Watlow Series D8 - Manual (Page 221)

Series D8 User’s Guide Glossary
Doc. 0600-3120-2000 Watlow Anafaze 203
Thermocouple (T/C)
A temperature sensing de vice made by joining tw o
dissimilar metals. This junction produces an electrical
voltage in proportion to the dif ference in temperature
between the hot junction (sensing junction) and the
lead wire connection to the instrument (cold junction).
Thermocouple Extension Wire
A grade of wire used between the measuring junction
and the reference junction of a thermocouple. Exten-
sion wire and thermocouple wire have similar proper-
ties, but extension wire is less costly.
Transmitter
A device that transmits temperature data from either a
thermocouple or RTD by way of a two-wire loop. The
loop has an e xternal po wer supply . The transmitter
acts as a variable resistor with respect to its input sig-
nal. Transmitters are desirable when long lead or
extension wires produce unacceptable signal degrada-
tion.
U
Undershoot
The amount by which a process v ariable falls below
the set point before it stabilizes.
V
Volt (V)
The unit of measure for electrical potential, voltage or
electromotive force (EMF). See also Voltage.
Voltage (V)
The dif ference in electrical potential between tw o
points in a circuit. It is the push or pressure behind
current fl w through a circuit. One volt (V) is the dif-
ference in potential required to mo ve one coulomb of
charge between two points in a circuit, consuming one
joule of energy. In other w ords, one volt (V) is equal
to one ampere of current (I) fl wing through one ohm
of resistance (R), or V = IR.
Z
Zero Cross
Action that provides output switching only at or near
the zero-voltage crossing points of the ac sine wave.