RFID chips – function and differences between collar tags and implanted chips

• The function of the animal door is based on a two-stage detection process.
• The basic function of the animal door is to detect the movement of a living being in front of the door. This is detected by the two PIR sensors (1 x outside and 1 x inside). The PIR for inside is located above the door leaf on the electronics (black metal cover plate with S/N sticker) near the middle and is a small, black cylinder that is mounted at an angle. You can see the black mechatronic cover with the sticker when the animal door is removed, as well as when it is installed in a tunnel. The PIR for outside is located on the lower edge of the door leaf in the middle (installed) and is only visible when the door leaf is open. You can see the small round prism cover of the sensor on the vertical surface. If one of the two sensors detects movement, this is indicated by the corresponding house symbol lighting up orange. If the corresponding function: Open when movement is activated (symbol: House IN/House OUT = green), the animal door opens as soon as a corresponding movement is detected.
• As an additional security function, the RFID-based access control can now be switched on for motion detection (symbol: lock = green). If the access control is activated, the animal door does not open immediately when it detects movement, but instead tries to read a valid RFID chip for around 10 seconds (symbol: lock = flashes orange).
• The microchip in or on your cat or dog does not contain a battery, but is powered by the antenna in the petWALK pet door. As soon as the chip receives enough energy, it begins to send its identification like a radio station on a specific frequency.
• The petWALK pet door now listens to this frequency for about 10 seconds (orange flashing lock symbol) and as soon as it detects a known chip, it opens the door.
• If a known chip is recognized, the animal door opens and displays the animal's number. However, if no valid chip is recognized within 10 seconds of the reading cycle, the entire process is aborted and the animal door reinitializes the entire sensor system (symbol: door = lights up red). In this state, the animal door cannot be used because all functions are blocked during initialization.
• After this process (initialization), the animal door returns to its normal basic function and waits to see if MOVEMENT of an animal is detected. Then the cycle begins again and the animal door tries to read a valid RFID chip for about 10 seconds (symbol: lock = flashes orange). This means that if the chip of an animal cannot be read within 10 seconds when access control is activated, nothing else happens after the 10 seconds have elapsed until the animal door is triggered again by MOVEMENT!
• The position in front of the door is very important for optimal detection of the RFID chips. Please refer to the sketch in the enclosed information sheet. It must also be taken into account that the implanted chips have a much shorter range than the collar tags. This means that the animal must be in the optimal position and much closer to the door than with the tag. If the implanted transponder is too small, it may even be that it cannot be read correctly even when the animal is in the optimal position. If in doubt, please ask your veterinarian about the exact type and, above all, size of the implanted transponder.
• The position of the RFID chip is also very important. Changing the position of the chip in the three dimensional axes helps you to find out in which position the recognition works better or worse. The best way to test this is to hold your pet in the optimal position in front of the pet door (in the middle of the door leaf - see sketch) and turn and tilt it during the RFID reading cycle.
  
  

• The petWALK pet door is technically compatible with all conventional animal identification chips according to the ISO standard 11784 / 11785 FDX-B.
• However, this technology dates back to the 1970s and was standardized almost 20 years ago (1996). This makes it hopelessly outdated and brings with it a number of annoying restrictions. But it does allow such an implanted chip to be used as a key for the petWALK pet door.
• However, as the manufacturer of the pet door, we have no influence on the quality of the transponder in your pet and therefore cannot provide any guarantee with regard to its function or range.
• We therefore recommend checking with your animals before installation whether the detection range is sufficient. If it doesn't work, this is not a malfunction of the device, but rather a technical limitation of the ID chip.
  
  

• The typical reading distance of a well-tuned implanted chip is about 5 cm to a maximum of 20 cm. The collar tags supplied should offer a reading distance of at least 15-25 cm, the large chips at least 20-30 cm. In learning mode, the distance is usually half the normal reading distance.
• However, the actual achievable range depends on many factors. The biggest challenges are the power supply of the transponder, the transmission frequency and the position of the transponder in relation to the antenna.
• On the first point, there are legal regulations about how much energy the antenna can emit without disturbing other electronic devices in the vicinity (EMC standard). Depending on the quality of the chip in or on your pet, it needs more or less energy to activate, which means it can be further or closer to the antenna. The principle is called near-field transmission or inductive coupling. The distance between the two coils represents the wireless transmission path and should be as small as possible. If the distance between the two coils is greater, the stray flux increases significantly, which reduces the inductive coupling and reduces the efficiency. Typical distances that can be bridged with this method are approximately the coil diameter up to twice the coil diameter. The coil diameter of the transponder in your animal is only a few millimeters, so the theoretically achievable distance is limited to a few centimeters. This is also the reason why the much larger collar tag works so much better.
• The second challenge is the correct transmission frequency. This is set in the standard and the petWALK pet door adheres to it very precisely (it even adjusts it daily). However, the implanted chips in particular often show considerable deviations, which means that they do not transmit at the agreed frequency. To put it simply, you can imagine it as if you were listening to a radio program on a radio with the frequency adjusted. There will be noise and you will hardly be able to understand anything. Only when the signal becomes much stronger, in our case when the animal comes closer to the antenna, can you recognize the data.
• The third factor is the position of the transponder in the electromagnetic field. This means how the chip, which looks like a grain of rice, is aligned with the antenna in the door leaf. It works best when it is perpendicular to the door leaf and very poorly when it is in a parallel position. This is due to physical reasons (magnetic field of coils) due to the design of the implanted transponder. This circumstance has a dramatic influence on the reading range, from working great to not working at all.
• In order to maximize the range, petWALK does not read the numerical value of the chip like veterinarians' devices do. Instead, petWALK analyzes the frequency spectrum of the chip using complex mathematical methods and compares it with previously stored patterns.
• The range of the chip cannot be adjusted at the door.
  
  

• Positioning: As a rule, an identification chip is implanted by the vet in the left neck. For use with a petWALK pet door, it would be advantageous if this was as far forward as possible, preferably behind the ear. It is also helpful if the vet injects the chip so that it lies horizontally in the body with one of the tips facing the door, ie standing normally on the door leaf. This way the chip can absorb the most energy and of course also release it again.
• Implant: If possible, we recommend testing the microchip on our pet door before implanting it. It is important to note that the chip in the syringe is very well shielded by the metal needle. However, if you move the syringe with the tip pointing forwards towards the door, the chip should be able to be detected at a distance of around 3-5 cm. If this is successful, the chip will also work in the animal's body in front of our pet door. Of course, the animal may also need to practice a little to get the corresponding body part as close to the door as possible. However, pets usually learn this very quickly. The range depends on the quality of the transponder. Transponders from brand manufacturers such as Virbac or "Back Home Biotec" usually work well.
  
  
  

Possible errors when using RFID

An overview of possible sources of error in the detection of RFID chips can be found here .