Industrial Pressure Switches GLOSSARY

1. Absolute Pressure

The difference between zero pressure (a perfect vacuum) and some known pressure.

2. Accuracy (Repeatability)

The maximum allowable set-point deviation of a single pressure switch under one given set of environmental and operational conditions.

3. Actuation Point (Set Point)

The point at which the switch is actuated to either open or close the electrical circuit, depending on how the switch is wired.

4. Ambient Pressure

Adjacent (not necessarily atmospheric) pressure immediately surrounding the switch .

5. Ambient Temperature

Adjacent (not necessarily atmospheric) temperature immediately surrounding the switch .

6. Atmospheric Pressure

The actual weight of the earth's atmosphere at a given locale and altitude. Atmospheric pressure at sea level is approximately 14.7 psia or 30 inches of mercury.

7. Deadband (Differential / Hysteresis)

The difference between the actuation point and the deactuation point.

8. Deactuation Point

Once the switch is actuated (See Actuation Point), the point at which the switch then changes state (open or closed depending on wiring) to return it to its initial state.

9. Differential

See Deadband.

10. Double-Pole Double-Throw (DPDT)

switch es which make and break two separate circuits. This circuit provides a normally open and normally closed contact for each pole.

11. Differential Pressure

The differential between two independent pressures.

12. Electrical switch ing Element

Opens or closes an electrical circuit as a result of the movement it receives from the pressure sensing element.

13. Explosion-Proof switch

A UL listed switch capable of withstanding an internal explosion of a specified gas without igniting surrounding gases.

14. Factory Set

A pressure switch design that can be set only at the factory to customer's requirements.

15. Field Adjustable

A pressure switch design that provides for adjustment of set points in the field.

16. Hermetically Sealed

An enclosure completely sealed from escaping or entry of gases or liquids. All joints are soldered or welded to insure sealing integrity. Hermetically sealed electrical assemblies are metal to metal or glass to metal infusion.

17. Hysteresis

See Deadband.

18. Maximum System Pressure

Maximum continuous pressure which may be applied to any switch without causing permanent degradation.

19. Normally Closed (N/C)

Provide a normally closed circuit when actuator is in free position.

20. Normally Open (N/O)

Provide a normally open circuit when actuator is in free position.

21. Pressure Sensing Element

The portion of the pressure switch that is in contact with the media and moves as a result of a change in pressure of the media.

22. Pressure switch

An electromechanical device that upon the increase or decrease of pressure, opens or closes an electrical switch ing element at a predetermined set point.

23. Proof Pressure

Maximum momentary pressure including surges, which may be applied to any switch without causing permanent degradation.

24. Rise Rate or Ramp Rate

The rate at which the pressure will increase in a unit of time.

25. Set Point

See Actuation Point.

26. Single Pole Single Throw (SPST)

Continuity of circuit is only possible through one leg of circuit.

27. Single Pole Double Throw (SPDT)

Continuity of circuit is possible through either/both legs of circuit but not at the same time.

28. Surge Pressure

A transient pressure varying in amplitude, frequency, and duration.

29. Wetted Parts

Components of a pressure switch that are directly exposed to the media.

switch

In electronics, a switch is an electrical component which can break an electrical circuit, interrupting the current or diverting it from one conductor to another. The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts. Each set of contacts can be in one of two states: either 'closed' meaning the contacts are touching and electricity can flow between them, or 'open', meaning the contacts are separated and nonconducting.

In the simplest case, a switch has two pieces of metal called contacts that touch to make a circuit, and separate to break the circuit. The contact material is chosen for its resistance to corrosion, because most metals form insulating oxides that would prevent the switch from working. Contact materials are also chosen on the basis of electrical conductivity, hardness (resistance to abrasive wear), mechanical strength, low cost and low toxicity.

Sometimes the contacts are plated with noble metals. They may be designed to wipe against each other to clean off any contamination. Nonmetallic conductors, such as conductive plastic, are sometimes used.

The moving part that applies the operating force to the contacts is called the actuator, and may be a toggle or dolly, a rocker, a push-button or any type of mechanical linkage.

Contact arrangements

A pair of contacts is said to be 'closed' when there is no space between them, allowing electricity to flow from one to the other. When the contacts are separated by an insulating air gap, an air space, they are said to be 'open', and no electricity can flow at typical voltages.

switch es can be and are classified according to the arrangement of their contacts in electronics fields— but electricians in the electrical wiring service business and their electrical supplier industries use different nomenclature, such as "one-way", "two-way", "three-way" and "four-way" switch es—which have different meanings in North American and British cultural regions as is delineated in the table below.

