User Guide

107
DEFINITIONS
DEVIATION Same as proportional band, but expressed in units of the
controlled magnitude (eg. 1pH, 50 mV).
EEPROM Electrically Erasable Programmable Read-only Memory (per-
manent memory).
FAIL SAFE ALARM Signaling of the alarm by de-energizing the alarm relay in-
stead of energizing it. That protects against power failures
and interruptions of the alarm relay external wires.
GLP Good Laboratory Practice.
HYSTERESIS Interval that must be passed over by the controlled magni-
tude in the opposite direction after having activated a relay,
before deactivating it, in order to avoid uninterrupted activa-
tion/deactivation of the relay.
IN-LINE CLEANING Automatic procedure to stop control, clean the electrode and
then activate control again.
NIST National Institute of Standards and Technology.
PID Proportional Integrative Derivative control.
POTENTIAL MATCHING PIN Pin for connection of the potential matching (or grounding)
steel bar, which must be immersed into the measured fluid,
and is used together with a differential input to avoid dam-
age of the reference electrode due to ground loop current.
PROPORTIONAL BAND Interval, measured in percentage of the input range, where
the proportional action spans from 0 to 100 %.
PWM Pulse Width Modulation.
RAM Random Access Memory (non-permanent memory).
RTC Real Time Clock.
SETPOINT Value at which the measurement needs to be controlled.
SOLUTION COMPENSATION Technique for compensating the differences on the
pH of the solution under measurement when its temperature
varies.
THRESHOLD Value above/below which a control or alarm relay is acti-
vated or deactivated.
TRIGGER An event or command that acts like a mechanical trigger in
initiating a process.
WATCHDOG Mechanism for issuing a reset of the device in case it gets
stuck.