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LD400 and LD400P DC Electronic Loads: Technical Specifications

Maximum Input Ratings
Current80 Amps max. through the rear panel terminals. 30 Amps max. through the front panel terminals
Voltage80 Volts max. while conducting current. Surge suppressors start to conduct at 120V (nominal), Max. non-repetitive surge energy: 80 Joules
Power Continuous400 Watts max. up to 28°C, derating to 360 watts at 40°C
Power Short Term Note 1600 Watts max. up to 28°C, for up to 60 seconds on-time, with off time at least double the on time.
Min. Operating Volts<2V at 80A; typically equivalent to 25mOhm above 100mV (at 4A).
Off State Leakage<10 mA (including voltage sense circuit input resistance)
Reverse PolarityDiode will conduct; 80 Amps max.
Isolation Voltage± 300Vdc max, either load input to chassis ground

Rear Panel InputSafety terminals accepting 5mm diameter wire, or 8mm spades up to 80 Amps max., or 4mm plugs at 30 Amps max.
Front Panel InputSafety terminals accepting 4mm diameter wire, 4mm plugs or 6.5mm spades up to 30 Amps max.

ConnectionTerminal block on rear panel. Sense selection by slide switch
Input Impedance680kOhm each input to load negative
Max. Sense Offset6V (allowance for backing-off supply for zero volt operation)

Constant Current Mode (CC)
Current Ranges0 to 8 A (1 mA resolution) and 0 to 80 A (10 mA resolution)
Setting Accuracy ± 0.2% ± 30 mA
Regulation< 30 mA for 90% load power change (V > 2 Volts)
Temp. Coefficient< (±0.02% ± 5 mA) per °C.
Slew Rate Ranges Note 28 A range: <2.5 Amp per s to >250 Amp per ms.
80 A range<25 Amp per s to >2500 Amp per ms.
Min. transition time Note 350 µs
Constant Power Mode (CP)
Power Range0 to 400 (or 600) Watts
Setting Accuracy± 0.5% ± 2 W ± 30mA
Regulation< 2% over 5 V to 75 V source voltage change (using remote sense)
Temp. Coefficient<(± 0.1% ± 5mA) per °C
Slew Rate Ranges Note 2<40 W per s to >6000 W per ms
Min. transition time Note 3150 µs
Constant Resistance Mode (CR)
Resistance Ranges0.04 to 10 Ohm (0.01 Ohm resolution); 2 to 400 Ohm (0.1 Ohm resolution)
Setting Accuracy±0.5% ± 2 digits ± 30 mA
Regulation< 2% for 90% load power change (V > 2 Volts, using remote sense)
Temp. Coefficient < (±0.04% ± 5 mA ) per °C
Slew Rate Ranges Note 210Ohm range: <1Ohm per s to 100Ohm per ms
400 Ohm range<40 Ohm per s to 4000 Ohm per ms
Min. transition time Note 3150 µs
Constant Conductance Mode (CG)
Conductance Ranges<0.01 to 1 A/V (1 mA/V resolution); <0.2 to 40 A/V (0.01 A/V resolution)
Setting Accuracy± 0.5% ± 2 digits ± 30 mA
Regulation< 2% for 90% load power change (V > 2 Volts, using remote sense)
Temp. Coefficient< (±0.04% ± 5 mA) per °C
Slew Rate Ranges Note 21 A/V range: <0.1 A/V per s to >10 A/V per ms
40 A/V range<4 A/V per s to >400 A/V per ms
Min. transition time Note 3150 µs
Constant Voltage Mode (CV)
Voltage RangesVmin to 8 V (1 mV resolution) and Vmin to 80 V (10 mV resolution)
Vmin depends on currenttypically <2V at 80A
Setting Accuracy± 0.2% ± 2 digits
Regulation< 30 mV for 90% load power change (using remote sense)
Temp. Coefficient< (0.02% + 1 mV) per °C
Slew Rate Ranges Note 28 V range: <0.8 V per s to >80 V per ms
80 V range80 V range: <8 V per s to >800 V per ms
Min. transition time Note 3150 µs

Transient Generator
Pulse Repetition RateAdjustable from 0.01Hz (100 seconds) to 10kHz
Pulse Duty Cycle1% to 99% (percentage of period at Level A)
Setting Accuracy±1 %
Slew Rate Control
The slew rate control applies to all changes of level whether caused by manual selection, remote control or the transient generator. The level change is a linear slew between the two level settings. The range available in each mode is shown above
Setting Accuracy± 10% (on linear part of slope, excluding high frequency aberrations)
Variation in Level Settings± 5 digits of specified setting resolution for present mode and range
Oscillator Sync Output
ConnectionTerminal block on rear panel. Opto-isolated open collector output conducts during Level B phase of internal transient generator
RatingsMax Off State Voltage: 30V. Collector Current: 2mA (typical)

The load will cease to conduct if the applied voltage falls below the Dropout Voltage setting; active in all modes except Constant Voltage. The Dropout Voltage setting is also the threshold for the Slow Start facility and acts as an offset voltage in Constant Resistance mode
Setting Accuracy± 2% ± 20mV
Slow Start
If Slow Start is enabled, the load will not conduct any current until the source voltage reaches the Dropout Voltage setting; it will then ramp the controlled variable up (in CC, CP and CG modes) or down (in CR and CV modes) to the Level setting at a rate determined by the Slew Rate setting.

