Tektronix PS 501 User manual

DC POWER
SUPPLY
PS 501
PS 501-1
PS
501-2

7~I~ronbc
INSTRUCTION MANUAL
Tektronix, Inc .
P .O . Box 500
Beaverton, Oregon

97077

Serial
Number
COMMITTED TO EXCELLENCE
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF
THIS MANUAL .
DC POWER
SUPPLY
PS 501
PS 501-1
PS
501-2
070-1301-02

First Printing APR 1972
Product
Group 75

Revised MAY 1983

Copyright ©1972,1980 Tektronix,
Inc
.
All rights reserved
.
Contents of this publication may
not be reproduced
in any
form without the written
permission of Tektronix,
Inc .
Products of
Tektronix, Inc . and its subsidiaries
are covered
by U .S . and
foreign patents and/or pending
patents .
TEKTRONIX,
TEK, SCOPE-MOBILE, and

are
registered
trademarks of Tektronix, Inc .
TELEGUIPMENT
is a registered
trademark of Tektronix U .K
. Limited .
Printed
in U .S .A . Specification
and price change
privileges
are
reserved .
INSTRUMENT SERIAL
NUMBERS
Each
instrument has a
serial numberon
a panel insert, tag,
or
stamped on
the chassis .
The first number or letter
designates the
country of
manufacture . The last five digits
of
the serial
number are assigned
sequentially and are
unique to each
instrument . Those
manufactured in the
United States
have six unique
digits . The country of
manufacture is
identified as follows :
8000000

Tektronix, Inc .,
Beaverton, Oregon, USA
100000

Tektronix Guernsey,
Ltd ., Channel Islands
200000

Tektronix United
Kingdom, Ltd ., London
300000

Sony/Tektronix, Japan
700000

Tektronix Holland,
NV, Heerenveen,
The Netherlands

TABLE OF
CONTENTS
THE FOLLOWING
SERVICE I NSTRUCTIONS ARE FORUSE BY QUALI FI ED
PERSONNEL ONLY . T O AVOID PERSONAL INJURY, DO NOT PERFORM
ANY SERVICING OTHER THAN THAT CONTAINED IN
OPERATING
INSTRUCTIONS UNLESS YOUARE QUALIFED TO DOSO .
Page
LIST OF ILLUSTRATIONS ...................... . .........................

ii
Section
1

Specification .................. . .........................
1-1
Section 2

Operating Instructions ......... . ...........................

2-1
WARNING
Section 3

Theory of Operation ........ . . .............................

3-1
Section 4

Calibration Procedure ....... . ..............................

4-1
Performance Check . . . . . ................................

4-1
Adjustment
Procedure . . . . ............................... 4-4
Section s

Maintenance ......... .... ...............................

5-1
Section 6

Options ............. ... ................................

6-1
Section ?

Replaceable Electrical Parts . . ............................. . .

7-1
Section 8

Diagrams and Illustrations ................................ ...

8-1
Section 9

ReplaceableMechanical
Parts ............................. ...

9-1
PS 501 (- 1, -2)
REV D NOV 1980

PS 501 (-1, - 2) .
LIST
OF
ILLUSTRATIONS
Fig . No .

Page
2-1

PS 501 (-1,-2)
Installation and Removal . . . ......................

2-1
2=2

Controls and Connectors ............. . . . ............~~~~~~.

2-3
2-3

Controls and
Connectors ............. . . ........-~~~~~~~~~-~

2-4
2-4

Series-connected
supplies ............... . ............~~~~~~~

2-5
2-5

Parallel-connected supplies ................ . ...........~~-~~.

2-5
2-6

Differential measurement
connections ........ . . ................

2-5
2-7

Stair-step output
characteristics of series and parallel
connected supplies .

2-5
2-8

Multiple load
connections .................. . . ......~~~~~~~~~

2-6
2-9

Monitor Connections ... .................... . .~~~~~~~-~~~~.

2-6
2-10

Ground-loop current caused by
remote grounded load ..............

2-7
2-11

Reverse-current shunt
(Rs) with active load ........ ..... .........

2-7
3-1

Simplified
diagram of PS 501 (-1,-2) .................. . . ........

