Sometimes, you just gotta get brutal ...

[Wild_Bill]

Hi, John.. I have one of the Tone Ohm units, but I'm not sure where it is at
the moment.

I agree, that milliohm meters are very useful in finding circuit faults (on
bare or populated boards), and some ESR meters may also be useful if the
circuitry isn't massively large.
I've recommended milliohm testers in SER over the years, although I'm not
sure that I included any details wrt the probes.
There are likely SER archived posts which may include ToneOhm milliohm meter
or Polar Instruments comments.

The obvious advantage to a real milliohm meter is the digital display,
although they also incorporate an audio tone which changes with differences
in readings/actual circuit board resistance changes.

The probe for the Tone Ohm model I have (white case with red panel
silkscreening), IIRC, is a fairly common 4-pin connector used for
transceivers (CB, amateur radio etc) with 2 sections of small, flexible coax
(one for each probe), where the 2 conductors of each probe make a 4-wire
bridge-type input circuit.
The 2 probes themselves aren't anything special, just ordinary probes with
sharp steel tips.
There is a Cal pot and built-in test point on the back panel of the ToneOhm
unit I have, so there is some wiggle room for what materials might be
suitable for the brobes and cables.
I got some Fluke probes with sharp steel points for my Blue Bob Parker
Anatek ESR meter, and they're working fine.

FWIW, some instruments as you probably already know, are more critical of
Zero-Set settings, and I've found that steel points break thru any surface
oxides on a test piece (a coin, single solder pad or other metallic surface)
and sharp steel points appear to be less problematic IME.
I generally don't rely on touching probe tips together for Zero-Set,
although not an issue with Bob Parker's tester, but some instruments are
more fiddly.. so I like to pierce any surface contamination and use an
actual reading for zero.

After I bought the used Tone Ohm a number of years ago, a friend bought a
similar unit by Polar Instruments (older model 900 maybe, marketed by a US
company) without a probe, and I made a probe set for him from two sections
of thin coax (maybe RG 174) and it worked correctly.. I vaguely recall that
the probes for the Polar model utilized two sections of coax per probe using
the shields as separate ground connections.. definite maybe, I guess.

--
Cheers,
WB
..............


"John Robertson" <spam@flippers.com> wrote in message
news:b92dna39g9CcFt_SnZ2dnUVZ5sWdnZ2d@giganews.com...

Or you could track down a Shortsqueek by Global Specialties Model
SQ-1.Made in the 1970s and 80s it is a handy device to keep to track down
shorts on PCBs. Using a small op-amp that changes pitch depending on how
low the resistance is you can find shorts such as you describe fairly
quickly as long as your ear is good for tone changes of a few Hertz. Polar
Devices (UK) made Tone Ohm which was a similar device (I need a probe if
anyone has a spare) that I haven't been able to test (because I'm missing
the probe!).

Here is the manual for Shortsqueek (470k PDF)

http://www.flippers.com/pdfs/GlobalSpecialities_ShortSqueek_Model_SQ-1.pdf

These turn up on eBay from time to time - I bought two for my shop and
they do save hours of time (and chopping traces) every now and then...

John :-#)#


--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Arfa Daily]

"Jon Elson" <jmelson@wustl.edu> wrote in message
news:nOSdncYyoLKPxNjSnZ2dnUVZ_hCdnZ2d@giganews.com...

Arfa Daily wrote:


Oddly, a couple of months ago, I had two radio mic receivers in the space
of a couple of weeks, which both had the demodulator tank mis-tuned by a
good half turn. Neither had been 'got-at' as far as we know, and both
remained stable and correctly tuned over a soak test of several days.
Neither has come bouncing back either, so it's a bit of a mystery as to
why they were like it.
Same make of unit? Sounds like a screw-up at the factory, and really weak
QC. Somebody had the wrong tuning procedure, or the transmitter they were
using to tune it was set to the wrong freq.

Well, that's China for you.

Jon

Nope. Two different makes, two different owners and both had been in service
and previously working just fine (apparently) for a long time ...

Arfa

 

[Arfa Daily]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:siq8k7tf9755g2605m2auib1aan69o6kgs@4ax.com...

On Wed, 22 Feb 2012 02:36:14 -0000, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

I actually have a non-contact IR thermometer, and it's just about OK on
biggish items like chips, but nothing like tight enough on its sensing
area,
to be able to detect a gnat's bollock cap getting hot !

