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Quiescent
Supply Current -the supply current being drawn
when the pressure sensor is at null. Ratiometric (Ratiometricity
Error) -at a given supply voltage, sensor
output is a proportion of that supply voltage. Ratiometricity
error is the change in this proportion resulting from
any change to the supply voltage. Usually expressed
as a percent of full scale output. -the measurand values over which the sensor
is intended to measure, specified by the upper and
lower limits. -a device that converts alternating current
into direct current. -technology where the reed contacts are designed
to be actuated by a magnet. When a magnetic field
is brought close to the reed contacts, the contacts
are drawn together to make the circuit. -a scanning technique in which the light
source is aimed at a reflective surface to illuminate
the photosensor. Retroreflective, specular, diffuse
scan and convergent beam are all reflective scan techniques. -the ratio of voltage extremes due to loading
or line fluctuations. The process of holding constant
a quantity such as voltage by means of a system that
automatically corrects errors. For example, as more
current is drawn from a battery or power supply, the
output voltage tends to decrease (load regulation).
With a power supply derived from AC, the DC output
voltage can vary with the variation in AC voltage
(line regulation). -the level to which force on the plunger
must be reduced to allow the contacts to snap from
the operated contact position to the normal contact
position. -that position of the plunger at
which the contacts snap from the operated contact
position to the normal contact position.
-as an operating characteristic of a switch,
release travel is the distance through which the plunger
moves when traveled from the release point to the
free position. As a characteristic of the actuation
applied to the switch, release travel is the distance
the plunger is released past the release point.
-the ability of a sensor to reproduce output
readings when the same value is applied to it consecutively
in the same direction, for a specified number of cycles,
or specified time duration. -the magnitude of output step changes as
the pressure is continuously varied over the range.
This term applies primarily to potentiometric sensors.
Resolution is best specified as average and maximum
resolution. Usually expressed in percent of full scale
output. -the time it takes for a device to respond
to an input signal. The sum of the sensor,
amplifier, and output response is the total response
time. -the reflective scan technique that uses
a special reflector (retroreflector) to return light
along the same path it was sent. -circuitry, usually a diode which prevents
current from flowing into the control in case of accidental
mis-wiring of the plus (+) or minus (-) terminals,
preventing damage to the unit. -the alternating component of voltage from
a rectifier or generator. A slight fluctuation in
the intensity of a steady current.
-a measure (10% to 90%) of the time required
for an output voltage to rise from a state of low
voltage to a high voltage level, once a level change
has started. -ambient environmental conditions under which
sensors must commonly operate, which have been established
as follows: (a) Temperature: 25 +
-10 %C (77 + - 18 degrees F). (b)
Relative humidity: 90% or less. (c)
Barometric pressure: 26 to 32 inches Hg.
Note: Tolerances closer than shown are frequently
specified for sensor calibration and test environments.
Saturation
Voltage -the voltage drop appearing across
a control device that is fully turned On. -a method of scanning objects. The two general
categories are through and reflective scan. -a photoelectric control in which all three
phases of control - sensing, signal conditioning,
and output - occur in a single device. -a proximity sensor in which all three phases
of control, sensing, signal conditioning, and output,
occur in a single device. -the maximum recommended distance between
the sensor and standard target at which sensor will
effectively and reliably detect the target. -that part of a sensor which responds directly
to changes in input pressure. -maximum recommended distance between the
sensor and standard target at which sensor will effectively
and reliably detect the target. -a change in sensitivity resulting from an
environmental change such as temperature.
-a sensing element. The basic element that
usually changes some physical parameter to an electrical
signal. -a circuit in which current has only one
path to follow. -a sensor which "senses" only to the front
of its face and ignores metals to its side. The presence
of such side metal, however, may cause a slight shift
in operating characteristics. -to process the form or mode of a signal
so as to make it intelligible to or compatible with,
a given device, including such manipulation as pulse
shaping, pulse clipping, digitizing, and linearizing.
-1) broadly, the comparison of light seen
by a photosensor when the beam is blocked to the light
seen when the beam is not blocked; 2) More specifically,
the comparison of photocell resistance when sensor
is dark to when it is illuminated. Proper control
application involves establishing a large dark-to-light
ratio. -switch which may either make or break a
circuit, depending on how it is wired. -switch with only one moving and one stationary
contact. Available either normally open (N.O.) or
normally closed (N.C.). -a short pulse of acceleration, usually lasting
only a few milliseconds. A typical shock test pulse
is a half-sine acceleration wave having 100g peak
and .007 second duration. -the condition whereby the target approaches
the sensing face of the proximity sensor in such a
direction that its center will cross the axis of the
sensing face at right angles. -indoor locations, non-industrial areas,
office buildings. -in strict terms, snap action is a property
of a switch such that the moving contact accelerates
without added travel of the plunger beyond that travel
which was required to separate the contacts. National
Electrical Manufacturers Association defines snap
action as "a rapid motion of the contacts from one
position to another position, or their return. This
action is relatively independent of the rate of travel
of the actuator." The word "relatively" is important.
In actual fact, the acceleration of the moving contact
is partially dependent upon the velocity of the plunger.
The important point is that, once the plunger reaches
the operating or release point, the movable contact
immediately transfers to its opposite position without
further travel of the plunger. A non-snap acting switch
lacks this feature. -the algebraic difference between limits
of the pressure range. -a reflective scan technique in which reflection
from a shiny surface illuminates the photosensor,
which must be precisely positioned to receive the
reflected light. The angle of incidence equals the
angle of reflection. -the extent to which an operating characteristic
such as operating point remains constant during a
specified number of cycles of switch operation, under
specified conditions of actuation, electrical loading
and environment. Most clearly expressed as a graph
of the characteristic versus cycles of switch operation.
