CPX400 Series
Single & dual output PowerFlex dc PSUs - 420 watts per output
high performance autoranging outputs, 60V and 20A maximum
true analog controls with digital functionality including S-Lock
isolated tracking for easy series/parallel use - up to 120V or 40A
GPIB, RS-232, USB and LAN interfaces; LXI class C compliance |
CPX400D - Dual 420 watt PowerFlex dc power supply (840W total)
View and adjust setting limits
at any time.
High accuracy four digit
meters have a fixed resolution
for consistent readings at-aglance.
Range Control gives a choice
of PowerFlex (60V/20A) or
fixed range operation (60V/7A
or 20V/20A).
True analog controls make
adjustment quick and simple.
Voltage sensing can be
changed between local
and remote at the flick of a
Safety binding post terminals
can accept fixed-shroud 4mm
plugs** as well as normal
plugs, bare wires, and fork
S-Lock digitally locks voltage
and current settings at the
touch of a button.
DC output switches enable
voltage and current to be set
up before connecting the load.
Individual over-voltage
protection for each output.
Custom Limits enables the
analogue controls to cover
any voltage or current range.
Both On/Off provides
synchronous switching of the
Isolated voltage tracking
facilitates tracking voltage
rails or control for series or
parallel wiring (120V max. or
40A max.).
Choose voltage and current combinations
to suit your applications !
The CPX series is a different type of laboratory power supply designed to meet
the need for flexibility in the choice of voltage and current.
A conventional PSU has a fixed current limit giving a power capability that
reduces directly with the output voltage.
The TTi PowerFlex design of the CPX series enables higher currents to be
generated at lower voltages within an overall power limit envelope.
Each output can provide considerably higher current than a conventional PSU
of the same maximum voltage and power (see power curve).
Example voltage & current combinations include 60V/7A, 42V/10A, 28V/15A,
and 20V/20A.
Building upon success
The CPX400 series, now comprising five models, was developed from the
CPX400A - one of the most successful power supplies ever.
Analog controls with digital stability
As technology has changed, many products have moved from analog controls
to digital ones. Although digital controls suit many instruments, they do not
necessarily suit a bench power supply.
Customer research shows that many users prefer the speed and simplicity of
conventional analog controls for setting voltage and current. Digital controls
may offer greater precision, but often at the expense of ease-of-use. With this
in mind, the CPX400 series retains the true analog controls of its predecessor.
Lock your settings
at the touch of
a button !
The main disadvantage of analog controls is stability and security. The settings
of analog potentiometers can drift over time. More importantly, the settings
can be changed accidentally with potentially serious consequences.
The CPX400 series incorporates S-Lock. One press of the Lock button transfers
control of voltage and current from the analog controls to internal digital
circuitry. This offers not just complete security, but exceptional stability as
well with each setting controlled by an instrumentation quality DAC.
Isolated voltage tracking for maximum flexibility
The two outputs of the CPX400D are completely independent and electrically
isolated from each other.
With V-Track selected, the two outputs remain electrically isolated, but the
voltage control of the Master output sets an identical voltage on the Slave
This enables the user to create two rails of either
polarity and to reference them to different grounds
if necessary (e.g. digital ground and analog ground).
Alternatively the outputs can be wired in series or
parallel to create a voltage capability up to 120V or
a current capability up to 40A with the voltage set
using a single control.
Independent and simultaneous output control
The Both On/Both Off button is in addition to the individual switches for each
output, and allow both outputs to be turned on or off synchronously by a
single button press.
Synchronous switching of the outputs is of increasing importance for circuitry
which can be damaged if one voltage rail is present without the other.
New CPX400S - Single Output 420W
PowerFlex design gives variable voltage and current
combinations within a maximum power envelope
Up to 60V and up to 20A per output (420W maximum)
Constant voltage or constant current operation
Low output noise and good transient response
PowerFlex or fixed-range operation plus custom limits
True analogue controls with digital settings locking
Independent outputs or isolated voltage tracking (dual)
Outputs can be wired in series or parallel for 120V or 40A
Variable OVP trips; safety binding-post terminals
4 digit fixed resolution meters; selectable remote sensing
Compact ½ rack 3U case (dual) or ¼ rack 3U case (single)
Duplicate terminals at rear on CPX400SA, SP & DP
Isolated analogue control interface (CPX400SA only)
GPIB, RS-232, USB and LAN interfaces with LXI class C
compliance (CPX400SP & CPX400DP only)
Low noise and good dynamic response
The PowerFlex regulation system used on the CPX400 series combines a high
frequency pre regulator with a linear post regulator to give both low noise
and good transient response. Each output can operate in constant voltage or
constant current mode with automatic crossover and mode indication.