I made an attachment that resembles a black (non-reflective) soda
straw, about 8 mm in diameter. It is fitted to the lens on my IR
thermometer with an ugly mess of electrical tape. The idea is for
only the light coming down the soda straw to hit the pyrometer. Works
fine for measuring individual components (although the readings appear
to be lower than expected).

Got $2,000 and up?
http://www.flir.com/cvs/americas/en/personalvision/view/?id=44756

I like your "big bang" method of troubleshooting. I've used when
desperate, with variable success. In one case, I destroyed a
transceiver when the PCB traces decided to immitate a fuse. Other
times, it clearly identified a shorted capacitor, by exploding.
Tantalums are rather interesting, producing a bright red glow, and
belching toxic fumes.

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

Yeah, it was a bit of a last resort. The print on the power rail was
actually quite good quality and size, so I wasn't expecting to get a track
burn up. With only 4 volts on there, I was actually expecting something to
just get hot to the touch or possibly smoke gently. But yes, you are right.
There was certainly a good pyrotechnic display and a lot of smoke
considering how small the cap was, in very short order. I'll give your soda
straw idea a try next time.

Arfa

 

[Jeff Liebermann]

On Thu, 23 Feb 2012 02:44:16 -0000, "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

I'll give your soda
straw idea a try next time.

What worked the best was a sheet of black construction paper.
<http://www.staples.com/Construction-Paper-9-x-12-Black/product_402652>
The idea is the same as in a telescope. You don't want anything that
reflects light or heat. My first attempt was a brass tube and brass
washer to fit over the lens. Even painted flat black, the IR
thermometer would read the temperature of the brass tube, and not the
heat source. I substituted ordinary paper, which proved to be IR
transparent. I also stupidly left the brass washer, which again
caused local heating. Eventually, the gears operating the brain
engaged, and I realized that I needed something that was opaque to IR
and had minimal thermal mass. Black construction paper was the best I
could find. I wanted it corrugated to minimize reflections, but that
proved to be difficult to build.

Several variations were built. The one that worked best was a conical
like construction, that covered the entire lens on the IR thermometer
end, and narrowed to almost a point on the other. However, attachment
of this arrangement to the IR thermometer proved fragile, so I tried a
soda straw shape, and washer cut from a shipping box. For light
proofing, I buried the mess under a layer of black electrical tape.

I suggest you try the cone first as it's easiest to build.

I just ordered a B&D TLD100 heat leak detector, which seems to have
more resolution over its narrow -30C to 150C range, than the wide
temperature range common IR thermometer. $50.
<http://www.blackanddecker.com/power-tools/TLD100.aspx>

Drivel: In the past, I've ranted on building several IR flying spot
scanners using bar code readers and various pyrometers. I never
really finished. I demonstrated that it worked, but was very slow to
respond. I'm tempted to resurrect that project and build a real far
IR imager.
<http://groups.google.com/group/sci.electronics.equipment/browse_thread/thread/92c3879a53a8f9f1>

Some ideas:
<http://spill.tanagram.com/2010/11/24/diy-thermal-imaging-system-for-under-200/>
Moving the camera for scanning sucks.


--
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

 

[N_Cook]

Jeff Liebermann <jeffl@cruzio.com> wrote in message
news:e5sck71nnamdsadmha8n1bo5v4stgfh1ci@4ax.com...

On Thu, 23 Feb 2012 02:44:16 -0000, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

I'll give your soda
straw idea a try next time.

What worked the best was a sheet of black construction paper.
http://www.staples.com/Construction-Paper-9-x-12-Black/product_402652
The idea is the same as in a telescope. You don't want anything that
reflects light or heat. My first attempt was a brass tube and brass
washer to fit over the lens. Even painted flat black, the IR
thermometer would read the temperature of the brass tube, and not the
heat source. I substituted ordinary paper, which proved to be IR
transparent. I also stupidly left the brass washer, which again
caused local heating. Eventually, the gears operating the brain
engaged, and I realized that I needed something that was opaque to IR
and had minimal thermal mass. Black construction paper was the best I
could find. I wanted it corrugated to minimize reflections, but that
proved to be difficult to build.

