UHF RFID Versus UHF RTLS

Many companies new to UHF (Ultra High Frequency) RFID (Radio Frequency Identification) confuse it with UHF RTLS (Real Time Location Systems). While both indeed do use UHF RFID, they differ substantially in what they can actually do for you in your business.

Many companies new to UHF (Ultra High Frequency) RFID (Radio Frequency Identification) confuse it with UHF RTLS (Real Time Location Systems). While both indeed do use UHF RFID, they differ substantially in what they can actually do for you in your business.
UHF RFID

Standard UHF RFID systems can see multiple tags on equipment and products up to several meters away, if set up properly. With emphasis on “set up properly.” While UHF RFID works quite well, its unique characteristics require testing in the environment where it will be used to ensure success.

UHF RFID has several purposes:

    • To see if an item has passed a certain point, commonly known as a choke point. Examples of this are items being loaded on or off a trailer at a shipping door or items passing from one area to another in a plant.
    • To verify if something is within a certain area when using a scanning device, such as a handheld reader. If one is scanning shelves of parts or equipment, it will help locate those items.
    • To track usage of equipment in MIS systems.
    • The tags can also have data written to them if needed.

The big thing that UHF RFID cannot do is effectively track the exact location of something at any given time in a cost-effective manner. Generally, UHF RFID uses what are called passive tags for the antennas to read. These tags have no battery and get energized from the antenna signal. If you placed enough antennas all over a facility and enough of these tags, then you could possibly locate something within a certain proximity, but not exactly, and this is hardly cost effective.

UHF Real Time Location Systems (RTLSs)

RTLS, on the other hand, are specifically designed to pinpoint the location of anything with a tag or transponder on it. In fact, RTLS refers to any system that can accurately determine an item or person’s location. An important aspect of RTLS is how frequently assets must be tracked. This data can be used in different ways depending on the application. For example, some RTLS applications only need timestamps when an asset passes through an area, while others require much higher visibility, requiring constant updating of time data.

An ideal RTLS can accurately locate, track, and manage assets, inventory, or people, and help companies make knowledgeable decisions based on collected location data.

Like regular UHF RFID, RTLS can use passive or active tags (tags with batteries), but they use triangulation of multiple antennas to determine the location of an object or person. The strength of the signal at each antenna, combined with the software attached to the antennas, allows the identification of the location of an object or person within less than 1 meter.

The system you choose depends on the needs at your location. They both work quite well when implemented properly by trained professionals.

Also, due to the inherent properties of ultra-high frequencies used in UHF RFID technology and RTLS, you should perform a feasibility study that actually tests the system in the real world environment of the plant prior to implementing these systems in any application.

RFID Replaces Bar Codes for Efficient Asset Tracking

Bar code technology has been around for many years and is a tried and true means for tracking asset and product movement, but it has its limitations. For example, a bar code reader must have an unobstructed view of the bar code to effectively scan. And the bar code label cannot be damaged, or it is then unreadable by the scanner.

In more recent years, additional RFID technologies have been more readily available for use to accomplish the same task but with fewer limitations. Using RFD, a scanner may be able to read tags that are blocked by other things and not visible to the naked eye. UHF RFID can scan multiple tags at the same time in a single scan, whereas most bar codes need to be scanned individually. This, therefore, increases efficiency and reduces the time required to perform the scans.

Then, of course, there is the human factor. RFID can help eliminate mistakes caused by human error. Most bar code scanning is done with hand scanners held by workers since the scanner has to be in the exact position to see the bar code to get a good scan. While manual/hand-held scanning can be done using RFID, most times a fixed scanner can be used as long as the position of the RFID tag can be guaranteed within certain tolerances. These tolerances are much greater than with a bar code scanner.

With the advent of inexpensive consumable RFID labels, the ease and cost of transitioning to RFID technology has become more feasible for manufacturers and end users. These labels can be purchased for pennies each in rolls of several thousand at a time.

It should be noted that several companies now produce printers that can actually code the information on a RFID label tag while also printing data, including bar codes, on these label tags so you have the best of both worlds. Tags can be scanned automatically and data that can be read by the human eye as well as a bar code scanner.

Some companies have expressed concern about the usage of RFID in different countries due to local regulations regarding the frequencies of radio waves causing interferences.

This is not an issue for HF  and UHF technology. HF is an ISO standard (ISO 15693) technology so it applies to most everywhere. For UHF, which is more likely to be used due to the ability to scan at a distance and scan multiple tags at the same time, the only caveat is that different areas of the world allow scanners to only operate in certain frequencies. This is overcome by the fact that almost all UHF tags that I have encountered are what are called global tags.