Precision metering and remote sense
Separate voltage and current meters on each output give a resolution of 10mV
and 10mA. The fixed resolution avoids the misinterpretation of readings that
can occur with auto-ranging 3 or 3½ digit meters where the decimal point
position moves as the reading changes.
Coarse and fine voltage controls are provided. The current control is
logarithmic enabling low current levels to be set accurately. A View Settings
button enables limit settings to be checked and adjusted at any time.
Each output incorporates remote sense terminals that can be enabled or
disabled at the flick of a switch. Remote sensing is essential for maintaining
precise regulation at the load and true metering of the load voltage.
Compact design uses minimum bench or rack space
Despite the high power output of 840 watts, the CPX400D & DP has a small
bench footprint taking up less space on a crowded bench.
For rack-mount applications the half-rack by 3U case size enables two units
(providing four outputs) to be fitted into a single rack slot.
New CPX400SP single output with digital remote control
Single output, ultra compact design
The new CPX400S is a single output version of the CPX400D providing up to 60
volts and 20 amps within its 420 watt power envelope.
It is housed in a ¼ rack width 3U high case that uses the minimum possible
space for either bench use or rack mounting.
Three variants
The single output version of the CPX400 is available in three variants. The
CPX400S has manual control only, for conventional bench-top use. The
CPX400SA adds isolated analogue remote control plus duplicate rear terminals.
The CPX400DP has digital remote control via USB, RS-232, GPIB and LAN (LXI)
along with duplicate rear terminals (see next page).
CPX400SA - isolated analogue remote control
Some applications require analogue remote control rather than digital. The
CPX400SA has fully galvanically isolated voltage driven remote control
for both voltage and current. In addition, voltage and current front panel
settings are provided as non-isolated control voltages, enabling master-slave
configurations to be used.
CPX400SP - digital remote control
(see next page)
Range control offers even more flexibility
As an alternative to PowerFlex operation (60V/20A subject to a power limit),
the CPX400 series can be used as conventional fixed range power supplies of
either 60V/7A or 20V/20A at the press of a button.
Fixed range mode ensures that, whatever the load, the output can only
be in constant voltage or constant current mode and never in power limit.
Additionally finer resolution is provided on the current or voltage controls
A further button offers full customisation of voltage and current limits which
can be set to suit the users application. This has the advantage that the
controls cover the exact voltage and current range required, providing easier
setting and reduced risk of error.
For example, the range could be set to 30V and 14A to create a 30 volt PSU of
maximum current capability. Alternatively it could be set to 5V and 3A if this
was all that was required for a particular application.
Safety binding-post terminals
All CPX series power supplies are fitted with the new TTi designed output
terminals. As well as acting as conventional binding posts for bare wires,
spade connectors, or standard 4mm plugs, these can accept a 4mm safety plug
with rigid insulating sleeve, a requirement specified by an increasing number
of laboratories for safety reasons.
combined with raised insulated
shoulders also make these
terminals “touch proof” for
voltages up to 250V.
CPX400SP and CPX400DP
Remote control via GPIB, RS-232, USB and LAN interfaces
CPX400DP Rear Panel
Voltage/Current/Power Levels
Bench and System use
The CPX400SP and DP are a bus programmable version of the CPX400S and
CPX400D respectively, and include all of their manual control features plus
comprehensive digital interfaces and rear terminals.
Rear output terminals
Power and sense terminals are duplicated on the rear panel for rack mount
applications or other situations where rear connection is more appropriate.
Digital remote control
To meet the varying needs of today’s engineers, a comprehensive array of
interfaces is provided. RS-232, USB, GPIB and LAN (Ethernet) with LXI support
are provided as standard. Each of the digital bus interfaces provides full control
of voltage, current, and output on/off, plus read-back of voltage, current and
status. The interfaces are at ground potential and are opto-isolated from the
output terminals.
The GPIB interface is compliant with IEEE-488.1 and IEEE-488.2. Currently
GPIB remains the most widely used interface for system applications.
An RS-232/RS-423 interface is provided for use with legacy systems. This type
of serial interface remains in common useage and is perfectly satisfactory for
the control of power supplies because data speed is not an issue.
USB provides a simple and convenient means of connection to a PC and is
particularly appropriate for small system use. A USB driver is provided which
supports Windows 2000, XP , Vista and Windows 7.
LAN (Ethernet)
The LAN interface uses a standard 10/100 base-T Ethernet hardware connection
with ICMP and TCP/IP Protocol for connection to a Local Area Network or direct
connection to a single PC. This interface supports LXI and is highly appropriate
for system use because of its scalable nature and low cost interconnection.
