RFID tags in Arctic conditions?

[Fatfreek]

I have an application in which RFID tags need to respond and send data while
at very cold (10 deg F to -30 deg F) temperatures. They will have been put
in place for up to one year. While not exactly the application, it's as if I
were attaching RFID tags to the entrances of Arctic Fox dens - a very cold
environment with the possibility of deep and total snow cover.

Readers would be protected and would have minimum exposure to the cold.

In such cases I would need to find certain ones of such a hidden collection.
I suspect the reader would need to be of special design, needing proximity
sensing as well. While GPS could get us in the approximate vicinity of a
known object, this special reader would need more exact proximity capability
that resembles some metal detectors and emit some sound that increases in
intensity the closer you get to the object.

Distance range, reader to tags, could vary to, say, 60".

Before contacting some development firm for price quotations, is what I've
described well within the realm of feasibility?
Len Miller

 

[Joerg]

I have an application in which RFID tags need to respond and send data while
at very cold (10 deg F to -30 deg F) temperatures. They will have been put
in place for up to one year. While not exactly the application, it's as if I
were attaching RFID tags to the entrances of Arctic Fox dens - a very cold
environment with the possibility of deep and total snow cover.

Readers would be protected and would have minimum exposure to the cold.

In such cases I would need to find certain ones of such a hidden collection.
I suspect the reader would need to be of special design, needing proximity
sensing as well. While GPS could get us in the approximate vicinity of a
known object, this special reader would need more exact proximity capability
that resembles some metal detectors and emit some sound that increases in
intensity the closer you get to the object.

Distance range, reader to tags, could vary to, say, 60".

Before contacting some development firm for price quotations, is what I've
described well within the realm of feasibility?
Len Miller

Sounds more like an application for radio direction finding. At 60" plus
snow cover it would almost have to be active. For example transmitters
that emit only brief bursts so the battery lasts a long time. Since this
makes direction funding tougher you might consider equipping the motes
with receivers so that they can turn to higher duty cycle or a timed
continuous transmission when the guy with the reader presses the "Mote
number 17 - please answer now for 5 minutes" button.

You could experiment with low power modulated AM transmitters, go up
into the mountains, throw some snow on them, try to find them using a
portable AM radio that has a good clean ferrite antenna. There are
tricks to overcome the 180 degree ambiguity to some extent but first I'd
try to locate a few hidden motes. Have someone else bury them so you
really don't know where they are. But mind the FCC limits on low power
AM. This can also be a concern depending on the jurisdiction in your
planned deployment area. Last but not least mind the animals. If arctic
foxes are anywhere as curious as the gray foxes that live near the
office here they'll try to "reverse engineer" anything that looks
interesting or unusual. Especially their kits.

 

[Fatfreek]

Sounds more like an application for radio direction finding. At 60" plus
snow cover it would almost have to be active. For example transmitters
that emit only brief bursts so the battery lasts a long time. Since this
makes direction funding tougher you might consider equipping the motes
with receivers so that they can turn to higher duty cycle or a timed
continuous transmission when the guy with the reader presses the "Mote
number 17 - please answer now for 5 minutes" button.

You could experiment with low power modulated AM transmitters, go up
into the mountains, throw some snow on them, try to find them using a
portable AM radio that has a good clean ferrite antenna. There are
tricks to overcome the 180 degree ambiguity to some extent but first I'd
try to locate a few hidden motes. Have someone else bury them so you
really don't know where they are. But mind the FCC limits on low power
AM. This can also be a concern depending on the jurisdiction in your
planned deployment area. Last but not least mind the animals. If arctic
foxes are anywhere as curious as the gray foxes that live near the
office here they'll try to "reverse engineer" anything that looks
interesting or unusual. Especially their kits.

Some good thoughts there, Joerg.

Ah, yes, those curious foxes. Thanks for that alert.

Len

 

[Nemo]

I get the impression the tags are static and possibly buried in snow for
a year, the readers are mobile but probably have to withstand the same
temperatures albeit not for a year at a time. If I have misread your
intentions well, alas. Soldiering on...

