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Flow meter Glossary
ac:
Alternating current; an
electric current that reverses its direction at
regularly recurring intervals.
Accuracy:
The closeness of
an indication or reading of a measurement device
to the actual value of
the quantity
being measured. Usually expressed as ±
percent of full scale output or reading.
Acoustics:
The
degree of sound. The nature, cause, and phenomena
of the vibrations of elastic
bodies;
which vibrations create compressional waves or
wave fronts which are transmitted through
various media, such as air, water,
wood, steel, etc.
Adapter:
A mechanism or
device for attaching non-mating parts.
ADC:
Analog-to-
Digital Converter: an electronic device which
converts analog signals to an
equivalent digital form, in either a
binary code or a binary-coded-decimal code. When
used for
dynamic waveforms, the
sampling rate must be high to prevent aliasing
errors from occurring.
Ambient Compensation:
The
design of an instrument such that changes in
ambient temperature
do not affect the
readings of the instrument.
Ambient Conditions:
The
conditions around the transducer (pressure,
temperature, etc.).
Ambient
Pressure:
Pressure of the air
surrounding a transducer.
Ambient Temperature:
The
average or mean temperature of the surrounding air
which comes in
contact with the
equipment and instruments under test.
Ampere (amp):
A unit used to
define the rate of flow of electricity (current)
in a circuit; units are
one coulomb
(6.28 x 1018 electronics) per second.
Amplitude:
A measurement of
the distance from the highest to the lowest
excursion of motion, as
in the case of
mechanical body in oscillation or the peak-to-peak
swing of an electrical waveform.
Analog Output:
A voltage or
current signal that is a continuous function of
the measured
parameter.
Analog-to-Digital Converter (A/D or
ADC):
A device or circuit that outputs
a binary number
corresponding to an
analog signal level at the input.
ATC:
Automatic temperature
compensation.
Background
Noise:
The total noise floor from all
sources of interference in a measurement system,
independent of the presence of a data
signal.
Bandwidth:
A symmetrical
region around the set point in which proportional
control occurs.
Baud:
A unit of data
transmission speed equal to the number of bits (or
signal events) per second;
300 baud =
300 bits per second.
Bearing:
A part which
supports a journal and in which a journal
revolves.
Beta
Ratio:
The ratio of the diameter of a
pipeline constriction to the unconstricted pipe
diameter.
BNC:
A
quick disconnect electrical connector used to
inter-connect and/or terminate coaxial cables.
BTU:
British
thermal units. The quantity of thermal energy
required to raise one pound of water at
its maximum density, 1 degree F. One
BTU is equivalent to .293 watt hours, or 252
calories. One
kilowatt hour is
equivalent to 3412 BTU.
Bus:
Parallel lines used to
transfer signals between devices or components.
Computers are often
described by their
bus structure (i.e., S-100, IBM PC).
Calibration:
The process of
adjusting an instrument so that its reading can be
correlated to the
actual value being
measured.
Cavitation:
The boiling of a
liquid caused by a decrease in pressure rather
than an increase in
temperature.
CE approval:
CE
marking is a declaration by the manufacturer that
the product meets all the
appropriate
provisions of the relevant legislation
implementing certain European Directives. The
initials
product meets the
requirements of the applicable European
Directive(s). Portaflow 330, 220A, 220B
models manufactured in accordance with
the following Directives and Standards: Directive
2004/108/EC, Directive 2006/95/EC. BS
EN 61010-1:2001, BS EN61326-1:2006, BS
EN613626-
2:2006.
Centre of Gravity (Mass
Centre):
The centre of gravity of a
body is that point in the body
through
which passes the resultant of weights of its
component particles for all orientations of the
body with respect to a uniform
gravitational field.
CFM:
The volumetric flow
rate of a liquid or gas in cubic feet per minute.
Closeness of
Control:
Total temperature variation
from a desired set point of system. Expressed
as
2°
C or a
system bandwidth with 4°
C, also
referred to as amplitude of
deviation.
Colour Code:
The
ANSI established colour code for thermocouple
wires in the negative lead is
always
red. Colour Code for base metal thermocouples is
yellow for Type K, black for Type J, purple
for Type E and blue for Type T.
Communication:
Transmission and reception of data among data
processing equipment and
related
peripherals.
Compensated
Connector:
A connector made of
thermocouple alloys used to connect
thermocouple probes and wires.
