Engineering Terms

AC: Acronym for Alternating Current usually mathematically represented by a sine wave.

Constant Current Power Source: A power supply that is regulated and delivers a constant current to a load, even when the load resistance changes.

Constant Voltage Power Source: A power supply that is regulated and provides a constant voltage to a load even when the load resistance fluctuates

Current limiting: A feature that helps protects the load from over current damage by limiting maximum current output at a predetermined value. The power is automatically restored following the removal of the overload.

DC: Abbreviation for Direct Current. It is the unidirectional flow or movement of electric charge carriers, usually electrons.

Earth Ground: The ground that connects to earth to protect from damage due to lightening or static electricity. It also establishes a zero voltage reference.

Electrical Isolation: When electrical devices are insulted form their surroundings, such that there is no physical electrical conductor connection.

EMI (Electro Magnetic Interference): EMI is the unwanted high frequency energy created by the switching transistors, zener diodes, and rectifiers used in switching power supplies. The portion that is radiated into the air is referred as EMI or RFI (Radio Frequency Interference). Usually most EMI frequencies are measured between 30MHz to 300MHz.

EMP: Stands for Electro Magnetic Pulse. A high frequency radiated pulse caused by a fast acting nuclear reaction.

Floating Output: The output which has no reference to any voltage, can generally be used in either positive or negative output applications.

Frame Ground: The ground plane that is usually connected to the chassis or frame of an electronic device is referred as the frame ground. It is normally connected to Earth Ground.

Line Regulation: It is a measurement of load voltage or current change when the power supply is operated at varying line voltages throughout a specified range. A rating of "0%" would mean perfect regulation.

Load Regulation: It is a measurement of load voltage or current changes between operating the power supply at no-load and full-load conditions. A rating of "0%" would mean perfect regulation.

Overload Protection: A technology by which an electronic power supply is protected from permanent damage due to short circuits, over loads, or reverse polarities connected across the load terminals.

Power consumption: The total input power required by the power supply at a full load output condition. Measured in Watts.

Peak-To-Peak AC Voltage: The difference between the maximum positive and the maximum negative amplitudes of an (Alternating Current) AC voltage waveform.

Recovery Time: The time taken by a power supply to adjust its output after a sudden change, such as from full load to no load or after recovery from a short circuit condition.

Regulation: The capability to uphold a constant voltage or current at the load despite changes in line voltage or load resistance.

Remote Sensing: A technology by which the output voltage is regulated in such a way to compensate for the voltage drop in the load leads

RFI (Radio Frequency Interference): Also known as EMI. It is the unwanted high frequency energy created by the switching transistors, zener diodes, and rectifiers used in switching power supplies. The portion that is radiated into the air is referred as EMI or RFI (Radio Frequency Interference). Usually most EMI/RFI frequencies are measured between 30MHz to 300MHz.

Ripple Noise Current: The part of unfiltered AC current and noise at the output of a filtered DC power supply.

Ripple Noise Voltage: The portion of unfiltered AC voltage present at the output of a filtered DC power supply. A zero ripple voltage would represent a perfect power supply with no noise what so ever riding the DC output.

RMS: Stands for root mean square. It is the effective value of an AC or periodic voltage or current wave form. The amount of work accomplished by a given rms value equals the amount of work accomplished by an equal DC value. The rms value of a pure sine wave is 0.707 times the peak value (RMS = Vp x 0.707), while the rms value of a square wave is 0.5 times the peak value Vp = Peak Value = Vpp/2 .

Signal Ground: The circuitry ground used in system electronics, processor and peripheral cards. This ground may be directly connected to Frame Ground or left isolated depending on the application.

Temperature Coefficient: The fluctuation in the output voltage of a power supply caused by temperature change. It is measured in milivolts per degree.