Several variations were built. The one that worked best was a conical
like construction, that covered the entire lens on the IR thermometer
end, and narrowed to almost a point on the other. However, attachment
of this arrangement to the IR thermometer proved fragile, so I tried a
soda straw shape, and washer cut from a shipping box. For light
proofing, I buried the mess under a layer of black electrical tape.

I suggest you try the cone first as it's easiest to build.

I just ordered a B&D TLD100 heat leak detector, which seems to have
more resolution over its narrow -30C to 150C range, than the wide
temperature range common IR thermometer. $50.
http://www.blackanddecker.com/power-tools/TLD100.aspx

Drivel: In the past, I've ranted on building several IR flying spot
scanners using bar code readers and various pyrometers. I never
really finished. I demonstrated that it worked, but was very slow to
respond. I'm tempted to resurrect that project and build a real far
IR imager.

http://groups.google.com/group/sci.electronics.equipment/browse_thread/thre

ad/92c3879a53a8f9f1>

Some ideas:

http://spill.tanagram.com/2010/11/24/diy-thermal-imaging-system-for-under-2

00/>

Moving the camera for scanning sucks.


--
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

I used some matt black rubber tubing .about 5mm diameter as a shroud but as
I say the resolution , down to SMD dimensions , seemed to be no different
with or without the tube

 

[Tom Del Rosso]

N_Cook wrote:

I used some matt black rubber tubing .about 5mm diameter as a shroud
but as I say the resolution , down to SMD dimensions , seemed to be
no different with or without the tube

Mine has a short metal tube, or more like a cup, that is reflective. It
seems to me that a reflective tube would work better at conducting the IR
from the endpoint.


--

Reply in group, but if emailing add one more
zero, and remove the last word.

 

[Jeff Liebermann]

On Mon, 12 Mar 2012 15:54:56 -0400, "Tom Del Rosso"
<td_03@verizon.net.invalid> wrote:

N_Cook wrote:

I used some matt black rubber tubing .about 5mm diameter as a shroud
but as I say the resolution , down to SMD dimensions , seemed to be
no different with or without the tube

Mine has a short metal tube, or more like a cup, that is reflective. It
seems to me that a reflective tube would work better at conducting the IR
from the endpoint.

A reflective tube is better for conducting IR to the sensor. The
problem is that it also picks up plenty of IR from the sides. The
point of the black construction paper tube was to measure only the IR
that goes directly from the hot component to the sensor, not the junk
that comes in from other components. Ideally, that could be done with
a lens that focuses to a point. Lacking one of those, the tube is a
tolerable 2nd best.

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

 

[josephkk]

On Tue, 13 Mar 2012 15:35:50 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Mon, 12 Mar 2012 15:54:56 -0400, "Tom Del Rosso"
td_03@verizon.net.invalid> wrote:


N_Cook wrote:

I used some matt black rubber tubing .about 5mm diameter as a shroud
but as I say the resolution , down to SMD dimensions , seemed to be
no different with or without the tube

Mine has a short metal tube, or more like a cup, that is reflective. It
seems to me that a reflective tube would work better at conducting the IR
from the endpoint.

A reflective tube is better for conducting IR to the sensor. The
problem is that it also picks up plenty of IR from the sides. The
point of the black construction paper tube was to measure only the IR
that goes directly from the hot component to the sensor, not the junk
that comes in from other components. Ideally, that could be done with
a lens that focuses to a point. Lacking one of those, the tube is a
tolerable 2nd best.

Now what do they make lenses out of for that wavelength range?

?-)

 

[William Sommerwerck]

Now, what do they make lenses out of for that
wavelength range [IR]?

Germanium.

 

[Jeff Liebermann]

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
<http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314>

Much cheaper are various plastic formulations, that pass IR.
<http://www.fresneltech.com/materials.html>
<http://www.fresneltech.com/materials_graph.html>
<http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting>

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
<http://www.glolab.com/pirparts/pirparts.html>
<http://www.futurlec.com/PIR_Sensors.shtml>

There are also a tangle of band pass, low pass, and specialty filters.
<http://www.edmundoptics.com/products/browse.cfm?categoryid=41>

Or, you can just be weird:
<http://amasci.com/amateur/irgoggl.html>


--
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

 

[Jim Yanik]

