https://www.30mhz.com/sensor/pointed-temperature-sensor/

Check digikey.ca for your specs

By using thermocouple and also with the help of induction heating measurement and calibration method

Thanks Farid for the link. Proper selection of device in monitoring temperature during electromagnetic heating (RF heating) is significant. The electromagnetic signal can interfere the readings of some measurement device. For example, thermocouple is susceptible to RF energy, and thus, its reading is not accurate. However, there are alternative device which can measure temperature under during RF heating using IR and Resistance dependent device. They cannot be altered by electromagnetic energy.

I would explore a so-called "time division multiplexing" approach. In this approach, the RF heating signal is at regularly spaced intervals, like 20 times per second, switched OFF, and then "radiometer" circuitry is, during the RF OFF interval, switched ON. Suitably designed and calibrated, the radiometer circuitry can estimate the physical temperature of the specimin on the basis of the "noise temperature" of the RF thermal radiation it emits. Radiometer circuits which compare the "unknown" temperature to the known temperature of a reference target can achieve accuracies approaching a degree or so. A further nice feature of this approach is that some of the bigger components, like the "antenna array" used for the heating function, then do double duty in the temperature sensing function. ("Radiometer" can be googled, of course.)

Use fiber thermocouples for accurate measurements

Why not to use infrared probes to detect a temperature for this case? Or methods with photo of heated object in infrared.

Given that graphene is IR transparent, yet highly conductive, it should provide a workable window for most any Faraday cage.

Article Infrared–transparent Films Based on Conductive Graphene Netw...

I just skimmed the article but I think this may work as a window too, unless the substate blocks IR...

https://www.chemistryworld.com/news/loudspeakers-in-your-window/3002353.article

Article Flexible and transparent graphene films as acoustic actuator...

Then all you would need is a... https://www.fishersci.com/shop/products/fisher-scientific-traceable-noncontact-infrared-thermometers-3/p-203736

I am not 100% on this. However, I believe it is worth some experimentation.

All Negative criticism greatly appreciated.

Hi

I think use of fiber-optic temperature sensor is proper. but this is so expensive.

Hi Roland,

A good old optical pyrometer would also do the trick. Try and give me news!