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Designing a RAIN RFID Sensor. Simple, or Is It?

Mar 23, 2016

中文版 Chinese version

Combine identification, sensors, low cost and years of life time together and you certainly end up with a disruptive mixture that is set to boil over in the near future. RAIN RFID sensors may not be a huge market just yet, but we can see many companies putting a lot of development effort on them. Read on to see an introduction to the six topologies that I’ve seen utilized so far.

1) Affecting Antenna to Chip Matching

Right from the beginning of the UHF RFID, engineers have been aware of the inlay antenna’s sensitive nature to change its parameters whenever just about anything changes in its proximity. So, it didn’t take long for scientists to call it a sensor. No added energy was wasted on sensing electronics, therefore potentially long sensing ranges were expected. In practice, however, these type of sensors never got too much of a foothold on the market, as the tags were still sensitive to many measurable parameters, and not just one.

The impedance of the antenna is affected, making a detectable change in frequency tuning, activation power, or RSSI.

2) The Dual Tag Relative Approach

To address the real world problems of the previous approach, a simple improvement was soon used. This time, two similar inlays were encapsulated into one physical tag casing, but one of the antennas is made more sensitive to one particular property. For example, if salt impregnated foam is placed over one of the inlay antennas, it doesn’t affect the antenna when dry. However, when humidity rises, it will deteriorate the performance of this antenna at a much faster rate. The reader would poll both of these tags, typically of a sequential EPC code, and monitor the difference between the two RSSI levels.

The impedance of one of the antennas is made much more sensitive to the parameter to be measured.

3) The Embedded Tag

A few years ago the most common type of sensor tag was the embedded type of tag. In this form one or several sensors and inputs can be monitored, logged into memory and read from there when needed. Practically any type of sensoring can be performed in this way, but the solution requires a battery. Although the battery does not sound like a too bad thing to have inside, however the advantage to other technologies, like Bluetooth LE, is rapidly lost. There are also several RFID chips that work with the same principle, but alone without a separate microcontroller.

The RAIN tag uses an I2C interface to interact with a separate sensing circuitry. All this requires more power that the tag can harvest from the RF field, thus a battery is added.

4) Using Automatic Chip Impedance Tuning

Adaptive chip impedance tuning was long awaited, and finally RF Micron was among the first to arrive to the market with a chip with that capability built-in. It didn’t take long till it was used to detect changes in the antennas proximity just like in the case 1. The biggest difference is that now the sensing result can simply be read from the tag memory and not from the RF properties of the tag.

An RAIN RFID IC with automatic chip impedance tuning capability stores the data in the tag memory where it can simply be read with a reader.

5) Binary Sensing

Several ICs have a special pin called the tamper detection pin. Whether this pin is in contact with ground or not can be polled by the reader. It is thus not so difficult to turn this tamper function into a sensor with a bimetallic strip, mercury switch, level float, magnetic switch, NTC resistor, etc. The fact remains that this topology of sensor remains binary.

ICs with tamper detection can be turned into a binary sensor with relative ease.

6) Inbuilt Sensing Capability

To bring potential cost down and optimize the energy consumption of the tag, the sensor is best integrated into the RFID IC itself. As no busses, microcontrollers, sensors, etc. need to be powered externally, the reading range can be potentially close to that of industry standard tags. The range of measured properties are more limited with this approach, temperature being the simplest candidate.

Built-in sensors can be powered from the RF field without a battery.

All this is to say that RFID sensoring can, in fact, be really simple. However, to get the solution working right also on-site with a known level of sensing accuracy requires advanced methods and a correct set of tools.

Getting It Right With Proper Tools

A number of RFID sensor developers are already using diverse functionalities in the Voyantic Tagformance systemto accelerate tag development cycles, optimize designs and to characterize their products. The more data there is in the sensor tag datasheet, the easier it is for anyone to take it into use!

If there is a particular type of testing you need to get done, but cannot find that particular function in our software GUI, please do not hesitate to contact us! Check out also our earlier blog post of passive RFID sensing!


Learn How to Design Passive Sensor Tags

Download our application note “Utilizing Voyantic Tagformance to Speed Up Development of UHF RAIN RFID Sensor Tags” to learn how to design passive sensor tags!

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Leadership in the RFID Era

Mar 02, 2016

中文版 Chinese version

So you want to be a successful leader in the RFID industry. Well, many leadership principles that are widely accepted in the high tech space will apply to RFID as well. But there are some concepts that are specific in the RFID industry. Here is a short glossary of buzz words for leadership in the RFID era.

1. Factory programming: The most important decisions that you will make are related to who you hire. A good rule of thumb is to hire people that are smarter than you. But I would put even more emphasis on how well the new team member fits the company culture. After all, new skills can be taught but changing someone’s factory programming is a lot harder. A good way to find out who to hire is to let the other team members interview the candidate before making the final decision.

2. Downlink: Ignorance is bliss? Maybe. But if you share information with your team on a need-to-know basis, how do you expect them to come up with new ideas? The better they understand the higher level goals of the company, the better they are able to help you reach them. I guarantee that the time spent explaining “why” will be returned ten-fold in commitment and creativity.

3. Listen before talk (LBT): What do you do when you are making a business decision that potentially has a big impact on the future of the company? Remember that you already have people smarter than you working for you. Why not listen what they have to say? Make them a part of the decision making process. Of course, the final decision is your responsibility but your team will be more committed to the decision if they have had their say. And I guarantee that the decision will be better.

4. Anti-collision: Every successful organization has people that don’t think alike, and that will cause some friction from time to time. But as long as all team members are acting in the best interest of the company, a healthy amount of conflict fosters growth. After all, if everyone is in complete harmony, some opportunities and ideas will be missed. So hold back with your anti-collision procedures, and resist your natural urges to act as a referee in every disagreement.

5. Error correction: The only way to avoid mistakes is not to do anything. And I believe in a corporate culture where people do not need to be afraid of making mistakes. Sometimes the mistakes may be visible to the customers as well: Maybe the new software release has a bug that was not caught in quality assurance, or maybe an item is accidentally left out of a delivery. The most important thing is to decisively make it right for the customer. The overall customer experience can still be positive if error correction is quick and professional.

This post was inspired by the AIM RFID Glossary.

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