måndag 27 maj 2013

A Sound Decision in Real Time Location Systems

A Sound Decision in Real Time Location Systems

Issue #103 | May 25, 2007 | by Andy Kowl

One benefit RFID offers, I was told back when I just learned what RFID was, is to save lives in a hospital setting. As the story went, hospitals have a certain amount of equipment on each floor. Hospitals are busy places. When doctors need a defibrillator to save someone from a heart attack, they need it now. If one is supposed to be in Room B down the hall, but isn’t, that can be a big problem.

Since then I have met hospital executives who assure me the defibrillator story is not only a perfect example of RFID’s asset tracking value, it is the tip of the iceberg. We spoke to a Connecticut hospital that spent almost $2 million to replace lost, leased equipment – every year! (This is the medical version of Erik Wood’s story last week
 RFID's Strange Secret.)

Other benefits some hospitals find include knowing where staff and/or patients are at any given point. The most obvious people-tracking need is that of newborns. With an investment in uniquely identified medical equipment, reading the tag of every staff member who interacts with pharmaceutical storage areas, IV equipment, monitors and other essentials becomes an excellent value proposition to consider.

Once you start thinking about this and consider the terrific possibilities, RFID is not always the answer. This past year, both Sonitor Technologies and Red Prairie have done ultrasound technology implementations in (separate) hospitals to provide these auto identification benefits.

Ultrasound refers to sound waves that are higher than 20,000 cycles per second, which is beyond what the human ear can hear. The ultrasound used for asset tracking is not the same ultrasound we often first encounter as expectant parents viewing a fetus in the womb, which operate on far higher frequencies. 

Accurate to the room
Unlike radio waves, which are on the electro-magnetic spectrum, acoustic waves have a physical component. They actually push the air, and can be moved by air, just as you have more difficulty hearing someone shout across a field on a windy day. This is one of their advantages in real time location systems, according to Terje "Terry" Aasen, president of Sonitor, because ultrasound is contained by walls. This is a prime factor in assuring asset trackers precisely what room an item is in. Unless you had fire retardant or other materials in the walls or ceilings that contain the radio waves, the RF will act as if the walls are not there. Sound waves, though stopped by physical barriers, are not garbled by other electro-magnetic frequency noise generated by machines or other RF transmissions, a big advantage in buildings full of electronic devices.

When using RFID, you should do a site survey for all implementations, hospital or otherwise. This would show you where you have bleed-through of radio waves and where you have reflection. Ultrasound has no similar considerations, although you are certainly better off indoors – as in a hospital – than in open spaces where sound waves can dissipate. Unlike the unlucky resident of an apartment with thin walls, the ultrasound software can filter our amplitude below whatever amount the user calibrates.

Even within the rooms, ultrasound can provide location accuracy, Terry Aasen assures. He explains the Detectors, which are microphones, receive the acoustic waves from the tags, and the signal strength tells indicates the relative location of each tag. Louder is closer. Digital Sound Processor (DSP) algorithms determine where the signal came from. The detector converts it from its analog state, so the DSP can do its work. Each detector has its own channel, an IP address, and passes the signal over the network.

Commercial ultrasound tags
Each tag has its own unique identifier, of course, the base ingredient of all auto ID technology. That ID is associated with a database to tell you which tag is on which hardware and which is on a physician. Its range is up to about 50 feet, since acoustic signal strength, like spoken words, dissipates over distances in the air. There would typically be one detector in each room. Sonitor's system transmits at 40 KHz.

Ultrasound tags are battery powered and comparable in some ways to active RFID tags, with prices ranging from the mid $20’s to the mid-$30’s. They can be set to transmit at certain intervals, when they move, or both, with options like tamper sensors. Since often the power of auto ID shines most in exception processing, a nice bonus on the Sonitor tags are buttons that can be preset to flag different alerts for different items tracked. For example, a pushed button on the tag of a machine involved with transfusions might mean it is time for a cleaning, while an orderly in the psychiatric wing might have a button (the red one, of course) that when pushed means, "Help, I’m in danger!"

Although dogs cannot hear ultrasound, as they famously can other sound frequencies human ears don’t pick up, Terry reminded me that bats are the original ultrasound innovators. They use these high frequencies to navigate and to find prey. Without adding the unique identifier, they may not know which prey is which; but it does the job for dinner. 

Last edited by AndreaC : 05-27-2007 at 11:15 PM.
2009-09-22 21:28 

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