Answers to Electronic Load Questions 
Executive Engineering at Exec-Eng.Com



  • What is Constant Current operation and what does it do for me? ( Normal Operation )
    Answer; In constant current operation as you adjust the current, voltage has no effect on how the load handles the current. The load will always try to draw the current that it is set for no mater what the voltage is doing.
  • How can an electronic load work at  0 Volts?
    It can't and there is just no such thing as working at 0 volts, you need voltage to produce current. Always make sure that the load will start at the low voltage and work both in the positive and negative direction.  Some of our competitors loads require more voltage to start and run, then they will work to a lower voltage. Executive Engineering electronic loads will always work (sink current) at there low voltage specification. 
  • How does Constant Power operation work? 
    Answer; As the voltage of the power source (UUT) unit under test increases the current that the Electronic Load draws decreases. This protects the Electronic Load from having to much power put into it.
  • What is Constant Resistance, and how does it work?
    Answer; As the voltage changes the current is adjusted so as to maintain the same resistance at all times.
  • What is Quasi-Constant Power? ( Stand Alone Operation )
    Answer; For the electronic loads we produce. The Electronic Load starts up in constant resistance mode, and switches over to constant current mode and allows the power foldback circuit to control how much constant current the load is allowed to draw when in operation.
    I.E. Once the current is set for a certain voltage the electronic load will try to sink (dissipate) that amount of power for any voltage it will see.

    EXAMPLE; if you have a 5 Vdc power source at 2 amps you are dissipating 10 watts of power. If you change that voltage to the load and do not adjust the electronic load it will still try to dissipate 10 Watts. If the first supply is 5 Vdc at 2 amps, 10 watts and the new supply is 12 Vdc the load will adjust it's current from about 2 amps to about 0.80 amps to dissipate 10 watts.
    Our Electronic Load can be adjusted from 0 - 125 / 0 - 300 Watts of power.
    The quasi-power control circuit is broken up into three straight line parts that follows the approximation of what a real constant power circuit would do. I.E. Quasi-constant power.

    This allows the Electronic Load to be operated in a production type of environment with reduced problems in a burn-in type operation.
  • What is Start-up Mode or switch mode point, and what benefits does it have?
    Answer: When your power source is first turned on, in most cases, they start at 0 volts and increase their voltage to a voltage regulation point. At some point the source must provide current to the Electronic Load. This is the voltage point where the Electronic Load turns on and starts drawing current from the power source UUT.
  • How does the Slew Rate effect my power source?
    Answer; Most power sources have a current slew rate, the speed or rate of change that current can be supplied and the voltage regulated. If an Electronic Load turns on too fast (draws too much current to fast) some power sources will go into current limit or the supply will shut down. We have a preprogrammed slew rate that should fit most cases, or if you need to shorten or lengthen it; you can add an external timing capacitor.
  • What is Current Share, and how does it work?
    Answer; This allows your Electronic Load to share the current with another or other Electronic Load of the same type. Usually allowing you to control all the loads with one control device ( pot / resistor / D to A).
  • What is Paralleling Electronic Loads, what benefit does it have?
    Answer; In some cases you many have two Electronic Loads, one a high power or high current, and another lower power or lower current. In most cases you can connect both Electronic Loads to the same source. You might want to use the high power for a course adjust and the low power for a fine adjust. Or two loads just to get more power from the power source (power supply).
  • How does Current Monitor work, and what does it tell me?
    Answer; The current from the power source flows into the Electronic Load and is measured by the loads circuits, it is then changed into a voltage and sent to the current monitor output pin. 
  • What is Dynamic Load Regulation?
    Answer; This is the rate of change or slew rate that a power source connected to an electronic load can change in voltage and have the electronic load follow that rate of voltage change. If the output of a power supply has a lot of ripple you want electronic load to be able to follow it.
  • How do I measure Common Mode Noise & what is it.
    Common mode noise is measured from the chassis ground to a power input terminal. Each measurement is made separate (one power terminal at a time), the return must be isolated from the ground to do this measurement. Note: All switching power supplies generate common mode noise. If this noise amplitude is high enough it can cause problems in measurements or operation of other test equipment..
  • What is reflected ripple.
    The ripple and/or current that a switching power supplies pulls through its input. Each time it switches a current pulse is sent to the input then a reflected current is sent back through the input line. This works just like a standing wave on a coax.
  • What is a switching Electronic Load?
    Answer; Some electronic load companies make a load that operates like a switching power supply, turning on and off power devices at a fast rate to control the average current through the load. This can and does have bad side effects, under some conditions it can cause the power source to over heat, blow-up, or just be unstable.

Executive Engineering Home

Terminology of Electronic Loads

Current Ctrl of Electronic Loads

Powering the Electronic Loads

Heat Sinks for Loads

Using DtoA's & AtoD's

Selecting an Electronic Load




Constant Power Mode

Constant Resistance Mode

Quasi-Constant Power

Start-Up Mode

Slew Rate of Current

Current Share

Paralleling Electronic Loads

Current Monitor

Dynamic Load Regulation

Common Mode Noise

Reflected Ripple

Switching Type Load