Display Type256 x 112 pixel backlit graphic LCD
Measured Values
Volts & AmpsMeasured values of current through and voltage across the load
Watt & OhmsPower and equivalent load resistance, calculated from Volts and Amps
Voltage Accuracy± 0.1% ± 2 digits
Current Accuracy± 0.2% ± 3 digits

Output Terminals4mm safety sockets on front panel or terminal block on rear panel
Output Impedance600W nominal, for >1MW load (e.g. oscilloscope)
Scaling50mV per Amp (4 Volts full scale)
Accuracy± 0.5% ± 5mV
Common Mode Range± 3V dc max. See note note 4

External Control Input Characteristics
ConnectionTerminal block on rear panel
Input Impedance400kOhm each input to load negative
Common Mode Range± 100V to load negative
External Analogue Voltage Control
Operating ModeThe applied voltage sets the operating level within the selected range
Scaling4 Volts full scale
Accuracy± 2% ± accuracy of selected range
Common Mode RejectionBetter than –66dB
External Logic Level (TTL) Control
Operating ModeThe applied signal selects between Level A and Level B settings
Threshold+ 1.5V nominal. A logic high selects Level B
Remote Disable Input
ConnectionTerminal block on rear panel. Input to the LED of an opto-isolator through 1kW resistor
ThresholdApply >+3V to disable load input (+12V maximum)

The LD400P model provides LAN, USB, GPIB and RS232 interfaces for full remote control
LANEthernet 100/10base-T connection with auto cross-over detection. LXI v1.4 Core 2011 compliant
USBStandard USB 2.0 connection. Operates as virtual COM port
GPIBOption on LD400P. Conforming to IEEE488.1 and IEEE488.2. Capabilities: SH1, AH1, T6, L4, SR1, RL2, PP1, DC1, DT0, C0, E2
RS232Standard 9-pin D connection. Baud rate: 9600

Excess PowerThe unit will attempt to limit the power to approx. 430 Watts; if this fails the unit will trip into the fault state at about 460 Watts. If intermittent mode operation is enabled, these levels are 610W and 630W
Protection CurrentThe input is disabled if the measured current exceeds a user set limit
Excess CurrentThe unit will trip into the fault state at nominally 92 Amps
Protection VoltageThe input is disabled if the measured voltage exceeds a user set limit
Excess VoltageThe unit will conduct a current pulse (to absorb inductively generated spikes) for 1ms at about 90V. The unit will trip into the fault state at nominally 106V. Surge suppressors will start to conduct above 120V
TemperatureThe unit will trip into the fault state if the heatsink temperature exceeds safe levels
Sense ErrorThe unit will trip into the fault state if the external voltage sense is more than 6V below the internal sense

AC Input110V–120V or 220V–240V AC ±10%, 50/60Hz. Installation Category II
Power Consumption30VA max. Mains lead rating 6A
Operating Range+ 5°C to + 40°C, 20% to 80% RH
Storage Range-40°C to + 70°C
EnvironmentalIndoor use at altitudes up to 2000m, Pollution Degree 2
CoolingVariable speed fan. Air exit at rear.
SafetyComplies with EN61010-1 and EN61010-2-030
EMCComplies with EN61326
Size130mm H (3U) x 212mm W (½ rack) x 435mm D
Weight5.7 kg

OptionRM460 4U 19-inch rack mount kit

Specification Notes

  • Note 1 In 600 Watt short-term operation mode the dynamic response is not specified, and both the slew rate and the transient oscillator frequency range are restricted. The slew rate limitation applies also to external voltage control. This mode is primarily intended for limited duration operation at a fixed level setting.
  • Note 2 Slew Rate Ranges refer to the theoretical slope of the transition between two levels, regardless of whether that transition can be achieved when taking into account the level difference, the set transition duration, the minimum transition time, and the characteristics of the source.
  • Note 3 Minimum Transition Time specification is an indication of the fastest available transition using a benign battery source and low inductance connections, with a minimum terminal voltage of 5V and a minimum current of 1A. The actual performance attainable with electronically regulated power supplies depends on the combination of source and load loop bandwidths and interconnection inductance.
  • Note 4 The common mode capability of the current monitor is to provide tolerance of voltage drops in the cables. The monitor negative must be connected at some point to the load negative circuit.

Accuracy specifications apply for 18°C – 28°C, at 50W load power (in normal 400W mode), after 30 minutes operation at the set conditions; regulation specifies variation at other powers. Setting accuracies apply with slew rate at the ‘Default’ setting.