AimTTi PowerFlex QPX1200 Series User manual

INSTRUCTION MANUAL
QPX1200 Series
PowerFlex DC Power Supplies

Table of Contents
Specification 2
EMC 6
Safety 7
Installation 8
Connections 9
Initial Operation 11
Manual Operation 13
Remote Operation 20
Remote Commands 29
Maintenance 33
Note: The latest revisions of this manual, device drivers and software tools can be downloaded from:
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This manual is 48511-1400 Iss 6
1

Specification
General specifications apply for the temperature range 5°C to 40°C. Accuracy specifications
apply for the temperature range 18°C to 28°C after 1 hour warm-up with no load and calibration at
23°C. Typical specifications are determined by design and are not guaranteed.
OUTPUT SPECIFICATIONS
Voltage Range: 0V to 60V
Current Range: 0.01A to 50A
Power Range: Up to 1200W
Voltage Setting: Resolution 1mV
Accuracy: 0.1% of setting ± 2mV
Current Setting: Resolution 10mA
Accuracy: 0.3% of setting ± 20mA
Operating Mode: Constant voltage or constant current with automatic cross-over
provided that the power demanded stays within the power envelope,
see graph. Outside of this envelope the output becomes unregulated.
CV, CI or UNREG mode indication in display.
QPX 1200
POWER ENVELOPE
Output Switch: Electronic, with ON indication.
Preset voltage and current displayed when off.
Output Terminals: Front panel safety terminals accepting 6mm wire diameter, 6mm
plugs or 8mm spades at 50 Amps max, or 4mm plugs at 30 Amps
max. Duplicate rear panel terminals.
Sensing: Switchable between local and remote. Screwless remote sense
terminals on both front and rear panels. Sense miswiring trip and
indication.
Ripple & Noise
(20MHz bandwidth): Typically <3mVrms, <20mV pk-pk at maximum load, CV mode
Load Regulation: Change in output for any load change within PowerFlex envelope,
using remote sense:
Constant voltage: <0.01% ± 5mV
Line Regulation: Change in output for a 10% line change:
Constant voltage: <0.01% ± 5mV
Transient Response: <250us to within 100mV of set level for a 5% to 95% load change.
2

Output Protection: Output will withstand an applied forward voltage of up to 70V.
Reverse protection by diode clamp for reverse currents up to 3A.
Over-voltage Protection
(OVP):
Range 2V to 65V. Resolution 0.1V; accuracy: 0.2% ± 0.2V.
Response time typically 100µs.
Over-current Protection
(OCP):
Range 2A to 55A. Resolution 0.1A; accuracy: 0.5% ± 0.2A.
Response time typically 100ms.
Over-temperature Protection: The output will be tripped off if a fault causes the internal
temperature to rise excessively.
Temperature Coefficient: Typically <100ppm/°C
METER SPECIFICATIONS
Display Type: 5-digit (Volts), 4-digit (Amps), black-on-white backlit LCD.
Voltage (CI Mode and Unreg): Resolution 1mV
Accuracy: 0.1% of reading ± 2 digits
Current (CV Mode & Unreg): Resolution 10mA
Accuracy: 0.3% of reading ± 2 digits
V x A: Resolution 0·1W
Accuracy: 0·5% ± 0·1W
V/A: Meter shows calculated nominal V/A value, together with
uncertainty range; 5 digit resolution.
LOGIC CONTROL INPUT and OUTPUT
LOGIC IN is a rear-panel opto-isolated input that is activated at an input current greater than
approximately 1mA. User can set LOGIC IN (via the keyboard) to enable the output, disable the
output, or be ignored when it is activated.
LOGIC OUT is an isolated rear-panel open-collector output that will sink up to 2mA when
activated (‘switch closure’); the maximum voltage that can be applied to LOGIC OUT is 30VDC.
User can set LOGIC OUT to be ‘closed’ or ‘open’ for output enabled or disabled, current limit (CI
mode), power limit (UNREG mode), or for any fault trip.
ANALOG REMOTE CONTROL and MONITORING
Non-isolated inputs and outputs to set voltage and current limit and to monitor actual output
voltage and current. These signals are referenced to the positive output and have a range of 0 to
10V or 0 to 5V (selectable via the keyboard).
Analogue Control Accuracy: Voltage: 0.3% ± 4mV; Current: 0.5% ± 40mA
Analogue Monitor Accuracy: Voltage: 0.3% ± 4mV; Current: 0.5% ± 40mA
KEYBOARD & ROTARY CONTROL
All functions, including the selection and set-up of the remote control interfaces, can be set from
the keyboard. The rotary Jog control can be used to adjust output voltage and current settings in
a quasi-analogue mode.
DISPLAY FEATURES
The display is a 240 x 64 pixel transflective LCD, backlit by white LEDs; contrast is software-
controlled and can be adjusted from the keyboard.
The default status display shows the VOLTS (5 digits) and AMPS (4 digits) in 10mm high
characters, plus the present output mode. At other times, for example during store or recall of
instrument set-ups, the display shows up to 6 lines of information, instructions, or prompts.
3

INTERFACES
Full digital remote control facilities are available through the RS232, LAN and USB interfaces.
Setting and readback resolutions are the same as the Output and Meter specifications
respectively.
RS232: Standard 9-pin D-connector. Baud rate 9600.
USB: Standard USB 2.0 hardware connection.
LAN: Ethernet 100/10base-T hardware connection.
LXI V1.2, Class C compliant.
GPIB (factory option): Conforming with IEEE488.1 and IEEE488.2.
Remote Command
Processing Time:
Typically <100ms between receiving the command terminator for a
step voltage change at the instrument and the output voltage
beginning to change.
GENERAL
AC Input: 110V – 240V AC ± 10%, 50/60Hz.
Installation Category II.
Power Consumption: 1600VA max.
Operating Range: +5ºC to +40ºC, 20% to 80% RH.
Storage Range: −40ºC to + 70ºC.
Environmental: Indoor use at altitudes up to 2000m, Pollution Degree 2.
Store/Recall: Up to 10 set-ups can be saved and recalled via the keyboard or
remote interfaces.
Safety: Complies with EN61010-1.
EMC: Complies with EN61326.
Size: 130mm H (3U) x 356mm W x 413mm D
Weight: 9.2kg
Options: 19-inch rack kit.
4