Some contacts are normally open (Abbreviated "n.o." or "no") until closed by operation of the switch , while others are normally closed ("n.c. or "nc") and opened by the switch action, where the abbreviations given are commonly used on electronics diagrams for clarity of operation in assembly, analysis or troubleshooting. They serve to synchronize meaning with possible mistakes in wiring assembly, where wiring part of switch one way and part another (usually opposite) way will pretty much guarantee things won't work as designed.

A switch with both types of contact, that can switch on a circuit in one position & can switch another circuit on in other position, is called a changeover switch or "make-before-break" switch contact, whereas most switch es have a spring loaded action which momentarily disconnect the load and so are "break-before-make" types by contrast— which type is used could be important, if for example, the switch selects two different power sources instead of switch ing circuit loads, or the circuit load will not and cannot tolerate any interruption in applied power.

The terms pole and throw are also used to describe switch contact variations. A pole is a set of contacts, the switch 's electrical terminals that are connected to and belong to a single circuit, usually a load. A throw is one of two or more positions (the nomenclature is also applied to rotary switch es, which can have many 'throw' positions) that the switch can adopt, which normally, but not always correspond to the number positions the switch handle or rotor can take when connecting between the common lead of the switch and a pole or poles. A throw position which connects no terminals (poles) has a mis-match between positions and positions which connect terminals, but are quite useful to turn things "Off" or for example, alternatively select between two scaled modes of operation. (e.g. Bright illumination, moderate illumination, no illumination.)

These terms give rise to abbreviations for the types of switch which are used in the electronics industry such as "single-pole, single-throw" (SPST) (the simplest type, "on or off") or "single-pole, double-throw" (SPDT), connecting either of two terminals to the common terminal. In electrical power wiring (i.e. House and building wiring by electricians) names generally involving the suffixed word "-way" are used; however, these terms differ between British and American English and the terms two way and three way are used in both with different meanings.

Micro switches

In electronics, the micro switches is an electrical component which can break an electrical circuit, interrupting the current or diverting it from one conductor to another. The most familiar form of the micro switches is a manually operated electromechanical device with one or more sets of electrical contacts. Each set of contacts can be in one of two states: either 'closed' meaning the contacts are touching and electricity can flow between them, or 'open', meaning the contacts are separated and nonconducting.

Since the advent of digital logic in the 1950s, the term has spread to a variety of digital active devices such as transistors and logic gates whose function is to change their output state between two logic levels or connect different signal lines, and even computers, network switches, whose function is to provide connections between different ports in a computer network. The term 'switched' is also applied to telecommunications networks, and signifies a network that is circuit switched, providing dedicated circuits for communication between end nodes, such as the public switched telephone network. The common feature of all these usages is they refer to devices that control a binary state: they are either on or off, closed or open, connected or not connected.

RadioShack recalls electrical switches

WASHINGTON, April 3 (UPI) -- The U.S. Consumer Product Safety Commission announced a voluntary recall of RadioShack electrical micro switches due to faulty installation instructions.

The wiring instructions that come with the illuminated round rocker switches, catalog number 275-0021 with date codes of 01P09 or January 2009 or early, are incorrect, specifically a diagram on the package, the Commission said.

About 18,000 of the switches were sold nationwide from June 2008 and January 2009 for about $4.

Consumers were advised to contact RadioShack Corp. (NYSE:RSH) of Fort Worth, Texas, for correct installation instructions.

Permanent Magnets from Stanford Magnets Company

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Micro switch history

Micro switch ? technology has launched most sensing and switching products Sensing and Control produces. View early versions of micro switch devices, in addition to the legacy of micro switch products.

1942

In 1943, the V3 switch was named to represent Victory in Europe, Victory in Asia, and a Victory for micro switch products. The first class postage stamp at the time was an eagle with outspread wings in the form of a “V”. The cost was 3 cents. The V3 and postage size stamp of the switch all seemed to go together, so V3 it became.

1944

The development of the EN micro switch line was just in time to catch the front end of the jet engine age. Landing gear switches had become a particular problem since available switches filled with water. It was necessary in many cases to drill holes to allow water to drain out. The excellent sealed features of the switch, together with its size, operating features and circuitry, were just what the aircraft industry was looking for. The EN was soon established as Military Standard.

1951

The need for attachment of lead wires directly to the switch was met by designing and providing the E and V die cast switch enclosures. This enclosed switch became one of the most popular micro switch product lines, sold year after year in volume for literally millions of applications. The enclosures started out as zinc die castings which were changed to aluminum during WWII for weight saving in aircraft applications. This family of switches became known as the “die cast” line, which has persisted as part of micro switch terminology for years.