3-1
3-2

Operating characteristics with varying
currents, voltages, and
loads . . ...

3-2
5-1

Semiconductor
device lead configurations found in
the TM 500 family ...

5-5
5-2

Color code
for resistors and capacitors . . ..................... . .

5-6
@ NOV 1980

The general
safety information in this part of the summary
is
for
both
operating and servicing personnel . Specific
warnings and cautions will be found throughout
the
manual where they apply, but may not appear
in this
summary .
Terms I
n This Manual
CAUTION statements identify
conditions or practices that
could result
in damagetothe equipment or other property .
WARNING statements identify
conditions or practices
that could result in personal injury or loss
of life .
Terms As
Marked on Equipment
CAUTION indicates a personal
injury hazard not im-
mediately accessible as
one reads the marking, or a
hazard to property including
the equipment itself .
DANGER indicates
a personal injury hazard immediately
accessible as
one reads the marking .
Symbols In This Manual
OPERATORS
SAFETY SUMMARY
This symbol
indicates where applicable
I

cautionary or other information is to be
found .
Symbols As Marked on
Equipment
DANGER - High voltage .
Protective ground
(earth) terminal .
ATTENTION - refer to manual .
@ NOV 1980
Grounding the
Product
Use only a power cord that is in good condition
.
PS
501 (-1, - 2)
This product is grounded through thegrounding
conduc-
tor of the power cord . To avoid
electrical shock, plug the
power cord
into a properly wired receptacle before
connecting
to the product input or output terminals .
A
protective ground connection by way of the grounding
conductor in the power cord is
essential for safe opera-
tion .
Danger
Arising From Loss of Ground
Upon
loss of the protective-ground connection,
all
accessible conductive parts (including knobs
and con-
trols that may appear to be
insulating) can render an
electric shock .
Use the Proper Power Cord
Use
onlythe power cord and connector specified for your
product .
For detailed
information on power cords and connectors,
see
maintenance section .
Refer cord and connector
changes to qualified service
personnel .
Use the Proper
Fuse
To
avoid fire hazard, use only the fuse of correct type,
voltage rating and current rating as
specified in the parts
list for your
product .
Refer fuse replacement to qualified service
personnel .
Do
Not Operate in Explosive Atmospheres
To
avoid explosion, do not operate this product in an
explosive atmosphere unless it has
been specifically
Power Source

certified for such operation
.
This product is intended to operate from a power source
that will not apply more than 250 volts rms between
the

Do NOt Remove Covers or Panels
supply conductors or between either supply
conductor
andground .Aprotectivegroundconnectionbywayofthe

To avoid personal injury, do
not remove the product
groundingconductor
in the power cord is essential for

covers or
panels . Do not operate the product without the
safe
operation .

covers and panels properly installed .

SERVICE SAFETY SUMMARY
FOR QUALI FI ED
SERVICE PERSONNEL ONL Y
Do not perform internal service or adjustment of this
product unless anotherperson
capable of rendering first
aid and resuscitation is present .
Refer also to
the preceding Operators Safety Summary .
PS 501 (- 1, -2)
Do Not Service Alone

Disconnect power before removing protective panels,
soldering, or replacing components .
Power Source
This product is intended to operate
from
a power source
Use Care When Servicing With Power On

that will not apply
more than 250 volts rms between the
supply conductors or between either supply conductor
Dangerous voltages exist at several
points in this product .

and ground . A protective ground connection by way of the
To avoid personal
injury,
do
not touch exposed connec-

grounding conductor in the power cord is essential for
tions
andcomponents while power is on .

safe operation
.

