Watlow Series D8 - Manual (Page 220)

Glossary Series D8 User’s Guide
202 Watlow Anafaze Doc. 0600-3120-2000
Proportional Band (PB)
A range in which the proportioning function of the
control is acti ve. Expressed in units, de grees or per -
cent of span. See also PID.
Proportional Control
A control using only the P (proportional) value of PID
control.
Pulse Input
Digital pulse signals from de vices, such as optical
encoders.
PV
See Process Variable.
R
Ramp
A programmed increase in the temperature of a set
point system.
Range
The area between tw o limits in which a quantity or
value is measured. It is usually described in terms of
lower and upper limits.
Recipe
See Job.
Relay
A switching device.
Electromechanical Relay
— A power switching
device that completes or interrupts a circuit by
physically mo ving electrical contacts into contact
with each other. Not recommended for PID control.
Solid State Relay (SSR)
— A switching de vice
with no moving parts that completes or interrupts a
circuit electrically.
Reset
See Automatic Reset, Manual Reset.
Resistance
Opposition to the fl w of electric current, measured in
Ohms.
Resistance Temperature Detector (RTD)
A sensor that uses the resistance temperature charac-
teristic to measure temperature. There are tw o basic
types of RTDs: the wire RTD, which is usually made
of platinum, and the thermistor , which is made of a
semiconductor material. The wire R TD is a positi ve
temperature coef ficient sensor onl , while the ther -
mistor can have either a negative or positive tempera-
ture coefficient
Reverse Action
An output control action in which an increase in the
process variable causes a decrease in the output. Heat-
ing applications usually use reverse action.
RTD
See Resistance Temperature Detector.
S
Serial Communications
A method of transmitting information between
devices by sending all bits serially o ver a single com-
munication channel.
Set Point (SP)
The desired v alue of the process v ariable. For exam-
ple, the temperature at which a system is to be main-
tained.
Shield
A metallic foil or braided wire layer surrounding con-
ductors that is designed to pre vent electrostatic or
electromagnetic interference from external sources.
Signal
Any electrical transmittance that conveys information.
Solid State Relay (SSR)
See Relay, Solid State.
Span
The difference between the lower and upper limits of
a range expressed in the same units as the range.
Stability
The ability of a de vice to maintain a constant output
with the application of a constant input.
T
Thermistor
A temperature-sensing device made of semiconductor
material that exhibits a large change in resistance for a
small change in temperature. Thermistors usually
have negative temperature coefficients, although th y
are also a vailable with positi ve temperature coef fi
cients.