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How to test upper limit on IR thermometer?

G

Gone Fishin'

Jan 1, 1970
0
I have a cheap IR thermometer (pistol grip kind) that says upper limit is
500f. I'd like to read temps in the range of 600-700 with not great accuracy
(+/- 5 or even 10 deg would be fine).

What can I point it at that is a relatively known temperature in this range?

(Hoping the upper limit isn't in the firmware...)

Thanks.
 
G

GregS

Jan 1, 1970
0
An ordinary incandescent light bulb with a dimmer switch, glowing
almost red in the dark (not toaster orange or yellow) or an electric
stove top hotplate.
http://en.wikipedia.org/wiki/Color_temperature
You'll need to convert from kelvin to Fahrenheit to read the chart.

Get a large soldering iron tip on a temperature controlled iron.
Use that. Get close.

greg
 
R

Rich Grise

Jan 1, 1970
0
Paper bursts into flame spontaneously at about 451degF.

Did you get this from the movie, or the book? ;-P

Cheers!
Rich
 
D

Don Klipstein

Jan 1, 1970
0
An ordinary incandescent light bulb with a dimmer switch, glowing
almost red in the dark (not toaster orange or yellow) or an electric
stove top hotplate.
http://en.wikipedia.org/wiki/Color_temperature
You'll need to convert from kelvin to Fahrenheit to read the chart.

A couple things:

1. The wavelengths used do not pass through glass and largely do not pass
through quartz.

2. IR non-contact have a minimum source size requirement to read
accurately. Objects less than 10-15 mm wide may not come up accurately.

However, an electric hot plate should push an IR non-contact thermometer
past reading 500 F, since they get to about 1400-1500 F.

- Don Klipstein ([email protected])
 
S

spamme0

Jan 1, 1970
0
Gone said:
I have a cheap IR thermometer (pistol grip kind) that says upper limit is
500f. I'd like to read temps in the range of 600-700 with not great accuracy
(+/- 5 or even 10 deg would be fine).

What can I point it at that is a relatively known temperature in this range?

(Hoping the upper limit isn't in the firmware...)

Thanks.
You can test the firmware limit by pointing at a stovetop electric element.
 
D

Don Klipstein

Jan 1, 1970
0
Oh right, I'll remember to put your hand next to a light bulb, I'll wear
a glove.


Oh right, I'll remember quartz halogen bulbs don't get hot and call
the men in white coats to change your headlights.

The radiant heat you feel from lightbulbs consists of two parts:

1. The portion from the filament - entirely (or nearly enough so) of
wavelengths too short to be in the range of an IR thermometer,
because the bulb material is opaque (or nearly enough so) to them.

2. The portion radiated by the bulb material - which is what an IR
thermometer will sense.

- Don Klipstein ([email protected])
 
L

life imitates life

Jan 1, 1970
0
I have a cheap IR thermometer (pistol grip kind) that says upper limit is
500f. I'd like to read temps in the range of 600-700 with not great accuracy
(+/- 5 or even 10 deg would be fine).

What can I point it at that is a relatively known temperature in this range?

(Hoping the upper limit isn't in the firmware...)

Thanks.

The unit will usually switch to "off scale" indicator of some kind.
With a voltmeter, it is like "OV" for overvoltage. OT would be over temp,
but not all that intuitive, so it would probably flash off scale or
something.

The way you check it is by finding someone with, or renting an IR
thermometer that will read that high, take a reading, and see what your
meter does at the same time. A high temp thermocouple will get you in
the ball park as well.

I doubt it will continue to display much over (or under) its calibrated
range. Since they do not guarantee calibration and damage can even occur
to a resistor bolometer (likely is that), they usually switch the display
to an error message.
 
M

Mycelium

Jan 1, 1970
0
A couple things:

1. The wavelengths used do not pass through glass and largely do not pass
through quartz.

2. IR non-contact have a minimum source size requirement to read
accurately. Objects less than 10-15 mm wide may not come up accurately.

There are spot focused units available. The chiropracty <sp>
profession uses (years ago) them to examine spinal column temps on a one
inch focus unit, calibrated from ice to just over human body temperature,
about 30° to 120° F. It has a cone shaped nose, and about a half inch
opening, and usually has a little arm with a rolling ball on the end that
is used to maintain a one inch distance from a surface (like flesh or a
vertebral 'high spot').
However, an electric hot plate should push an IR non-contact thermometer
past reading 500 F, since they get to about 1400-1500 F.

Depends. If it is a coil shaped heater, just like on a stove, then
yes. If it is a "pan" or inverted pan, which is heated from beneath (by
a coil shaped heater), it usually passes through a heat spreader of sorts
between the heater and the pan. This makes for a much more uniform
temperature, but it would also be a bit lower. They usually do not get
to the "red hot" temp., so... what... maybe 1000° F? Better to check it
with a higher range device.

A nice, hot teflon skillet is pretty damned evenly heated right after it
comes of the stove (not the sides).

Pretty weird how the bottom does not radiate much heat toward your
cheek, but the teflon side does... a lot. Pretty good lesson in
emissivity.
 
M

Mycelium

Jan 1, 1970
0
Lead melts at 327.5 °C (that's 621.5 °F for Imperials).

Tom Davidson
Richmond, VA

Solder, which is what most electronics industry soldering irons melt,
melts at right around 500° F (for 63/37).

