Watlow Series F4S/D - Manual (Page 136)

Glossary
ac (Е Е)
— See alternating current.
ac/dc (ı ı)
— Both direct and alternating current.
alternating current — An electric current that
reverses at regular intervals, and alternates posi-
tive and negative values.
American Wire Gauge (AWG)
— A standard of
the dimensional characteristics of wire used to con-
duct electrical current or signals. AWG is identical
to the Brown and Sharpe (B & S) wire gauge.
auto-tune — A feature that automatically sets
temperature control PID values to match a particu-
lar thermal system.
battery
— BR1225, retains volatile memory. Seven-
year shelf life, indefinite life with power applied to unit.
baud rate
— The rate of information transfer in
serial communications, measured in bits per second.
burst fire
— A power control method that repeat-
edly turns on and off full ac cycles. Also called zero-
cross fire, it switches close to the zero-voltage point
of the ac sine wave. Variable-time-base burst fire
selectively holds or transits ac cycles to achieve the
desired power level. See zero cross.
calibration accuracy
— Closeness between the
value indicated by a measuring instrument and a
physical constant or known standard.
calibration offset
— An adjustment to eliminate
the difference between the indicated value and the
actual process value.
cascade — Control algorithm in which the output
of one control loop provides the set point for anoth-
er loop. The second loop, in turn, determines the
control action.
CE — A manufacturer’s mark that demonstrates
compliance with European Union (EU) laws gov-
erning products sold in Europe.
chatte
r — The rapid on-off cycling of an electrome-
chanical relay or mercury displacement relay due
to insufficient controller bandwidth. It is commonly
caused by excessive gain, little hysteresis and short
cycle time.
CJC
— See cold junction compensation.
closed loop — A control system that uses a sensor
to measure a process variable and makes decisions
based on that feedback.
cold junction
— See junction, cold.
cold junction compensation
— Electronic means
to compensate for the effective temperature at the
cold junction.
control mode
— The type of action that a con-
troller uses. For example, on/off, time proportion-
ing, PID, automatic or manual, and combinations of
these.
cycle time — The time required for a controller to
complete one on-off-on cycle. It is usually expressed
in seconds.
deadband
— The range through which a variation
of the input produces no noticeable change in the
output. In the dead band, specific conditions can be
placed on control output actions. Operators select
the deadband value.
default parameters — The programmed instruc-
tions that are permanently stored in the micropro-
cessor software.
derivative — The rate of change in a process vari-
able. Also known as rate. See PID.
derivative control (D)
— The last term in the
PID control algorithm. Action that anticipates the
rate of change of the process, and compensates to
minimize overshoot and undershoot. Derivative
control is an instantaneous change of the control
output in the same direction as the proportional er-
ror. This is caused by a change in the process vari-
able (PV) that decreases over the time of the
derivative (TD). The TD is in units of seconds.
Deutsche Industrial Norm (DIN) — A set of
technical, scientific and dimensional standards de-
veloped in Germany. Many DIN standards have
worldwide recognition.
droop
— In proportional controllers, the difference
between set point and actual value after the system
stabilizes.
duty cycle — The percentage of a cycle time in
which the output is on.
EIA — See Electronics Industries of America.
EIA/TIA -232, -422, -423 and -485 — Data com-
munications standards set by the Electronic Indus-
tries of America and Telecommunications Industry
Association. Formerly referred to as RS- (Recog-
nized Standard).
Electronics Industries of America (EIA) — An
association in the US that establishes standards for
electronics and data communications.
external transmitter power supply
— A dc volt-
age source that powers external devices.
filter, digital
— A means to slow the response of a
system when inputs change unrealistically or too
fast. Equivalent to a standard resistor-capacitor
(RC) filter.
A . 2 ■ A p p e n d i x Wa t l o w S e r i e s F 4 S / D