EC Declaration of Conformity
We Thurlby Thandar Instruments Ltd
Glebe Road
Huntingdon
Cambridgeshire PE29 7DR
England
declare that the
QPX1200L Power Supply with GPIB option
meets the intent of the EMC Directive 2004/108/EC and the Low Voltage Directive 2006/95/EC.
Compliance was demonstrated by conformance to the following specifications which have been
listed in the Official Journal of the European Communities.
EMC
Emissions: a) EN61326-1 (2006) Radiated, Class A
b) EN61326-1 (2006) Conducted, Class A
c) EN61326-1 (2006) Harmonics, referring to EN61000-3-2 (2006)
Immunity: EN61326-1 (2006) Immunity Table 1, referring to:
a) EN61000-4-2 (1995) Electrostatic Discharge
b) EN61000-4-3 (2006) Electromagnetic Field
c) EN61000-4-11 (2004) Voltage Interrupt
d) EN61000-4-4 (2004) Fast Transient
e) EN61000-4-5 (2006) Surge
f) EN61000-4-6 (2007) Conducted RF
Performance levels achieved are detailed in the user manual.
Safety
EN61010-1 Installation Category II, Pollution Degree 2.
CHRIS WILDING
TECHNICAL DIRECTOR
2 May 2009
5

EMC
This instrument has been designed to meet the requirements of the EMC Directive 2004/108/EC.
Compliance was demonstrated by meeting the test limits of the following standards:
Emissions
EN61326-1 (2006) EMC product standard for Electrical Equipment for Measurement, Control and
Laboratory Use. Test limits used were:
a) Radiated: Class A
b) Conducted: Class A
c) Harmonics: EN61000-3-2 (2006) Class A; the instrument is Class A by product category.
Immunity
EN61326-1 (2006) EMC product standard for Electrical Equipment for Measurement, Control and
Laboratory Use.
Test methods, limits and performance achieved are shown below (requirement shown in
brackets):
a) EN61000-4-2 (1995) Electrostatic Discharge : 4kV air, 4kV contact, Performance A (B).
b) EN61000-4-3 (2006) Electromagnetic Field:
3V/m, 80% AM at 1kHz, 80MHz – 1GHz: Performance Bg(A) and
1.4GHz to 2GHz: Performance A (A); 1V/m, 2.0GHz to 2.7GHz: Performance A (A).
gminor regulation deviation at ~140MHz and ~250MHz at 3V/m.
c) EN61000-4-11 (2004) Voltage Interrupt: ½ cycle and 1 cycle, 0%: Performance B (B);
25 cycles, 70%: Performance A (C); 250 cycles, 0%: Performance B (C), if Function 11
set (Output status at power-up same as at last power-down), otherwise Performance C.
d) EN61000-4-4 (2004) Fast Transient, 1kV peak (AC line), 0·5kV peak (DC Output),
Performance B (B).
e) EN61000-4-5 (2006) Surge, 0·5kV (line to line), 1kV (line to ground), Performance B (B).
f) EN61000-4-6 (2007) Conducted RF, 3V, 80% AM at 1kHz (AC line only; DC Output
connections <3m, therefore not tested), Performance A (A).
According to EN61326-1 the definitions of performance criteria are:
Performance criterion A: ‘During test normal performance within the specification limits.’
Performance criterion B: ‘During test, temporary degradation, or loss of function or
performance which is self-recovering’.
Performance criterion C: ‘During test, temporary degradation, or loss of function or
performance which requires operator intervention or system reset occurs.’
Where Performance B is stated it is because DC Output regulation, or V & I measurement
accuracy, may deviate beyond Specification limits under the test conditions. However, the
possible deviations are still small and unlikely to be a problem in practice.
Note that if operation in a high RF field is unavoidable it is good practice to connect the PSU to
the target system using screened leads which have been passed (together) through an absorbing
ferrite sleeve fitted close to the PSU terminals.
Cautions
To ensure continued compliance with the EMC directive observe the following precautions:
a) after opening the case for any reason ensure that all signal and ground connections are
remade correctly and that case screws are correctly refitted and tightened.
b) In the event of part replacement becoming necessary, only use components of an identical
type, see the Service Manual.
6

