Absolute Pressure - The difference between zero pressure (which exists only in a perfect vacuum) and some known pressure. Absolute pressure may be determined by adding gauge pressure to atmospheric pressure (14.7 psi at a level).
Actuation Point - The point at which electrical switching element is operated on increasing or decreasing pressure. Neo-Dyn considers this point the increasing t point .
Ambient Pressure (or Temperature)- Pressure (or temp-erature)immediately surrounding the switch.
Atmospheric Pressure - The pressure caud by the weight of air. Atmospheric pressure at a level is considered to be 14.7 psia (or 29.9 inches of mercury or 407 inches of water absolute.)Burst Pressure - Burst pressure is the maximum pressure which may be applied to a switch without causing leakage. Permanent degradation may occur or the unit may become Inoperable if burst pressure is applied. Burst pressure is normally 2¹ ₂to 3 times maximum system pressure.
Charge Media - The fluid or gas with which the temperature nsing probe is filled.
Critical Set Point - The critical t point is the most important t point of the unit and is held to the clost tolerance. It can be either the actuation (increasing) or deactuation (decreasing) t point.Deact
uation Point - The point at which the electrical switching element is operated on increasing or decreasing pressure. Neo-Dyn considers this point the decreasing t point .
Deadband - The deadband, sometimes referred to as “differential”value, is the change in value between actuation and deactuation t points.
Differential Pressure - The difference between the two pressures being measured.
Direct Mount - A phra ud to refer to the mounting of an instrument directly at the source of the process variable (pressure or temperature) being nd.
Electrical Form - Industry standards have established letter designations for the various electrical arrangements. They are ‘C’ for SPDT, ‘CC’ for DPDT and ‘Z’ for double break.
Form ‘C’: Single Pole Double Throw (SPDT) Switching Element -An SPDT switching element has one normally clod, one normally open, and one common terminal. Three terminals mean that the element can be wired with the circuit either normally open (N/0) or normally clod (N/C).
Form ‘CC’: Double Pole Double Throw (DPDT) Switching Element - A DPDT switching element has six electrical terminals, two normally clod, two normally open and two common. Neo-Dyn us two
independent SPDT switching elements. Some units are designed for simultaneous operation whereas, others are for parate operation at different t points.
Form ‘Z’: Double Break Switching Element - A double break switching has two isolated circuits. Four terminals facilitate wiring one circuit normally open and the other normally clod.
Introduction
Types of Switches
Definitions
The following definitions and terminology describe the operating characteristics, specifications and other details relative to pressure,flow, and temperature switches. We hope this data provides the
answers to questions which may ari and helps you in lecting a switch.
ABSOLUTE PRESSURE SWITCH: A switch that compares the pressure being nd to that of a perfect vacuum. Construction requires the reference chamber to be evacuated.
项目助理DIFFERENTIAL PRESSURE SWITCH:A switch having both a high and low pressure port. Actuation occurs when pressure to the high port exceeds pressure to the low port by a predetermined value.FLOW SWITCH:A Neo-Dyn ®flow switch ns differential pressure generated by flow through a venturi to actuate an electrical switch at a predetermined flow level.
GAUGE PRESSURE (AND VACUUM) SWITCH: A switch that compares the pressure being nd to that of atmospheric pressure. Positive pressure switches n monitored pressure above atmospheric pressure while vacuum switches n pressure below atmospheric.
TEMPERATURE SWITCH: A Neo-Dyn ®temperature switch is identical to a pressure switch with the addition of a fluid-vapor charged nsing probe. The fluid-vapor charge is expod to the “basic nsor” and since probe pressure varies with temperature,discrete temperature ttings can be accomplished.
Electrical Switching Element- The electrical switching element opens or clos an electrical circuit in respon to movement by the pressure/temperature nsor. Most Neo-Dyn®products are available in SPST, SPDT and DPDT.
Enclosure (Housing)- That part of the instrument which, in varying degrees, protects the mechanism
from ambient conditions.
Explosion Proof- An enclosure which is capable of withstanding an explosion which may occur within, and capable of preventing the ignition of an explosive atmosphere which may surround it.
