin identification.
In the standby (non-Operate mode) the internal current generator
15-pi n
725 to the digital control. See Table 2-1 for pin
identification.
Triaxial Connector signal definition
is
"D"
pulled low. See Schematic 28630E.
type connector - permi ts connecting the
NOTE
-
J101, J102, JlO3
Inner conductor
Inner shield
Outer shield
=
HIGH
=
LOW
=
Chassis ground.
BCD
code (1 ,2,4). The
is
indicated
1
=
is
lOOmA
---.
d. Compliance Limit. Four internally adjustable potentiometers are provided for use
as preset compliance
accomplished by pulling the particular compliance relay line to low. The adjustments are
located just behind the top of the front panel. Access can be gained by removal of
the top cover. Compliance potentiometers are arranged such that compliance numbers
through 4 from left to right facing the front panel may be used at any particular time
to provide a larger number of compliance
the compliance voltage
If
none of the lines are pulled low, the compliance
This mode of operation should not be used because of the uncertainty of operation outside
of the specified
e. Programming Techniques. Programming can be done in any sequence. However,
suggested that standby be selected before a range
should be held until a new range has been selected, Standby should also be used when
making connections to the Model 725L
f.
Magnitude Programming. The magnitude of the current on a particular range
selected by programming a Kepco
725 is a basic voltage to current converter. An analog voltage,
supplied to the "analog input".
limits.
will
limits
Selection of a particular preset compliance
limits.
be less than the lowest preset compliance
(l2V-gOV). Loading of the compliance lines is
SE1-3
Diqital to Analog converter or equivalent. The
If
more than one line
limit
or
will
polarity is changed and standby
be approximately 125V.
0
to
+1OV,
limit
is
pulled low,
limit
lOmA
selected.
per line.
must be
is
is
it
1
is
2-6
AA
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