Safety
This power supply is a Safety Class I instrument according to IEC classification and has been
designed to meet the requirements of EN61010-1 (Safety Requirements for Electrical Equipment
for Measurement, Control and Laboratory Use). It is an Installation Category II instrument
intended for operation from a normal single phase supply.
This instrument has been tested in accordance with EN61010-1 and has been supplied in a safe
condition. This instruction manual contains some information and warnings which have to be
followed by the user to ensure safe operation and to retain the instrument in a safe condition.
This instrument has been designed for indoor use in a Pollution Degree 2 environment in the
temperature range 5°C to 40°C, 20% - 80% RH (non-condensing). It may occasionally be
subjected to temperatures between +5°C and –10°C without degradation of its safety. Do not
operate while condensation is present.
Use of this instrument in a manner not specified by these instructions may impair the safety
protection provided. Do not operate the instrument outside its rated supply voltages or
environmental range.
WARNING! THIS INSTRUMENT MUST BE EARTHED
Any interruption of the mains earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited. The protective action must not be
negated by the use of an extension cord without a protective conductor.
When the instrument is connected to its supply, terminals may be live and opening the covers or
removal of parts (except those to which access can be gained by hand) is likely to expose live
parts. The apparatus shall be disconnected from all voltage sources before it is opened for any
adjustment, replacement, maintenance or repair.
Capacitors inside the power supply may still be charged even if the power supply has been
disconnected from all voltage sources but will be safely discharged about 10 minutes after
switching off power.
Any adjustment, maintenance and repair of the opened instrument under voltage shall be avoided
as far as possible and, if inevitable, shall be carried out only by a skilled person who is aware of
the hazard involved.
If the instrument is clearly defective, has been subject to mechanical damage, excessive moisture
or chemical corrosion the safety protection may be impaired and the apparatus should be
withdrawn from use and returned for checking and repair.
Make sure that only fuses with the required rated current and of the specified type are used for
replacement. The use of makeshift fuses and the short-circuiting of fuse holders is prohibited.
Do not wet the instrument when cleaning it.
The following symbols are used on the instrument and in this manual:-
Earth (ground) terminal.
mains supply OFF.
l mains supply ON.
alternating current (ac)
direct current (dc)
7

Installation
Mains Operating Voltage
This instrument has a universal input range and will operate from a nominal 115V or 230V mains
supply without adjustment. Check that the local supply meets the AC Input requirement given in
the Specification.
Mains Lead
Connect the instrument to the AC supply using the mains lead provided. Should a mains plug be
required for a different mains outlet socket, a suitably rated and approved mains lead set should
be used which is fitted with the required wall plug and an IEC60320 C13 connector for the
instrument end. To determine the minimum current rating of the lead-set for the intended AC
supply, refer to the power rating information on the equipment or in the Specification.
WARNING! THIS INSTRUMENT MUST BE EARTHED.
Any interruption of the mains earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited.
Mounting
This instrument is suitable both for bench use and rack mounting. It is delivered with feet for
bench mounting. The front feet include a tilt mechanism for optimal panel angle.
A rack kit for mounting in a 19” rack is available from the Manufacturers or their overseas agents.
Ventilation
The power supply is cooled by intelligent multi-speed fans which vent at the rear. Take care not
to restrict the air inlets at the side panels or the exit at the rear. In rack-mounted situations allow
adequate space around the instrument and/or use a fan tray for forced cooling.
8

Connections
Front Panel Connections
The load should be connected to the positive (red) and negative (black) terminals marked
OUTPUT. The terminals accept 4mm plugs into the end (but note that 4mm plugs will only
support 32 Amps), 6mm diameter wire or plugs into the cross-hole or 8mm spade connections
(with a maximum blade width of 16mm). The wiring and connectors must be capable of
supporting the current required; for 50 Amps, 6mm2cable is needed.
Remote sense connections to the load, if required, are made from the positive (+) and
negative (−) REMOTE SENSE terminals. Remote sense operation is selected from the keyboard
or via a remote control interface; the front panel REMOTE SENSE lamp is lit when remote sense
is selected. Switching off remote sense returns the instrument to local sensing at the front panel
output terminals.
The terminal marked is connected to the chassis and safety earth ground.
Rear Panel Connections
Output Terminals
The output and sense terminals are duplicated on the rear panel; these connections are
paralleled with their front panel equivalents.
Remote sense operation is selected from the keyboard or via a remote control interface. When
the rear panel terminals are used, remote sense should always be selected to ensure that output
regulation is maintained within specification.
Logic Input
LOGIC IN is connected directly to the input of an isolating opto-coupler; there is no series
resistor. The input is activated when a current greater than approximately 1mA is forced between
LOGIC IN and LOGIC COMMON. The function of LOGIC IN is set from the keyboard.
Do not force a current exceeding 25mA between the terminals. Do not apply a voltage to LOGIC
IN / LOGIC COMMON exceeding 50V with respect to .
Logic Output
LOGIC OUT is the open-collector output of an opto-isolated NPN transistor that will sink up to
2mA when active (‘switch closure’). The function of LOGIC OUT is set from the keyboard.
The maximum operating voltage that can be applied between LOGIC OUT and LOGIC COMMON
is 30VDC.
Do not apply external voltages between the terminals exceeding 30VDC.
Analogue Control
V CONTROL and I CONTROL provide quasi-analogue control of the Output Voltage and Current
Limit respectively. The CONTROL inputs are read 4 times per second by the A-to-D converter
and the output is set according to the selected input scaling. The input scaling for both can be set
as 0 to 10 Volts or 0 to 5 Volts for maximum output. The Analogue Control functions and scaling
are both selected from the keyboard. The COMMON return signal is referenced to the positive
output of the power supply.
Do not apply external voltages between the terminals exceeding 20VDC.
9

