L
Lag: 1. A time delay between the output of a signal
and the response of the instrument to which the signal
is sent. 2. A time relationship between two waveforms
where a fixed reference point on one wave occurs after
the same point of the reference wave.
Laminar Flow: Streamlined flow of a fluid where
viscous forces are more significant than inertial forces,
generally below a Reynolds number of 2000.
LAN: Local Area Network. A network that takes
advantage of the proximity of computers to offer relatively
efficient, higher-speed communications than long-haul
or wide-area networks.
LAP: Link Access Protocol.
Latent Heat: Expressed in BTU per pound. The
amount of heat needed (absorbed) to convert a pound
of boiling water to a pound of steam.
Leakage Rate: The maximum rate at which a fluid
is permitted or determined to leak through a seal. The
type of fluid, the differential Limits of Error: A tolerance
band for the thermal electric response of thermocouple
wire expressed in degrees or percentage defined by ANSI
specification MC-96.1 (1975).
Least-squares Line: The straight line for which
the sum of the squares of the residuals (deviations)
is minimized.
Life Cycle: The minimum number of pressure cycles
the transducer can endure and still remain within a
specified tolerance.
Limits of Error: A tolerance band for the thermal
electric response of thermocouple wire expressed in
degrees or percentage defined by ANSI specification
MC-96.1 (1975).
Linearity: The maximum deviation of the calibration
curve from a straight line between zero and full scale,
expressed as a percent of full scale output and measured
on increasing measured only.
Line Pressure: The maximum pressure in the pressure
vessel or pipe for differential pressure measurement.
Line Protocol: A control program used to perform
data communication functions over network lines which
consists of handshaking and line-control functions that
move the data between the transmit and receive terminals.
LISP: List Processing Language.
Load Buttons: The spherical like shape of the
top surface of a load cell where the load is applied.
Load Impedance: The impedance presented to the
output terminals of a transducer by the associated external
circuitry.
Logarithmic Scale: A method of displaying data
(in powers of ten) to yield maximum range while keeping
resolution at the low end of the scale.
Loopback: Directing signals back toward the
transmitting terminal at some point along the communications
path. Used as a method of troubleshooting.
Loop Resistance: The total resistance of a thermocouple
circuit caused by the resistance of the thermocouple
wire. Usually used in reference to analog pyrometers
which have typical loop resistance requirements of 10
ohms.
LS-TTL Compatible: For digital input circuits,
a logic 1 is obtained for inputs of 2.0 to 5.5 V which
can source 20 µA, and a logic 0 is obtained for
inputs of 0 to 0.8 V which can sink 400 µA. For
digital output signals, a logic 1 is represented by
2.4 to 5.5 V with a current source capability of at
least 400 µA; and a logic 0 is represented by
0 to 0.6 V with a current sink capability of at least
16 MA. "LS" stands for low-power Schottky.
LS-TTL Unit Load: A load with LS-TTL voltage
levels, which will draw 20 µA for a logic 1 and
-400 µA for a logic 0.
LSD (Least-Significant Digit): The rightmost
active (non-dummy) digit of the display.
LVDT - Linear Variable Differential Transformer
LVDT: This has been taken from a paper prepared
at University of Ca. in Berkeley. Good Overview of operation.
LVDT: Very brief overview from Univ of Colorado.
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