Usable temperature range of copper resistance thermometers (RTDs): Select the typical operating range for a copper resistance thermometer in industrial service.

Introduction / Context:Resistance temperature detectors (RTDs) use the temperature dependence of metal resistivity. Copper, platinum, and nickel are common sensing materials. Choosing a sensor requires matching its linearity and stability to the expected temperature window. This question asks for the typical range of a copper RTD.

Given Data / Assumptions:

• Copper offers good sensitivity and linearity at low to moderate temperatures.
• Oxidation and material stability limit the upper range compared with platinum.
• We focus on commonly accepted industrial ranges rather than absolute extremes under laboratory conditions.

Concept / Approach:Copper RTDs are widely used from cryogenic service up to roughly 150–200 °C, beyond which oxidation and drift degrade accuracy and life. Therefore, a representative range of −200 to 150 °C is often cited in textbooks and specifications for copper elements in process applications, distinguishing them from platinum RTDs that reach higher temperatures with better long-term stability.

Step-by-Step Solution:

Verification / Alternative check:Vendor catalogs list copper RTD assemblies targeting HVAC, cryogenic, and moderate-temperature duties with upper limits around 150–200 °C depending on sheath and atmosphere.

Why Other Options Are Wrong:

• 0 to 150 °C: Omits valid sub-zero usage.
• 350–750 °C and 500–900 °C: Far above copper’s practical stable range; platinum is preferred there.
• −50 to 50 °C: Too narrow for typical copper RTD capability.

Common Pitfalls:Assuming all RTDs can reach high temperatures; material selection matters for stability as well as range.

Final Answer:-200 to 150 °C