Analogue Monitor
The output terminal voltage and output current may be monitored on V MONITOR and I
MONITOR respectively. The output scaling for both is the same as that set for V CONTROL and I
CONTROL, see previous section. The COMMON return signal is referenced to the positive
output of the power supply.
Do not apply external voltages to these terminals.
RS232
9−pin female D−connector with pin connections as shown below. Can be connected to a
standard PC port using a fully wired 1:1 male-female cable without any cross-over connections.
Pin Name Description
1 RI
Passively asserted (+V through 10kΩ)
2 TXD Transmitted data from instrument
3 RXD Received data to instrument
4 CTS
5 GND Signal ground
6 RTS
Passively asserted (+V through 10kΩ)
7 DSR No internal connection
8 DTR
9 CD No internal connection
Signal ground is connected to instrument ground.
USB
The USB port is connected to instrument ground. It conforms with USB 2.0 (Full Speed) and
accepts a standard USB cable. The Windows plug-and-play functions should automatically
recognise that the instrument has been connected. If the correct driver is not found, follow the
Windows on-screen prompts and install the required files from the CD supplied.
LAN
The LAN interface is designed to meet LXI ( Lan eXtensions for Instrumentation) version 1.2;
the instrument is Class C compliant. Remote control using the LAN interface is possible using a
TCP/IP Socket protocol. The instrument also contains a basic Web server which provides
information on the unit and allows it to be configured. Since it is possible to misconfigure the LAN
interface, making it impossible to communicate with the instrument over LAN, a LAN
Configuration Initialise (LCI) mechanism is provided via a recessed switch on the rear panel
(marked LAN RESET) to reset the unit to the factory default.
Further details are given in the Remote Operation chapter. For more information on LXI
standards refer to www.lxistandard.org/home
GPIB – Factory Option
The GPIB signal grounds are connected to the instrument ground. The implemented subsets are:
SH1 AH1 T6 L4 LEO SR1 RL2 PP1 DC1 DT0 C0 E2
The GPIB address is set from the front panel.
10

Initial Operation
This section of the manual is a general introduction to the controls and operation of the
instrument and is intended to be read before using the power supply for the first time.
In this manual front panel keys, connections and indicators are shown in capitals, e.g. ESCAPE,
JOG SET, OUTPUT, ON. Messages shown on the display are printed in a different type-font, e.g.
Enter V,Limits,CV,Store.
Switching On, Output On/Off
The power switch is located at the bottom left of the front panel.
At power-up the default behaviour is for the instrument's settings to be restored to those
automatically saved when it was switched off, but with the Output always off ( OUTPUT OFF is
shown in the display). However, the user can change this default setting such that the Output is
also restored at power-up to its status at power-down, see the Extra Functions section.
The DC Output is switched on and off electronically with alternate presses of the key; the
ON lamp illuminates when the Output is on. At the same time the message above the VOLTS and
AMPS display changes from OUTPUT OFF to CV (constant voltage) or CI (constant current) to
indicate the present operating mode; should the load cause the instrument to operate outside its
guaranteed power range the display will instead show UNREG (unregulated).
Keypad
Only the principles of operation are outlined here; the setting of individual parameters is given in
detail in later sections.
The paramount consideration in designing the user interface has been to make changing settings
as 'safe' as possible (i.e. with minimal risk of accidentally applying excessive voltages to a target
system) whilst achieving ease of use. This has been achieved by requiring the user to confirm
(OK) new numeric settings, with the option to ESCAPE at any point or even to simply pause until
the operation times-out and the instrument returns to its original settings. In addition, display
messages and LED indicators prompt, guide or warn the user such that entry or control errors are
minimised. Where some of these features (e.g. beeps) are considered unnecessary by regular
users, the option exists to disable them, see the Extra Functions section.
Under normal conditions the numeric keypad is disabled; pressing any key will cause the buzzer
to beep, indicating an illegal operation. To set a voltage with the keypad first press the V
NUMERIC SET key; the VOLTS display changes to show the present set value in a smaller font,
with the message Enter V or ESC below it, and the OK lamp starts flashing. The new value
is then entered from the keyboard; as it is entered it is displayed directly below the present
setting, replacing the prompt message. At any time during entry the new setting can be
confirmed with the OK key, e.g. it is sufficient to key in 1, OK to change the setting to 1Volt.
When OK is pressed the display reverts to show just the new setting in the full-size font and the
OK lamp stops flashing; if OK is not pressed within 10 seconds of the last numeric key the entry
is cancelled and the display returns to its original setting. If ESCAPE is pressed anytime in the
entry procedure, entry is cancelled and the display returns to its original setting. The current limit
is set in exactly the same way after first pressing I NUMERIC SET.
The OK key is used to confirm most keypad entries. At all other times it becomes the VIEW V/I
LIMITS key and pressing it will cause the display to show preset output voltage and current limit
for 3 seconds; during this period the Limits message shows in the display.
Pressing SHIFT illuminates the ▲lamp and gives the numeric keys the functions marked above
them, e.g. STR (Store), RCL (Recall), etc. When a shift function is selected SHIFT is cancelled
(the ▲lamp is no longer lit). The further key presses required to complete the selected function
are described in detail in the sections that follow; if no key is pressed within 10 seconds to
complete the function, the function will terminate as if ESCAPE has been pressed. SHIFT is a
toggle key; pressing SHIFT again when it has been selected will cancel SHIFT. SHIFT is also
cancelled by ESCAPE, or by pressing SET V or SET I.
11

