You can buy a temperature monitor with a surface probe. The probe itself is small and, in some models, can be taped or glued to the surface. A very small probe would usually be of the thermocouple type

Check out Omega.

thanks they are worth checking into i need the smallest foot print for the shortest time

Depending on the accuracy you need, make sure you choose the right one for your specifications.

Thermocouples are not very accurate unless the control wires are very short and well insulated. They have type J and type K thermocouples so find out about these.

If you need a higher accuracy I suggest you look up the P100 or PT100 types.

They can measure down to 0.01 degree difference. The true value with these is always dependent on how well they have been calibrated. Effectively they only measure the temperature difference so it is all down to the set point accuracy.

However, while the thermocouple can provide a very accurate temperature reading, won't it actually INCREASE the temperature at the location where it is bonded to the surface of the glass, as it will block the infrared radiation coming from the filament? I would think a non-contact infrared thermometer with a narrow field of view perhaps
further limited by a narrow tube which it would look through such that it was pointed towards a portion of the glass and without the filament in the field of view provide a more accurate temperature of the actual glass during operation.

What is the difference in the J and K type thermocouples?

Thanks!

John
Atlanta, Ga.

K-Type Thermocouple

Chromel-Alumel thermocouple with a temperature range of -200 to 1200°C.

J-Type Thermocouple

Iron-constantan thermocouple with a temperature range of 0 to 750°C.

E-Type Thermocouple

Chromel-constantan thermocouple with a temperature range of 0 to 800 °C.

T-Type Thermocouple

Copper-constantan thermocouple with a temperature range of -200 to 400°C.

There must be loads more but I don't know them all.

>There must be loads more but I don't know them all.

check the copgo.com or dataforth.com websites

"There must be loads more but I don't know them all."

Oops ! I guess I'll have to check the time frame of when a thread is a going concern.

Laser thermometers are readily available. They enable a surface temperature to be determined without touching it, at a distance.

Non-contact temperature measurement is based on infrared emission; the laser beam is used only as a 'pointing' device. The is not recommended at all for glass temperature measurement, specially in the case of a lamp bulb. The best manner to do it is using a 'tape thermocouple' as it provides a very fast response, thus the measurement will not be affected by the radiation coming from lamp filament, which may give the probe a higher temperature than the glass itself.

AD590

Very closest yet most practical will be a thermistor sensor +its associated calibrated readout.

If airflow cooling(must cool) is your doubt-then pad the thermistor with a wad of cottonwool locally aroundthe Thermistor -touching the glass shell.

And do not hold these onto the Glass shell longer than essential.--might locally overheat/crack.

good answers you have came up with a lot of help one of these days you will find out why it is so critical for this temp

You might want to turn the bulb off immediately before taking the measurement. The IR from the filament will quickly heat anything as close as the glass surface, giving you an erroneous reading. The glass itself will cool slowly, so if you let the filament cool for a couple seconds, then did a contact measurement of the glass (using a very low mass sensor) you could get quite close. You'd also want to experiment to be sure that the bulb temp has stabilized -- with a clear glass bulb this could take a while.

Apply reflective paint on the area for the probe to reduce radiation?

Reflectivity is more dependant on surface finishing than 'colour' itself when talking about IR spectrum. Colour reflectivity properties are particularly true for visible light spectrum. A metallic finishing shall give the desired effect, some types of metallic tape (aluminum) can play this role; although it will not significantly affect the measurement with a thermocouple for a couple of seconds.

ok you may think that you have a nut on your hands but i created an invention that does what it is supposed to do (15 prototypes and 30 or 40 revs in cad) i discovered a theory as to why it works

the temp of the glass is critical to prove the theory as i have been working on this for 10 years

ken has a good idea that just might work now i have to figure out the setup the bulb is in a kind of difficult place

^{ok you may think that you have a nut on your hands but i created an invention that does what it is supposed to do....}

Well when you put it like that. It does sound like we might have a nut.

cr3

Most lamp manufaturers will be able to give you "isothermal" charts for their bulbs. They've already done the really hard stuff. (We use these to design clearances between plastic moulded parts and the bulbs inside.)

Be careful when using wire junction thermocouples, they provide the average temperature of where the junction is and since only one side will be in contact with the glass, you could end up with "average" of the close air and the glass. (Found this out trying to measure temperature at solid metal surface.)

Also, if the bulb is like an Edison Screw, or bayonet type, there will be substantial differences across the bulb surface. (Near the base cool, near the filament hot)

Would try wire junction thermocouple in a small (clear) epoxy dob on the glass surface. (Epoxy reaches equilibrium with glass surface and completely encloses thermocouple in temperature bath.) Smallest size possible to minimize thermal disturbance of light bulb.

ALSO, photometric laboratory measurement of light usually expects lamps to be "on" for 10 minutes before any readings are taken to allow complete thermal and illumination equilibrium.

Indirect methods have proved erroneous, often providing the temperature of the reflected image rather than the shiny surface. (Measuring molten solder we could get the temperature of the machine cover on the other side.)