RAID - Redundant Array of Independent Disks It is a technology through which several physical storage disks are grouped into an array that appears to an operating system as one or more physical devices. RAID technology, when applied to storage disks, allows the RAID array drives to be configured into a variety of data configurations, which provide varying levels of data integrity protection and storage capacity.
Rated Output Current The maximum load current that a power supply can provide at a specified ambient temperature.
Regulation The ability of a power supply to maintain an output voltage within a specified tolerance as referenced to changing conditions of input voltage and/or load.
Regulation Band The total error band allowable for an output voltage. This includes the effects of all of the types of regulation: line, load, and cross.
Reinforced Insulation An improved basic insulation with such mechanical and electrical properties that, in itself, the insulation provides the same degree of protection against electrical shock as double insulation. It may consist of one or more layers of insulation material.
Remote Sensing A technique of regulating the output voltage of a power supply at the load by means of sensing leads which go from the load back to the regulator. This compensates for voltage drops in the load leads.
Reverse Voltage Protection A protection circuit that prevents the power supply from being damaged in the event that a reverse voltage is applied at the input or output terminals.
RFI - Radio Frequency Interference This is electrical noise which is present in communications or computing equipment that results from some parts of the equipment or attached wiring acting as a radio antenna. Under certain conditions the amplitude of this noise may be large enough to disrupt communications or cause computing errors.
Ripple The magnitude of AC voltage appearing superimposed on the DC output, specified in peak to peak volts or expressed as a percent of the nominal output voltage. A power supply with clean DC output is essential for computers with high-speed processors and memory chips. The AC component superimposed over the DC output voltage. In linear power supplies, this is the traditional "hum" at 60 or 120 hertz. In switching power supplies, it is a complex waveform. Although traditionally spec'd at 1%, it is often much lower. Ripple can increase at maximum loading and minimum input voltage.
RMS - Root Mean Square It is the square root of the average value of the squares of all the instantaneous values of current or voltage during one-half cycle of an alternating current. For a sine wave, the RMS value is approximately equal to 0.707 times the peak value of the waveform. RMS is also called the effective value.