LXI Compliance
The LAN interface is compliant with LXI-C. LXI (LAN eXtensions for
Instrumentation) is the next-generation, LAN-based modular architecture
standard for automated test systems managed by the LXI Consortium, and
is expected to become the successor to GPIB in many systems. For more
information on LXI and how it replaces GPIB, or operates along side it, go to:
IVI Driver
An IVI driver for Windows is included. This provides support for common highlevel applications such as LabView*, LabWindows*, and HP/Agilent VEE*.
Voltage Range:
0V to 60V.
Current Range:
0A to 20A.
Note: Actual maxima for voltage and current are typically 1% greater than the figures given above.
Power Range:
Up to 420W subject to power envelope.
The maximum current atany voltage settings is limited by the power envelope which is set to
give 7A at 60V rising to 20A at 20V under all ac supply conditions (both outputs loaded). At
lower output voltages the power is restricted by the 20 amps current maximum.
See PowerFlex power envelope graph on previous page.
Output Setting & Control
Voltage Setting:
Current Setting:
Output Mode:
Output Switch:
View Settings:
Status Indication:
By coarse and fine controls.
By single logarithmic control.
Constant voltage or constant current with automatic cross-over.
CC indicator lit in constant current mode.
Electronic, non isolating. Preset voltage and current limit displayed
when Output is off. Output rise time no load <10ms.
With the output On, the meters show actual voltage and current.
The preset levels can be viewed and adjusted at any time by pressing
the View Settings button.
LED indication of Output On, V/I Limits, CV, CI, Power Limit, Remote,
LAN status. Message on meter display for trip condition.
(Settings Lock) Voltage and current settings can be locked by a single button press.
Lock accuracy is equal to the meter accuracy (see Meter Specifications).
Output Performance
Ripple & Noise:
Load Regulation:
Line Regulation:
Transient Response: Temp. Coefficient: Output Protection
Output Protection: OVP Setting/Range:
Over-temperature: Safety Interlocks:
Typically <3mV rms, <15mV pk-pk, (5mV rms max.) in CV mode.
Voltage - <0·01% of maximum output for any load change within
the PowerFlex envelope (remote sense connected).
Current - <0·05% of maximum output for any load change within
the PowerFlex envelope.
Voltage - <0·01% of maximum output for a 10% line change.
Current - <0·01% of maximum output for a 10% line change.
<250µs to within 50mV of setting for a 5% to 95% load change.
Typically <100ppm/°C
Forward protection by Over-voltage Protection (OVP) trip.
Reverse protection by diode clamp for currents to 3A.
Via screwdriver adjustable preset on front panel. Range 1V to 66V
Output trips off for over-temperature.
Operations that could cause an unexpected change in voltage or
current settings are interlocked with the output switch.
Output Connections
Output Terminals: Universal 4mm safety binding posts on 19mm (0·75”) spacing at front.
Screw terminals at rear (CPX400SA, SP & DP only).
Terminals can accept fixed shroud 4mm plugs, standard 4mm plugs, fork terminals and bare wires.
Remote Sense
Sense Selection:
Sense Terminals:
Voltage sensing is selected as Local or Remote by front panel switch.
Sprung loaded screw-less terminals at front.
Screw terminals at rear (CPX400SA, SP & DP only).
Display Type:
Dual 4-digit meters, 10mm (0·39”) LED.
Voltage Meter
Resolution/ Accuracy: 10mV / ± 0·1% of reading ± 2 digits
Current Meter
Resolution/ Accuracy: 10mA / ± 0·3% of reading ± 20mA
Independent Mode
In the normal mode of operation, each output is fully independent and isolated. Operation
is equivalent to two single output power supplies.
Voltage Tracking Mode
The two outputs remain isolated, but the Slave voltage controls are disabled and the Slave
voltage is set equal to the Master voltage. This can be used to generate tracking bipolar
voltages, or tracking unipolar voltages relative to different grounds.
When voltages greater than 60V are required, the outputs can be wired in series to generate
0 to 120V with the voltage controlled from the Master.
When currents greater than 20A are required, the outputs can be wired in parallel to create
the equivalent of a 40A power supply with the voltage controlled from the Master.
Track Accuracy: Slave voltage = ± (0·1% of Master voltage setting + 10mV)
Each output has an independent DC On/Off control, however, an additional control button is
provided which turn both outputs on or off simultaneously.
Specifications (Continued)
The CPX400SA offers galvanically isolated analogue remote control of voltage and current
from control voltages. Voltage and current front panel settings generate non-isolated analogue
output voltages that can be used to control slave power supplies.
Input Scaling:
Input Accuracy:
Output Scaling:
Output Accuracy:
Remote On/Off:
0 to 100% control of voltage or current from 0 to 5V or 0 to 10V
Voltage: 0.3% ±20mV. Current: 0.5% ±50mA.
Input impedance 10kW
Set values of 0 to 100% of rated output voltage and current
generate 0 to 5V (not isolated)
Voltage: 0.3% ±20mV. Current: 0.5% ±50mA.