Jog Control
The rotary 'jog' control permits the output voltage or current limit to be incremented or
decremented in steps with a resolution set by the JOG SET keys; the output immediately follows
the setting, i.e. no OK is required.
At power-up jog is always off. To jog the voltage or current setting press the V or I JOG SET key;
the associated lamp will illuminate and the appropriate parameter display now changes to two
lines. With the output ON the top line continues to show the actual output, but the additional lower
display now shows the present Limits value; in the lower display, the JOG indicator ( ) is
positioned under the digit that was last jogged. Whilst the V or I JOG SET indicator is lit, each
further press of the V or I key moves the JOG indicator one digit to the left; the selection 'wraps-
round' such that when the largest value of jog increment has been reached the next press returns
it to the lowest. The default position at power-up is under the LSD, i.e. the lowest jog increment is
selected.
Turning the rotary jog control clockwise/anti-clockwise increments/decrements the selected digit;
digits to the left of the one being jogged are automatically incremented/decremented when the
decade overflow/underflow point is reached. Digits to the right of the one being jogged remain
unchanged unless the jog step overflows/underflows the maximum/minimum settings in which
case they are set to zero. For example, 59·861V goes to 59·961V goes to 60·000V for a 0.1V jog
increment; 1.60A goes to 0·60A goes to 0·01A for a 1A jog decrement.
The jog steps that can be selected are 1mV, 10mV, 100mV and 10mA, 100mA, 1A.
To disable the jog rotary control press the JOG SET OFF key; reselecting JOG SET V or I will
enable jog on the last used digit position. Jog is not cancelled by using numeric entry or any of
the SHIFT functions but it is disabled whilst that function is enabled.
Note that the dual display of the parameter being jogged is primarily of use if the output is ON;
with the output off both lines of the display show the Limits value and change simultaneously
as the parameter is jogged.
Display
At power-up the display briefly shows the instrument model number and installed firmware
revision (Keyboard and Control firmware revision on the left; Interface firmware on the right)
before reverting to the standard status display.
The standard status display shows the voltage on the left (above the front panel VOLTS marking)
and the current on the right (above the front panel AMPS marking) together with the present
output status, i.e. OUTPUT OFF, CV, CI, or UNREG; if the output is off then Limits is also
shown in the display above the V and I values. The status of the LAN connection is also shown in
the top left corner of the display, as required for LXI compliance. Refer to the 'LAN Status
Indication' paragraph in the LAN Interface section for details. During other operations, however,
the display capabilities are used more extensively to show, for example, prompts during function
settings, e.g. memory store and recall operations or the extra functions accessed via the #shift
function; details are given in the relevant sections of this manual.
The display contrast is set at the factory but can be adjusted from the keyboard to optimise it for
particular ambient operating conditions. Press SHIFT, # , select Extra Function 90, and follow the
on-screen prompts.
12

Manual Operation
New users should first read the Initial Operation chapter which describes the operating principles
of the keypad and rotary jog control.
Set Voltage
With the output off, the standard status display shows the set voltage; Limits shows as a
reminder beside OUTPUT OFF in the top line of the display. With the output ON the mode
changes to CV (constant voltage) or CI (constant current), depending on the set current limit and
load conditions, and the display shows the actual output voltage (measured at the sense point);
note that in CI mode the actual output voltage will be less than the set voltage. Both the set and
actual voltage are shown to a resolution of 1mV. If the set voltage and load conditions cause the
instrument to operate outside its guaranteed power range the display will show UNREG
(unregulated) and the actual output voltage will again be less than the set voltage.
The voltage can be set directly from the numeric keypad: press the NUMERIC SET V key, enter
the new value using the numeric keys and confirm by pressing OK. The broad principles of
keypad entry are explained in the Initial Operation chapter, which should be read by new users.
When SET V is pressed the VOLTS display changes to show the present set value in a smaller
font, with the message Enter V or ESC below it, and the OK lamp starts flashing. The new
voltage is then entered from the keyboard, e.g. 12·345V is entered as 1, 2, ·, 3, 4, 5. As it is
entered it is displayed directly below the present setting, replacing the prompt message.
The minimum voltage setting is 0·000V; the maximum setting is 60·000V.
Pressing OK at any point will set the voltage entered with any remaining digits set to zero,
e.g. 1, 2, ·, 3, OK will set 12·300V; 1, OK will set 1·000V. When OK is pressed the set voltage is
changed and the display reverts to the standard status mode.
Pressing ESCAPE at any time during the sequence, or making no further key press within
10 seconds of the previous one will cause the display to return to its original reading before
SET V was pressed.
Entering a voltage outside the range maximum (including trying to enter 3 digits before the
decimal point) or trying to enter more than 5 digits will cause the buzzer to beep; the last key
entry will be ignored.
The voltage can also be set using the Jog control. Pressing JOG SET V will illuminate the V JOG
SET lamp and the VOLTS display will again change to two lines. With the output ON the top line
continues to show the actual output, but the additional lower display now shows the present
Limits value; in the lower display, the JOG indicator ( ) is positioned under the digit that was
last jogged. Whilst the V SET lamp is lit, each further press will move the JOG indicator one
digit to the left; the selection 'wraps round' such that when the largest value of jog increment has
been reached the next press returns it to the lowest. The default position at power-up is under
the LSD, i.e. the lowest jog increment is selected. The jog steps that can be selected are 1mV,
10mV and 100mV.
With jog enabled the output voltage can be incremented or decremented with the rotary jog
control with a step resolution indicated by the position of the JOG indicator. The output
immediately follows the setting, i.e. no OK is required. In CV (constant voltage) mode the actual
output voltage shown in the upper display line will follow the set voltage being ‘Jogged’ in the
lower display; however, if the output goes into constant current mode (indicated by the CV status
message being replaced by CI) the upper display, showing actual voltage, will show a value
which is less than the set voltage.
Note that the dual display during JOG SET V is primarily of use if the output is ON; with the
output off both lines of the display show the Limits value and change simultaneously as the
voltage is jogged.
13

