Electronic loads, such as the Sorensen SL Series of DC Electronic Loads, are instruments that you would use to provide a programmable load when testing voltage and current sources, including power supplies and batteries. Modern electronic loads are actually sophisticated electronic test instruments that can offer a number of different modes, including Constant Current (CC) mode, Constant Resistance (CR) mode, Constant Voltage (CV) mode, and Constant Power (CP) mode.

CC Mode

In Constant Current (CC) mode, the load will sink a current equal to the programmed current setting regardless of the input voltage, up to the maximum current rating of the load. You might use the constant current mode to ensure that your power supply can output the maximum specified current under all conditions.constant-current-mode

CR Mode

In Constant Resistance (CR) mode, the electronic load will act like a fixed resistor. It senses the voltage at its input and sinks a current linearly proportional to the input voltage. You might use the constant resistance mode to test the capacity of batteries. Constant resistance mode is also most often used to measure the start-up conditions of electronic devices.

constant-resistance-mode

CV Mode

In Constant Voltage mode, the load will attempt to sink enough current to maintain the programmed voltage setting at its input terminals. Of course, if there are some limitations on how much current that the load is able to sink.

constant-voltage-mode

CP Mode

In Constant Power (CP) mode, the load will attempt to sink whatever load power is programmed. It senses the voltage at the input, calculates the appropriate current, and then attempts to sink that amount of current. You might use this feature to ensure that your power source is able to supply the specified output power over the entire output voltage range of the source.

constant-power-mode

A very similar curve is the power contour of the electronic load. In practice, the power contour curve of an electronic load shows how much current that a load can sink at various voltages when programmed to their maximum power level. The figure below shows the power contour for a Sorensen SLM 60-60-300 Electronic Load. It has a maximum input voltage of 60 VDC, a maximum input current of 60 A, and a maximum power capability of 300 W.

power-contour

For more information on electronic loads, contact AMETEK Programmable Power by sending an e-mail to sales.ppd@ametek.com or phoning 800-733-5427.

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