-an object used for making comparative measurements
of operating distance. A square of mild steel, 1mm
thick. The length of the side of the square is equal
to either: A: the diameter of the
circle inscribed on the active surface of the sensitive
face of the sensor, or B: three times
the rated operating distance, whichever is the greater.
-the minimum and maximum specified temperature
which may be applied to the pressure sensor without
causing a permanent change in the output characteristics.
-a sensing device providing a change in electrical
resistance proportional to the level of applied stress.
-the change of state of a materiel from solid
to vapor and back to solid without going through a
liquid state. -units = Amps or milliamps. The amount of
current necessary to maintain operation of a photoelectric
control, proximity sensor or control base. Sometimes
referred to as Current Consumption.
-units + Volts. The range of power required
to maintain proper operation of a photoelectric control,
proximity sensor or control base. The difference in
potential (or range of difference in potential) necessary
to operate the unit. -the actual number of targets to which the
sensor can respond in a given time period, usually
expressed as Hertz (cycles per second). Target -the
part or piece being detected. -T.B.L. (End Point Linearity) - a method
of defining linearity. The maximum deviation of any
data point on a sensor output curve from a straight
line drawn between the end data points on that output
curve. (T.B.L. is approximately twice the magnitude
of B.F.S.L.). -a theoretical slope for which the theoretical
end points are normalized at 0 and 100% of both measurand
and output. Interchangeability error is referenced
to this line. -the maximum change in output, at any input
pressure within the specified range, resulting from
a change in temperature. -a chart illustrating sensor operating variance
due to changes in temperature. -technology using silk screened pastes to
form conductor, resistor, themistors, and insulator
patterns; screened onto the substrate (usually ceramic)
and cured by firing at elevated temperatures. -a technology using vacuum deposition of
conductors and dielectric materials onto a substrate
(frequently silicon) to form an electrical circuit.
-a control type that responds to the change
in input signal level. Plug-in amplifiers are either
threshold or transition responsive. -the number of circuits that each individual
pole of a switch can control. The number of throws
is completely independent of the number of poles and
number of breaks. A single-pole double-throw single-break
switch connects the common terminal of the switch
to the normally closed terminal when the plunger is
free, but connects the common terminal to the normally
open terminal when the plunger is depressed. A single-pole
single-throw single-break switch has a common terminal
and either a normally open terminal or a normally
closed terminal but not both. -a scanning technique in which the emitter
(light source) is aimed directly at the receiver.
Also called direct scan and transmitted scan, since
light is transmitted directly, not reflected to the
sensor. Presently, it is the only scanning technique
commonly used to scan distances greater than 40 feet. -also know as False Pulse Protection. Outputs
are turned Off when power is first applied during
this time period. -the distance from the plunger free position
to the full overtravel point.
-a fully packaged, signal conditioned, compensated
and calibrated sensor. -circuitry to guard against spikes induced
on the supply lines by inductive sources such as heavy
motors or solenoids turning On and Off. -in electronic usage, usually refers to an
unwanted, temporary, large increase or decrease in
a current or supply voltage that only occurs occasionally.
Almost always due to reactive components during rapid
changes in voltage or current. -a control type that responds to the rate
of change in light intensity rather than the level
change. Used to detect fast moving objects that cause
little change in light intensity level. -allows light to pass through. Detecting
translucent objects is often best done with retroreflective
scan, during which the light must pass through the
object twice, thereby causing more of a signal change
(larger signal ratio). -a transducer with a current loop output,
typically 4 to 20 mA, enabling transmission of a signal
over a longer distance. -a generic term for Transistor Logic which
is used extensively in digital electronics systems.
-TTL (transistor-transistor-logic) requires
NPN (current sinking) input signals. Reliable operation
demands maximum input sensor voltage drop of 0.8 V.
Most TTL compatible interface devices have voltage
drops of less than 0.7V. -(as used herein): refers to the target value
or where a range is given, represents an estimate
of where 2/3 of the total population of several production
runs would be. UL -Underwriter's
Laboratories, Inc., a non-profit organization that
establishes, maintains and operates laboratories for
the examination and testing of devices, systems and
materials primarily for safety. -a differential pressure sensor requiring
the greater input pressure to be applied to a specified
pressure port. -a sensor with limited side and front sensing
capabilities. -sensing distance after temperature range
tolerance and manufacturers tolerance are taken into
account. Velocity -the
rate at which the position of a moving object is changing.
Velocity has two characteristics: magnitude (speed)
and direction. -units = Volts (DC) or Volts RMS (AC). The
term used to designate the electrical energy, differential
that exists between two points and is capable of producing
the flow of current when a closed path is connected
between the two points. -units = Volts (DC) or Volts RMS (AC). Sometimes
referred to as Saturation Voltage. In any solid state
control that switches a load, there will be some voltage
dropped across the output. This voltage drop or saturation
voltage will often vary with the amount of current
going through the output section and the load. It
should be specified with current conditions.
Welding, Contact
-one of several conditions that may cause switch
contacts to fail to separate at the intended point
of plunger travel. As the name implies, the contacts
literally are welded together as a result of the electrical
and thermal effects at the contact interface. |
