# Will this poor-man's single band pyrometer work?

One of the unsolved problems I still have is measuring temperature in furnace at 700-1100C range (I need some +-0.1% repeatability and +-1% precision).

Obviously, contact thermometers are quite rare & expensive for this range, everything I was able to find is rated at 450-500C max (especially as this should work in aggressive oxygen/ozone/chlorine atmosphere).

Consumer grade pyrometers does not work above ~400C.

I've checked blackbody emission for 700-1100C objects, and it seems that even at 500C objects start to emit at 1um range (not much though), which is easily measurable by cheap silicon photo-diodes (ones I have on the desk have maximum at 880nm, with 70% sensitivity at 1um and 10% at 1.1um, visible light filtered).

As my target is always the same with fixed emissivity, there should be no vital need for 2-band measurement.

Are there any issues with this single-band temperature measurement approach? Alternatively, I might add PbS photoresistor (2.1um maximum), but they are not that precise, quite expensive and scarce. What are your thoughts or suggestions?

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this one goes up to 1000C: technodepot.com/product/view/product/… –  user2963 Jul 18 '11 at 16:34

I got it a surplus for 35$. There out there. – Fortunato Jul 7 '11 at 1:22 As far as I see, it require separate RTD probe which at these temperatures have to be made out of quartz & platinum, and this is the main problem ) – BarsMonster Jul 7 '11 at 6:54 The TJ36-CAXL-316U-6-CC-XCIB is a ceramic insulated type K probe it will do the job for$51 –  Fortunato Jul 7 '11 at 19:20