Belajar PLC dan SCADA

Just another Blog about Programmable Logic Controller & SCADA.


Written by Kang Abu on 12:11 PM

You don’t need to be a rocket scientist to understand them; they are just a different way of encoding numbers and letters by using a combination of bars and spaces of varying widths. Think of them as another way of writing since they replace key-data entry as a method of gathering data. In business, the correct use of bar codes can reduce inefficiencies and improve a company’s productivity thereby growing their bottom line.  Optical Barcode Scanners

Simply put, barcodes are a fast, easy, and accurate way of entering data.

This may come as a surprise to you! A barcode doesn’t contain descriptive data. Just as your social security number doesn’t contain your name or address, a bar code is also a reference number that a computer uses to look up an associated record that contains descriptive data and other important information. 

Barcode Reading

Bar codes are read by sweeping a small spot of light across the printed bar code symbol. Your eyes only see a thin red line emitted from the laser scanner. But what’s happening is that the scanner’s light source is being absorbed by the dark bars and reflected by the light spaces. A device in the scanner takes the reflected light and converts it into an electrical signal.

The scanner’s laser (light source) starts to read the bar code at a white space (the quiet zone) before the first bar and continues passing by the last bar, ending in the white space which follows it. Because a bar code cannot be read if the sweep wanders outside the symbol area, bar heights are chosen to make it easy to keep the sweep within the bar code area. The longer the information to be coded, the longer the bar code needed. And as the length increases, so does the height of the bars and spaces to be read.

Barcode Scanners

There are three basic types of bar code scanners—fixed, portable batch, and portable wireless.

Fixed scanners (hand held or mounted) remain attached to their host computer or terminal, and transmit one data item at a time as the bar code is scanned.

Portable batch scanners are battery operated and store data in memory for later batch transfer to a host computer.

Wireless portable scanners also store data in memory, however data is transmitted to the host in real time. This allows for instant access to all data for management decisions. HHP Dolphin 9500 scanning pallettes

Barcode Symbologies

Bar codes come in many flavors. Most of us are familiar with the ones seen in grocery or retail stores, but there are many others that are used as standards in various industries. Healthcare, manufacturing, retail, etc. all have symbologies unique to their industry and aren’t interchangeable. Why are there so many different types of bar codes? Simply because different symbologies evolved to solve specific problems. Let’s take a quick look at a few of the most common symbologies*, and how, where, and why they’re used:

UPC/EAN - This is the symbol used on items destined for the check-out line. UPC symbols are fixed length, are mandatory in the retail and food industry, and not used anywhere else for the most part. They were developed to meet the needs of grocery retailing as it fits 12 digits into a reasonably compact space.

Code 39 - Developed because some industries needed to encode the alphabet as well as numbers into a bar code, Code 39 is by far the most popular bar code symbology of choice. It is typically the non-food standard bar code, and is used for ID, inventory, and tracking purposes in various industries such as manufacturing. However, Code 39 produces relatively long bar codes and may not be suitable if label length is a consideration.

Code 128 - This bar code came about when the need for a wider selection of characters arose than Code 39 could provide. When label length is a consideration, Code 128 is a good alternative because it’s very compact and results in a dense symbol. This symbology is often used in the shipping industry where label size is an issue.

Interleaved 2 of 5 - Another popular symbology in the shipping industry, Interleaved 2 of 5 is widely used by the warehousing industry, too. This is also a very compact symbology and you’ll see them on the corrugated boxes in which things are shipped to the grocery store.

Postnet - Unique to the United States Postal Service, this symbology encodes zip codes for processing mail for speedy delivery.

PDF417 - Known as a 2D (two-dimensional) bar code, this is a high-density, non-linear symbology that reminds you of a crossword puzzle. But the difference between this and the other bar codes listed above is that PDF417 is really a portable data file (PDF) as opposed to simply being a reference number. Some states require a 2D bar code be printed your driver’s license. If your state has this requirement, it’s interesting to know that there’s room enough in this bar code to encode your name, photo and summary of your driving record, and other pertinent information. As a matter of fact, a PDF417 bar code can encode the Gettysburg Address in a space the size of a postage stamp!

An important fact to remember is that the larger the width of the bars and spaces, the more space it takes to print the bar code; therefore, the lower the bar code density. The thinner the bars and spaces, the less space is required and the higher the bar code density.

To the left, you'll see pictured Banner Engineering's new line of Optical Bar Code Readers.  Capable of reading normal bar code labels as well as 2D labels (at any angle), these readers are state of the art in quality and bare special mention here because they significantly lower the price to quality ratio.

Barcode Scanners

A basic bar code scanner consists of a scanner, a decoder, and a cable that interfaces between the decoder to the computer or terminal. The scanner’s function is to scan the bar code symbol and provide an electrical output to the computer that corresponds to the bars and spaces of the bar code. However, it’s the decoder that recognizes the barcode symbology, analyzes the content of the bar code scanned, and transmits that data to the computer in a traditional data format. A scanner can either have the decoder built into its handle or be “un-decoded” which requires a separate box, called an interface or wedge. Un-decoded scanners are also used when connecting to portable batch terminals as the decoding is performed by the terminal itself.

Fixed Scanners

bulletKeyboard Wedge Readers.  A keyboard wedge reader is attached to a computer through a port called the keyboard interface. When a bar code is scanned, the information is transmitted as though it were keyed in from the keyboard. Sometimes they’re referred to as wedge readers because they physically wedge between the keyboard and the computer and attach as a second keyboard. One great advantage of a keyboard wedge is that bar code reading can be added with no software changes necessary; the software thinks that the data received was entered by a speedy typist. With a wedge reader, any program that accepts keyed data will accept bar code data with no change.
bulletSerial Bar Code Scanners.  Another way to transmit data from a bar code reader to a computer is to connect it to the computer’s RS-232 serial port. The bar code information read will be transmitted in ASCII format and look just like keyed data to the computer. Using a serial port connection is ideal for a multi-user computer. With serial ASCII terminals for each user, the bar code reader can attach between the terminal and host computer and transmit ASCII data just like the terminal.  To the left, see pictured a barcode print and apply application.  The barcode is printed, then verified by a reader, then the pallet is rotated and the same barcode is printed and read on the other side.

Portable Batch Barcode Scanners

Portable batch scanners are hand-held battery operated readers which store data in memory for uploading to the host at a different time. A portable batch reader contains a bar code scanner, an LCD-display to prompt the user to perform a task, and a keyboard to enter variable data such as quantities. A cradle must also be purchased to upload information to the computer. Portable batch scanners are ideal when mobility is a must and when collected data isn’t immediately needed. These scanners come in a variety of styles including hand-held, wearable and truck mounted. Your application will determine which style is best.

Wireless Portable Barcode Scanners

When you need to collect information at a remote location, and need the information immediately, a wireless solution is the perfect one. A wireless scanner is also built into a terminal, and uploads data to the host as it’s scanned, instantly and accurately. Wireless products let the user scan the information at the point of activity which makes it ideal for many industries.

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