Watlow Series D8 - Manual (Page 217)

Series D8 User’s Guide Glossary
Doc. 0600-3120-2000 Watlow Anafaze 199
Direct Action
An output control action in which an increase in the
process variable causes an increase in the output. Usu-
ally used with cooling applications.
Direct Current (DC)
An electric current that fl ws in one direction.
Distributed Zero Crossing (DZC)
A form of digital output control in which the output
on/off state is calculated for e very ac line c ycle.
Power is switched at the zero cross, which reduces
electrical noise. See also Zero Cross.
DZC
See Distributed Zero Crossing.
E
Earth Ground
A metal rod, usually copper , that provides an electri-
cal path to the earth, to pre vent or reduce the risk of
electrical shock.
EIA/TIA
Electronic Industries Alliance (EIA) and Telecommu-
nications Industry Association (TIA). See also Serial
Communications.
EIA/TIA-232
— A standard for interface between
data terminal equipment and data communications
equipment for serial binary data interchange. This
is usually for communications over a short distance
(50 feet [15 m] or less) and to a single device.
EIA/TIA-485
— A standard for electrical charac-
teristics of generators and recei vers for use in bal-
anced digital multipoint systems. This is usually
used to communicate with multiple de vices over a
common cable or where distances o ver 50 feet (15
m) are required.
Electrical Noise
See Noise.
Electromagnetic Interference (EMI)
Electrical and magnetic noise imposed on a system.
There are many possible causes, such as switching ac
power inside the sine w ave. EMI can interfere with
the operation of controllers and other devices.
Electrical-Mechanical Relays
See Relay, Electromechanical.
Emissivity
The ratio of radiation emitted from a surf ace com-
pared to radiation emitted from a blackbody at the
same temperature.
Engineering Units
Selectable units of measure, such as de grees Celsius
or F ahrenheit, pounds per square inch, ne wtons per
meter, gallons per minute, liters per minute, cubic feet
per minute or cubic meters per minute.
F
Fahrenheit
The temperature scale that sets the freezing point of
water at 32° F and its boiling point at 212° F at stan-
dard atmospheric pressure. The formula for con ver-
sion to Celsius is °C = 5/9 (°F - 32).
Failed Sensor Alarm
Warns that an input sensor no longer produces a v alid
signal.
Filter
Filters are used to handle v arious electrical noise
problems.
Digital Filter
— A filter that sl ws the response of
a system when inputs change unrealistically or too
fast. Equi valent to a standard resistor -capacitor
(RC) filte
Digital Adaptive Filter
— A filter that reject
high frequency input signal noise (noise spikes).
Heat/Cool Filter
— A filter that sl ws the change
in the response of the heat or cool output. The out-
put responds to a step change by going to approxi-
mately 2/3 its final alue within the numbers of
scans that are set.
Frequency
The number of cycles over a specified period of time
usually measured in c ycles per second. Also referred
to as Hertz (Hz).
G
Gain
The amount of amplification used in an electrical ci -
cuit. Gain can also refer to the proportional (P) mode
of PID.