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.

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.

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.

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.

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.

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: 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.

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.

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.

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.

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

The terms and definitions for this issue’s Word Search come from a glossary of terms compiled by the U.S. Environmental Protection Agency (