High-temperature non-contact thermometry: if the operating range must span approximately 800 to 1600 °C, which pyrometer type is typically selected?

Introduction / Context:
At elevated temperatures beyond the safe range of contact sensors, non-contact pyrometers are used. Selecting the right type depends on target temperature, emissivity, and sighting conditions. The classic optical (disappearing-filament) pyrometer is well established in the 700–3000 °C region.

Given Data / Assumptions:

• Required span: ~800 to 1600 °C.
• Target is hot, glowing surfaces suitable for visual/optical sighting.

Concept / Approach:
Optical pyrometers compare the brightness of a heated filament to the target’s brightness at a specific wavelength. They are effective from about 700 °C upward, covering 800–1600 °C comfortably. While “radiation pyrometer” is a broader category including optical and total radiation devices, the classic textbook answer for this span is the optical (disappearing-filament) instrument. Photoelectric ratio pyrometers also cover high temperatures and mitigate emissivity effects but are usually described explicitly as “ratio” units; the stem points to the general selection where optical pyrometers are archetypal.

Step-by-Step Solution:
Identify temperature window above 700 °C.Map to non-contact instruments: optical pyrometer fits 800–1600 °C.Choose the specific type named in the options.

Verification / Alternative check:
Catalogs and handbooks show optical pyrometers widely specified for steels and furnaces in this temperature band.

Why Other Options Are Wrong:
Radiation (total): Broad term; answer seeks the specific well-known instrument.Photoelectric: Also plausible, but the conventional selection for the stated band is optical (disappearing-filament).None/Resistance thermometer: Contact RTDs do not reach 1600 °C safely.

Common Pitfalls:
Ignoring emissivity and window transmission; in real practice, ratio pyrometers may be preferred for variable emissivity, but the core knowledge item is the optical pyrometer’s range.

Final Answer:
Optical (disappearing-filament) pyrometer