AIM & THURLBY THANDAR INSTRUMENTS
Electronic DC Loads - 80A, 80V, 400W
LD400 & LD400P
constant current, resistance, voltage and power
transient generator, variable slew rate, soft start
current monitor output, analogue remote control
short term high power mode of up to 600 watts
thirty non-volatile memories for complete settings
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USB, RS-232, GPIB and LAN interfaces (LD400P)
LD400 & LD400P Electronic DC Loads | 80 amps, 80 volts, 400 watts
Versatile solution for testing dc power sources
Constant current, resistance, conductance, voltage and
power modes
Wide voltage and current range, 0 to 80V and 0 to 80A
400 watts continuous dissipation at 28oC (360W at 40oC)
600 watts short-term dissipation (up to 60 seconds)
Low minimum operating voltage of <1V at 40A
High resolution and accuracy for level setting
Built-in transient generator with variable slew
Current monitor output for waveform viewing
Variable drop-out voltage for battery testing
High resolution backlit graphic LCD with soft key control
Analog remote control of levels and TTL control of on/off
and transient switching
Front and rear input terminals (front terminals 30A max.)
Full bus control via USB, RS232, GPIB and LXI compliant
LAN interfaces (LD400P)
Compact electronic DC load
The LD400 is an inexpensive electronic load which is suitable for
testing and characterising a wide variety of dc power sources.
It can be used to investigate the behaviour of many different
types of power source such as batteries and solar cells, as well as
electronic power supply units.
Its wide voltage/current range, multiple operating modes and built-
in transient generator give it the versatility to offer test solutions
from the design laboratory through to the component test area.
The LD400P adds full bus remote control via USB, RS-232, GPIB and
LAN (Ethernet) interfaces.
Low minimum operating voltage
The LD400 can operate at voltages below 500mV for currents up to
10 amps. At higher currents the fixed minimum resistance (typically
better than 25mW) gradually raises the minimum operating voltage,
but it remains below 1 volt up to 40 amps and below 2 volts up to
80 amps.
This low operating voltage allows it to be used for many low voltage
applications for which other electronic loads are unsuitable.
600 watts intermittent power
The LD400 can operate at power levels up to 600 watts for periods
of up to 1 minute.
Short term loading can be sufficient for many testing applications and
significantly extends the usefulness of the LD400.
Constant current mode is used for
load testing of normal voltage-source
power supplies and for constant current
discharge testing of batteries.
This mode provides rapid measurement
of power source regulation (V/I
characteristics).
Constant power mode simulates a
load whose power consumption is
independent of the applied voltage.
This is true of many types of equipment
that incorporate switch-mode regulators.
This mode may be particularly suitable
for testing power sources of portable
devices such as Lithium-ion batteries.
Constant voltage mode is used for
load testing of constant current power
supplies. The unit operates as a high
power shunt regulator.
Transient generator and variable slew
The LD400 incorporates
a full variable frequency,
variable duty cycle
transient generator.
Switching between the
two preset levels can be
done at any frequency
between 0.01Hz and
10kHz. The transient
generator can be used in all operating modes.
The rate of change between levels (slew rate) is controllable over a
wide range.
Slew rate control applies to all changes of level including remote
control and manual changes between level A and level B.
A slow-start function can be selected for situations where latching
would otherwise occur at switch-on.
High resolution setting/measurement
The two operating levels for each operating mode are settable to
high precision.
Levels are displayed using four digit meters which provide resolution
down to 1mA, 1mV and 1mW.
The meters have an accuracy of 0.1% for voltage and 0.2% for
current.
Setting Memories
Thirty non-volatile memories are provided which store all of the
parameters of the load.
This makes the LD400 highly suitable for repetitive test use.
Remote control
The LD400 incorporates analogue remote control for all modes of
operation. When “external voltage” is selected the level becomes
linearly proportional to the voltage applied to the remote control
inputs on the rear panel.
Any waveform can be used as the control voltage allowing complex
load conditions to be simulated using, for example, an arbitrary
waveform generator.
Alternatively, a logic signal can be used to switch between levels.
When “external TTL” is selected, the level is switched between the
two defined levels in response to an external logic signal.
The remote control inputs have a wide common mode range
allowing the control voltage to be referenced independently of the
load terminal voltages.