Output impedance 125W
Output On/Off can be controlled by external switch closure
(not isolated)
The CPX400SP & CPX400DP offers full remote control and read-back using RS-232, USB, GPIB
or LAN (compliant with LXI class C). All interfaces are at ground potential and opto-isolated
from the output terminals. Note: Remote/Local Sense, is manually selectable only.
IVI Driver
An IVI driver for Windows is supplied. This provides support for common applications such as
LabView*, LabWindows*, HPVEE* etc.
USB Driver
An installation file is supplied which calls a standard Windows* USB driver.
* LabView and LabWindows are trademarks of National Instruments.
HPVEE (now Agilent VEE) is a trademark of Agilent Technologies.
* USB interface is supported for Windows 2000, XP, and Vista.
Windows is a trademark of Microsoft.
Rack Mounts
RM460 19 inch 4U rack mount suitable for up to four single or two dual power supplies.
Dual output units can also be fitted into the RM300A 3U rack
Accuracy specifications apply for the temperature range 18oC to 28oC after one hour warm-up.
Thurlby Thandar Instruments Ltd. operate s a policy of continuous development and reserves the
right to alter specifications without prior notice.
Standard 9-pin D connector. Baud rate 9,600.
USB 2.0 connection (backwards compatible with USB 1.x). Operates as a virtual COM port.
The interface conforms with IEEE-488.1 and IEEE-488.2.
Ethernet (LAN)
Standard 10/100 base-T hardware connection. ICMP and TCP/IP Protocol for connection to
Local Area Network or direct connection to a single PC.
LXI Compliance
Model Table
Analogue RS-232
LAN interface is compliant with LXI class C. (LXI is the abbreviation for Lan eXtensions for
Instrumentation). For more information visit:
Voltage Setting
Resolution/Accuracy: 1mV / ± (0.05% +10mV)
Current Setting
Resolution/Accuracy: 1mA / ± (0.3% +5mA)
Programming Speed
Command Delay:
Typically <25ms (this must be added to any of the figures below)
Voltage Up Time:
<10ms* to 1%
Voltage Down Time: <80ms* to 1% (full load); <1.5s* to 1% (no load)
* The up and down times vary with range and voltage step size. More information is
contained in the operating manual which can be downloaded from our web site.
AC Input:
Input Power:
110 to 240 volts ±10% 50/60Hz. Installation Category II.
Single - 625VA, Dual - 1250VA max.
Temperature & Environmental
Operating Range:
Storage Range:
+5ºC to +40ºC, 20% to 80% RH
-40ºC to + 70ºC
Indoor use at altitudes up to 2000m, Pollution Degree 2.
Rear discharge variable speed fan.
Safety & EMC
Complies with EN61010-1
Complies with EN61326
Single - 107 x 130 (¼ rack 3U) x 398mm
Dual - 210 x 130 mm (½ rack 3U) x 377mm
(size excludes feet, knobs and terminals).
Single - 4.25kg (9.35lb), Dual - 6.3kg (13.9lb)
Designed and built in Europe by:
Thurlby Thandar Instruments Ltd.
Glebe Road, Huntingdon, Cambridgeshire. PE29 7DR United Kingdom
Tel: +44 1480 412451 Fax: +44 1480 450409
Email: [email protected] Web:
Brochure Part No. 82100-1400 Iss. 4A
Product Summary
Company name and product brands
Laboratory Power Supplies
Bench and system power supplies from 30 watts up to
1200 watts using linear, mixed-mode and PowerFlex
regulation technologies.
Thurlby Thandar Instruments Ltd. (TTi) is one of Europe’s leading
manufacturers of test and measurement instruments.
Waveform Generators
Analog and digital (DDS) function generators, true
arbitrary generators, arbitrary/function generators and
pulse generators.
In the future, however, the full product range will be branded Aim-TTi.
Products have been sold under two brand names:
TTi and Aim.
This changeover will be gradual and many products will continue to carry
the TTi or Aim brands for some time to come.
Web Addresses (URLs)
Precision Measurement Instruments
Benchtop DMMs, frequency counters, component
measurement instruments (LCR), electronic dc loads,
current probes.
The preferred URL for obtaining information concerning Aim-TTi products
is: (international customers)
Customers in the UK should use the URL:
RF and EMC Test Equipment
Spectrum analyzers, signal generators, frequency counters,
power meters, emc measurement instruments.
Customers in the USA should use the URL:
Note that previous URLs such as will continue to operate
for the time being.
Designed and built in Europe by:
Thurlby Thandar Instruments Ltd.
Glebe Road, Huntingdon, Cambridgeshire PE29 7DR England (United Kingdom)
Tel: +44 (0)1480 412451 Fax: +44 (0)1480 450409
Email: [email protected] Web:
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