Watlow MICRODIN - Manual (Page 94)

A . 8 Wa t l o w M i c r o D I N
Glossary
annunciator — A visual display that uses pilot lights to indicate the former or
existing condition of several items in a system.
burst fire — A power control method that repeatedly 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 offset — An adjustment to eliminate the difference between the
indicated value and the actual process value.
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.
default parameters — The programmed instructions that are permanently
stored in the microprocessor software.
derivative — The rate of change in a process variable. 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 error. This is caused by
a change in the process variable (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 developed in Germany. Many DIN standards have
worldwide recognition.
DIN — See Deutsche Industrial Norm.
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.
external transmitter power supply — A dc voltage source that powers
external devices.
filter, digital (DF) — A filter that slows the response of a system when inputs
change unrealistically or too fast. Equivalent to a standard resistor-capacitor
(RC) filter.
form A — A single-pole, single-throw relay that uses only the normally open
(NO) and common contacts. These contacts close when the relay coil is
energized. They open when power is removed from the coil.
form B — A single-pole, single-throw relay that uses only the normally closed
(NC) and common contacts. These contacts open when the relay coil is
energized. They close when power is removed from the coil.
form C — A single-pole, double-throw relay that uses the normally open (NO),
normally closed (NC) and common contacts. The operator can choose to wire for
Appendix