Current waveform monitor
It is often important to be able to observe the load current waveform
on an oscilloscope. The LD400 provides a calibrated monitor
output for this purpose as well as a sync output from the transient
generator.
The monitor output has several volts of compliance with respect
to the load input, thus allowing it to be connected to a grounded
oscilloscope without current diversion.
CI, CR, CG, CV and CP modes | transient generator, variable slew rate
Constant
Voltage
Constant
Power
Constant
Resistance
Multiple modes of operation
Constant
Current
Constant resistance mode simulates a
standard resistive load by providing a
current drain proportional to voltage.
Settings are displayed in Ohms or milli-
Ohms.
Unlike fixed resistors or rheostats, the
load provides a precisely controllable
resistance with high power dissipation
and high temperature stability over a
wide value range.
Constant Conductance
Constant conductance (CG) mode is also
incorporated.
As well as showing settings in amps per
volt, this mode provides better resolution
when setting very low equivalent
resistance values.
Adjustable voltage
drop-out
Some power sources, such as rechargeable
batteries, can be damaged if their output
voltage falls below a certain level.
The LD400 provides automatic protection
by incorporating fully variable voltage
dropout (CI, CR, CG and CP modes).
Resistive discharge
(conductance mode)
with voltage dropout.
Note that in CR mode
the load performs
the equation
I = (V -Vd)/R where
Vd is the dropout
voltage.
If the voltage applied to the load falls
below a preset level, the load current is
rapidly reduced to zero.
LD400P - USB, RS-232, GPIB & LAN
LD400P - comprehensive bus remote control
To meet a wide variety of needs, the LX400P adds a comprehensive array
of digital bus interfaces. RS-232, USB, GPIB and LAN (Ethernet) with LXI
support are all provided as standard.
Each of the digital bus interfaces provides full control of and read-back of
settings and status. The interfaces are at ground potential and are opto-
isolated from the 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 load devices 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 operating systems.
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.
The LAN interface is LXI compliant.
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: www.aimtti.com/go/lxi
IVI Driver
An IVI driver for Windows is included. This provides support for common
high-level applications such as LabView*, LabWindows*, and HP/Agilent
VEE*.
* LabView and LabWindows are trademarks of National Instruments.
HPVEE (now Agilent VEE) is a trademark of Agilent Technologies.
* Windows is a trademark of Microsoft.
INPUT SPECIFICATIONS
Maximum Input Ratings
Current: 80 Amps max. through the rear panel terminals.
30 Amps max. through the front panel terminals
Voltage: 80 Volts max. while conducting current.
Surge suppressors start to conduct at 120V (nominal),
Max. non-repetitive surge energy: 80 Joules.
Power Continuous: 400 Watts max. up to 28ºC, derating to 360 watts at 40ºC.
(1)Power Short Term: 600 Watts max. up to 28ºC, for up to 60 seconds on-time, with off time
at least double the on time.
Min. Operating Volts: <2V at 80A; typically equivalent to 25mW above 100mV (at 4A).
Off State Leakage: <10 mA (including voltage sense circuit input resistance).
Reverse Polarity: Diode will conduct; 80 Amps max.
Isolation Voltage: ± 300Vdc max, either load input to chassis ground.
Input Terminals
Rear Panel Input: Safety terminals accepting 5mm diameter wire, or 8mm spades up to
80 Amps max., or 4mm plugs at 30 Amps max.
Front Panel Input: Safety terminals accepting 4mm diameter wire, 4mm plugs or 6.5mm
spades up to 30 Amps max.
External Voltage Sense
Connection: Terminal block on rear panel. Sense selection by slide switch.
Input Impedance: 680kW each input to load negative.
Max. Sense Offset: 6V (allowance for backing-off supply for zero volt operation)
OPERATING MODES
Constant Current Mode (CC)
Current Ranges: 0 to 8 A (1 mA resolution) and 0 to 80 A (10 mA resolution).
Setting Accuracy: ± 0.2% ± 30 mA.
Regulation: < 30 mA for 90% load power change (V > 2 Volts).
Temp. Coefficient: < (±0.02% ± 5 mA) per ºC.
(2) Slew Rate Ranges: 8 A range: <2.5 Amp per s to >250 Amp per ms.
80 A range: <25 Amp per s to >2500 Amp per ms.
(3) Min. transition time: 50 µs.