1. Battery types: this will be critical to the readers as many types
have reduce capacity below 0C (uh, 32F), significantly lower at -10C and
freeze at almost exactly -20C (-10F). So avoid normal alkalines, lithium
ion etc. Special alkaline types for low temperatures are available from
one of the big battery manufacturers, Duracell I think, but for non
rechargeables you'll need to be careful about circuit current
consumption. Lead Acid may be your only option for rechargeable cells
(heavy!). I strongly recommend you do far more testing than you
originally assumed because batteries are often the Achilles Heel of
instruments when operated in extreme environmental conditions; the
battery manufacturers may CLAIM operation at -20C but capacity will be
way down and they may gradually degrade if left that way for months.

2. However I have good news! I was looking into RFID tags myself
recently and discovered SAW types are excellent at extreme environmental
conditions, PLUS they can be self powered from the incoming RF pulse,
PLUS their range is generally better than other types. Have a look at
this page...

http://www3.sympatico.ca/colin.kydd.campbell/

If you scroll down to figures 21 and 21a you'll see the implementation
of these things as tags is pretty straightforward, and already in use.

See the comparison between SAWs and different RFID technologies on page
4 of this document:

http://www.transense.co.uk/downloads/articles/edn_europe_0604.pdf

I would be interested to hear others' views of this technology. I'm a
newbie to RFID. Have I missed something or is it really rather good?

 

[Joerg]

I get the impression the tags are static and possibly buried in snow for
a year, the readers are mobile but probably have to withstand the same
temperatures albeit not for a year at a time. If I have misread your
intentions well, alas. Soldiering on...

1. Battery types: this will be critical to the readers as many types
have reduce capacity below 0C (uh, 32F), significantly lower at -10C and
freeze at almost exactly -20C (-10F). So avoid normal alkalines, lithium
ion etc. Special alkaline types for low temperatures are available from
one of the big battery manufacturers, Duracell I think, but for non
rechargeables you'll need to be careful about circuit current
consumption. Lead Acid may be your only option for rechargeable cells
(heavy!). I strongly recommend you do far more testing than you
originally assumed because batteries are often the Achilles Heel of
instruments when operated in extreme environmental conditions; the
battery manufacturers may CLAIM operation at -20C but capacity will be
way down and they may gradually degrade if left that way for months.

That's right, materials is a very important consideration. Many Lithium
batteries are spec'd down to -20C but will work further down. It is
important to have an indepth conversation with an engineer from a
company such as Duracell.

Other parts are of concern, too. For example, I would not use
electrolytics. This means you either have to have the space for lots of
ceramic caps to bridge the transmit current surges or the battery has to
be large enough so the voltage won't collapse.

2. However I have good news! I was looking into RFID tags myself
recently and discovered SAW types are excellent at extreme environmental
conditions, PLUS they can be self powered from the incoming RF pulse,
PLUS their range is generally better than other types. Have a look at
this page...

http://www3.sympatico.ca/colin.kydd.campbell/

If you scroll down to figures 21 and 21a you'll see the implementation
of these things as tags is pretty straightforward, and already in use.

See the comparison between SAWs and different RFID technologies on page
4 of this document:

http://www.transense.co.uk/downloads/articles/edn_europe_0604.pdf

I would be interested to hear others' views of this technology. I'm a
newbie to RFID. Have I missed something or is it really rather good?

Passive sensors would be a stretch here, I don't think it'll work in
this case. IIUC the distance can be tens of meters and the devices may
have a thick layer of snow over them.

 

[Nemo]

Passive sensors would be a stretch here, I don't think it'll work in
this case. IIUC the distance can be tens of meters and the devices may
have a thick layer of snow over them.

