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New Tool Day: RS Programmable DC Electronic Load

Electronic Loads

Taking a look at the sub-£400 RS Pro RS-KEL103 Electronic Load, and seeing what functionality it offers.

What is it?

An electronic load is a device that can accurately sink current, acting as a controllable electrical load - they are the next step up from a dummy load which is often just a fixed resistance. Electronic loads can vary in size, from small benchtop units (such as the RS Pro unit), up to units that can handle tens, or even hundreds, of kilowatts - which generally require a lot of space and some even require water cooling!

The RS Pro Programmable DC Electronic Load (180-8788) is a 300W, 0-120V or 0-30A DC capable programmable load, with USB, Ethernet and serial connectivity; giving the unit the ability to be remotely controlled and arbitrary constant voltage/current/power/resistance test points to be inputted.

The Unit

The RS Pro unit is a small, benchtop device, measuring only 107x215x386mm and weighing 5.2kg. All the controls are located on the front panel, with the main load input also on the front panel, along with the large easy to read display. The rear panel features the communications interfaces (serial, Ethernet and USB-B), the mains power inlet, and a small screw terminal block with remote sense and a trigger input.

Also included in the box is the instruction manual and a CD containing drivers & documentation, a UK power cable, an EU power cable, a USB cable, a serial cable and a pair of rather nice flexible 10AWG cables terminated in fork terminals.

Once powered on, the unit is deceptively quiet for a 300W load - thanks to the thermostatically controlled fan that varies as load increases.

The load offers four modes of operation - constant current, constant voltage, constant power and constant resistance, which all behave as expected. In addition to these four modes, the load also offers a battery test, which features controllable discharge current, termination voltage, discharge capacity and discharge time - when one of the criteria is met the discharge will stop.

Documentation for the unit is clear and well written, which makes getting started even easier - the only small downside is the software is provided on a CD.

The Software

RS includes remote control software on a CD, that either supports serial, USB or network control of the electronic load.

Once installed and opened, the software presents a screen with controls that mirror what is available on the front panel, graphs of voltage and current, programmable test points and a battery discharge function.

Electronic Loads

Using the software is fairly self-explanatory, and the programmable test points feature supports mixing control modes.

In the future, we will be using the programmable test points feature to test our Raspberry Pi Industrial PSU to see how it endures overcurrent situations and load step changes.

Also included in the documentation is the SCPI command set, that enables easy control of the load parameters from a script environment, or an existing test setup. To demonstrate some SCPI commands, I opened RealTerm and connected to the serial port of the instrument. I made sure the input was turned off, then set a current of 2A, then turned the input on and measured the consumed wattage.

It is important to note that when querying the device commands should end in a question mark, otherwise no value will be returned.

Electronic Load


The RS-Pro electronic load is an ideal first step up from using a bank of resistors as a load and offers a wide function set that makes it an incredibly versatile device.

Engineer of mechanical and electronic things by day, and a designer of rather amusing, rather terrible electric "vehicles" by night.
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