PS
501 (-1, -2)
PS
501 (-1, -2) Power Supplies
.
REV
C NOV 1980

Introduction

The
electrical characteristics in this specification
are
valid
with the following conditions :
The PS 501 is a constant-voltage,
current-limiting, Oto
20 Vdc power supply
designed to operate in any compart-

1 . The i nstrument must have
been adjusted at an ambient
ment of a
TM 500 Series Power Module .
The PS 501 is a

temperature between
+20°C and +30°C .
floating power supply in which either
terminal may be
grounded, or floated to 350 Vdc
+ peak ac . Front-panel

2 . The
instrument must be in a non-condensing
environ-
controls provide continuously
variable voltage selection,

mentwhoselimitsaredescribed
under Environmental .
as well as current
limiting from 0 to at least 400
mA .
3 . Allow twenty minutes
warm-up time for operation to
specified
accuracy ; sixty minutes after
exposure to or
The floating supply is
suited for powering discrete

storage in a high humidity
(condensing) environment .
transistor
circuitry, or acting as a bias or reference
supply .
Several PS
501's or other suitable supplies
can be com-
bined for applications involving
complementary circuitry,

The electrical and environmental
performance limits
linear

integrated

circuits,

or

any

circuitry requiring

together with their related
validation procedures comprise
cascaded DC levels .

a complete statement
of the electrical and environmental
performance
of a calibrated instrument .
A
ground-referenced +5 V auxiliary
supply is also
included that is suitable for bipolar
logic, light-emitting
diodes, incandescent displays
and similar applications .
With the floating supply
available for powering
discrete
interface
circuits and level shifting,
the PS 501 can be
used for many digital/analog
applications .
Instrument differences between the PS
501-2 and

The supplemental
information listed here represents
the PS 501 (-1) are listed in
this manual at various

limits that
ensureoptimuminstrumentoperation.Theyare
places .

Where no
differences are indicated, the

not instrument specifications, but are intended
to be used
PS 501 information
applies to the PS 501-2 .

only as maintenance or operational
aids .
REV E NOV 1980
SPECIFICATION
Section 1-PS 501 (-1, -2)
NOTE

SUPPLEMENTAL
INFORMATION

Specification-PS 501 (- 1, -2)
20 Volt Floating Suppty
Voltage
Range

~

0 V to at least 20
V .

~

19 .99 V in PS 501-1
.
Rated Output Current

400mA, 0°C to
+30°C, Berating linearly,
to
300 mA at +50° C .
Overload
Protection

Automatic current
limiting and over-
temperature
shutdown, continuous opera-
tion at
rated output current at low
voltages may actuate a Power Module
thermal cutout .
Current Limit Range

510 mA to at least 400 mA .

Current limiting is indicated by
front
panel LED .
Maximum Floating Voltage

~

I

350 Vdc
+ peak ac .
Display Accuracy
Table 1-1
ELECTRICAL CHARACTERISTICS
Characteristics

~

Performance
Requirements

~

Supplemental Information
PS
501-1

~

± (0 .5% of reading
+ 10 mV) .

~

Digital dial readout
.
PS 501-2

~

±
0 .4 V .

~

Analog meter readout .
Resolution
(Setability)
PS 501-1

I

Typically 1 .6 mV determined by a 10-turn
potentiometer .
PS
501-2

~

~

Typically 10
mV .
Load Effect (Regulation)

~

±1
mV for a 400 mA load change
measured at output terminals .
Source Effect
(Line

±5 mV for a ±10%
line voltage
Regulation)

change .
NOTE
Ripple and
noise increase unpre-
dictably
when current is being
limited .
Stability

Typically less than 0 .1% +5 mV for 8
hours
at constant line, load, and temperature
.
Temperature Coefficient

~

I

Typically less than (0 .01%
+ 0 .1 mV) 1°C .
PARD
(Ripple & Noise)

50 .5 mV
peak-to-peak with

10 Hz to 5
MHz, supply not in current
(Periodic and Random

400 mA load .

limiting .
Deviations)
Transient Recovery Time

20 ps or less to recover within 20
mV
of final
output voltage after a
400 mA change in output
current .
REVC NOV 1980

Stability

Typically
less than 30 mV (0 .5%) for 8 hours
at
constant line, load, and
temperature .
Temperature Coefficient

I Typically less
than 0 .5 mV/°C .
PARD
(Ripple & Noise)

<5
mV peak-to-peak with 1 A load .

10 Hz to 5 MHz, supply not in current
limiting .
Rear Interface
Inputs/
Outputsa
Table 1-1 (cont)
Characteristics

Performance
Requirements

Supplemental Information
5 V Supply
Output Voltage

+4
.75 V to +5 .25 ground referenced .