1953

Almost as soon as the basic switch was put into use, people began to find ways to use it as a pushbutton switch. Through the years, ’s micro switch push button line has been used for military aircraft (originally advertised as a unit that would allow aircraft to use wing and tail lights to signal to ground stations using Morse Code), military tanks, and firing switches for nuclear warhead torpedoes on submarines.


1955

A development in ’s Solid State Research Center in Minneapolis led to the development of “Hall” micro switch components, named after the phenomena known as the Hall Effect. Researchers discovered that when an integrated circuit chip was moved through a magnetic field (or vice versa), a minute electrical current would be generated. This development led to the introduction of keyboard pushbutton units for the first IBM? computers, technology predecessor to the keyboards we use today.


1956

Experience with unsealed switches on aircraft during WWII pointed to the need for a hermetically sealed micro switch design. Rapid ascent and descent of aircraft from humid ground conditions to cold flight conditions often caused switch malfunction which was traced to icing of contacts. A glass-to-metal seal was conceived, and the new technology quickly became widely used, and is still popular to this day.

1957

In 1937, the Explosion Proof micro switch family of products was introduced, ushering in a safer working environment in industrial settings. The switch was engineered to ensure that volatile gases that entered the switch and exploded would not ignite gases outside the switch enclosure. The configuration and size of the switches made it the smallest explosion proof switch on the market, a position it has maintained since its existence.

1971

pioneered the designs for basic, miniature, subminiature, heavy-duty and limit switches. These core designs are the standard footprint for most electromechanical switches manufactured by switch providers globally today.

1972

Sensing and Control maintains a global manufacturing and service footprint, with customer service and factory locations in North America, Europe and Asia. micro switch products are currently made in Freeport, IL, Galena, IL, Juarez, Mexico, and Newhouse, Scotland.

micro switch

Honeywell's micro switches EX Series Hazardous Location line of switch
products received the International Electrotechnical Commission's Certification to Standards relating to Equipment for use in Explosive Atmospheres (IECEx). With this international certification, Honeywell's global customers can be assured their explosion-proof switch meet the IEC's high standards for equipment used in explosive atmospheres.



In addition to IECEx certification, the EX family of products currently holds North American UL/CSA and European ATEX approvals. With this certification, manufacturers can specify one Honeywell micro switches
EX Series switch for a machine that may potentially be used in Europe, Asia, or North America.



"Now that we have this certification, our customers can apply our products almost anywhere in the world and meet ever-increasing levels of safety regulations," said Brad Kautzer, vice president and general manager of the electromechanical line of business for Honeywell Sensing and Control.



"Honeywell offers a wide range of differentiated solutions to meet virtually any application requirement."

Swedes Develop Netbook Kill Switch

The problem: You are a telco, and you give away netbooks in order to lock customers into lengthy 3G internet contracts. The customer does a runner and stops paying his bills. With a cellphone, simply cutting the service from afar would make the handset useless. But with a netbook? The customer still has a fully working computer.
The solution: Fit a kill switch that can disable the netbook from afar. This is exactly what Ericsson has done, and it even has a catchy name for the tech: "We call it a 'kill pill," Ericsson VP Mats Norin told the Associated Press.
The mobile broadband card, called the F3607gw, has other features, such as low power consumption and wake-on-wireless capability, but its the remote control that is the most interesting. By sending an SMS to the unit, the card speaks to Intel's ATT (Anti-Theft Technology) inside the machine. This not only locks down the hard drive but the actual computer itself. Even swapping in a new drive wouldn't wake the computer from its deathly slumber.
Morally, we're confused on this one. When you sign a contract, you are agreeing to honor an agreement. Break it and the injured party has a right to redress, and to repossess its property. On the other hand, handing life or death control of our equipment over to somebody else is always a chilling thought. Our advice? Buy your own machine and stick a 3G USB dongle in the side. But then, we're control freaks. In fact, give us the handle of the kill switch so we disable our machines if they are stolen.

Three fingers been cut

Yesterday afternoon, a chinese working man, when he cleared the meat grinder machine, his hand was swallowing into it and three fingers been truncated, the doctors said that can only cut his toe for replantation.

Mr GU is 32-year-old this year, and work at a supermarket which about fresh meat. Yesterday 11:30, He looked many residues in the grinder, so he clean up it, but he does not turn off the machine switch. When he clear it with his left hand, suddenly his hand was been swallow. Other workers heard the scream, immediately unplug the power switch, too late, His hand was bloody.Other peoples help him out it, the index finger, middle finger and ring finger all be cut off and be crushed. Others sent him to the Provincial People's Hospital and take the fingers also. When the doctor prepare to do a finger replantation surgery, found that three fingers are broken badly. So the doctor only can cut one toe for replantation which ensure that his left hand have the general function.