Constant Power Mode (CP)
Power Range: 0 to 400 (or 600) Watts.
Setting Accuracy: ± 0.5% ± 2 W ± 30mA).
Regulation: < 2% over 5 V to 75 V source voltage change (using remote sense).
Temp. Coefficient: <(± 0.1% ± 5mA) per ºC.
(2) Slew Rate Ranges: <40 W per s to >6000 W per ms.
(3) Min. transition time: 150 µs.
Constant Resistance Mode (CR)
Resistance Ranges: 0.04 to 10W (0.01W resolution); 2 to 400W (0.1W resolution).
Setting Accuracy: ±0.5% ± 2 digits ± 30 mA.
Regulation: < 2% for 90% load power change (V > 2 Volts, using remote sense).
Tem. Coefficient: < (±0.04% ± 5 mA ) per ºC.
(2) Slew Rate Ranges: 10W range: <1W per s to 100W per ms.
400W range: <40W per s to 4000W per ms.
(3) Min. transition time: 150 µs.
Constant Conductance Mode (CG)
Conductance Ranges: <0.01 to 1 A/V (1 mA/V resolution); <0.2 to 40 A/V (0.01 A/V resolution).
Setting Accuracy: ± 0.5% ± 2 digits ± 30 mA.
Regulation: < 2% for 90% load power change (V > 2 Volts, using remote sense).
Temp. Coefficient: < (±0.04% ± 5 mA) per ºC.
(2) Slew Rate Ranges: 1 A/V range: <0.1 A/V per s to >10 A/V per ms.
40 A/V range: <4 A/V per s to >400 A/V per ms.
(3) Min. transition time: 150 µs.
Constant Voltage Mode (CV)
Voltage Ranges: Vmin to 8 V (1 mV resolution) and Vmin to 80 V (10 mV resolution).
Vmin depends on current: typically <2V at 80A
Setting Accuracy: ± 0.2% ± 2 digits.
Regulation: < 30 mV for 90% load power change (using remote sense).
Temp. Coefficient: < (0.02% + 1 mV) per ºC.
(2) Slew Rate Ranges: 8 V range: <0.8 V per s to >80 V per ms.
80 V range: <8 V per s to >800 V per ms.
(3) Min. transition time: 150 µs.
TRANSIENT CONTROL
Transient Generator
Pulse Repetition Rate: Adjustable from 0.01Hz (100 seconds) to 10kHz.
Pulse Duty Cycle: 1% to 99% (percentage of period at Level A).
Setting Accuracy: ±1 %
Slew Rate Control
The slew rate control applies to all changes of level whether caused by manual selection, remote
control or the transient generator. The level change is a linear slew between the two level settings.
The range available in each mode is shown above.
Setting Accuracy: ± 10% (on linear part of slope, excluding high frequency aberrations).
Variation in Level
Settings: ± 5 digits of specified setting resolution for present mode and range.
Oscillator Sync Output
Connection: Terminal block on rear panel. Opto-isolated open collector output
conducts during Level B phase of internal transient generator.
Ratings: Max Off State Voltage: 30V. Collector Current: 2mA (typical).
LD400 & LD400P - Technical Specifications
LD400 & LD400P - Technical Specifications (continued)
DROPOUT VOLTAGE
The load will cease to conduct if the applied voltage falls below the Dropout Voltage setting; active
in all modes except Constant Voltage. The Dropout Voltage setting is also the threshold for the
Slow Start facility and acts as an offset voltage in Constant Resistance mode.
Setting Accuracy: ± 2% ± 20mV.
Slow Start
If Slow Start is enabled, the load will not conduct any current until the source voltage reaches the
Dropout Voltage setting; it will then ramp the controlled variable up (in CC, CP and CG modes) or
down (in CR and CV modes) to the Level setting at a rate determined by the Slew Rate setting..
METER SPECIFICATIONS
Display Type: 256 x 112 pixel backlit graphic LCD.
Measured Values
Volts & Amps: Measured values of current through and voltage across the load.
Watt & Ohms: Power and equivalent load resistance, calculated from Volts and Amps.
Voltage Accuracy: ± 0.1% ± 2 digits.
Current Accuracy: ± 0.2% ± 3 digits.