Gauge Pressure- Gauge pressure is the difference between atmospheric pressure and a variable pressure.
Hermetically Sealed- An enclosure completely aled from the environment. Neo-Dyn®hermetically aled electrical asmblies are all metal with a glass header. All joints are soldered or welded to insure aling integrity.
Mass Rate of Flow- An expression of flow by weight in a given time, such as pounds per hour (PPH).
Media- The liquid or gas being nd by the instrument.
NEMA Classifications
Ref: NEMA Standards Publication, Pub. No. ICS6-1988
NEMA Type 1 - General Purpo - Indoor
Type 2 - Dripproof - Indoor
Type 3 - Dusttight, Raintight and Sleet (Ice)
Resistant - Outdoor
Type 3R - Rainproof and Sleet (Ice) Resistant
- Outdoor
Type 3S - Dusttight, Raintight and Sleet (Ice)cda文件
Proof - Outdoor
Type 4 - Watertight and Dusttight - Indoor and
Outdoor
Type 4X- Watertight, Dusttight and Corrosion
Resistant - Indoor and Outdoor
Type 5 - Superded by Type 12 for Control郁金香生长周期
菊花的作文
Apparatus
Type 6 - Submersible, Watertight, Dusttight and
Sleet Resistant - Indoor and Outdoor
Type 7 - Class I, Group A, B, C or D Hazardous
Locations; Airbreak Equipment - Indoor
Type 8 - Class I, Group A, B, C or D Hazardous
Locations; Oil-Immerd Equipment
- Indoor
Type 9 - Class II, Group E, F or G Hazardous
Locations; Airbreak Equipment - Indoor
Type 10 - Bureau of Mines
Type 11 - Corrosion Resistant and Dripproof;
Oil-Immerd - Indoor
男生和女生聊天Type 12 - Industrial U, Dusttight and Driptight炒油菜花
- Indoor
Type 13 - Oiltight and Dusttight - Indoor Non-Critical Set Point- The non-critical t point is the least important tting and the tolerances are not held as clo as the
critical t point. It can be either the actuation or deactuation point. Polyimide- An engineering thermoplastic polymer characterized by
high tensile strength, excellent wear resistance, chemical and radiation inertness, and good dielectric properties over a wide temperature range. Neo-Dyn®us DuPont Kapton®Type F teflon coated flexible polyimide film as a diaphragm material.
Note:Although excellent for most applications, polyimide
泰国怎么样is subject to cracking after prolonged exposure to water
above 140°F.
Pressure- Force per unit of area.
Pressure Sensing Element- The pressure nsing element is that component part which moves as pressure increas or decreas, operating an electrical switching element at a predetermined point.
Neo-Dyn “Nega-Rate®” pressure switches utilize a diaphragm or
piston as a media al with a Belleville negative-rate disc spring system.
Pressure Switch- A pressure switch is an instrument designed to convert pressure into motion to operate an electrical switching element—thereby making or breaking an electrical circuit.
Proof Pressure (or Temperature)- Normally 1¹⁄₂to 2 times system, it
is the maximum momentary pressure (or temperature) including surges, which may be applied to any switch without causing permanent degradation.
Remote Mount- A phra ud to refer to the mounting of an instrument away from the source of the process variable being nd (usually via a capillary tube).
Repeatability- Repeatability is the maximum t point deviation of a
single pressure switch under one given t of environmental and operational conditions.
Special Switch- A unit which is modified outside the limits of a standard catalog item.
System (Working) Pressure- System pressure is the operating pressure of any hydraulic or pneumatic system.
Tolerance- Tolerance is the maximum allowable tting deviation between two or more production units under all specified environmental and operational conditions. Tolerance reprents the
sum total of tting deviations due to calibration and manufacturing variations, temperature changes, etc.
Variable Pressure- Changing pressure, generally the pressure which
is being measured or controlled.
Volume Rate of Flow- An expression of flow by volume in a given
关于大自然的作文time, such as gallons per minute (GPM).
Wetted Materials- That portion of the unit which comes in contact
with the pressure media.
Form #090-rev.a
