Four thermographic phosphors, QMK24/N-C7, QMK66/F-A1, MK24/F-X and EQD25/F-U1, were applied to brass substrates using an inorganic Ceramabind 643-2 binder. A thin brush coating and a syringe-applied coating were compared. The samples were spectrally characterized under 405 nm and 365 nm excitation and tested in an automated dual-channel phosphor-thermometry system with detection near 635 nm and 660 nm. Only QMK24/N-C7 and EQD25/F-U1 provided a sufficient signalto-noise ratio for stable exponential fitting at several temperatures. Values digitized from the recorded plots indicate sensitivities from −15, 6 to −20, 1 µs/ ◦C for QMK24/N-C7 and from −7, 8 to −8, 4 µs/ ◦C for EQD25/FU1. QMK24/N-C7 was nominally more sensitive, while EQD25/F-U1 produced higher SNR and therefore more repeatable temperature characteristics. The results show that spectral matching, coating thickness and coating homogeneity must be considered together when selecting a phosphor for a practical measurement system.
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