CURRENT MONITOR OUTPUT
Output Terminals: 4mm safety sockets on front panel or terminal block on rear panel.
Output Impedance: 600W nominal, for >1MW load (e.g. oscilloscope)
Scaling: 50mV per Amp (4 Volts full scale).
Accuracy: ± 0.5% ± 5mV.
REMOTE CONTROL (All Models)
External Control Input Characteristics
Connection: Terminal block on rear panel.
Input Impedance: 400kW each input to load negative.
Common Mode
Range: ± 100V to load negative.
External Analogue Voltage Control
Operating Mode: The applied voltage sets the operating level within the selected range.
Scaling: 4 Volts full scale.
Accuracy: ± 2% ± accuracy of selected range.
Common Mode
Rejection: Better than –66dB.
External Logic Level (TTL) Control
Operating Mode: The applied signal selects between Level A and Level B settings.
Threshold: + 1.5V nominal. A logic high selects Level B.
Remote Disable Input
Connection: Terminal block on rear panel.
Input to the LED of an opto-isolator through 1kW resistor.
Threshold: Apply +3 to +5 V to disable load input.
REMOTE CONTROL (LD400P only)
Digital Remote Interfaces
The LD400P model provides LAN, USB, GPIB and RS232 interfaces for full remote control.
LAN: Ethernet 100/10base-T connection with auto cross-over detection.
LXI v1.4 Core 2011 compliant.
USB: Standard USB 2.0 connection. Operates as virtual COM port.
GPIB: Conforming to IEEE488.1 and IEEE488.2.
Capabilities: SH1, AH1, T6, L4, SR1, RL2, PP1, DC1, DT0, C0, E2.
RS232: Standard 9-pin D connection. Baud rate: 9600.
PROTECTION
Excess Power: The unit will attempt to limit the power to approx 430 Watts; if this fails
the unit will trip into the fault state at about 460 Watts. If intermittent
mode operation is enabled, these levels are 610W and 630W.
Protection Current: The input is disabled if the measured current exceeds a user set limit.
Excess Current: The unit will trip into the fault state at nominally 92 Amps.
Protection Voltage: The input is disabled if the measured voltage exceeds a user set limit.
Excess Voltage: The unit will conduct a current pulse (to absorb inductively generated
spikes) for 1ms at about 90V.
The unit will trip into the fault state at nominally 106V
Surge suppressors will start to conduct above 120V.
Temperature: The unit will trip into the fault state if the heatsink temperature exceeds
safe levels.
Sense Error: The unit will trip into the fault state if the external voltage sense is more
than 6V below the internal sense.
GENERAL
AC Input: 110V–120V or 220V–240V AC ±10%, 50/60Hz. Installation Category II.
Power Consumption: 30VA max. Mains lead rating 6A.
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.
Cooling: Variable speed fan. Air exit at rear.
Safety: Complies with EN61010-1 and EN61010-2-030.
EMC: Complies with EN61326.
Size: 130mm H (3U) x 212mm W (½ rack) x 435mm D.
Weight: 5.7 kg.
Option: 19-inch rack mount kit.
Specification Notes
(1) In 600 Watt short-term operation mode the dynamic response is not specified, and both the
slew rate and the transient oscillator frequency range are restricted. The slew rate limitation
applies also to external voltage control. This mode is primarily intended for limited duration
operation at a fixed level setting.
(2) Slew Rate Ranges refer to the theoretical slope of the transition between two levels, regardless
of whether that transition can be achieved when taking into account the level difference, the set
transition duration, the minimum transition time, and the characteristics of the source.
(3) Minimum Transition Time specification is an indication of the fastest available transition using a
benign battery source and low inductance connections, with a minimum terminal voltage of 5V and
a minimum current of 1A. The actual performance attainable with electronically regulated power
supplies depends on the combination of source and load loop bandwidths and interconnection
inductance.
Accuracy specifications apply for 18°C – 28ºC, at 50W load power (in normal 400W mode), after
30 minutes operation at the set conditions; regulation specifies variation at other powers. Setting
accuracies apply with slew rate at the ‘Default’ setting.
Thurlby Thandar Instruments Ltd. operates a policy of continuous development and reserves the right to
alter specifications without prior notice.
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: info@tti-test.com Web: www.tti-test.com
LD400 Brochure Iss. 1-D6