OK have a look again at that page

http://www3.sympatico.ca/colin.kydd.campbell/

Down around "question 40" they mention one of the benefits as being up
to 20m range. Now, I've never designed an RFID system ("aha!" says the
reader, and stops reading) but I suspect the range will depend more on
the ariel design than anything else. I had a long chat once with one of
the guys at http://www.telegesis.com/ who impressed me because where
other blokes who'd try to sell me RFID and PICs with built in RF
circuits were basically trying to sell a predesigned system, which they
didn't really understand, he BEGAN talking at a level above me and I had
to ask him several times to explain some concept which was, to him,
basic. However I could tell he was not bullshitting. Telegesis offer a
variety of radio comms solutions and one thing I learnt was to tailor
the frequency to the situation (f'rex we wanted underground comms, turns
out this IS possible, but not with the out-of-the-box solutions offered
by microcontroller manufacturers etc). He was quite scathing about
supermarket RFID tags, pointing out they've chosen a poor frequency -
blocked by water, which most of their produce contains - and most people
just use rectangular ariels, which are very directional, simply because
they're well known; if you understand rectangular ariels'
characteristics you can shoplift in relative safety by sneaking produce
out of shops in certain orientations...

Anyhow, though I have no connection with Telegesis, I would suggest that
if your budget can stretch to it, you discuss frequency choice and ariel
design with them - or someone else who really understands the
fundamentals of RFID and radio propagation, rather than just a reseller
of an extant system.

Many Lithium batteries are spec'd down to -20C but will work further
down. It is important to have an indepth conversation with an engineer
from a company such as Duracell.

I have heard that sea emergency buoys used to use Li thionyl chloride,
but not any longer, because it was found that after a few years of
storage their peak current was much, much lower than in the lab tests
when they were designed, so the flashing lights didn't flash, etc. THAT
is the kind of nasty feature which will bite a project for extreme
conditions like this.

 

[Joerg]

this case. IIUC the distance can be tens of meters and the devices may
have a thick layer of snow over them.

OK have a look again at that page

http://www3.sympatico.ca/colin.kydd.campbell/

Down around "question 40" they mention one of the benefits as being up
to 20m range. Now, I've never designed an RFID system ("aha!" says the
reader, and stops reading) but I suspect the range will depend more on
the ariel design than anything else. I had a long chat once with one of
the guys at http://www.telegesis.com/ who impressed me because where
other blokes who'd try to sell me RFID and PICs with built in RF
circuits were basically trying to sell a predesigned system, which they
didn't really understand, he BEGAN talking at a level above me and I had
to ask him several times to explain some concept which was, to him,
basic. However I could tell he was not bullshitting. Telegesis offer a
variety of radio comms solutions and one thing I learnt was to tailor
the frequency to the situation (f'rex we wanted underground comms, turns
out this IS possible, but not with the out-of-the-box solutions offered
by microcontroller manufacturers etc). He was quite scathing about
supermarket RFID tags, pointing out they've chosen a poor frequency -
blocked by water, which most of their produce contains - and most people
just use rectangular ariels, which are very directional, simply because
they're well known; if you understand rectangular ariels'
characteristics you can shoplift in relative safety by sneaking produce
out of shops in certain orientations...

Says "up to 20m" and that's the point. When you have a load of snow on
top of the target you wouldn't even get anywhere close. Of course, this
all depends on the energy you pump in but there are typically legal
limits in place.

It's easy to pick on commercial systems. The fact is, however, that one
must comply with FCC rules and similar rules in other countries. Yep,
there may be a much better frequency but that does not mean you can have
that frequency or the desired power level.

Anyhow, though I have no connection with Telegesis, I would suggest that
if your budget can stretch to it, you discuss frequency choice and ariel
design with them - or someone else who really understands the
fundamentals of RFID and radio propagation, rather than just a reseller
of an extant system.

That's true for any "RF system in the can". Often I have to deal with
the aftermath where a client had designed one in at it performs
marginally. After the initial fix so they won't have a line stop I
always suggest to them to build from scratch and get the required
engineering help if needed.

I have heard that sea emergency buoys used to use Li thionyl chloride,
but not any longer, because it was found that after a few years of
storage their peak current was much, much lower than in the lab tests
when they were designed, so the flashing lights didn't flash, etc. THAT
is the kind of nasty feature which will bite a project for extreme
conditions like this.

Yes, the battery needs to be thoroughly researched out. IMHO it is the
most critical part in the whole design.