Printing and data communications are often key application requirements for weighing equipment. Changes in technology can add complication that we don’t need. This article is intended both as a refresher and an introduction to new label printing technology.
Weighing equipment data communication fits into four categories
- Printing results
- Printing extended reports
- Electronic data records
- Remote scale commands.
To keep it simple, this article will focus on local printing of simple weight results.
The basic requirements for direct scale printing have not changed much over the years. Most scale applications are still limited by speed of human interaction with the scale – so RS232 is still fast enough for direct printing. RS232 adapters and converters are available to extend distance or interface to modern USB only tablets, computers, wired and wireless networks and even smart cell phones. If the features of wireless or network solutions are not needed, RS232 is often still the best practical choice for direct printing and remote commands for most scales.
There are three basic need factors to consider for scale printing:
1 – What Data Needs to be Printed?
Frequently, printing needs include 1) time and date stamp, 2) gross, net, tare or 3) GLP compliance. The scale and printer user manuals are the best source for print features and formats. GLP or ISO mandates have made enhanced print formats and built-in scale reports for calibration history, equipment settings or performance diagnostics important selling features. It is not enough to say “GLP compliant”, since GLP or ISO print compliance is interpreted differently by manufacturers.
There are two printer types commonly used with scales. 1) Paper printers (also known as receipt printers) using “line” data format and producing paper records and 2) Label printers using “page” data format and producing formatted labels.
In the scale industry, the standard is line format. Typically scales provide at least a simple line print format consisting of formatted weigh data (including units), < 20-25 total characters, and line termination by special control characters, CR and LF. Most RS232 receipt printers today are a good match as long as the serial cable is correctly wired, they have the right cable connectors and the scale and printer have compatible RS232 settings.
However there is no simple standard label print format – so direct label printing from scales (without computers and label software) is complicated. Label printer manufacturers have different programming languages. Label making requires print formats that understand the label printer language. For direct scale label printing, the label print format must be included in the scale firmware. The scale manufacturer must make firmware for a specific label printer. The result is a turnkey solution, but with little flexibility.
So here’s what new – labels from any scale by RS232. How is this done? The label roll is replaced by a roll of self-adhesive, strong thermal paper – sticky enough to be a label but not so sticky that it will gum up the printer. It is called “liner-less” since there is no backing (liner) material, as found in normal roll labels. It is just continuous roll label media, but with a very special proprietary adhesive on the back and a very high quality top coating.
But there are important advantages – besides not needing a label printer and special label firmware in the scale including 1) removable labels are a benefit in some cases, 2) the certified printer also works with normal thermal paper, so one printer can use both thermal paper and thermal labels with changeover in seconds, and 3) some new label media has great chemical resistance for lab or industry – so a solvent or cleaning solution splash will not erase a label. The chemically resistant brands also do well in freezer cold, at least to -10°C, in our testing.
The table below is an overview of printer types, print formats and media. The following table details the chemical resistance of one brand of self-adhesive thermal label media. A test report is available.
Knowing the cable distance from the scale to the printer is important for data interface consideration. For direct connected printers next to the scale, RS232 can be used with up to 50 feet of cable length. USB connections are limited to 15 feet of cable unless extended with devices.
Once the scale application needs for printing are known, then equipment review is simplified to the following three factors:
4 – Does the Scale Print the Required Information?
The scale user manual is the first place to look for scale print capability. If the documentation is unclear, ask the scale manufacturer or supplier to provide example printouts. This is a common question and most suppliers will be happy to provide answers. There may be additional documentation available to supplement the user manual.
Some scales allow print customization including multi-language printing. Print formats that are not documented are probably not in the scale. You may be able to find the needed print format in another scale. Print format features and enhancements are often used to distinguish scales competitively.
If the scale prints the needed data but not in the desired format, sending data to a computer is one way to get around print format limits. Once weigh data is in the computer, printing may be customized within limits of the computer printer, printer driver and the printing software.
For a printer located within a 50 foot cable run to the scale, the RS232 printer recommended by the manufacturer should work fine. You may need to extend or replace the supplied cable to get the distance.
For a printer located away from the scale area, consider the options for getting RS232 over the distance. Keep it simple. Remember, you are connecting a printer directly to a scale – not a computer. RS232 is a good option for direct scale to printer connection and extensions can be done completely with hardware devices and wires, totally avoiding the IT department or the local computer network.
Even if your scale is not network ready, you can ride on existing networks to extend RS232. You need only a pair of RS232 serial servers to launch and receive the RS232 signal anywhere over the network that the administrator allows. Plug in the RS232 printer to the second device. Like magic, it works. And you can avoid the spiders in the crawl space pulling wires.
Other wireless interface technologies (Wi-Fi, Bluetooth) or wired (Ethernet) can be used to establish the scale as a truly network connected device. These technologies may be more complicated to configure and while great for scale to computer links, they can be excessive overhead for local scale printing.
If you need paper printing and not labels, most RS232 line impact or thermal printers will print from a scale. The line protocol is so generic that as long as the number of characters per line in the printer matches or exceeds your scale print format – it works. Paper roll media, standard or thermal, are today considered generic at least for basic operation.
If long term archival of printed records is important, you need impact permanent ink printing or good archival quality thermal paper. Some have guaranteed image retention to 7, 10 or even 25 years, if stored properly. This can eliminate the need for photocopying thermal prints to avoid faded records. Most thermal printers support archival quality media.
For permanent labels, check and see if the scale supports a directly connected label printer and, if so, if that label printer and media meet the needs. There may be little flexibility with this solution, but also fewest headaches for everyone and it will provide true permanent labels.
For removable labels, consider the new self-adhesive thermal roll paper and certified printers. If the scale does not support a direct connected label printer, and if thermal printing is acceptable, this solution requires no programming, and will provide all line print formats as continuous roll labels – the same format exactly as if printed to thermal paper. It is great for general removable labels for use in the office, lab or industry.
When a permanent label is needed and the scale does not support a label printer, consider an RS232 label printer that supports line to page emulation. Some label page printers support a limited degree of line to page print emulation. Technical skill and programming is required however.
If none of the above meet the label requirements, then the last choice is to take scale data to computer, where full label capability can be managed though drivers, software and a true label printer. Modern label making software has eliminated most of the programming but technical setup effort is needed to get scale data to the right place on the label. For large scale applications, often custom contracted programming solves this hurdle.
While many printing technology advancements have bypassed our industry due to lack of a computer in most scale applications, it is nice to see a new technology like self-adhesive thermal roll media and certified line format printers that are directly applicable to our products, markets, and customers. This new label technology and certified matching printers can provide valuable and affordable alternative labeling solutions for weighing applications with equipment from all manufacturers.
Rich Puestow is a recent addition to the Intelligent Weighing Technology team. He is an industrial chemist with experience in test and research labs for government, research and industry. He supplies applications support to dealers in North America.
Intelligent Weighing Technology, Inc. is a wholesale master distributor and value added integrator for weighing products and components, located in Camarillo, CA. The company founders and co-owners Richard Sharpe and Paula Sharpe have an extensive background in the weighing industry for products and components. Intelligent Weighting Technology provides additional services and support to the dealer network beyond the manufacturer.