A B C D E F G H I K L M N O P R S T U V W
Kilohm One thousand ohms (1,000 or 1 K ohms).
Leakage Current The maximum current which a solid state device still conducts when in the OFF state. Leakage current is usually measured in milliamperes (mA).
LED Light Emitting Diode, used in information displays and as status indicators.
Life A specific number of operations or amount of time during which a particular device is expected to operated reliably.
Line Frequency Frequency of electrical service provided by local utility, typically 50 or 60 Hertz.
Line Voltage Initiation The initiation of a control function by application of line voltage to either the controller’s input terminals or start switch terminals. Line Voltage Nominal voltage of electric service provided by local utility, typically 120 or 240 VAC.
Load Any device which consumes power to do work.
Load Rating A specification of the output capability of a particular controller. Typically parameters for load rating are: controllable current range, maximum AC and/or DC voltage, horsepower or Power Factor and maximum inrush current.
Lock Shaft (Locking Bushing) A mechanical means to inhibit further adjustment of a rotary type device such as a potentiometer.
Low Voltage Voltage which is typically less than 30 Vrms.
Magnal Plug A circular, 11-pin male connector with an indexing key for proper orientation in the mating socket.
Make A term used to denote the action of completing an electrical circuit.
Metal Oxide Varistor (MOV) A device whose impedance decreases dramatically when subjected to voltages greater than the rated clamping voltage. It is typically placed in parallel with the input and/or output of a switching device to effectively clamp transient voltage spikes to a certain level.
Megohm One million ohms (1,000,000 or 1Meg ohms).
Micro A metric prefix which is used to multiply a standard unit by 10-6
Milli A metric prefix which is used to multiply a standard unit by 10-3
Milliamperes One-one thousandth of an ampere (.001 or 10-3 ampere).
Ms One one-thousandth of a second (.001 or 10-3 second).
Minimum Load Current For electromechanical contacts, it is the minimum current the contacts will reliably switch without the contact resistance contributing a substantial error in the circuit. See Holding current.
Mode of Operation Logical function of a controller based on input parameters.
Momentary Initiation The initiation of a controller cycle by a start pulse of shorter duration than the complete cycle. The initiation could be with a momentary contact closure or voltage pulse.
Momentary Loss of Power A short removal of input power to the controller or controlled circuit. See Brownout.
Momentary Switch A spring loaded set of contacts, that when the actuator is pressed, the contacts either close or open depending on contact configuration. When the actuator is released the contacts will resume their normal state.
MOV Metal oxide varistor.
Noise An undesirable electrical phenomenon which is generated by various means (e.g., switching large loads, light dimmers, electrical storms). This phenomenon consists of random voltages and currents induced into electrical circuits, if severe enough, erratic operation of these circuits can result.
Nominal Voltage The middle point of two extremes of voltage as defined by the tolerance.
Normally Closed Contact (NC) The condition or position of a particular contact with respect to a common contact in its normal or quiescent (unenergized) state. A normally closed contact represents a closed circuit.
Normally Open Contact (NO) The condition or position of a particular contact with respect to a common contact in its normal or quiescent (unenergized) state. A normally open contact represents an open circuit.
Octal Plug A circular 8-pin male connector with an indexing key for proper orientation in the mating socket.
Offset A fixed difference between the controller setpoint and the actual control point of a system under stable operating conditions.
Ohm A unit of electrical resistance and impedance named after Georg S. Ohm. A conductor has a resistance of one ohm when a current of one ampere flows through it with a potential of one volt across its terminals.
ON/OFF Time Ratio The ratio of ON time to OFF time specified as a fraction or percentage of the total period.
On State Voltage The voltage measured across a solid state output device when it is in the ON state. For all practical considerations the value is the same for Peak or RMS measurements. NOTE: The portion of the sine wave before the solid state device turns ON is not to be included in this measurement.
Operating Temperature The range of ambient temperature in which a controller is designed to operate within its specifications. May be stated in Fahrenheit or Celsius.
Operating Voltage The range of input voltage within which a controller is designed to operate. Usually, it is stated as a nominal value with a maximum and minimum tolerance (e.g., 120 VAC ±10%).
Optical Isolation Utilizing light to isolate one control circuit from another; mainly used to safely interface a low level control signal with a high power output, as in a solid state relay.
Output The result delivered by a circuit or device. Also, the terminal or other location where such result is delivered.
Parallel A type of circuit connection in which loads are connected side by side across a common voltage source.
Phase The instantaneous angular position which a sine wave occupies in its cycle. The position is usually measured in degrees as referenced to zero and referred to as phase angle.
Polarity The positive and negative orientation of a source of power or signal.
Potential Difference The voltage differential between two points.
Potentiometer (POT) A three terminal device which consists of a fixed resistor with terminations on each and a moveable contact (wiper) that can travel between the two terminations. Also called a variable resistor.
Power In a Direct Current circuit it is the product of applied potential difference and current. In an Alternating Current circuit it is the product of the effective values of the voltage and current with the cosine of the phase angle between current and voltage. The units of measurement are VA or watt.
Power Factor The ratio of true power to apparent power in an alternating current, or a ratio of resistance to impedance.
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