LM309K 5V regulator integrated
circuit .
Rated Output Current

1 A .
Current Limit

Non-adjustable
and typically 1 .5 A to 3
A .
Load
Effect (Regulation)

±100
mV for a 1 A load change .
Source Effect (Line

±50 mV for a 10% line voltage
Regulation)

~
change .
20 V
Floating Supply

Pins 22A
(+), 21A (-) . Same as front
panel output terminals .
Remote Sense

~

~ Pin 23A .
Reference Common

~

~ Pins 24A, 24B .
Current Monitor

Pins 19B,
22A . Voltage is 2 f2 times the
actual output current, ±5% . Pin
22A is same
as + output . Pin 19B is
same as emitter of
NPN series
pass transistor .
Slaving Connections

Pin 26B for current limit slaving .
Pin
25B for voltage slaving .
a
Warning-Floating potentials
will appear superimposed on
all rear interface inputs and outputs .
REV C NOV 1980
Specification-PS 501 (- 1,
-2)

Specification-PS 501 (-1,
-2)
Temperature
Operating
Storage
Altitude
Operating
Storage
Characteristics
Vibration
Operating and non-operating
Shock
Operating and non-operating
Transportation
Height
Width
Length
Table
1-2
ENVIRONMENTAL CHARACTERISTICS
Net Weight
(Instrument only)
0° C to 30° C (with derati
ng
to
50°C)
-40° C to +75° C .
To
15,000 feet . Maximum operating temperature
decreased by
1°C/100 feet from 5000 to 15,000 feet .
To 50,000 feet .
With the instrument complete,
vibration frequency swept from
10 to 55 to 10
Hz
at
1 minute per sweep . Vibrate 15 minutes
in
each of
the three major axes at 0 .015 inch total
displacement . Hold
10 minutes at any major resonance ; or,
if none, at 55 Hz . Total
time, 75 minutes .
30 g, 1/2 sine, 11 ms duration, 3
shocks in each direction along
3 major
axes, for a total of 18 shocks .
Qualified under National Safe
Transit Committee Test Procedure 1A,
Category II .
Characteristics
Table 1-3
PHYSICAL
CHARACTERISTICS
Overall Size
(measured
at maximum points)
Information
Dimensions
4 .96 in (126 mm)
2 .6 in (66 .8
mm)
11 .65 in (296 mm)
2 Ibs (0 .906 kg)

To
install the PS 501 (-1) (-2), align the upper and
lower
rails of the plug-i n with the Power
Module tracks and i nsert
until the plug-in
panel is flush with the Power Module
panel (see Fig . 2-1) . To remove, pull the release
latch
to
disengage the PS 501 (-1) (-2) from the
PowerModule .
REV C
NOV 1980
OPERATI NG
I
NSTRUCTI
ONS
CAUTION
~
,
~0
-- "' .-s,
.
.
.

.
/
.~
Fig . 2-1 . PS 501 (-1,
-2) Installation and removal .
TOP
GROOVE
NOTE
SLOT
Section 2-PS 501 (-1, -2)
PREPARATION

The following procedure is intended to
prepare the
instrument
for immediate use and
demonstrate the basic
The PS 501 (-1) (-2)
is calibrated and ready for use

function of the unit . Operation
of the Power Module and
when received .
It
is
designed to operate in any compart-

other plug-ins
in this system are described
in their
ment of a TM 500 Series Power Module . Refertothe
Power

respective
instruction manuals . Functions
of front-panel
Module Instruction Manual for line voltage
requirements .

controls, indicators and connectors are
described in Fig .
2-2
and Fig . 2-3 .
Before
using the PS 501 (-1) (-2) read the Operating
Considerations in this section
regarding proper
techniques for
connecting various loads, etc .
Turn the Power Module off before inserting theplug-

The presence of output voltage is
verified by a voltage
in ; otherwise, damage
may occur to the plug-in

indicator light on
the front panel . The brightness of this
circuitry .

light varies with output voltage .
(1431-21 )1576-27

Operating Instructions-PS 501
(-1, -2)
A
panel-mounted, light-emitting diode lights when
the

NOTE
PS 501 goes into current-limiting . This is
a very sensitive
indicator that starts to glow
before hard limiting occurs .

