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9758B DC Electronic Load Module

  • The 9758B electronic load module works by putting a required DC load across a power source under test. It can be also be used to investigate the behaviour of many different types of power source such as batteries, solar cells, fuel cells or wind generators, as well as electronic power supply units. Comprehnsive features include:

    Multiple Modes of Operation
    Constant Current: 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 Voltage: Constant voltage mode is used for load testing of constant current power supplies. The unit operates as a high power shunt regulator.

    Constant Power: Constant power mode simulates a load whose power consumption is independant of the applied voltage. This is true of many types of equipment that incoporate switchmode regulators. This mode may be particularly suitable for testing power sources of portable devices such as Lithium-ion batteries.

    Constant Resistance: 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: 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 9758B provides automatic protection by incoprorating fully variable voltage dropout (CI, CR, CG and CP modes). If the voltage applied to the load falls below a preset level, the load current is rapidly reduced to zero.

    Transient generator and variable slew
    The 9758B incorporates a full variable frequency, variable duty cycle transient generator. Switching between the two preset levels can be done at any frequency between 0.1Hz 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 and measurement
    The levels for each operating mode are set using high quality ten turn potentiometers for both level A and level B. Levels are displayed using four digit meters which provide resolution down to 1mA, 1mV and 1mΩ. Settings for slew rate, transient frequency, duty cycle and dropout voltage can also be displayed. In measurement mode the meters have an accuracy of 0.1% for voltage and 0.2% for current.

    Current waveform monitor
    It is often important to be able to observe the load current waveform on an oscilloscope. The 9758B 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 divertion. 

  • Technical Specifications

    Voltage and Current 80 volts maximum, 80 amps maximum.
    Power Dissipation 320 watts maximum continuous at 28°C. Derating to 300 watts continuous at 40°C.
    Min. Operating Volts Increases with current, <0.5V at 10A, <1V at 40A, <2V at 80A.
    Operating Modes

    Constant Current Mode

    Setting Range: 0 to 80A in 2 ranges, set by 10 turn control.
    Meter Resolution: 1mA on 8A range, 10mA on 80A range.
    Setting Accuracy: ± (0.2% + 20mA).
    Regulation: <30mA for a 20W to 280W power change.
    Slew Rate Range: <8mA/ms to >2500A/ms

    Constant Resistance Mode

    Setting Range: 0.04Ω to 100Ω in 2 ranges, set by 10 turn control.
    Meter Resolution: 10mΩ on 10Ω range, 100mΩ on 400Ω range.
    Setting Accuracy: ± (0.5% + 2 digits).
    Regulation: <2% for a 20W to 280W power change.
    Slew Rate Range: <3.3Ω/s to >4000Ω/ms.

    Constant Conductance Mode

    Setting Range: 0.01A/V to 40A/V in 2 ranges, set by 10 turn control.
    Meter Resolution: 0.001A/V or 0.01A/V depending on range.
    Setting Accuracy: ± (0.5% + 2 digits).
    Regulation: <2% for a 20W to 280W power change.
    Slew Rate Range: <33mA/V/s to >400A/V/ms

    Constant Voltage Mode

    Setting Range: Vmin to 80V in 2 ranges, set by 10 turn control.
    Vmin varies with current: see Ratings.
    Meter Resolution: 1mV on 8V range, 10mV on 80V range.
    Setting Accuracy: ± (0.2% + 2 digits).
    Regulation: <30mV for a 20W to 280W power change.
    Slew Rate Range: <2.5V/s to >800V/ms

    Constant Power Mode

    Setting Range: 0 to 320W, set by 10 turn control.
    Meter Resolution: 1W.
    Setting Accuracy: ± (0.5% + 2 W).
    Regulation: <2% for a 20W to 280W power change.
    Slew Rate Range: <0.1W/ms to >3,200W/ms.

    Level Control
    Control Modes Level A, Level B, Transient Internal (switching between A and B using the built-in generator), Transient External (switching between A and B using an external switching signal), and Remote (level proportional to an external voltage).
    Level A, Level B Each set by 10-turn potentiometer. Range, resolution and setting accuracy as shown above.
    Slew Rate Control All changes of level are subjected to slew rate control which is adjustable over a 30,000:1 range by a 3 position switch and vernier.
    Input Enable Latching switch which turns the load condition on.
    Slow Start Engages slew rate control to limit the speed of the ON transition when the input is enabled.
    Dropout Voltage Defines a minimum voltage below which the load current will reduce to zero (as may be required for testing batteries or power sources that can not be short circuited). Adjustable from 0V to 80V.
    Transient Generator
    Pulse Repetition Rate 0.1Hz to 10kHz in 3 overlapping ranges.
    Setting Resolution 0.1Hz, 1Hz, 10Hz depending on range.
    Setting Accuracy ± 2% of range.
    Pulse Duty Cycle 1% to 99% continuously variable.
    Sync Output Pulse synchronous with transient level change.
    Displays and Metering
    Displays Dual 4 digit LED displays showing a variety of settings or measurements as set by a five position switch.
    Setting Displays Level A and Level B, Frequency and Duty Cycle, Slew Rate and Drop Out.
    Measurements Amps and Volts, Watts and Ohms (calculated from V and I measurements).
    Meter Accuracy Voltage ±(0.1% + 1 digit), Current ±(0.2% + 20mA).
    Current Monitor
    Signal An analogue signal representing the current waveform is available for connection to an oscilloscope or external meter.
    Scaling & Compliance Scaling is 50mV/Amp and compliance is ±3V with respect to the load negative terminal.
    Limiter Circuit & Fault Trip The load incorporates both a power limiter circuit and a fault trip which responds to excess voltage, current, power or temperature. The trip puts the load into a high impedance state.
    Surge Suppessors Surge suppessors are incorporated to limit transient voltage spikes.

    General Specifications

    Front Terminals Input via 4mm terminal/binding posts (30A max.). Current monitor via 4mm sockets.
    Module Width 295mm (primary console fitting only)

    Ordering Information

    9758B DC Electronic Load Module

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    9758B Data Sheet



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