Set Current Limit
With the output off, the standard status display shows the set current limit; with the output on it
shows the actual output current in all modes (CV, CI or UNREG). Both the actual current and the
current limit are shown to a resolution of 10mA.
The current limit can be set directly from the numeric keypad: press the NUMERIC SET I key,
enter the new value using the numeric keys and confirm by pressing OK. The broad principles of
keypad entry are explained in the Initial Operation chapter, which should be read by new users.
When SET I is pressed the AMPS display changes to show the present current limit value in a
smaller font, with the message Enter I or ESC below it, and the OK lamp starts flashing.
The new current limit is then entered from the keyboard, e.g. 12·34A is entered as 1, 2, ·, 3, 4. As
it is entered it is displayed directly below the present setting, replacing the prompt message.
The minimum current setting is 0·01A; the maximum setting is 50.00A, i.e. there is no over-range
capability.
Pressing OK at any point will set the current entered with any remaining digits set to zero,
e.g. 1, 2 ·, 3, OK will set 12·30A; 1, OK will set 1·00A. When OK is pressed the current limit is
changed and the display reverts to the standard status mode.
Pressing ESCAPE at any time during the sequence, or making no key press within 10 seconds of
the previous one will cause the display to return to its original reading before SET I was pressed.
Entering a value outside the range maximum (including trying to enter 3 digits before the decimal
point) or trying to enter more than 4 digits will cause the buzzer to beep; the last key entry will be
ignored.
The current limit can also be set using the rotary jog control. Pressing JOG SET I will illuminate
the I JOG SET lamp and the AMPS display will again change to two lines. With the output ON
the top line continues to show the actual output, but the additional lower display now shows the
present current limit; in the lower display, the JOG indicator ( ) is positioned under the digit that
was last jogged. Whilst the I SET lamp is lit, each further press will move the JOG indicator one
digit to the left; the selection 'wraps round' such that when the largest value of jog increment has
been reached the next press returns it to the lowest. The default position at power-up is under
the LSD, i.e. the lowest jog increment is selected. The jog steps that can be selected are 10mA ,
100mA and 1A.
With jog enabled the current limit can be incremented or decremented with the rotary jog control
with a step resolution indicated by the position of the JOG indicator. The output immediately
follows the setting, i.e. no OK is required. With the output ON and in CV mode the upper line of
the display showing actual current will be a lower value than the current limit being ‘Jogged’ in the
lower display; however, if the output goes into constant current mode (indicated by the CV status
message being replaced by CI) the upper display, showing actual current, will follow the current
limit value being ‘Jogged’ in the lower display.
Note that the dual display during JOG SET I is primarily of use if the output is ON; with the output
off both lines of the display show the Limits value and change simultaneously as the current
limit is jogged.
Instantaneous Current Output
The current limit control can be set to limit the continuous output current to levels down to 10mA.
However, in common with all precision bench power supplies, a capacitor is connected across the
output to maintain stability and good transient response. This capacitor charges to the output
voltage and short-circuiting of the output will produce a current pulse as the capacitor discharges
which is independent of the current limit setting.
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Output Power (V x A)
If SHIFT, V x A is pressed the display shows the product of measured output voltage x measured
current in the form nn.n VA. . The V x A value is updated at the same measurement rate as
for V and I. Pressing ESCAPE cancels V x A mode.
Calculated Load Impedance (V/A)
If SHIFT, V/A is pressed the display shows the calculated result of measured output voltage ÷
measured current; this is a sampled result which can be updated by further presses of the OK
key. Pressing ESCAPE cancels V/A mode.
The display shows the calculated nominal V/A value with a resolution of 5 significant digits (10µΩ
resolution for V/A <1Ω). The accuracy is calculated from the uncertainty of the individual voltage
and current measurements and is indicated by showing the minimum and maximum possible
values (in brackets) beside the nominal. The uncertainty is worst when either (or both) V and I
are small.
This function is extremely useful for measuring low impedances at high currents, e.g. RDS(on) of
power MOSFETs. Always use the Remote Sensing function to eliminate the effects of connecting
lead and contact resistance when making low value V/A measurements.
Current Measurement Averaging
Press SHIFT, IAVG to select current averaging; IAV G shows in the top line of the display beside
the mode status. The AMPS reading is still updated at the same rate (4 times per second) but the
value displayed is the rolling average of the last 4 current measurements made.
Connection to the Load
The load should be connected to the positive (red) and negative (black) OUTPUT terminals. Both
are fully floating and either can be connected to ground.
Remote Sensing
The instrument has a very low output impedance, but this is inevitably increased by the
resistance of the connecting leads and the contact resistance between terminals and leads. At
high currents this can result in significant differences between the indicated source voltage and
the actual load voltage (even two 2mΩconnecting leads will drop 0·2V at 50 Amps, for instance).
This problem can be minimised by using short, thick, connecting leads, but where necessary it
can be completely overcome by using the remote sense capability.
This requires the sense terminals to be connected to the output at the load instead of at the
source; insert wires into the spring-loaded REMOTE SENSE terminals and connect directly to the
load.
Select remote sense by pressing SHIFT, SENSE; the message Turn On Remote sense?
OK to confirm, ESCAPE to cancel is shown in the display and the OK lamp flashes.
Press OK to confirm or press ESCAPE to exit without changing state; the REMOTE SENSE lamp
above the front panel terminals lights when remote sense is selected. Remote sense is turned off
by pressing SHIFT, SENSE again; the message Turn Off Remote Sense? OK to
confirm, ESCAPE to cancel is shown in the display and the OK lamp flashes. Press
OK to confirm or press ESCAPE to exit without changing state; the REMOTE SENSE lamp above
the front panel terminals is off when remote sense is deselected.
To avoid instability and transient response problems, care must be taken to ensure good coupling
between each output and sense lead; this can best be done by twisting the leads together. An
electrolytic capacitor directly across the load connection point may also be beneficial.
The voltage drop in each output lead must not exceed 0.5 Volts.
The power supply has rear panel output and sense terminals, appropriate for when the instrument
is used in a rack. The rear panel remote sense terminals should always be used with the rear
panel output connections.
15

