3
Introduction
This DC electronic load is intended for use in investigating the behaviour of many different types
of DC power sources such as batteries, solar cells, fuel cells or wind generators, as well as
electronic power supply units.
It is designed to have very low internal resistance to allow operation at high currents with low
voltage drop. The voltage of the source can be sensed either internally for convenience or
externally for better accuracy.
The unit provides five different operating modes: constant current, constant power, constant
resistance, constant conductance and constant voltage.
It operates over the current range 0 to 80 Amps and the voltage range 0 to 80 Volts with a
continuous power dissipation capability of up to 400 Watts. It also permits short term dissipation
up to 600W, for brief or intermittent testing of higher power sources.
A low voltage dropout facility is provided to protect sources such as batteries from damaging
levels of discharge by reducing the load current when the source voltage falls below the dropout
threshold setting.
An internal transient generator can repeatedly switch the load between two different operating
levels, level A and level B. The frequency and duty cycle of the transients can be set over a wide
range. The transients can also be initiated by an external logic signal. The transitions between
the levels have a true linear slewing characteristic in all modes, with the slew-rate being
adjustable over a wide range.
The unit meters and displays measured values of Volts & Amps and equivalent Watts & Ohms. A
monitor output providing a voltage proportional to the current flowing allows the behaviour of a
source to be viewed on an oscilloscope or external meter.
All adjustable system parameters can be set via numeric keyboard entry or via the digital remote
interfaces for quick and convenient instrument control.
Up to 30 non-volatile storage locations can be used to store and recall instrument parameter set
ups, ideal for test and calibration procedures.
An external control voltage can also be used to set the level of the load. Any desired waveform
can be applied, with the internal slew rate control circuit remaining active to provide additional
control.
The unit is fully protected against excessive current, power dissipation or internal temperature,
and minimises audible noise by automatically controlling the fan speed according to the power
dissipation.
