How To Choose Air Compressors

There are three main types of air compressors. Which you need will depend on the air pressure you need and how portable your compressor needs to be.

Reciprocating compressors come in a range from 5 HP to 1000 HP. The smaller compressors are portable, sometimes being mounted on wheels. These may be petrol driven or electrically powered. They compress air by a series of pistons in cylinders. The pistons are driven by a camshaft. Reciprocating compressors are often used in Auto Body Repair shops.

Larger reciprocating compressors are gradually being replaced by simpler rotary screw compressors. A large reciprocating compressor can discharge air at 35 Mpa, more than 5,000 psi.

If you are looking for a compressor for continuous use a rotary screw compressor may be suitable. These compressors use helical screws to compress the gas into a smaller volume. Portable and fixed rotary screw compressors are available. These compressors vary in size from 5 HP to 500 HP. You will find rotary screw compressors that give you a low pressure gas output, or a high pressure output, up to 8 Mpa. These compressors are used to power pneumatic drills when workers are digging up roads and pavements.

For continuous, heavy industrial uses you need a centrifugal compressor. A centrifugal compressor uses a rotating disk with vanes. Output from centrifugal compressors can be as high as 70 Mpa, 10,000 psi. Snow blowing machines use this type of compressor. Superchargers and turbochargers in car engines are centrifugal compressors.

When you buy compressed air for diving the air has been compressed using a three stage, reciprocating compressor. The cylinders in the compressor are ceramic lined, so no lubrication is needed. This avoids the air in the cylinders being contaminated with lubricating oil. If a non-recommended lubricating oil is used it can undergo partial combustion and cause carbon monoxide to enter the air cylinder.

The compressed air is filtered through silica gel to remove water, then through activated charcoal to remove any traces of oil.

Sometimes air from a cheap, low powered compressor will be stored in a bank of large high pressure cylinders. Air from these cylinders is then used to quickly fill diving cylinders. The diving cylinders need to be filled slowly to prevent the compressed air inside them from getting hot. If the gas inside is hot, it will expand and the cylinder maximum pressure will be reached with less air inside. The gas cools and the cylinder may only be half full.

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Daffi Shacy Electronics

A Review of Popular Metal Detector Products

Metal detectors come with a control box that contains the circuitry, controls, speaker, batteries and the microprocessor; a shaft that connects the control box and the coil; a search coil that actually senses the metal; and a stabilizer that keeps the unit steady as it is moved. The performances of the detectors are based on the features of these parts. 

Tesoro Metal Detectors

At less than 2½ pounds, the Tesoro Golden Max lets you control what you want to find. It is the lightest detector in the market with full size depth, sensitivity, four tone audio ID and a user adjustable Notch Filter Discriminate.  The Tesoro DeLeon is a Target Identification Detector (TID), named after the famous explorer Ponce de Leon, who searched Florida looking for treasure and the Fountain of Youth. The DeLeon is designed as an easy to use, turn-on-and-go detector. 

Whites Metal Detectors

The Whites E-series metal detectors include the following models.  DFX™ brings together the ultimate combination of sophisticated microprocessor technology, and turn-on-and-go simplicity. It has an operational frequency of 3 kHz and 15 kHz.  The XLT® Metal Detector is high-performance simplicity and versatility at its best. It has five programs to choose from along with 10 Basic Adjustments, and 29 Pro Options.  The MXT has three completely separate operating modes -- gold prospecting, coin/jewelry, or relic. 

Prizm Series

The Prizm series include Prizm II, III, IV, and V. All have a pinpoint mode that zeroes in on target location, instruction videos that show when and where to hunt. 

Fisher Metal Detectors

Dr. Gerhard Fisher, a German immigrant, obtained the first patent ever issued on aircraft radio direction finders in the late 1920s.  Fisher's 1266-X comes factory shipped with 8-inch Open Center Spider Coil, instruction manual and Fisher's 5 Year Warranty. It has a duel discrimination system, which will allow you to search at a great depth. This unit does not work very well on wet saltwater beaches. 

Garrett Metal Detectors

The Garrett Super Scanner hand-held detector can detect a medium-sized pistol from distance of 9" and even a tiny 1” piece of jewelry. Simplicity of operation of this metal detector is unmatched.  The Garrett SuperWand Security metal detector is one of the most popular metal detectors. It provides uniform sensitivity 360° along the scan area and pinpointing at the tip to detect weapons and other metal objects with extreme accuracy.  The Garrett Magna Scanner PD 6500 Walk through metal detector has some unique features. Its ultra-enhanced multi-coil detection field pinpoints the exact location of any metal object within 33 distinct areas of the archway. 

