Express information: how to choose a barcode scanner?
The choice of bar code scanner depends on the type of bar code being scanned and the occasion in which it is used.
Hand-held bar code scanners have always been a key part of the application of automatic identification technology, and have been in a decisive position in bar code systems in industry and applications. Today's manufacturers have provided a number of products with a choice of performance-price ratios to meet the various needs of consumers.
The three main types of handheld barcode scanners are: contact light pen, CCD reader (image-type barcode scanner), laser scanner, and so on. When considering which scanner can better meet your needs, you must first understand some of the main functional components of the handheld barcode scanner, namely 1) the light source and image barcode acquisition device; 2) decoding equipment; ) Interface method.
The three types of barcode scanners are determined by their scanning engine. The scanning engine is used to generate light and scan barcodes. The scanning engine of the light pen uses light emitting diodes (LEDs), and the CCD barcode scanner uses electronic coupling devices. (CCD), the scanning engine of the laser barcode scanner is a visible laser diode (VLD). The scanning engine is a major factor affecting the performance-price ratio of handheld barcode scanners, and determines its suitability for various uses. Once you understand the difference, you can choose a handheld barcode scanner with the best performance and value.
Successfully choose a barcode scanner that matches the target needs. The user has three main criteria: working distance, label size, and barcode density. The working distance refers to the distance between the scanner and the label during scanning. The scanning distance can be from zero (contact) to several feet. The scanning distance is determined by the barcode scanner; the label size refers to the entire width of the barcode being scanned; the barcode density refers to Meet the width of the smallest bar or empty module to read. These three factors are interrelated, for example, the size of the label and the bar code, and the larger bar code of the empty module can also support a larger scanning distance. Light pens, CCD bar code scanners, and laser bar code scanners have different performances and have different price points and usage cycles. In each aspect, users must make different considerations.
1. Working distance (depth of field)
The depth of field of the barcode scanner must be clearly defined. Does the operator touch the barcode scanner to the label surface or keep it a certain distance during operation? In general, contact or close-range scanning is used in retail, office, and factory applications, while long-range scanning is typically used in warehouse, distribution, and transportation applications.
The depth of field of the three types of barcode scanners is very different. From their naming, we can see that the contact light pen needs to be in contact with the label surface; the working distance of the CCD barcode scanner is limited to 0-30cm, but the newly produced CCD barcode The scanner has effectively extended the depth of field to 60cm); the depth of field of the laser barcode scanner is the longest, between (20-100cm), some special laser guns specially used to scan large barcodes, the depth of field can reach several feet.
The difference in depth of field can be reflected by the price of the barcode scanner. No matter from the cost or the cycle, the light pen is usually the most economical bar code, the laser gun is the most expensive, and the price of the CCD bar code scanner is between the two.
2.Label size / Label density
Label density refers to the minimum width of a bar or empty unit, which is measured in thousandths of an inch, that is, "Mill". For linear and one-dimensional bar codes, the size of the label is considered the width of the label. High-density barcodes (less than 7 mils) need to be scanned at closer distances, and low-density barcodes (more than 15 mils) can be scanned at longer distances.
When choosing a CCD barcode scanner, be sure to know the entire width of the barcode being scanned. In most cases, the maximum width of a bar code that can be scanned by a CCD bar code scanner is limited by the width of the opening of the scanner. Some special bar code scanners for reading large bar codes need to be specially designed. Because the light generated by the light pen and laser gun can move on the surface of the bar code, both readers can scan wider bar codes.
If you decide to choose a light pen, in terms of hardware, you must consider the aperture of the light pen. The width of the aperture must be approximately the same as the width of the narrowest bar or space of the X-dimensional barcode to be scanned. If the aperture is too large, adjacent barcodes will appear in the scanning window during scanning, making scanning more difficult; if the aperture is too small, the scanner will mistake some printing defects on the barcode as if the barcode should not exist Strips or blanks, causing scan errors.
3. Image decoding
Once the scanner's beam and recognition system captures the bar code or empty cells, the information must be converted into symbols that can be recognized by the main computer system. This process is called decoding. The decoding function module can automatically identify the type of bar code being scanned, and load the corresponding decoding algorithm to realize the decoding of the bar code on the label.
The decoded information is formatted as standard RS-232 serial port data, or converted into keyboard commands and transmitted to the host computer system. The decoded information is transmitted to the RS-232 communication interface through a cable, and the keyboard data is transmitted to the keyboard port of the terminal through a "Y" cable.
"Interface" is used to indicate the connection technology between the barcode scanner and the host or terminal. The serial port inserts the scanned data into the RS-232 signal between the host or the terminal, and the keyboard port treats the data as a series of keyboard signals. Through programming software, the bar code scanner can scan the bar code menu to select terminal and interface parameters.
A few years ago, the decoding and communication functions of the barcode scanner needed to be completed by separate devices. The barcode scanner outputs a laser calibration signal (HHLC) or a light pen simulation signal to an external decoding box, and the decoding box performs the functions of decoding and transmission. Manufacturers of bar code scanners have now integrated the decoding components of three types of bar code scanners into one part, the Decoding Output Scanner (DOS). The decoded output scanner uses a plug-in, which provides exactly the same performance as a code box, and at a lower price.
When two or more different types of scanning devices work in their respective decoding states or require an auxiliary port (for integrated measurement, printing or other I / O devices), additional decoding ports are still required. However, in terms of the convenience of integration and low system cost, this integrated decoding scanner is still an excellent choice.
4. Interface equipment
After the data on the tag is decoded, it must be transmitted to the host computer system. The functions of the serial port and keyboard port for formatting data and output have been explained earlier. Of course, the barcode scanner must be physically connected to the host computer system, so consumers need to identify the type of physical interface of the PC or system. Manufacturers of handheld barcode scanners support hundreds of terminal types, and also provide hundreds of interface cables. Users can order the appropriate interface cable as needed.
Since the decode output scanner can support many terminal interfaces with one component, some manufacturers of CCD and laser handheld scanners have standardized a common interface cable scheme, so that users do not need to reserve a large number of interface cables, and use a universal interface cable Can support CCD scanner and laser scanner at the same time, saving time and money at the same time.
Light pens, CCD scanners, and laser scanners are three types of handheld barcode scanners with superior performance-to-price ratios in applications. After understanding some key features and price differences, I hope you can choose the most suitable handheld barcode scanner.