The soldering iron is pretty good. The calibrate a tip temp, one has an
iron which is a bit hotter, so if it says 700°, the actual heating
element is likely a couple tens of degrees hotter. The tip taper is the
reason.

That is why I like Metcal. They sense the temp when you soak away heat
during an operation, and they fire it right back up within a second or
two. Five seconds on power up. Two second basic recovery.
 
F

Fester Bestertester

Jan 1, 1970
0
More important, what temperature destroys the sensor?

These are *non-contact* sensors. How can pointing it at an IR source from a
distance damage it?
 
In sci.physics Fester Bestertester said:
These are *non-contact* sensors. How can pointing it at an IR source from a
distance damage it?

It is going to depend on the sensor.

Eyeballs are non-contact sensors, try staring at the sun.
 
R

Rich Grise

Jan 1, 1970
0
It is going to depend on the sensor.

Eyeballs are non-contact sensors, try staring at the sun.

Your eyeballs have lenses, which focus the light/radiation onto a very
small spot on the retina - haven't you ever lit a piece of paper (or
ants!) on fire using a magnifying glass?

Do IR pyrometers have that kind of focus?

Thanks,
Rich
 
In sci.physics Rich Grise said:
Your eyeballs have lenses, which focus the light/radiation onto a very
small spot on the retina - haven't you ever lit a piece of paper (or
ants!) on fire using a magnifying glass?

Do IR pyrometers have that kind of focus?

Thanks,
Rich

Like I said, it depends.

Most instruments have a lens system.

http://www.wintron.com/infrared/irproducts.htm

http://www.processsensorsir.com/index.html?gclid=CKX75NDyo5wCFSYoawodR1iUjw

http://www.thermoworks.com/products/ir/index.html?gclid=COr66NLyo5wCFRxNagodJj2Sjw
 
G

Gone Fishin'

Jan 1, 1970
0
The unit will usually switch to "off scale" indicator of some kind.
With a voltmeter, it is like "OV" for overvoltage. OT would be over temp,
but not all that intuitive, so it would probably flash off scale or
something.

You win the booby prize ("You may now choose your booby."). The display says
"OL" when the stovetop coil exceeds 500f.

So the limitation is in firmware. Damn!

Thanks for all who contributed.
 
D

DarkSucker

Jan 1, 1970
0
These are *non-contact* sensors. How can pointing it at an IR source from a
distance damage it?

The resistor bolometer has limits to what IR it can be exposed to.

Did you even read the instructions?

There IS "contact". It is just that some of you are too stupid to get
the fact that light also has the potential to move matter.

It is a hard to miss fact for some of us. For some of you, however,
setting your alarm clock poses difficulties.

Yes, LIGHT IMPINGES on the sensor, idiot.
 
M

Mycelium

Jan 1, 1970
0
Your eyeballs have lenses, which focus the light/radiation onto a very
small spot on the retina - haven't you ever lit a piece of paper (or
ants!) on fire using a magnifying glass?

Do IR pyrometers have that kind of focus?

Thanks,
Rich

Pure optics. Take the field of view. Say you are looking at a 6 inch
spot.

That spot is focused down to what is typically a 2 mm resistor
bolometer sense element. It usually sits a couple mm down in the
"transistor can" under a germanium window or other such IR window media.

That 2mm spot has the entire "image" cast upon it. It is exactly like
when you put a pinhole in a box and look at the sun on the back wall of
the box. That image of the sun is a perfect casting of the actual image.

Same with IR. Instead of a CCD of whatever size like with video, the
resistor bolometer is only 2 mm square.

Just do not point your IR meter toward the sun. It will fry the sense
element.
 
M

Mycelium

Jan 1, 1970
0
Like I said, it depends.

Most instruments have a lens system.

Actually, the best instruments go straight from the primary mirror to
the sense element.

IR video has a lens system, and cheap IR has a fresnel <sp>, but most
radiate directly onto the sensor.

Most are set up like a reflector telescope.

Lens systems cut energy, raising the noise floor.
 
L

life imitates life

Jan 1, 1970
0
You win the booby prize ("You may now choose your booby."). The display says
"OL" when the stovetop coil exceeds 500f.

So the limitation is in firmware. Damn!

Thanks for all who contributed.


Better not tell anyone here. It will ruin their claims that I am never
correct. Won't be the first time.

If you want to know who to filter, just filter all of the idiots that
mouth off at this post.
 
M

Mycelium

Jan 1, 1970
0
I noticed you snipped all the links showing IR pyrometers with lenses.

I notice that you snipped where I mentioned that lenses ATTENUATE the
signal!

I did make an entire line of high temp devices that used a Pyrex lens.
They get placed in a cooled jacket, and get put right on a glass gob line
looking at blazing hot molten glass gobs.

A single parabolic mirror yields the absolute best image on the sense
element. The ultimate mirror is gold. All first surface, of course.

Usually, a thin film is over the tube as a dust shield.

____
(____·<<<< The bolometer is at the end of the tube.
^
The mirror goes at the rear of the tube.
____ <<<<<<<<<<
(____·<<<<<<<<<< IR energy goes in here.
<<<<<<<<<<

The focus and field of view is determined by the tube length and
diameter, and the mirror focal length. The bolometer gets placed at the
focal point of the mirror. Exactly like a telescope.

Are there any lenses on the Hubble Space Telescope's primary light
gathering system?

I rest my case.
 
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