Bounty Hunter Metal Detectors

Bounty Hunter metal detectors are made by First Texas Products. The Tracker IV priced at $160 is streamlined in appearance, with only two operating controls and a mode selection switch. The Tracker IV has a built-in Automatic Ground Tracker that maintains ground balance.  The Bounty Fast Tracker offers value for your money. It is a user-friendly instrument that delivers effective performance over a wide range of conditions and applications. 

Minelab Metal Detectors

The Minelab Explorer II priced at approximately $1395 is a coin and jewelry detector with an operating frequency between 1.5 – 100 kHz. The signal travels deeper at a lower frequency and the signal detects objects close to the surface at a higher frequency.  The Minelab Quattro MP, priced at approximately $1300, is suited for use in parks, beaches or the battlefields. Minelab’s FBS technology provides outstanding performance even on saltwater beaches.

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A Brief History Of Pocket Watches

Everything has its beginning. And if you believe that time starts from somewhere, also consider the beginning of time measurements. 

Early people have devised a system to tell the exact date. But a device that exactly tells the precise time comes much later. Water clocks, sundials, and candle clocks are the earliest instruments that somehow manage to tell time but accuracy is far from achievable. 

In the 13th century, weight-driven clocks were developed. It used gears while hour hand was already used while the minute hand was an indication of luxury and wealth. The weight-driven clocks were publicly displayed on church towers, city halls, and monasteries.

In the 16th century, clocks were produced using spring instead of weight. The portable clocks or the pocket watches were the first timepieces that the public can own. During this time, the only persons who can own them were the rich and owning one signified the status, authority, and wealth of the person. Often, portable watches were placed on the wall of the house. The term “portable” though did not mean it could be carried on your pocket. The term changed its meaning some years later. 

The first transportable watches or pocket watches was used also in the 16th century. This time, clocks no longer had to stay at one place. Pocket watches can already be worn around the neck or carried on a pocket. The same era also brought revolution to the development of pocket watches. Mechanisms were introduced to bring time-telling precision. Some packet watches even had an alarm. 

The entry of the 17th century made pocket watched even more desirable. The box-like image was removed and was replaced by more rounded and slimmer cases. Clockmakers also became instant artists as they infuse designs and craftsmanship to every pocket watch the made. 

When Christian Huygens discovered the law of pendulum, which for your information was different from Galileo’s, clock had yet again moved one step further. The law proved to be very helpful in the development of pocket watches. 

In the 18th century, pocket watches continued to evolve. This time, jewels were used as bearings. Diamonds became part of some pocket watches that boosted the price of a single pocket watch to the ceiling. Oil was also became part of pocket watches during this period. This was to lubricate and smoothen the movement of the watch’s hands. In the second half of the 18th century, pocket watches were produced with three hands. Contrary to the inclusion of the minute hand during the 16th century, second hand made sense since accuracy in telling time was far better. 

In the 19th century came the glory days of the packet watches. This era brought the several watchmakers into the picture. Names such as LeCoultre & Cie, Ulysse Nardin, Minerva, Heuer, IWC, and many others were established in this period. The quality of pocket watches became better than ever. 

By the turn of the 20th century, certificates were issued to those watchmakers that created precise watches. Unlike the previous years, issuance of certificate became more of a requirement than luxury. 

And as the years gone by, the popularity of pocket watches diminished as wristwatches became more popular. 

Although pocket watches are not so much used today, it has served as one of the important instruments for several centuries.

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Daffi Shacy Electronics

A Citizen Promaster Sports Watch Made For Divers

Did you know that the Citizen Promaster sports watch is among the top in its class. Especially the eco drive air divers sport wrist watch.

For example, the Citizen Professional Diver, its a member of the Promaster eco drive sports watch line. This watch is water proof up to 200 meters. It is equipped with a urethane band and stainless steel watch casing. For mixed gas divers, its perfect for air divers. The next step up is one which has a stainless steel band. Finally the top model has a titanium case and a deluxe band designed out of urethane.

With long lasting quartz movement, the Citizen Promaster sports watch has large hands and markers that glow, a ratcheted bezel with a feature that tracks how much time has gone by. Its eco drive technology has a six month reserve of power.

These Citizen Promaster air divers watches are designed to handle any tough conditions. They are built big with a diameter of 46 millimeters for the case, plus it is 18 millimeters thick. A travel case can also be purchased for your Citizen Promaster eco drive sports watch. For further protection the case is zippered and padded, ensuring safety against dropping or accidents.

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