Glossary of Terms

Delay on Make       Same as delay on energization.

Dielectric Strength The continuous voltage a dielectric can withstand
                    without deteriorating.

Effective Power     In ac measurements, effective power (measured in watts)
                    equals the product of voltage, current and power factor (the
                    cosine of the phase angle between the current and the
                    voltage).

Full Scale (F.S.)   The specified maximum value of the input quantity being
                    measured that can be applied to a transducer without causing
                    a change in performance beyond specified tolerance.

Full Scale Output   The specified maximum output value for which the stated
                    accuracy condition applies.

Guaranteed Range    Refers to a range of adjustment or operating range
                    whereby the control device must at least operate or
                    cover the "guaranteed" range.

Hysterisis          An error resulting from the inability of an electrical signal or
                    mechanical system to produce identical readings or position
                    when approached slowly from either direction. Also referred to
                    as deadband.

Impedance           The opposition in an electrical circuit to the flow of alternating
                    (AC) current. Impedance consists of ohmic resistance (R),
                    inductive reactance (XL), and capacitive reactance (XC).

Inrush              The initial surge of current through a load when power is first
                    applied. Lamp loads, induction motors, solenoids, contactors,
                    valves, and capacitive loads all have inrush currents higher
                    than the normal running or steady state currents. Resistive
                    loads, such as heater elements, have no inrush.

Instrument Transformer   A transformer which is intended to reproduce in its secondary
                         circuit, in a definite and known proportion, the current or
                         voltage of its primary circuit with the phase relations
                         substantially preserved.
Isolation           To be electrically separate. A measure of the strength of the
                    dielectric providing the electrical division or separation.

Linearity           A measure of departure from straight-line response in the
                    relationship of two quantities, where the change in one is
                    directly proportional to a change in the other. Normally
                    expressed as a maximum percentage.

Loop Powered        The transducer uses the power supplied to the output current
                    measuring loop. No auxiliary power supply is required.

Loop Resistance     The electrical resistance, in ohms, of a complete transducer
                    circuit exclusive of an instrument's internal resistance.

Non-Linearity       In an ideal system, the input-output relationship between
                    variables is linear(i.e. straight line) Any departure from straight
                    line is expressed as non-linearity.

Operating Voltage   A nominal voltage with a specified tolerance applied. The
                    design voltage range to remain within the unit's operating
                    tolerances.

Phase Angle         The difference in time by which an alternating signal lags or
                    leads another signal.  Phase angle may be a measure of
                    power factor when used to indicate the relationship of a
                    voltage to current signal for a non-resistive load.  Phase angle
                    may also be used to measure the different in phase between
                    the primary and secondary of an current or voltage
                    transformer.

Polyphase Wattmeter A wattmeter consisting of 2 or 3 single phase wattmeters
                    mounted in the same package. The watt sensing elements can
                    be electronic transducers. A dual element wattmeter will
                    measure power in a 3 phase system regardless of power
                    factor, voltage or current variations between phases. Most
                    common types are 2,2« or 3 element forms. In 4 wire circuits,
                    with the 4th wire carrying current, the 2« or 3 element type is
                    used. If there is voltage imbalance, only the 3 element units
                    can be employed.

Power               A source or means of supplying energy. The unit of
                    measurement is the watt. 1 Horsepower is equal to 745.7
                    Watts.

Range               Nominal operating limits, specified by the lowest calibration
                    point to the highest calibration point.

Rated Output        The output at standard calibration

Ratios              The relationship between the primary input value divided by
                    the secondary output value.  For example: a current
                    transformer that has a primary input value of 100 Amps and a
                    secondary value of 5 Amps will have a Current Ratio of 100:5
                    and a Turns Ratio of 20:1.  It is important to use the term
                    Current Ratio for most applications because it defines the
                    current handling capacity of wire used in the secondary
                    winding.  The Turns Ratio only refers to the winding ratio and
                    does not define the current handling capacity of the either
                    primary or secondary windings.
     
Real Power          Same as Effective Power.

Reactive Power      A component of apparent power (volt-amps) which does not
                    produce any real power (watt) transfer.

Repeat Accuracy     The maximum deviation from one timing operation to the next.

Self Powered        The power required for correct operation of a transducer is
                    supplied via the line being measured.

Separately Powered  The power required for correct operation of a transducer is
                    supplied via an external or auxiliary power source, rather than
                    via the line being measured.

Setting Accuracy    The ability to accurately set a knob, switch, or other
                    adjustment to the time delay, or other monitored parameter.

Snubber Network     A form of suppression network which consists of a series
                    connected resistor and capacitor connected in parallel with the
                    output device. Helps to limit the maximum rate of rise of a
                    voltage. Used to prevent false turn-on of solid state outputs.

Snubber             A resistance/capacitor or diode/resistor circuit used to
                    dissipate transient energy peaks.

Transducer          A device for converting an electrical signal into a useable
                    direct current or voltage for measurement purposes.

RMS                 The effective value of alternating current or voltage. The RMS
                    value equates an ac signal to a dc signal which provides the
                    same power transfer.

True RMS Amps       The effective value of an ac signal. For an amp signal, true
                    RMS is a precise method of stating the amp value regardless
                    of waveform distortion. An ac measurement which is equal in
                    power transfer to a corresponding dc current.

True RMS Volts      The effective value of an ac signal. For a voltage signal, true
                    RMS is a precise method of stating the voltage value
                    regardless of waveform distortion. An ac measurement which
                    is equal in power transfer to a corresponding dc voltage.

Unbalanced Loads    Refers to an unequal loading of the phases in a
                    paleface system (current and/or phase angle)

Watt                Unit of electrical power.
                    WATTS=E*I*PF

VA                  The product of the RMS voltage applied to a circuit and the
                    RMS current, in amperes, flowing through it.

VAR(Volt-Amperes Reactive) The unit of reactive power as opposed to real power
          		   (watts)