Sense Miswiring Trip
The output will be tripped off if the voltage between an output terminal and its corresponding
sense terminal exceeds approximately 1V; this will happen if the sense wires are wired at the
load to the wrong output or if an attempt is made to draw power from the sense wires.
If the sense terminals are miswired in this way the output is turned off and the message Sense
Error – Check Connections is displayed. Pressing ESCAPE at this point removes the
message and the display now shows the preset voltage and current limit. When the cause of the
trip has been corrected the output can be turned on again.
Series or Parallel Connection with Other Outputs
The outputs of the power supply are fully floating and may be used in series with other power
supply units to generate high DC voltages up to 300VDC.
The maximum permissible voltage between any terminal and earth ground ( ) is 300VDC.
WARNING! Such voltages are exceedingly hazardous and great care should be taken to shield
the output terminals for such use. On no account should the output terminals be touched when
the unit is switched on under such use. All connections to the terminals must be made with the
power switched off on all units.
It should be noted that the unit can only source current and cannot sink it, thus units cannot be
series connected in anti-phase.
The unit can be connected in parallel with others to produce higher currents. Where several units
are connected in parallel, the output voltage will be equal to that of the unit with the highest output
voltage setting until the current drawn exceeds its current limit setting, upon which the output will
fall to that of the next highest setting, and so on. In constant current mode, units can be
connected in parallel to provide a current equal to the sum of the current limit settings.
Note that the output terminals are rated at 60A maximum; if several outputs are operated in
parallel to source higher currents than this the junction should be made at a separate point, not
one of the terminals.
Over-Voltage Protection
Over-Voltage Protection (OVP) can be set from 2·0V to 65.0V. If the output voltage exceeds the
set OVP the output is immediately turned off (typically within 100µs), thus avoiding damage to the
circuit under test. The OVP circuit will trip if an excessive voltage is accidentally set from the front
panel or via a remote control interface, or is the result of a failure in the control circuitry of the
instrument itself. OVP will also trip if an excessive voltage is impressed across the terminals from
an external source; however, when the output is tripped off, the external voltage will still be
present and it is up to the user to remove the source to avoid possible damage.
To set OVP press SHIFT, OVP. The display changes to show only the present OVP setting
together with the prompt Numeric Entry: Range 2-65 ; the OK lamp flashes. Enter the
new OVP value using the numeric keypad, exactly as described for setting output voltage, and
press OK to confirm the new setting; to exit without entering a new value press ESCAPE. The
factory default setting is 65·0V.
If the OVP is tripped the display shows the message OVP - Press ESC to Reset and
the output is turned off. Pressing ESCAPE at this point removes the message and the display
now shows the preset voltage and current limit. When the cause of the OVP has been removed
(or the OVP limit changed) the output can be turned on again.
Note also that it is possible and valid to set OVP below the set voltage. If the supply is in
constant current mode the output voltage will be below the set voltage; OVP could be set such
that is was above the actual output voltage but below the set voltage. This could be used to trip
the output under a fault condition which caused the load impedance to increase and the actual
output voltage to therefore rise above the OVP point.
16