Compensation:
An
addition of specific materials or devices to
counteract a known error.
Confidence Level:
The range
(with a specified value of uncertainty, usually
expressed in percent)
within which the
true value of a measured quantity exists.
Connection Head:
An enclosure attached to the end of a thermocouple
which can be cast iron,
aluminium or
plastic within which the electrical connections
are made.
Convection:
1. The
circulatory motion that occurs in a fluid at a
non-uniform temperature owing to
the
variation of its density and the action of
gravity. 2. The transfer of heat by this automatic
circulation of fluid.
CPS:
Cycles per second; the
rate or number of periodic events in one second,
expressed in Hertz
(Hz).
Critical Damping:
Critical
damping is the smallest amount of damping at which
a given system is
able to respond to a
step function without overshoot.
Critical Speed:
The
rotational speed of the rotor or rotating element
at which resonance occurs in
the
system.
Damping:
The reduction of vibratory movement through
dissipation of energy. Types include
viscous, coulomb, and solid.
dB (Decibel):
20
times the log to the base 10 of the ratio of two
voltages. Every 20 dBs
correspond to a
voltage ratio of 10, every 10 dBs to a voltage
ratio of 3.162. For instance, a CMR of
120 dB provides voltage noise rejection
of 1,000,000/1. An NMR of 70 dB provides voltage
noise
rejection of 3,162/1.
DC:
Direct current; an
electric current flowing in one direction only and
substantially constant in
value.
Dead Volume:
The
volume of the pressure port of a transducer at
room temperature and ambient
barometric
pressure.
Default:
The value(s) or
option(s) that are assumed during operation when
not specified.
Degree:
An incremental value
in the temperature scale, i.e., there are 100
degrees between the ice
point and the
boiling point of water in the Celsius scale and
180°
F between the same two points in
the Fahrenheit scale.
Density:
Mass per unit of
volume of a substance. I.E.: grams/. or pounds/.
Deviation:
The
difference between the value of the controlled
variable and the value at which it is
being controlled.
Differential:
For an on/off
controller, it refers to the temperature
difference between the
temperature at
which the controller turns heat off and the
temperature at which the heat is turned
back on. It is expressed in degrees.
Digital Output:
An output signal which represents the size of an
input in the form of a series of
discrete quantities.
Digital-to-Analog Converter (D/A or
DAC):
A device or circuit to convert a
digital value to an
analog signal
level.
DIN (Deutsche
Industrial Norm):
A set of German
standards recognized throughout the world.
The 1/8 DIN standard for panel meters
specifies an outer bezel dimension of 96 x 48 mm
and a
panel cutout of 92 x 45 mm.
Doppler
Technology:
An acoustic pulse is
reflected back to the sensor from particles or
gases in
the flowing liquid. The flow
rate of any fluid can be measured as long as it
contains air bubbles or
solids. It is
ideal for wastewater, slurries, sludge and most
chemicals, acids, caustics and lubrication
fluids.
Drift:
A change of a reading
or a set point value over long periods due to
several factors including
change in
ambient temperature, time, and line voltage.
Duplex:
Pertaining to simultaneous two-way independent
data communication transmission in both
direction. Same as
Echo:
To reflect received
data to the sender. For example, keys depressed on
a keyboard are
usually echoed as
characters displayed on the screen.
Electrical Interference:
Electrical noise induced upon the signal wires
that obscures the wanted
information
signal.
EMI:
Electromagnetic interference.
Emissivity:
The ratio of
energy emitted by an object to the energy emitted
by a blackbody at the
same temperature.
The emissivity of an object depends upon its
material and surface texture; a
polished metal surface can have an
emissivity around 0.2 and a piece of wood can have
an
emissivity around 0.95.
End Point (Potentiometric):
The apparent equivalence point of a titration at
which a relatively
large potential
change is observed.
Environmental Conditions:
All conditions in which a transducer may be
exposed during shipping,
storage,
handling, and operation.
Error:
The difference
between the value indicated by the transducer and
the true value of the
measurand being
sensed.
Explosion-proof
Enclosure:
An enclosure that can
withstand an explosion of gases within it and
prevent the explosion of gases
surrounding it due to sparks, flashes or the
explosion of the
container itself, and
maintain an external temperature which will not
ignite the surrounding gases.