This means these tags can be used in any of the global frequency ranges of UHF signals. For example, in the North America, the FCC restricts the frequency range for UHF RFID scanners to 902-928 MHz, whereas MIC in Japan restricts them to 952-954 MHz, ETSI EN 300-220 in Europe restricts them to 865-868 MHz, and DOT in India restricts them to 865-867 MHz. These global tags can be used in any of these ranges as they work from 860 to 960 MHz.

On the subject of UHF, it should be mentioned that in addition to the frequency ranges restricted by various part of the world, maximum antenna power is also locally restricted.

For more information on RFID for asset tracking, visit https://www.balluff.com/local/us/products/product-overview/rfid/

 

Using Long-Range RFID for Metal Stamping Die Identification

Using incorrect dies for metal stamping operations can result in lost time and production as well as severe damage to the presses and a risk to human lives.

In recent years, there was a case where the use of the incorrect die caused catastrophic press damage resulting in significant downtime and, because the press was so large, it had to be cut up before it could be removed and replaced. These types of occurrences can prove disastrous to the survival of a company.

When not in use, dies are generally stored in specified storage areas. Often, the die is in the wrong place, and the crane operator needs to know what he/she is retrieving for the next process in the correct die.

To help ensure that these types of errors do not occur, some manufacturers use long-range UHF RFID technology. This can ensure that the correct dies are chosen when they are staged outside of a press. And with handheld devices, it can help the operator find the correct die in storage if it has been misplaced.

Since long-range UHF RFID technology allows the verification of the correct dies from as little as one foot away to as far as several meters, it can be used in both large and small stamping presses. The long-range allows the reader antennas to be placed in strategic locations where the correct readings will be possible but in positions where they will not be damaged by the operation of the press and dies.

I recently assisted with a metal stamping operation that first brought this idea to my attention. This manufacturer was having the problem of the wrong dies being staged for installation into the press. So far, none of the dies had made it past the staging area and into the press. Still, the possibility of that happening was clearly present, and they were experiencing lost production due to having to remove the incorrect die and find the correct one.

The manufacturer wanted to interlock the press so that if the incorrect dies were not in place, the machine would not be able to run. He also wanted to know ahead of time of a wrong die so that it could be replaced promptly to not impact production.

The solution we developed was to place multiple reader antennas at multiple staging locations at the press and interlock the RFID reads with the PLC that controlled the press.

Additionally, he incorporated handheld readers to help find misplaced dies in the storage area.

This solution required testing and tuning of the UHF RFID system to ensure that all die RFID tags were being read when the dies were staged. But once this was completed, it proved to work effectively and reduce the errors and downtime.

It should be noted that due to the physics of UHF RFID technology versus other types of RFID technology, implementing long-range UHF RFID systems in any application should be preceded by a feasibility study that tests the system in the real world environment of the plant.

Manufacturers Track Goods, Reduce Errors, Decrease Workload with RFID

More and more, retailer sellers are starting to require that manufacturers place RFID tags on their products before they leave the production facility and are shipped to those retail locations. From high-end electronics all the way down to socks and underwear are being tagged.

These tags are normally supplied by the retailer or through a contracted third party. Typically disposable UHF paper tags, they are only printed with a TID number and a unique EPC that may or may not correspond to the UPC and barcode that was used in the past. Most cases I have seen require that the UPC and a barcode be printed on these RFID tags so there is information available to the human eye and a barcode scanner when used.

While this is being asked for by the retailers, manufacturers can use these tags to their own advantage to track what products are going out to their shipping departments and in what quantities. This eliminates human error in the tracking process, something that has been a problem in the past, while also reducing workload as boxes of finished goods no longer must be opened, counted and inspected for accuracy.

A well-designed RFID portal for these items to pass through can scan for quantities and variances in types of items in boxes as they pass through the portal. Boxes that do not pass the scan criteria are then directed off to another area for rework and reevaluation. Using human inspection for just the boxes that do not pass the RFID scan greatly reduces the labor effort and expedites the shipping process.

I recently assisted with a manufacturer in the garment industry who was having to tag his garments for a major retailer with RFID tags that had the UPC and a barcode printed on them. The tags were supplied through the retailer and the EPCs on the tags were quite different then the UPC numbers printed on them.

The manufacturer wanted to know how many garments of each type were in each box. Testing showed that this could be done by creating a check point on his conveyor system and placing UHF RFID antennas in appropriate locations to ensure that all the garments in the box were detected and identified.

In this case, the manufacturer wanted was a simple stand-alone system that would display a count of different types of garments. An operator reviewed the results on a display and decided based on the results whether to accept the box and let the conveyor forward it to shipping or reject it and divert it to another conveyor line for inspection and adjustment.

While this system proved to be relatively simple and inexpensive, it satisfied the desires of the manufacturer. It is, however, possible to connect an RFID inspection station to a manufacturing information system that would know what to expect in each box and could automatically accept or reject boxes based on the results of the scans without human intervention and/or human error.