Laurel Electronics LAUREATE SERIES 2 SERIAL INPUT METER & REMOTE DISPLAY - Manual (Page 31)

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16. GLOSSARY OF TERMS
Alarm, latched: An alarm which stays actuated until reset. Latched alarms can shut down
machinery or a process when an operating limit has been exceeded, or maintain an
alarm condition until acknowledged by an operator.
Alarm, non-latched: An alarm which changes state automatically when the reading rises
above a specified limit and changes back automatically when the reading falls below a
limit.
Custom ASCII protocol: A simplified protocol for use with panel meters, counters and timers.
It allows 31 digital addresses. Not an industry-standard protocol, like the more complex
Modbus protocol.
Deviation band: A band in counts which controls relay action symmetrically around a setpoint.
The relay actuates when the reading falls within the deviation band, and de-actuates
when the reading falls outside of this band. A deviation limit (e.g., 50 counts) is set up
around both sides of the setpoint to create a deviation band (e.g., 100 counts). Setting
up a passband around a setpoint is often used for component testing. Deviation limits
are programmed by entering menu item dEUn1b for Alarm 1 and dEUn2b for Alarm 2.
Function reset: A rear panel input or keystroke action which resets any latched alarms.
Hysteresis band: A band in counts which controls relay action symmetrically around a
setpoint. The relay closes (or opens) when the reading goes above the setpoint plus
one hysteresis limit, and opens (or closes) when the reading falls below the setpoint
less one hysteresis limit. A narrow hysteresis band is often used to minimize relay
chatter around a setpoint due to electrical noise or signal feedback caused by load
switching. A wide hysteresis band can be used for control applications.
Item #: A numerical value generate by a counter and available for display or data output via
serial communications. For example, in the A+B totalizer mode, the sum of A+B is Item
#1, Total A is Item #2, and Total B is Item #3. Each item can be displayed by a Remote
Display if the appropriate Display Type is selected under the Input+Display tab.
Meter Reset: A rear panel input or front panel keystroke action which resets the meter like
Half duplex: RS485 serial communications implemented with two wires, allowing data trans-
mission in both directions, but not simultaneously.
Full duplex: RS485 serial communications implemented with four wires, allowing data trans-
mission in two directions simultaneously.
Setpoint: A value compared to the reading to determine the state of a relay. Term often used
interchangeably with “alarm setpoint.”
Time-out: How long a serial reading will be displayed in the absence of a new serial input. If
timeout is set to 0, the display will persist indefinitely in the absence of a new input.