11 responses to “RFID and hamburger don’t mix”

  1. Miss Outlier

    How cool!

    An interesting thought is if you can also take advantage of the very fact that RFID tags are affected by the backing material. For instance, you can design a tag that has a metal plate behind it. And then put the tag on either a shape memory polymer, or a block of ice. If the temperature gets too high, the shape memory polymer deforms, or the ice melts, and the tag falls on to the metal, the signal changes, and you know that your milk is probably spoiled.

    Or use the tag on beer glasses in a pub, to tell if you need a refill. Now that’s what I call a practical application… 🙂


  2. GEARS

    But how much more expensive is that versus just printing a barcode? Most (dare I say all?) products have a label of some sort. Printing a barcode as part of the label seems a little bit easier. Sure, you need LOS, but that keeps cashiers on their toes.

  3. Chris Shepherd

    Other things they might want to do is to track what happens to the packaging when it is disposed of, track the goods when they are being used and do it all remotely where there is no line of sight. WalMart got into quite a bit of trouble with civil liberties groups about this type of thing when they were doing trials.

  4. paul hopwood

    Actually most of the is that Walmart has never realised what problem they are trying to solve.

    When I worked on the contract in 99-02 the problems were:
    Read range
    Speed of response
    Tag price
    No single tag standard
    Price of reader.

    Most, if not all of the above can be solved but in typical engineering ways impact on the other requirements, also they had a major problem with specification creep. “Well you’ve done what we asked but actually what we wanted was a performance 10th times that” the shift from lf to hf to uhf was a key example of that.

    To be fair though, they’re not the only company looking at RFID doing that, mainly in my opinion because the field attracted IT project managers, the IEEE had a great spectrum issue 2-3 years back highlighting reasons for project failures, the key difference being Walmart aren’t running a project in house so aren’t losing vast amounts of cash in doing this.

  5. Dustin

    Nice article Cherish.

    It seems to me that the problem of cashier-less checkout will never be completely solved by RFID. There will always be ways to fool a given “dumb” technology, e.g. tin-foil wrap your items for UHF RFID. A form of cash-register AI would really be required to make sure the customer isn’t trying to fool the system and steal merchandise.

    On the other hand, accurate item level inventory that doesn’t miss hidden objects such as in a reader’s blind spot, will likely be solved using tags with multiple sources of energy scavenging and/or communication at multiple wavelengths with complementing strengths and weaknesses.

  6. Wulf The Engineer


    I’m quite interested in the fact you are interested in EM. I work (try to) as an Engineering Consultant in EM these days and have been at it about 20 years or so. I took an interest in Engineering Blogs, but I see a lot of issues that are not on the radar (no pun intended).

    I’ve noticed over the years that Engineering a device is a much different animal than how a physicist approaches a design. I even had a physicist who had no idea that Epsilon_0 = 8.854 e -12 pF/m and so on. There is a loss of hands-on work experience, but of course this takes a lot of time. Everything is getting more complicated, but I think there are some real basics that engineers don’t get these days (or in my day for that matter, I’m amazed how much I learn on a daily basis) that would really help.

    I was shocked at how different EM was taught in the physics classes compared with my work in Engineering. I’ve been in a situation where one office was all physicists and ours was all trained as engineers. There is a very different viewpoint and I have a strong view as to which group produced better (overall) engineered designs, mechanical, electrical, thermal etc.

    I’ve done work designing RFID antennas over the last three years or so and find myself a bit chagrined at the lack of knowledge about just the fact that water has a permittivity of about 81, and it should be no surprise that putting RFID on a water bottle will cause problems. Ice has a permittivity of about three. Meat?—has a lot of water and salt. Metal? Yes, when a professor points out that the tangential electric field vector goes to zero that means the antenna will not function at a metal surface. Technicians I worked with always had a way of bringing this down to earth. They called it shorting out the antenna. Very descriptive and very accurate.

    There is a complete difference in how Engineering appears to be practiced in Aerospace/Government positions and those in (what’s left) of Commercial enterprises. This is something I might expect to see discussed.

    What about having a P.E.? The history of why Engineers do not have to be licensed to work on Air Craft and Automobiles would be an interesting topic. It is essentially a hidden one these days. If you’ve never heard of Robert Boisjoly his story (and his lectures) are interesting.


    I’m a huge proponent that the last hillbilly holdout in the world that does not use the metric system would switch. This is a very important issue from my standpoint. I seldom hear it discussed, and so far have not seen it mentioned here. Each of us pays about $10.00 per day because we don’t use metric. Aerospace/NASA clings to Firkins, Hogsheads and much of Commercial (mostly) allows metric. Try buying true metric wire in the US, R10, R20 or R40 ISO values. Westinghouse is now arguing with the British about building a new nuclear reactor in the UK. They don’t like the fact that it has not metric in it.


    The bigger issues of bridges falling down in Minnesota and water main breaks throughout the US each week are important issues that affect the life of all citizens. Civil Engineering was the first discipline to Civilize our lives. It is taken too much for granted in my view.

    I could not find an email address to send this to you personally, so I put this rather rambling (I apologize for that) set of paragraphs up on the comments. I think the Engineering Blogs have great potential. I just wanted to throw in some thoughts.

    I’ve found EM very rewarding over the years. I hope you do also. I wrote my own FDTD code, it will teach you a lot about EM. But may not be the best method. The changes in EM have been dramatic over the years. I solve problems in a few days that literally used to take months to years.