Exposed Junction:
A form of
construction of a thermocouple probe where the hot
or measuring
junction protrudes beyond
the sheath material so as to be fully exposed to
the medium being
measured. This form of
construction usually gives the fastest response
time.
Fahrenheit:
A temperature
scale defined by 32°
at the ice point
and 212°
at the boiling point of
water at sea level.
Ferrule:
A compressible
tubular fitting that is compressed onto a probe
inside a compression fitting
to form a
gas-tight seal.
Field
Balancing Equipment:
An assembly of
measuring instruments for performing balancing
operations on assembled machinery which
is not mounted in a balancing machine.
Field of View:
A volume in
space defined by an angular cone extending from
the focal plane of an
instrument.
File:
A set of
related records or data treated as a unit.
Flow Rate:
Actual speed or velocity of fluid movement.
Flow:
Travel of
liquids in response to a force (i.e. pressure or
gravity).
FPM:
Flow velocity in feet per minute.
FPS:
Flow velocity in feet
per second.
Freezing
Point:
The temperature at which the
substance goes from the liquid phase to the solid
phase.
Frequency
Output:
An output in the form of
frequency which varies as a function of the
applied
input.
Frequency, Natural:
The
frequency of free (not forced) oscillations of the
sensing element of a
fully assembled
transducer.
Frequency:
The number of
cycles over a specified time period over which an
event occurs. The
reciprocal is called
the period.
Full Scale
Output:
The algebraic difference
between the minimum output and maximum output.
GPH:
Volumetric flow rate in gallons per hour.
GPM:
Volumetric
flow rate in gallons per minute.
Ground:
1. The electrical
neutral line having the same potential as the
surrounding earth. 2. The
negative side
of DC power supply. 3. Reference point for an
electrical system.
Grounded
Junction:
A form of construction of a
thermocouple probe where the hot or measuring
junction is in electrical contact with
the sheath material so that the sheath and
thermocouple will
have the same
electrical potential.
Handshake:
An interface
procedure that is based on status/data signals
that assure orderly data
transfer as
opposed to asynchronous exchange.
Hardware:
The electrical,
mechanical and electromechanical equipment and
parts associated with a
computing
system,
Heat Sink:
1.
Thermodynamic. A body which can absorb thermal
energy. 2. Practical. A finned
piece of
metal used to dissipate the heat of solid state
components mounted on it.
Heat Transfer:
The process
of thermal energy flowing from a body of high
energy to a body of low
energy. Means
of transfer are: conduction; the two bodies
contact. Convection; a form of
conduction where the two bodies in
contact are of different phases, i.e. solid and
gas. Radiation: all
bodies emit
infrared radiation.
Heat
Treating:
A process for treating metals
where heating to a specific temperature and
cooling
at a specific rate changes the
properties of the metal.
Heat:
Thermal energy. Heat
is expressed in units of calories or BTU's.
Hertz (Hz):
Units in which frequency is expressed. Synonymous
with cycles per second.
ID:
Inside diameter
Infrared:
An
area in the electromagnetic spectrum extending
beyond red light from 760
nanometers to
1000 microns (106 nm). It is the form of radiation
used for making non-contact
temperature
measurements.
Insulated
Junction:
See Ungrounded Junction
Insulation
Resistance:
The resistance measured
between two insulated points on a transducer
when a specific dc voltage is applied
at room temperature.
Interchangeability Error:
A
measurement error that can occur if two or more
probes are used to
make the same
measurement. It is caused by a slight variation in
characteristics of different probes.
Interface:
The means by
which two systems or devices are connected and
interact with each other.
Intrinsically Safe:
An
instrument which will not produce any spark or
thermal effects under normal
or
abnormal.
IP
Rating:
(or
BS EN
60529:1992, European IEC 60509:1989). They are
used to define levels of sealing
effectiveness of electrical enclosures
against intrusion from foreign bodies (tools, dirt
etc) and
moisture.
IP66:
First digit is the
intrusion protection, in this case 6 is totally
dust tight. Second digit is
moisture
protection, in this instance protection against
string water jets and waves.
IP67:
Total dust ingress
protection and protected against temporary
immersion between 15cm and
1m depth.
Isolation:
The
reduction of the capacity of a system to respond
to an external force by use of
resilient isolating materials.
Joule:
The basic
unit of thermal energy.
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