High-temperature measurement capability: which of the following instruments cannot measure a temperature as high as about 1600 °C under normal usage?

Introduction / Context:
Instrument selection depends strongly on the temperature range. Industrial measurements around 1600 °C are encountered in furnaces, kilns, and metallurgical processes. Not all sensors can survive or give reliable readings at such extremes.

Given Data / Assumptions:

• The target temperature is approximately 1600 °C.
• We compare common sensors: resistance thermometers, thermocouples, and non-contact pyrometers.
• Normal usage and materials limits apply.

Concept / Approach:
Platinum resistance thermometers (PRTs) are highly accurate but limited typically to about 650–850 °C for standard designs; specialized versions may extend somewhat higher but far below 1600 °C. Thermocouples (e.g., Type B, R, S, or W-Re) and radiation or photoelectric pyrometers are designed for very high temperatures and can cover 1600 °C and beyond without contacting the process directly (for pyrometers) or with high-temperature thermocouple alloys.

Step-by-Step Solution:
Identify PRT operating envelope: usually ≤ 850 °C.Identify high-T options: noble-metal thermocouples and non-contact pyrometers.Compare with the target: 1600 °C exceeds PRT capability.Conclude that PRT cannot measure 1600 °C under normal practice.

Verification / Alternative check:
Manufacturer datasheets and standards (ITS-90 implementation) specify PRT ranges well below 1600 °C, whereas high-temperature thermocouples and pyrometers explicitly cover this domain.

Why Other Options Are Wrong:
Thermocouple (Type B/R/S or W-Re): Suitable for ≥ 1600 °C.Photo-electric/radiation/two-color pyrometers: Non-contact optical methods designed for high-temperature targets.

Common Pitfalls:
Assuming PRTs are “best” at all temperatures due to accuracy; accuracy does not imply suitability beyond material limits. Also, confusing emissivity adjustments required for pyrometers with a limitation on maximum temperature.

Final Answer:
Platinum resistance thermometer