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:uid9m7lqaifu5v69bbpkj6m9p81j70e0ht@4ax.com:

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=
314

Much cheaper are various plastic formulations, that pass IR.
http://www.fresneltech.com/materials.html
http://www.fresneltech.com/materials_graph.html
http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Tran
smitting

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
http://www.glolab.com/pirparts/pirparts.html
http://www.futurlec.com/PIR_Sensors.shtml

There are also a tangle of band pass, low pass, and specialty filters.
http://www.edmundoptics.com/products/browse.cfm?categoryid=41

Or, you can just be weird:
http://amasci.com/amateur/irgoggl.html

often,they use curved mirrors instead of lenses,for IR.

and sapphire for a window. ;-)

--
Jim Yanik
jyanik
at
localnet
dot com

 

[Arfa Daily]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:uid9m7lqaifu5v69bbpkj6m9p81j70e0ht@4ax.com...

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314

Much cheaper are various plastic formulations, that pass IR.
http://www.fresneltech.com/materials.html
http://www.fresneltech.com/materials_graph.html
http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
http://www.glolab.com/pirparts/pirparts.html
http://www.futurlec.com/PIR_Sensors.shtml

There are also a tangle of band pass, low pass, and specialty filters.
http://www.edmundoptics.com/products/browse.cfm?categoryid=41

Or, you can just be weird:
http://amasci.com/amateur/irgoggl.html


--
Jeff Liebermann

Hows about the lens from a an old CD laser ? Just thinking out loud ...

Arfa

 

[Jeff Liebermann]

On Tue, 20 Mar 2012 18:42:03 -0000, "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

Hows about the lens from a an old CD laser ? Just thinking out loud ...
Arfa

Maybe. The common DVD laser diode is 632nm, which is in the visible
light range. Laser printers and CDROM drives are 780nm, which is near
IR. Since outside light sources do not enter into a CDROM drive,
there's no need for an IR bandpass filter. I couldn't find anything
on the optical characteristics of the CD or DVD lens. The dark ones
might be a possible bandpass filter. The clear lenses are probably
not.

--
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

 

[Arfa Daily]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:j9khm79e3em8s3dn9seoujfljs768cbutv@4ax.com...

On Tue, 20 Mar 2012 18:42:03 -0000, "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

Hows about the lens from a an old CD laser ? Just thinking out loud ...
Arfa

Maybe. The common DVD laser diode is 632nm, which is in the visible
light range. Laser printers and CDROM drives are 780nm, which is near
IR. Since outside light sources do not enter into a CDROM drive,
there's no need for an IR bandpass filter. I couldn't find anything
on the optical characteristics of the CD or DVD lens. The dark ones
might be a possible bandpass filter. The clear lenses are probably
not.

--
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

DVD lasers operate at visible red as you say, whilst CD lasers are near IR.
CD laser lenses often appear to be optically coated, but for what reason
exactly, I'm not sure.

Arfa

 

[Jeff Liebermann]

On Fri, 23 Mar 2012 01:31:39 -0000, "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

DVD lasers operate at visible red as you say, whilst CD lasers are near IR.
CD laser lenses often appear to be optically coated, but for what reason
exactly, I'm not sure.

Reflective coatings are usually to minimize reflections and/or to
improve signal to noise ratio by reducing the optical bandwidth.
<http://rick_oleson.tripod.com/index-166.html>

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

 

[josephkk]

On Sat, 17 Mar 2012 06:01:37 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

Now, what do they make lenses out of for that
wavelength range [IR]?

Germanium.

That may work well, but it is rather spendy. Any other materials?

?-)

 

[josephkk]

On Sat, 17 Mar 2012 09:27:23 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314

Much cheaper are various plastic formulations, that pass IR.
http://www.fresneltech.com/materials.html
http://www.fresneltech.com/materials_graph.html
http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
http://www.glolab.com/pirparts/pirparts.html
http://www.futurlec.com/PIR_Sensors.shtml

There are also a tangle of band pass, low pass, and specialty filters.
http://www.edmundoptics.com/products/browse.cfm?categoryid=41

Or, you can just be weird:
http://amasci.com/amateur/irgoggl.html

Mid to far as i understand it. I want to look at thermal maps of
electronics that may be too hot to touch thermally or electrically.

The idea of forming an image with inexpensive optics and sensors appeals
to me.

