BENCHTOP.JUL–benchtop power supplies– SC– Page
Benchtop power supplies meet diverse testing needs
More instruments allow either local or remote control of test sequences
BY SPENCER CHIN Associate Editor
The basic function of benchtop power supplies, to supply variable power
for laboratory and testing needs, has not changed over the years. But make
no mistake about it, these instruments are coming under pressure to keep
up with the needs of an increasingly digital world. At first glance, many
of the latest benchtop supplies don't appear much different from their
predecessors; they retain the familiar analog readout and provide
front-panel-adjustable control of voltage and current. However, many of
these same supplies now also allow remote control of test sequences
through the IEEE-488 bus, when an IEEE-488 control card is added inside
the supply. Benchtop supplies continue to be offered in a range of prices
ranging from a few hundred to a few thousand dollars. At the higher price
range, benchtop supplies are starting to provide the control functions of
the more expensive programmable supplies–which sometimes allow only
remote control. A good example is the MBT series supply from Kepco. The
supply's most significant feature is its IEEE-1118 port, which allows
communication over the two-wire IEEE-1118 serial bus at distances up to
300 m away (at a 375-kbaud rate). This capability is especially useful for
industrial applications. By comparison, the common IEEE-488 interface
permits a maximum transmission distance of 20 m. An optional single-board
computer has IEEE-488-2 and RS-232-C interfaces for additional control
flexibility. When operating over the IEEE bus, the MBT series can control
up to 27 other supplies in a master-slave configuration. A two-line,
16-character display on the front panel prompts the user, via a
menu-driven sequence, to set control and output parameters using the
instrument's keypad or control knobs. The supply is available in eight
output combinations spanning 0 to 6 V at 32 A through 0 to 150 V at 2.4 A.
It costs $1,889 without the single-board computer and $2,499 with the
computer. The MBT series is available from stock. Perhaps more typical of
today's benchtop supply is the series 3610A digital supply from
Hewlett-Packard, available in three models. The E3614A is rated 8 V at 6
A, the E3615A 20 V at 3 A, and the E3617A 60 V at 1 A. All three supplies
exhibit a line regulation of 0.01% +2 mV and load regulation of 0.01% +250
microamps. Transient response time is less than 50 microsecond for a
half-load to full-load change in output current. The supplies have
10-turn potentiometer controls to set voltage and current. The supplies
allow remote analog programming. Other features include overvoltage
protection, autoranging meters, and a user-changeable input. Multiple
supplies can be combined in auto-parallel, auto-series, and autotracking
modes to increase output voltage and current capacity. The list price for
the HP supplies ranges from $500 each, depending on model.
For simpler test
and measurement needs, the WP-702B from the Vector Group provides dual
outputs, each rated 0 to 20 Vdc at 0 to 200 mA. Dual 3 1/2-in. analog
meters read both voltage and current. Line and load regulation are +/-0.
05% +/-2 mV. The supply has switch-selectable 115/230-Vac operation and is
protected from overloads. It measures 8 1/2 x 5 1/8 x 9 1/2 in. The supply
costs $365 with an availability of 4 weeks ARO. Electro Industries has
introduced a dual-range benchtop supply, the Model 3670. It outputs 0 to
18 V at 0 to 7 A, or 0 to 36 V at 0 to 3.5 A. The supply has
constant-current and constant-voltage modes with automatic crossover.
