Pet ID chip range - theoretical limit - Page 1
Forum section: electronics / general

author: fcb
author_rank: Super Contributor
timestamp: July 25, 2021, 08:45:07 pm
content: So one of our cats has gone missing (actually my favourite cat) and we fear the worst. She is ‘chipped’.Got me thinking about the RFID chip and what is the theoretical range limit would be for:1. Detecting presence of an RFID.2. Reading the RFID chip.Anyone know if there is a fundamental limit to reading these or what defines it, even with an impractically large antenna or multiple antennae or requires some TEC cooled receiver etc..

author: Benta
author_rank: Super Contributor
timestamp: July 25, 2021, 09:13:24 pm
content: About the same as the loop antenna diameter. It's not just about detecting, it's about powering the RFID chip from the antenna.

author: Cerebus
author_rank: Super Contributor
timestamp: July 25, 2021, 10:30:49 pm
content: Quote from: fcb on July 25, 2021, 08:45:07 pmSorry to hear that.Word of advice:don't let the other cats hear you saying that bit about "favourite cat".

author: fcb
author_rank: Super Contributor
timestamp: July 25, 2021, 10:47:36 pm
content: Quote from: Benta on July 25, 2021, 09:13:24 pmSo a ten foot diameter loop would perhaps have a ten foot range?Presumably powering the RFID is about getting the field strength right and the read back is done with some sort of backscatter or change in impedance.And thanks Cerebus for the advice - both the remaining cat and the doggo knew something was up before I did.

author: Benta
author_rank: Super Contributor
timestamp: July 25, 2021, 11:23:06 pm
content: The RFID pellets implanted in animals consist of a parallel tank circuit tuned to a certain frequency, the coil at the same time delivers power to the chip, and the chip responds by modulating the tank circuit. Quite simple, really.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 25, 2021, 11:51:19 pm
content: Yes. That's short range communication. RFID is near field.

author: DrG
author_rank: Super Contributor
timestamp: July 26, 2021, 12:20:39 am
content: Quote from: fcb on July 25, 2021, 10:47:36 pmWhen she was chipped, you likely gave your info into a registry - is the info still accurate? Not sure about where you are at but here all the Vets and animal personnel know to check for a chip and then the registry to contact the owner. Just a thought - hope she shows up soon.

author: fcb
author_rank: Super Contributor
timestamp: July 26, 2021, 07:40:04 am
content: Quote from: DrG on July 26, 2021, 12:20:39 amI checked recently as there have been some issues with Petlog highlighted in the media. Fortunately our vet registered them with a different provider.

author: fcb
author_rank: Super Contributor
timestamp: July 26, 2021, 08:04:39 am
content: Quote from: SiliconWizard on July 25, 2021, 11:51:19 pmFrom my reading-up most of these pet RFID chips are now ISO 11784 or ISO 11785, and operate on 134.2KHz.https://www.pet-detect.com/pages/Interpreting-microchip-numeric-codes.aspx?pageid=610Looks like the bigger the loop, the further the range, but the smaller the received return modulation will be. Perhaps if chipageddon gets worse and I run out of existing projects to work on..

author: Berni
author_rank: Super Contributor
timestamp: July 26, 2021, 09:48:39 am
content: More of a problem is that the receive antenna on the RFID implant is rather tiny because the implant itself has to be small.So in my opinion even a large antenna with a lot of transmit power is going to have a hard time picking up the tiny modulation signal such a tiny antenna would be able to send back.The usual RFID cards (usually 125KHz) use the whole outer edge of the card to form a coil antenna, this gives them way more usable loop area. Yet even those typically only read about 2 to 25 cm from a reader (depending on how good the reader is). You can probably construct a special long range reader that gets perhaps 2 or 4 x this range. Even that would be fairly useless for locating a cat. At best you could possibly create an array of receivers around your fence to detect the cat leaving your property. An array of smaller antennas with separate receivers has a easier time picking up the tags modulated signal.That being said if this is a cat that is typically outdoors, then you probably don't have much reason to worry. They remember a pretty wide area around the house and will eventually find a way back and if they are hungry they will find something to eat. It's more of a problem with house cats that don't know the area around the neigborhood and don't know how to hunt and defend, they might have a hard time finding it back on there own. Tho sometimes people adopt a random cat that wanders by and care for it (especially if the cat has a tendency to act nice to everyone like ours, he can get just about anyone to give him food, and he uses it to his advantage)

author: tszaboo
author_rank: Super Contributor
timestamp: July 26, 2021, 10:01:27 am
content: Sorry about your pet. But this is the sort of project, if you work really hard on it, and use a lot of power for transmission, then maybe it works from 20cm instead of 2.When people say that the 'man' uses chips in vaccines to track, and control you from satellites... They have no idea how difficult any step of this to be done.