The PS 501 (-1) (-2) has internal
diodes connected
Hard limiting is indicated by
maximum brightness of the

across the output
to protect any of the series-
light-emitting diode as
well as a dimming of the voltage

connected supplies against reverse polarity if the
indicator
light . These functions are easily evaluated by

load is shorted, or one of the supplies is
not on .
momentarily shorting the output of the supply
.
PS 501-1 is
identical to the PS 501 except that the
output voltage is selected by a 10-turn
precision poten-
tiometer with a 3-digit
in-line dial and a range pushbutton .
The turns-counting
dial allows the output of the PS 501-1
to be set
accurately without an expensive external
meter .
The dial provides accuracy equivalent
to that obtained
with a 3 1/2 digit
DVM .
The PS 501-2 is identical to
the PS 501 except that a
front-panel
meter is provided to aid in accurately setting
the
output current or voltage of the PS 501-2 . See
Figs . 2-2
and 2-3, Controls and Connectors .
Constant Voltage/Current
Limited Output
1 . Press the
OUTPUT button to apply power to the
plug-in . Observe that the VOLTS indicator
light comes on
(the light will be very dim at
low voltages) .
2-2
2 . Adjust the VOLTS control for approximately
2V .
NOTE
The use
of
an
external meter is not required for the
PS 501-2 . The PS 501-2 internal
meter can perform
the function described in step 3
.
3 .
Set the CURRENT LIMIT control
fully
ccw
(to
protect the ammeter) . Connect an
ammeter across the +
and - terminals and adjust the
CURRENT LIMIT control
for the maximum desired
current output .
4 . Remove the ammeter, connect theload to
the+and
- terminals and adjust the VOLTS
control for the desired
output .
Parallel
Operation
The outputs of two or more current-li mitt ng,
automatic-
crossover supplies can be
connected in parallel as shown
in Fig . 2-5 to obtain an output
current equal tothe sum of
the output
currents from each supply . Each supply must
be
adjusted individually to obtain the desired output
current .
One supply should be set for the desired output voltage
and the other should be set for a
slightly higher voltage .
The supply set for
the desired voltage will then become a
constant voltage source, while the supply with the higher
voltage output becomes a current-limited source
(due to
automatic crossover) which results
in their output voltage
decreasing to that of
the supply with the lowest output
voltage .
Differential Voltage Measurements
Very small do voltage
changes or unknown voltages
can be measured by
connecting the PS 501-1, a null
detector,
and the source under test in a
differential
configuration as shown in Fig . 2-6 .
Inexpensive com-
parison measurements at
nearly the accuracy and sen-
sitivity of costly differential
voltmeters can be made with
the PS
501-1 . The ultimate accuracy and sensitivity of the
measurement depends on the PS 501-1 and the type of
null detector used . A cali brated do am
pl iffier i n a high-gai n
oscilloscope such
as the TEKTRONIX 5100-Series
Oscilloscope
with a 5A20N Differential Amplifier plug-in
will serve as a convenient null detector, or
a sensitive
milliammeter
with a series resistor is also satisfactory .
Series Operation
Series- and
Parallel-Connected Stair-Step
The outputs of two or
more supplies can be connected

Operation
in series as shown
in Fig . 2-4 to obtain an output voltage
equal to
the sum of the output voltages from
each supply .

Series- and
parallel-connected PS 501 (-1) (-2)'s can be
The maximum output is
limited to 350 Vdc + peak ac (i .e .,

operated to provide
a "stair-step" output characteristic by
the isolation voltage rating
between the output terminals

choosing proper load limits and control settings
. For
and ground) .
Each supply must be adjusted
individuallyto

example, Fig . 2-7 shows
the stair-step output from two
obtain the desired output voltage .

series-connected
supplies . With each supply set for
APPLICATIONS
NOTE
Examine the circuit for ground loops when using a
null detector with one input terminal
grounded (see
Grounded and Floating
Operation) .
REVC NOV 1980

