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

One of the unsolved problems I still have is measuring temperature in furnace at $$700-1100^\circ\mathrm{C}$$ range (I need some $$\pm0.1\%$$ repeatability and $$\pm1\%$$ 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 $$~400^\circ\mathrm{C}$$.

I've checked blackbody emission for $$700-1100^\circ\mathrm{C}$$ objects, and it seems that even at $$500^\circ\mathrm{C}$$ objects start to emit at $$1\,\mu\text{m}$$ range (not much though), which is easily measurable by cheap silicon photo-diodes (ones I have on the desk have maximum at $$880\ \mathrm{nm}$$, with $$70\%$$ sensitivity at 1um and $$10\%$$ at $$1.1\ \mu\text{m}$$, 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 $$\mathrm{PbS}$$ photoresistor ($$2.1\,\mu\text{m}$$ maximum), but they are not that precise, quite expensive and scarce. What are your thoughts or suggestions?

• I got it a surplus for 35$. There out there. Jul 7, 2011 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 ) Jul 7, 2011 at 6:54 • The TJ36-CAXL-316U-6-CC-XCIB is a ceramic insulated type K probe it will do the job for$51 Jul 7, 2011 at 19:20