The electronic loads, in single channel or multichannelsystem, have been generally designed for testing DC power supplies, DC generators, betteries, etc.. In combination with an AC/DC converter, they can be used as AC loads. Using a three-phase AC/DC converter, three-phase generators can be tested too.
In conjunction with an external source, battery or power supply, the electronic load is expanded to a constant current source. In this way, constant current source with high precision an stability can be implemented.
Traditional procedures limit the tests to static loading. The electronic loads offer more expanded facilities. All types of static and dynamic loads - without feeding back - can be tested within the pwer tange from milliwatts up to 5 kilowatts. By connecting two or more units respectivles channels in series or parallel, the load voltage or the current respectively the load power, can be further increased.
The electronic load is a controllable and high-precision laod. It draws the externally offered power an converts it completly into heat. Because of the large bandwith, it is possible to give the load behavoir any functional pattern. For example it is possbile to dynamically test power supply units by means of a jump functionh by programming the amplitude an time.
More channels my be operated either in tesistance or constant current mode. At option a constant voltage mode or a constant power mode - for testing constant current sources - is available.
The load input for each channel is floating. Therefore power supplies with any reference to ground are testable.
For exact voltage measurments the elctronic loads contain sense lines.
Load settings may be set individual by 10-turn potentiometers or by an external analog input. The device under test may then be switched between load settings by a built-in oscillator from 10 Hz to 1 KHz or till 20 kHz (external analog input). This Dynamic test is possible by external analog input only for current mode.
In the electronic loads various load modes can be set:
- R-load: the electronic load behaves like a resistor, however with the enormous range of four decades without load reduction.
- I-load: the present load current remains independent of the available input voltage with makes it very easy to test the capacity (Ah) of batteries an the load behavoir of power supplies.
- P-load: the power supply is subjected to a constant load. In this wa series produced equipment such as uninterruptible power supplies, generators and amplifiers can be tested for their conformance to the design specifications.
- U-Load: this is a special case ot the R-load with adjustable input voltage threshold for the load current. Permits complete simulation of a battery for testing chargers.
For incorporation into autmatic test or burn-in systems, all functions can be controlled from an IEEE 488 bus (option). All channels are connected with one master interface. The input of resistance is done with 400 steps between 0,1 Ohm to 1000 Ohm. The input of current is done in 1 °/. . steps for the nominal value. The load-input can be opened, closed and shorted under program control. Measured values of voltage an current on theload-inputs, as well as the calculated values of resistance and power are available on the IEEE 488 bus under programm control.
Protection circuits are built in. Over power, over voltage, over current an over temperatures events all disconnet the electronic load from the source an automatically reconnect the elctronic range conditions is removed. The over load is indicates in a digital display in clear text. A protection against wrong polatity is provided.