Datasheet

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.