Provides 0 to 10 V output
range in the out position .
tNheo pressed, a one : (1( is
displayed in the window
and
the output range
becomes '10
V
to 20
V .
NOV 1980
RangePushbutton
and Window
OUT
0-10V
VOLTS
Control
and Indicator
Coniinuousiy
v,miabli " c~ . n
irol that v " Iccre
from O~tn
zo v m~tp~t ht tl,e ",
and
-
_
terminals . Front
panr_I
marked in 1 V increment, .
Voltage ind~c .rtor lights
when powe " .r
is applied to
the PS501 (OUTPUT
pushhutton
pressedl-
Brightnrn : -
varies wWh the
V11117Ut VUItagf' .
- and
+
Floating
Output Tenninais
5-way binding-post termi-
nals that provide a 0 to
20 V " 400 mA, output .
PS 501-~

POWEH SUPPLY
VOLTS
Fig . 2-2 . Controls and Connectors
.
Operating Instructions-PS 501 (-1, -2)
VOLTS Control
and Readout
10-turn precision potenti-
ometer with 3tiigit in-line
readout that accurately
select, from 0 to 20 V
output at the ~ and
term inal, .
VOLTS Indicator
Liyhts whan power is
applied to the PS 501-1
(OUTPUT pushbutton
pressed) . Bnyhtness varies
with the output voltaye .
1301-03
OUTPUT Pushbutton
Pushbutton that,
when
pressed applies
power
frnrn the
Power Module to
the PS 5011
11 .
CURRENT LIMIT Control
and Indicator
Cuntinuou,ly vari ;nblo " con
rrol rlrat sel~ " cts the output
rent I,mit from 0 to al
30U mA . Light
ny
diode indicates
when the PS 50l I l1 goes
intrn current limiting . Maxi-
rnum
brightness indicates
when hard limiuny occurs .
'5 V Ground-Raferenced
Output Terminals
.i may binding-post termi-
mi15 that provide a yround-
reterenced +5 V, 1 A,fixed
output .
2-3

Operating
Instructions-PS 501 (-1, -2)
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Fig . 2-3 . Controls
and Connectors .
a NOV 1980

@ NOV 1980
POWER

POWER
SUPPLY I

I SUPPLY
LOAD
Fig . 2-5 . Parallel-connected supplies .
POWER

POWER
SUPPLY I

I SUPPLY
1301-05
1301-06
Operating Instructions-PS 501 (-1, -2)
POWER

SOURCE
SUPPLY I

I UNDER
TEST
NULL
DETECTOR
O O
Fig . 2-4 . Series-connected supplies .

Fig . 2-6
.
Differential measurement connections .
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1
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2
CURRENT IN
AMPERES
LOAD
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0 01
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Io 01 I
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40
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w
3
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S
s
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1301-07
20
LOAD
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1301-08
Fig . 2-7 . Stair-step output characteristics of series and parallel
connected supplies .
2- 5

Operating Instructions-PS 501 (-1,
-2)
maximum voltage and current (20 V, 400
mA) the output
voltage remains constant
from open-circuit (~) until the
load
reaches approximately 100 S2 (as illustrated by the
solid line in Fig . 2-7) . At this crossover
point the output
voltage decreases with
the load and the output current is
limited at 400
mA . Therefore, with resistances below
approximately 100
O,
both supplies act as current
sources
with output voltage variable with
the load . Since both
supplies are set
for the same output voltage, each supply
shares
equally in the power output (I z R) . If one supply is
set for
a lower output voltagethantheother, output
power
is shared at the same ratio as the output voltage
.
Now,
by
setting supply
Ez
for a current limit of 200 mA
and
varying the load over the same range, the supplies act
as constant voltage sources until the load
reaches ap-
proximately 200 S2 . At that
crossover point, the supply set
for 200 mA
(Ez)
becomes a current source and its output
voltage decreases with the load (as illustrated by the
dotted line in Fig . 2-7) . At approximately
100 S2 and 20 V,
supply Ez no longer
contributes to the power output .
Subsequently, supply E, supplies all the output power
and
operates as a constant voltage source with
output current
variable with the load . Then, at
approximately 50
O,
supply E, crosses over
and becomes a current source at its
maximum output of 400 mA . Thus, by choosing
the
appropriate load limits and control
settings, any of thefour
operating
characteristics is possible .
Parallel-connected supplies exhibit the same
"stair-
step" characteristic as in series-connected
operation .
However, the
maximum voltage available is the highest
setting of
either supply while the maximum current is
I, + Iz .
Load and Monitor
Connections
2- 6
POWER
SUPPLY
LOAD LOAD LOAD
1

