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Analog Signal. A signal which
communicates or controls by changing an amount. The information in an analog signal
is of the “How Much?” variety. There may be “more” voltage or “less” voltage or more or less
electrical current, to represent more or less flow, for instance. See “Digital
Signal.” Bleed. The process of
dumping some of the chemical-laden water in a cooling tower. This is done at intervals to
prevent excessive buildup of chemicals. Cooling Tower. A piece of
equipment which is used to cool water which has been heated in an air conditioning or other
system. The cooling is done by letting the warm water fall through the air or by spraying it
through air. Cooling water is recirculated over and over, and water treatments
are added in the cooling
tower. Chemical Metering
Pump. A
specialized pump which delivers small, controlled amounts of chemical with each stroke or
over a given time period. See also “Pulse-responsive Metering Pump”. Data Logger. An electronic
memory device which accepts information from instruments and records it for future
use, usually in a form which can be read with the help of a personal computer. Digital Signal. A signal
which communicates or controls by a series of electronic pulses (“on” or “off” or “high” or
“low”) which can be translated at the receiving end into useful information. Divider. An electronic device
which accepts pulses in and after a certain number (the “divider factor”) puts a pulse
out. Dry Contact. Any switch which
has mechanical means as opposed to electronic means of switching with a 0.4 VA maximum
rating at 20V or less. It is called "dry" because the working of the switch is independent
of the electricity passing through it and there is not sufficient amount of electrical power to
clean the contacts. A reed switch is a dry contact, and doesn't need a specific voltage (12 Volts DC
for instance) in order to work. Electronic Metering
Pumps. See
“Pulse-responsive Metering Pump.” Engineering Units. The common
measurement units; in the case of liquid flow these are, for instance, gallons per
minute (GPM), liters per minute (LPM), cubic meters per hour, and so on. EPROM. A type of electronic
component which carries the program of a “computer” control. It is installed at the
factory when the control is built and can be erased for loading a new program. Four-to-twenty
Milliamp (4-20 mA). A commonly-used
analog control signal which varies in electrical current
(measured in milliamperes) between 4 and 20 milliamps. Ordinarily, four
represents the lowest value, for
instance zero flow, and twenty represents the maximum, for instance, 300 gallons per
minute (in a two-inch pipe). Hall-effect Sensor. An
electronic sensor which responds to magnetic fields. The sensors used by Hays “turn on” in the
presence of the field from a small magnet. Hot-Tap (also
Pressure Tap). A method of inserting
a meter into a pipe without shutting off the
flow or releasing the pressure in the pipe. Insertion Meter. Any flow
meter which is installed in a pipe by putting it in through a relatively small hole in the side of
the pipe. Jewel Bearings. The type
of bearings used in Hays IP meters are sapphire, consisting of a dough-nut-shaped ring jewel and
a flat end jewel, together in a tubular stainless steel housing. K-Factor. Also known as “Meter
Factor”, the number of pulses per unit (usually, per gallon) which an electronic meter
produces. Linearity. A measurement of
the ability of a meter to be accurate at any flow rate within its range. For electronic
meters, the degree to which K-factor remains the same at any flow rate. (See
“K-factor”). Makeup Water. Water which is
added to a closed circulating system to make up for that which has been lost by
evaporation or leaks. Usually used in reference to cooling towers or boilers. Of
interest because it is often
metered in order to add water treatment chemicals. Mag Meter (Magnetic
Flow Meter). A type of meter which
measures flow rate by detecting the electrical voltage
caused by the movement of a conductive liquid through a magnetic field. Microprocessor. A type of
electronic component which serves as the “brain” of the more complex electronic control.
This is the same type of “chip” or integrated circuit which gives personal
computers their capabilities. Open Channel. A type of liquid
flow which is not under pressure, and moves solely by gravity. A drainage ditch would
be one example, a half-full sewer pipe another. A special type of flow meter is necessary to measure
it. Percent of Reading (%
Reading). A
method of describing meter accuracy based upon percentage of actual reading (method
used by AWWA). This measuring method is tighter tolerenced than Percent of Full
Scale method. Percent of Full Scale
(% FS). A
method of describing meter accuracy which is based on a percentage of the maximum flow
rate. This method of measuring accuracy is less strict than Percent of Reading. Programmable Pulse. A feature
of an electronic control which allows the user to choose any desired pulse output
rate (pulses per gallon, gallons per pulse). Proportional Feed. A process
using a metering pump and meter to inject small amounts of chemical into a water flow, at
a rate matching the flow of the water. Pulse-responsive
Metering Pump. A type of metering
pump which responds to a signal from a pulse meter like the
Hays M Series. Each time the meter pulses once, the pump strokes once. Also called
“electronic metering pump”. Reed Switch. A tiny electrical
switch which turns on when a magnet comes close to it. The magnet
pulls a pair of hair-like metal fingers (the “reeds”) together, closing the
electrical circuit. Hall Effect Sensor — Solid state
sensor which detects the presence of a magnetic field. Hall-effect switches off and on
much like a transistor and needs a power source to function. Reed Switch Sensor— Provides a dry
contact closure to pumps and controls. No external power source is required. Sine-wave Signal. An
electronic signal which changes like a sea wave, continuously going higher and then lower and
higher and lower . . . See “Square-wave Signal”. Square-wave Signal. A signal
which jumps from one level to another and back, over and over again. Think of it as
being like a blinking light: on-off-on-off . . . See “Sine-wave Signal”. Telemetry. Automatic
measurement and transmission of data. This process is electrical and is used to measure
pressure, speed and temperature. Totalizing. Keeping track of
the total amount of flow which has gone through a meter, as opposed to “rate”, which is
the speed of flow at the present moment. VAC. Abbreviation for
“Volts of Alternating Current“. VDC. Abbreviation for
“Volts of Direct Current”. Velocity Profile. The
pattern of rates of flow within the pipe. The liquid closer to the center of the pipe flows faster
than that which is nearer to the wall. Regeneration. A process used
with water softeners in which the efficiency of the unit is restored by flowing some
chemical through it for a period of time. This has to be repeated at intervals
of so
many gallons. |
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