Why no scanning non-contact thermometer?

[james]

I would love to have a thermo infrared camera for home maintenance, but they
are prohibitively expensive ($5K and up).

Non-contact thermometer, on the other hand, is pretty cheap at $50 and up.

It seems you can mount a non-contact thermometer on a pan and tilt platform
and perform a scan to create an image. It would be slow (non real time) and
non portable, but for home maintenance purpose, it is ok. This could cost a
lot less than $5K -- a poor-man's thermo infrared camera.

Does such product exist? I couldn't find any with google. Why?

 

[Jeff Liebermann]

On Wed, 27 May 2009 13:17:54 GMT, "james" <nospam@nospam.com> wrote:

I would love to have a thermo infrared camera for home maintenance, but they
are prohibitively expensive ($5K and up).

Non-contact thermometer, on the other hand, is pretty cheap at $50 and up.

It seems you can mount a non-contact thermometer on a pan and tilt platform
and perform a scan to create an image. It would be slow (non real time) and
non portable, but for home maintenance purpose, it is ok. This could cost a
lot less than $5K -- a poor-man's thermo infrared camera.

Does such product exist? I couldn't find any with google. Why?

I'll assume you want a thermal imager (far infrared) rather than a
near infrared imager, which can be done with a modified CCD camera.

The magic buzzwords are:
"infrared pyrometer" (a detector)
"thermopile" (the most common detector)
"thermal imager" (the name of most products)
"thermal imaging" (the name of the technology)
"flying spot scanner" (the name of the rotating mirror scanner)
"infrared line Scanner" (flying spot scanner and imager)

For example:
<http://www.pyrometer.com/thermatrace.html>
which has a nifty description of how theirs works.

More than you ever wanted to know about thermal imaging and
measurement:
<http://www.omega.com/literature/transactions/volume1/thermometers1.html>

I built one about 10 years ago from of butchered supermarket bar code
reader, by substituting a do it myself thermocouple for the laser. I
was initially able to get a decent image on an oscilloscope using an
LED in place of the laser, but when I tried the thermocouple, nothing
worked. It turned out I had multiple problems. The thermocouple had
very slow response. My mirror was spinning far to fast. Checking the
frequency response, it was less than 1Hz or a 1 second response time.
The front surface mirrors worked at near IR, but not far IR. Using a
single thermocouple was also problematic because of the enormous gain
required to obtain a usable signal. The picture was mostly noise. I
gave up.

Later, I had the bright idea of using either a commercial SMD
thermopile detector, or perhaps the detector from an ear thermometer.
Something like this device:
<http://optoelectronics.perkinelmer.com/content/Datasheets/DTS_TPS333R3.pdf>
<http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=Thermopile+Detectors>
However, I never tried it.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Wed, 27 May 2009 10:24:52 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

Later, I had the bright idea of using either a commercial SMD
thermopile detector, or perhaps the detector from an ear thermometer.
Something like this device:
http://optoelectronics.perkinelmer.com/content/Datasheets/DTS_TPS333R3.pdf
http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=Thermopile+Detectors
However, I never tried it.

More reading on thermopile thermometers:
<http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_Ambientcompensation.pdf>
<http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_pyrometry.pdf>
from white papers at:
<http://optoelectronics.perkinelmer.com/Service/WhitePapers.html>
Looks like response time is going to be a big problem.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Sjouke Burry]

Jeff Liebermann wrote:

On Wed, 27 May 2009 10:24:52 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

Later, I had the bright idea of using either a commercial SMD
thermopile detector, or perhaps the detector from an ear thermometer.
Something like this device:
http://optoelectronics.perkinelmer.com/content/Datasheets/DTS_TPS333R3.pdf
http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=Thermopile+Detectors
However, I never tried it.

More reading on thermopile thermometers:
http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_Ambientcompensation.pdf
http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_pyrometry.pdf
from white papers at:
http://optoelectronics.perkinelmer.com/Service/WhitePapers.html
Looks like response time is going to be a big problem.

Problem is, you need a germanium lens and/or mirrors,

the detector is easier, get the thinnest platinum wire you
can get, make a very small(0.2 mm diameter and length) for a
fast response time at the focuspoint of the scanner, and put
a constant current through the wire, measure/amplify the voltage
across it, and voila, a (slow) IR scanner.

 

[Jeff Liebermann]

On Wed, 27 May 2009 23:56:40 +0200, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> wrote:

Jeff Liebermann wrote:
On Wed, 27 May 2009 10:24:52 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

Later, I had the bright idea of using either a commercial SMD
thermopile detector, or perhaps the detector from an ear thermometer.
Something like this device:
http://optoelectronics.perkinelmer.com/content/Datasheets/DTS_TPS333R3.pdf
http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=Thermopile+Detectors
However, I never tried it.

More reading on thermopile thermometers:
http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_Ambientcompensation.pdf
http://optoelectronics.perkinelmer.com/content/ApplicationNotes/APP_pyrometry.pdf
from white papers at:
http://optoelectronics.perkinelmer.com/Service/WhitePapers.html
Looks like response time is going to be a big problem.

Problem is, you need a germanium lens and/or mirrors,

The problem is that the OP didn't bother to mention what he's looking
at and for what application. Thermal imaging is very different from
FLIR imaging, which work at different wavelengths.
<http://en.wikipedia.org/wiki/Thermography>
<http://en.wikipedia.org/wiki/Flir>
I assumed thermal imaging (which is the most fun) from the thermometer
term in the subject line.

You need a long wave IR (8-20 um) pass filter or germanium window,
which can be made or purchased. I found mine at Edmund Scientific
when they were selling seconds and rejects. Today, the prices are
much higher:
<http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=1108>
While germanium is the best, there are some cheaper filters that will
work:
<http://www.edmundoptics.com/onlinecatalog/DisplayProduct.cfm?productid=1924>
There are some on eBay for tolerable prices:
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390054223556>
If you're totally cheap, a piece of exposed 35mm color film will make
a marginal substitute.

The front surface gold mirrors were salvaged from a supermarket
scanner. They weren't the best but they were cheap. As long as the
anti-reflective coating on the optics doesn't totally block IR, it
will work. The problem with the supermarket scanner is that it's
anything but portable. It was roughly a cube, about 10" on a side.
Not exactly portable.

the detector is easier, get the thinnest platinum wire you
can get, make a very small(0.2 mm diameter and length) for a
fast response time at the focuspoint of the scanner, and put
a constant current through the wire, measure/amplify the voltage
across it, and voila, a (slow) IR scanner.

That's exactly what I did. The problem is that a single thermocouple
just didn't generate enough voltage to be useful. The signal was
buried under useless noise. I used the best low noise amplifier I
could design, but it wasn't good enough. The solution was an array of
thermocouples, called a thermopile. If I did that with my home made
thermocouples, it would be too large to focus properly. In addition,
it was important to add thermal compensation to the thermocouple, so
that I would be measuring IR, and not heat from the electronics and
packaging. Most thermopile detectors have this built in.

Hint: The lack of do-it-thyself scanning thermal imaging projects on
the web should offer some clue as to the difficulty.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558