2

3
Fig . 2-13
. Multiple load connections .
POWER
SUPPLY
OUTPUT
TERMINAL
OPERATING
CONSIDERATIONS

VOLT

-

+
METER
Overheating
The PS 501 (-1) (-2)
is designed to operate at an am-
bient temperature from 0°C to +50°C .
However, when
operating several power supplies in a
multi-plug-in Power

LOAD
SCOPE
Module, especially at
low output voltages, or when

b

b
operating close to
other heat-producing equi pment, i nter-

Dc
nal temperature may exceed safe limits and
actuate a

VOLTMETER
thermal cutout . Refer to the Power
Module Instruction

1301_10
Manual for more complete information
.
Fig . 2-9 .
Monitor connections .
1301-09
Improper
connections between the power supply out-
put and the loads) and/or monitoring devices)
are a

Groundedand
Floating Operation
common cause of errors .
Multiple loads must be con-
nected with separate
pairs of leads as shown in Fig . 2-8 .

The
PS
501 (-1) (-2) is a "floating" supply since no
Monitoring devices must also be connected with separate

internal
connections are made to either the chassis
or
leads as
shown in Fig . 2-9 . Avoid using clip leads, since

ground . The supply can thus be used as a
positive or
their contact resistance can exceedthe
output impedance

negative supply by simply
grounding the negative or
of the PS 501 (-1) (-2)
and cause significant measurement

positive
output terminal . However, there may be un-
error
.

desirable effects caused by grounding the supply to the
@ NOV
1980

chassis whilethe load is grounded at some point removed

therefore will not work when the voltage is correctly
from the supply chassis . For example, if a remote load is

polarized . Connecting a shunt resistor (R s ) as shown in
connected as shown in Fig . 2-10, ground currents con-

Fig . 2-11 provides an external reverse current path so the
taining the power line frequency could result and create

power supply
sources
or delivers
current only .
excessive noise and ripple in series with the load .
Thus,
floating operation is recommended to insure against
problems caused by undersirable ground currents .

Overvoltage
The PS 501 (-1) (-2) is not protected from overvoltage
Reverse Current Loading

_

conditions . Component failure in the PS 501 (-1) (-2)
could result
in a load damage if external protection is not
In some bias supply and digital circuitry applications

provided .
Likewise, if the load (or other instruments
the load might behave as a current source for part of its

connected to the load) produce a voltage across the
operating cycle . Since the output circuit of a series

PS501(-1)(-2)terminalswhich isthesamepolaritybutof
regulated supply is unidirectional,
current will not pass in

greater amplitude, damage may result depending on the
the opposite direction except through undesirable paths .

amount of overvoltage and
the impedance
of
the load
The internal reverse-current diodes conduct only when

(source) .
the PS 501 (-1) (-2) terminal voltage reverses and
POWER
SUPPLY
LOAD
POWER

ACTIVE
SUPPLY I

I LOAD
Operating Instructions-PS 501 (- 1, -2)
Fig . 2-10 . Ground-loop
current caused by remote grounded load .

Fig . 2-11 . Reverse-current shunt (R,) with active load .
@ NOV
1980
1301-12
2-~

WARNING
THE
FOLLOWING SERVICING INSTRUCTIONS
ARE FOR USE BY QUALIFIED
PERSONNEL
ONLY . T
O
AVOID PERSONAL INJURY, DO
NOT
PERFORM ANY SERVICING OTHER
THAN THAT
CONTAINED IN OPERATING
INSTRUCTIONS
UNLESS
YOU ARE QUALIFIED TO DO SO .
REFER TO OPERATORS
SAFETY SUMMARY
AND SERVICE SAFETY
SUMMARY PRIOR TO
PERFORMING ANY SERVICE .