Other features include adjustable current limiting and built-in
short-circuit and reverse-voltage protection. A 10-turn current
potentiometer is optional. Line and load regulation are 0.25%, and
ripple-and-noise 500 microvoltsrms. The supply costs $275 with
availability from stock. B&K Precision has a new high-current benchtop
supply for continuous operation. The model 1686 produces 12 A continuously
at 3 to 14 Vdc. It has separate analog meters to display voltage and
current. Line and load regulation are +/-0.8%, and ripple is under 10
mVrms. Two or more supplies can be connected in series or parallel for
greater output. The supply measures 5.5 x 5.5 x 12 in. It costs $199 and
is available from stock. The VI-700 voltage and current source from IET
Labs allows setting of ranges through a manual thumbwheel on its front
panel, or optionally through external commands downloaded through a parallel
BCD or IEEE-488 interface. The instrument has three ranges of 200 mV, 2 V,
and 20 V, with 200 V optional. Resolution is 100 microvolts, 1 mV, 10 mV,
and 100 mV, depending on output range. The portable supply costs $495; the
IEEE option adds another $495. Among four new families of benchtop
supplies from Instek America are two programmable supplies, the PPS-3615
and PPT-3635. The triple-channel PPT-3615 outputs 0 to 36 V at 0 to 1.5 A,
while the single-channel PPS-3635 outputs 0 to 36 V at 0 to 3.5 A. Besides
programmable output voltage and current, other programming capabilities
include overvoltage and current protection, output enable and disable,
programmable syntax error detection, and auto-step running. The PPT-3615
costs $1,190; the PPS-3635 costs $1,310, with availability on both
supplies 6 weeks ARO. An optional IEEE-488.2 interface card costs an
additional $50. LabWindows, the software-based operator interface
pioneered by National Instruments, is a now standard feature on the series
BL1350 ac power source from the Behlman division of Astrosystems. With
LabWindows, the user can control the instrument's functions from a PC,
using an interactive graphics screen that emulates the supply's front
panel. The 1,350-VA power source provides a continuously adjustable
output from 0 to 135 Vrms. The frequency range is 45 to 500 Hz. Load
regulation is +/-0.5%, line regulation is +/-0.1%, and total harmonic
distortion is less than 0.5%. The supply costs $2,995; an IEEE-488
interface is $750. Availability is 4 weeks ARO. American Reliance has a new
series of benchtop supplies that have microprocessor control but claim to
cost no more than an analog supply. The LPS series is available in power
outputs ranging from 30 to 165 W. A built-in liquid-crystal display panel
monitors output voltage and current, and the supply can be equipped with
an RS-232 interface for remote talk and listen control. Other features of
the LPS include a voltage/current step-up/step-down function, power-off
memory for voltage and current settings, and output enable/disable. Of the
five models available, one has a single output, two have dual-range single
outputs, and two have triple outputs. The representative LPS-301 has dual
ranges of 30 V at 1 A and 15 V at 2 A. Prices for the LPS series range
from $225 to $599, depending on model, with availability from stock. In
the high-power programmable supply category, Sorensen has introduced its
Pro-T series programmable supply, available in both 5- and 10-kW versions.
Its programmable features include remote overvoltage programming and
shutdown. Specifications include an efficiency of 80%, line and load
regulation of 0.1%, transient response of 40 ms typ, and a programming
speed of greater than 150 ms. The list price for the 5-kW supply is $3,
695; the 10-kW supply is $4,700. An IEEE-488 interface costs $900 extra.
Moving up the power ladder is a series of 20-kW programmable supplies from
Magna-Power Electronics. The PXA series is available in seven output
voltages from 20 to 600 Vdc. It has programmable resistance, voltage, and
current, and can be optionally programmed through the IEEE-488 bus.
Several supplies can be connected in series or parallel to generate up to
100 kW in a master-slave configuration. The instrument's front panel has
digital voltage and current meters. The supply lists for $6,995 with
availability of 4 to 6 weeks ARO.
The following companies supplied information used in this article.
Please call or circle the reader service numbers for more information. A
complete list of benchtop power supply manufacturers can be found in
Electronic Engineer's Master, Vol. D.
American Reliance, Inc. El Monte, CA John Gosseff 818-575-5110
Astrosystems, Inc. Behlman Div. Lake Success, NY Mark Tublisky
800-645-8454
B & K Precision Maxtec International Corp. Chicago, IL Robert Kral
312-889-1448
Electro Industries, Inc. Chicago IL Nate Schwartz 312-736-0999
Hewlett-Packard Co. Loveland, CO HP Direct 800-452-4844
IET Labs, Inc. Westbury, NY Sam Sheena 516-334-5959
Instek America Corp. City of Industry, CA Michael Silverstein
818-336-6537
Kepco, Inc. Flushing, NY Paul Birman 718-461-7000
Magna-Power Electronics, Inc. Whippany, NJ Allan Hillman 201-428-1197
Sorensen Co. Paxton, IL Gerald J. Demirjian 800-525-2024
The Vector Group, Inc. Horsham, PA Frank Menichello 215-672-6702
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