Connecting The Load To The Source; Voltage Sensing; Principles Of Operation; Load Operating Modes - Aim TTi LD300 Manual De Instrucciones

This instrument provides a controllable DC load (a power sink) intended for testing all forms of
DC power supply including batteries, photo-voltaic cells, turbines and generators as well as
electronic power supply units.
New users should first read the Operating Controls section, which gives an overview of the
instrument's controls. This section gives detailed information on setting up and using the unit.
Application hints and cautions, particularly concerning stability and dynamic behaviour, are given
in the Application Notes section later.

Connecting the Load to the Source

The INPUT terminals of the load must be connected to the source to be tested using sufficiently
low resistance and low inductance connections. The wiring should be as short and as thick as
possible. The front panel terminals may be used for currents up to 30 Amps; for higher currents
the rear panel terminals should be used.
The load terminals of the instrument are floating from ground, and may be used at potentials of
up to ± 300 Volts from ground. Ensure that all wiring is safely insulated for the working voltage
involved.

Voltage Sensing

If the load is to be operated in Constant Current (CI) mode, then external voltage sensing will
only be needed if accurate readings are required on the voltage, power or equivalent resistance
meters. In all other modes the conductivity of the load depends on the applied voltage, so
external sensing is needed for proper accuracy of the load characteristics.
In the interests of stability, high frequency feedback is always taken from the internal sense
circuit; this minimises the possibility of phase shifts due to the external wiring affecting the unit.
Nevertheless, to avoid impact on the stability margin do not add phase shift in the sensing circuit;
in particular, the use of decoupling capacitors should be avoided. If the sensing connections are
likely to be subject to RF or magnetic fields, use twisted pair cable with an overall shield. The
shield should be grounded or connected to load negative.

Principles of Operation

The normal sequence of operation is to select the LOAD MODE and LEVEL CONTROL mode,
set the required operating level and dropout voltage, and then enable the input. If transient
operation is required, the second level setting and the slew rate parameters must be set, as well
as the frequency and duty cycle of the internal oscillator if it is to be used.
The meters can be used to view the settings before the INPUT is enabled; once the load is
conducting the actual Voltage and Current, or the Watts and Ohms calculated from those values,
can be read.
All controls except LOAD MODE can be adjusted as required while the input is enabled.
Attempting to change the LOAD MODE while the input is enabled will trip the fault latch and
cause the input to be disabled until reset.

Load Operating Modes

There are five possible operating modes, selected by the switch marked LOAD MODE; there are
two ranges for all modes except Constant Power. The INPUT ENABLE switch should be released
before changing modes; if the LOAD MODE switch is moved with the load enabled the fault latch
will be tripped.
16

Operation