• Versatile solution for testing dc power sources
• Constant current, resistance, conductance, voltage and power modes
• Wide voltage and current range, 0 to 80 V and 0 to 80 A
• 400 watts continuous dissipation at 28 degrees C
• 360 watts continuous dissipation at 40 degrees C
• 600 watts short-term dissipation capability
• Low minimum operating voltage of below 1V at 40A
• Built-in transient generator with variable slew
• Current monitor output for waveform viewing

The LD400 is an inexpensive electronic load which is suitable for testing and characterizing 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 and LAN (Ethernet) interfaces.

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.

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.

Compact Electronic DC load

The LD400 is an inexpensive electronic load which is suitable for testing and characterizing a wide variety of dc power sources

Low Minimum Operating Voltage

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

TTI-LD300-Modes

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.

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 over a wide value range.

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.

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 drop- out voltage.

If the voltage applied to the load falls below a preset level, the load current is rapidly reduced to zero.

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.

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 1mΩ.

The meters have an accuracy of 0.1% for voltage and 0.2% for current.

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.

To meet a wide variety of needs, the LX400P adds a comprehensive array of digital bus interfaces. RS-232, USB 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.

An RS-232/RS-423 interface is provided for use with legacy systems. This type of serial interface remains in common usage 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.