Over-Current Protection
Over-Current Protection (OCP) can be set from 2.0A to 55.0A. If the output current exceeds the
set OCP the output is shut down (typically within 100ms).
To set OCP press SHIFT, OCP. The display changes to show only the present OCP setting
together with the prompt Numeric Entry: Range 2-55 ; the OK lamp flashes. Enter the
new OCP value using the numeric keypad, exactly as described for setting the current limit, and
press OK to confirm the new setting; to exit without entering a new value press ESCAPE. The
factory default setting is 55·0V.
If the OCP is tripped the display shows the message OCP - Press ESC to Reset and
the output is turned off. Pressing ESCAPE at this point removes the message and the display
now shows the preset voltage and current limit. When the cause of the OCP has been removed
(or the OCP limit changed) the output can be turned on again.
Note also that it is possible and valid to set OCP below the set current limit. For example, the
power supply may be used to repetitively test a unit under test (UUT) which normally takes a
peak current of, say, 10 Amps. However, a faulty UUT would take a current of more than 10
Amps and would be damaged by being left in a 10 Amp current-limited state. In this case the
current limit could be set to 11A, say, and the OCP set to 10A to ensure that a faulty UUT will trip
the supply off.
Output Protection
In addition to OVP and OCP for forward over-voltage and over-current protection, the output is
protected from reverse voltages by a diode; the continuous reverse current must not exceed 3
Amps although transients can be much higher.
Temperature Trip and Other Faults
If the safe internal temperature limit is exceeded because, for example, the fan vents have been
blocked, the output is automatically tripped off. The display will show a message indicating that a
fault has occurred and that the AC supply must be turned off and on again to reset the unit. If
over-temperature is suspected, the cause of the fault should be rectified and the unit allowed to
cool before the AC supply is turned on again.
Note that an over-temperature trip shuts down the primary side of the instrument and it is that
condition that is detected and causes the fault message to be displayed. However, other faults
may occur which would also cause the primary side to shut down and these will not be
distinguishable from an over-temperature trip. If the unit does not restart after being allowed to
cool then another fault might be present and the unit should be returned for service.
Logic Control Input and Output
Digital signal connections LOGIC IN and LOGIC OUT are available on the rear panel; press the
orange actuators of the screwless terminals, insert the connecting wire and release the actuator
to secure the connection. LOGIC IN is connected directly to the input of an isolating opto-coupler;
there is no series resistor. The input is active when an input current greater than approximately
1mA is forced between LOGIC IN and LOGIC COMMON. LOGIC IN can be set to enable the
output, disable the output, or be ignored when it is activated, see the Extra Functions section.
Note that LOGIC IN can only be used to enable/disable the output if the output has already been
turned ON with the front panel key or by remote interface command; this permits the front
panel key to be used to turn the output off in an emergency, i.e. to override LOGIC IN. Note
also that, having turned the output ON with the key, the ON lamp remains lit even when the
output is disabled by the LOGIC IN signal.
LOGIC OUT is an isolated rear-panel open-collector output that will sink up to 2mA when active
(‘switch closure’); the maximum voltage that can be applied to LOGIC OUT is 30Vdc. LOGIC
OUT can be set to be ‘closed’ or ‘open’ for output enabled or disabled, current limit (CI mode),
power limit (UNREG mode), or for any fault trip. The default condition is for LOGIC OUT to be
‘closed’ for the Output ON; loss of AC power, which would deactivate the opto, is also reliably
detected with this setting. See Extra Functions section for further details.
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Analogue Control
Rear panel connections V CONTROL and I CONTROL provide quasi-analogue control of the
Output Voltage and Current Limit respectively. The CONTROL inputs are read 4 times per
second by the A-to-D converter and the output is set according to the selected input scaling. The
input scaling for both can be set as 0 to 10 Volts or 0 to 5 Volts for maximum output. The
Analogue Control functions and scaling are both selected from the keyboard, see Extra Functions
section.
The COMMON return signal is referenced to the positive output of the power supply.
Analogue Control is activated from the Bus menu, see Remote Operation section. When
activated, the top line of the display shows which functions (V and/or I) have been selected and
the corresponding functions on the front panel (NUMERIC SET / JOG SET for V and/or I ) are
inhibited to avoid contention between Analogue Control and front panel operation.
Analogue Monitor
The output terminal voltage and output current may be monitored on V MONITOR and I
MONITOR respectively. The output scaling for both will be the same as that set for V CONTROL
and I CONTROL, see above section. V MONITOR and I MONITOR are always available at the
rear panel terminals.
The COMMON return signal is referenced to the positive output of the power supply.
Store Settings
The instrument can store 10 set-ups in non-volatile memory; the parameters stored are voltage,
current limit, OVP and OCP. The output state and remote sense setting are not stored.
To store a set-up press SHIFT, STORE to show the store locations and the currently saved set-
ups on the Store screen.
The store location to be used can be selected directly by pressing any key 0 – 9 or by scrolling to
the appropriate store number in the list using the JOG SET control; the selected store is indicated
by the square brackets [ ] at that location. Press OK to store the set-up at the selected
location; the screen returns to the standard status display. A full store can be overwritten with
new settings. At any time before the OK key is pressed the store function can be exited without
saving a set-up by pressing ESCAPE or by waiting for the operation to time out.
Deleting Stored Settings
Any store can be returned to 'empty' as follows: press SHIFT, STORE, and select the appropriate
store number as described in the Store Settings section above; at that point press ·followed by
OK to confirm the operation. At any time before the OK key is pressed the delete function can be
exited without erasing a set-up by pressing ESCAPE or by waiting for the operation to time out.
Recall Settings
To recall a set-up press SHIFT, RECALL to show the store locations and the currently saved set-
ups on the Recall screen. Each store location is displayed with its output voltage, current limit,
OVP and OCP settings; the output status (on/off) and sense settings (local/remote) are not
stored. Empty store locations are shown without data.
The store location containing the setting to be recalled can be selected directly by pressing any
key 0 – 9 or by scrolling to the appropriate store number in the list using the JOG SET control; the
selected store is indicated by the square brackets [ ] at that location. Press OK to recall the
set-up at the selected location; the screen returns to the standard status display. Settings may be
recalled with the output on or off.
18

Extra Functions
Options for extra functions such as LOGIC CONTROL and ANALOGUE CONTROL/MONITOR,
plus variations on some of the factory default functions, can be set by the user by using the #
extra functions facility. The complete list of functions is accessed by pressing SHIFT, # ; the
required function can be selected directly by entering nn from the keyboard, where nn is the 2-
digit number in the list below, or by scrolling to the appropriate function in the list using the JOG
SET control; the selected function is indicated by the square brackets [ ] at that position in the
list. Press OK to initiate the selected function, following the on-screen prompts where
appropriate. At any time before the OK key is pressed the extra function can be exited without
implementation by pressing ESCAPE or by waiting for the operation to time out.
Selected functions are indicated by a 3beside the code in the on-screen list. Note that the
options within any decade group are mutually exclusive and selecting a function within any group
will automatically deselect any previously selected function in that group, including the factory
default option; for example, if #26 is selected, 20 -25 and 27 are all deselected.
# Code Function
10 Output always off at power-up (factory default)
11 Output status at power-up same as at last power-down
20 LOGIC OUT 'closed' for Output ON, 'open' for Output OFF (factory default)
21 LOGIC OUT ‘closed' for Output OFF, 'open' for Output ON
22 LOGIC OUT ‘closed’ for any trip
23 LOGIC OUT ‘open’ for any trip
24 LOGIC OUT ‘closed’ for UNREG
25 LOGIC OUT ’open’ for UNREG
26 LOGIC OUT ‘closed’ for CI (current limit)
27 LOGIC OUT ‘open’ for CI (current limit)
30 Buzzer on. A single beep indicates a wrong entry (factory default)
31 Buzzer off
40 V CONTROL and I CONTROL both selected (factory default)
41 V CONTROL only selected
42 I CONTROL only selected
50 V CONTROL and I CONTROL scaling 0 to 10 Volts (factory default)
51 V CONTROL and I CONTROL scaling 0 to 5 Volts
60 LOGIC IN ignored (factory default)
61 LOGIC IN active enables output
62 LOGIC IN active disables output
90 LCD contrast adjustment
91 Restores factory defaults, including these # settings
99 Enter calibration mode. Refer to Service Manual
Factory Default Settings
The ex-factory default settings (which will apply at first power-up) are as follows:
Voltage: 0.000V
Current Limit: 1.00A
OVP: 65.0V
OCP: 55.0A
Output: Output off; local sense
# Settings: 10, 20, 30, 40, 50, 60 active
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