?-)

 

[Jeff Liebermann]

On Tue, 27 Mar 2012 21:57:17 -0700, josephkk
<joseph_barrett@sbcglobal.net> wrote:

Mid to far as i understand it. I want to look at thermal maps of
electronics that may be too hot to touch thermally or electrically.

I had the same idea and decided that $2,000 and up for commercial
thermal imagers was too much. My idea was to convert either a
supermarket scanner or laser printer rotating mirror imager, into a IR
camera. Basically, it's a "flying spot scanner" and is identical to
what we were using in early weather satellites to generate thermal
images of the planet.

I've built two failed prototypes so far, but plan to continue. The
major problem is the response time of the IR detector. The guts of a
PIR sensor will work, but is depressingly slow.
<http://www.futurlec.com/PIR_Sensors.shtml>
<http://en.wikipedia.org/wiki/Infrared_detector>
Typical thermopile sensors:
<http://www.smartec.nl/pdf/DSSMTIR990X.PDF>
<http://www.smartec.nl/pdf/SMTIR9902SIL.PDF>
I was getting about 50msec response time. At that speed, a 500 pixel
line would take 25 seconds to scan. A tiny 25Kbit image would take 22
minutes. This is almost tolerable for a tripod mounted thermal
camera, but not for anything hand held.

There was also a major problem with thermal noise. Cryogenic cooling,
using a Peltier junction device, with some manner of lens fog
protection, will be needed.

The idea of forming an image with inexpensive optics and sensors appeals
to me.

Research old technology on "mechanical television". Then, build
something to work in the optical range. Once it's working as a
visible light camera, switch to IR with appropriate lenses and
filters.

--
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

 

[josephkk]

On Sat, 17 Mar 2012 09:27:23 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

Now what do they make lenses out of for that wavelength range?

Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital
cameras do near IR. The ideal material for mid IR is germanium.
However, that's rather expensive.
http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314

Much cheaper are various plastic formulations, that pass IR.
http://www.fresneltech.com/materials.html
http://www.fresneltech.com/materials_graph.html
http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting

For tinkering, the IR motion detectors (PIR) lenses are cheap and
easy:
http://www.glolab.com/pirparts/pirparts.html
http://www.futurlec.com/PIR_Sensors.shtml

There are also a tangle of band pass, low pass, and specialty filters.
http://www.edmundoptics.com/products/browse.cfm?categoryid=41

Or, you can just be weird:
http://amasci.com/amateur/irgoggl.html

Jeff, you are soo off the beaten path.

?-)

 

[josephkk]

On Wed, 28 Mar 2012 09:19:04 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Tue, 27 Mar 2012 21:57:17 -0700, josephkk
joseph_barrett@sbcglobal.net> wrote:

Mid to far as i understand it. I want to look at thermal maps of
electronics that may be too hot to touch thermally or electrically.

I had the same idea and decided that $2,000 and up for commercial
thermal imagers was too much. My idea was to convert either a
supermarket scanner or laser printer rotating mirror imager, into a IR
camera. Basically, it's a "flying spot scanner" and is identical to
what we were using in early weather satellites to generate thermal
images of the planet.

I've built two failed prototypes so far, but plan to continue. The
major problem is the response time of the IR detector. The guts of a
PIR sensor will work, but is depressingly slow.
http://www.futurlec.com/PIR_Sensors.shtml
http://en.wikipedia.org/wiki/Infrared_detector
Typical thermopile sensors:
http://www.smartec.nl/pdf/DSSMTIR990X.PDF
http://www.smartec.nl/pdf/SMTIR9902SIL.PDF
I was getting about 50msec response time. At that speed, a 500 pixel
line would take 25 seconds to scan. A tiny 25Kbit image would take 22
minutes. This is almost tolerable for a tripod mounted thermal
camera, but not for anything hand held.

There was also a major problem with thermal noise. Cryogenic cooling,
using a Peltier junction device, with some manner of lens fog
protection, will be needed.

The idea of forming an image with inexpensive optics and sensors appeals
to me.

Research old technology on "mechanical television". Then, build
something to work in the optical range. Once it's working as a
visible light camera, switch to IR with appropriate lenses and
filters.

I have been thinking along somewhat different lines. Not close to real
working ideas yet.

?-)