Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.24
after a US federal court split up the phone company into smaller units.
Read/Write (R/W) - a digital device that can store and retrieve data, such as RAM.
reagent - an chemical used in one or more chemical reactions. these are often used for identifying other
chemicals.
real-time - suggests a system must be able to respond to events that are occurring outside the computer in a
reasonable amount of time.
reciprocating - an oscillating linear motion.
redundancy - 1. added data for checking accuracy. 2. extra system components or mechanisms added to
decrease the chance of total system failure.
refreshing - is required of a computer screen to maintain the screen image. Phosphors, which glow to show
the image, decay at a fast rate, requiring the screen to be redrawn or refreshed several times a
second to prevent the image from fading.
regenerative braking - the motor windings are reverse, and in effect return power to the power source. This is
highly efficient when done properly.
register - a high speed storage area that can typically store a binary word for fast calculation. Registers are
often part of the CPU.
regulator - a device to maintain power output conditions (such as voltage) regardless of the load.
relay - an electrical switch that comes in may different forms. The switch is activated by a magnetic coil that
causes the switch to open or close.
relay - a magnetic coil driven switch. The input goes to a coil. When power is applied, the coil generates a
magnetic field, and pulls a metal contact, overcoming a spring, and making contact with a
terminal. The contact and terminal are separately wired to provide an output that is isolated from
the input.
reliability - the probability of failure of a device.
relief valve - designed to open when a pressure is exceeded. In a hydraulic system this will dump fluid back
in the reservoir and keep the system pressure constant.
repeatability - the ability of a system to return to the same value time after time. This can be measured with
a standard deviation.
repeater - added into networks to boost signals, or reduce noise problems. In effect one can be added to the
end of one wire, and by repeating the signals into another network, the second network wire has a
full strength signal.
reset - a signal to computers that restarts the processor.
resistance - this is a measurable resistance to energy or mass transfer.
resistance heating - heat is generated by passing a current through a resistive material.
resolution - the smallest division or feature size in a system.
resonant frequency - the frequency at which the material will have the greatest response to an applied
vibration or signal. This will often be the most likely frequency of self destruction.
response time - the time required for a system to respond to a directed change.
return - at the end of a subroutine, or interrupt, the program execution will return to where it branched.
reverberation - when a sound wave hits a surface, part is reflected, and part is absorbed. The reflected part
will add to the general (reverberant) sound levels in the room.
Reynolds number - a dimensionless flow value based on fluid density and viscosity, flow rate and pipe
diameter.
RF (Radio Frequency) - the frequency at which a magnetic field oscillates when it is used to transmit a
signal. Normally this range is from about 1MHz up to the GHz.
RFI (Radio Frequency Interference) - radio and other changing magnetic fields can generate unwanted
currents (and voltages) in wires. The resulting currents and voltages can interfere with the normal
operation of an electrical device. Filters are often used to block these signals.
RFS (Remote File System) - allows shared file systems (similar to NFS), and has been developed for System
V UNIX.
RGB (Red Green Blue) - three additive colors that can be used to simulate the other colors of the spectrum.
This is the most popular scheme for specifying colors on computers. The alternate is to use Cyan-
Magenta-Yellow for the subtractive color scheme.
ripple voltage - when an AC voltage is converted to DC it is passed through diodes that rectify it, and then
www.PAControl.com