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Appendix A Glossary
Page A.5
L
LED
See Light-emitting diode.
Light-emitting diode
A diode which light up when current flows through it. LED’s are usually
used as indicator lights on instruments.
Limit
Limits are upper and lower values between which a measured
parameter is expected to be. If the parameter is outside these limits, it
can trigger an alarm if you have set the system to do so.
Live
A value is live if it can be altered automatically as a result of some
internal calculation or transducer input. (See also: Set.)
Location
An area of computer memory where data is stored. Information can be
written to it from the keyboard, a remote computer, or automatically by
the sensors.
Location ID
A number which uniquely identifies a location.
M
Mass flow rate
The rate at which a given mass of fluid flows through a transducer.
MAU
Short for Media Access Unit, an Ethernet transceiver
MODBUS/TCP
MODBUS/TCP is a variant of the MODBUS family of simple, vendor-
neutral communication protocols intended for supervision and control of
automation equipment. Specifically, it covers the use of MODBUS
messaging in an ‘Intranet’ or ‘Internet’ environment using the TCP/IP
protocols. The most common use of the protocols at this time are for
Ethernet attachment of PLC’s, I/O modules, and ‘gateways’ to other
simple field buses or I/O networks.
Mode
The operational state of the instrument.
Monitor
To keep a constant check on the status of a system or process.
Multiples of numbers
T
M
m
tera
mega
milli
10
12
10
6
10
-3
G
k
P
giga
kilo
micro
10
9
10
3
10
-6
Multiview
A user-defined display which can show up to four lines of information of
your choice. Typically, each line comprises text (such as a parameter
name) and a value for the parameter.