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Electrical resistance thermometer range

Aviation Mechanic Airframe (AMA) practice question 14 of 20 on Aircraft Instrument Systems. ACS element AM.II.H.K4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONElectrical resistance thermometers used on aircraft are suited to measuring temperatures in which range?

  1. AHigh only, 0 °C to 1,200 °C
  2. BLow and medium, –70 °C to 150 °C
  3. CVery high, 400 °C to 1,600 °C only
Show the answer and explanation

Correct answer: B. Low and medium, –70 °C to 150 °C

  • A — incorrect That span matches the scale of a turbine exhaust gas temperature indicator, which is a thermocouple system rather than a resistance thermometer.
  • B — correct The handbook states that electrical resistance thermometers measure low and medium temperatures in the –70 °C to 150 °C range, such as carburetor air, oil, and free air temperature.
  • C — incorrect High temperatures of this kind are measured with thermocouples; a resistance bulb is not used in that range.

BACKGROUND

An electrical resistance thermometer consists of an indicating instrument, a temperature-sensitive element or bulb, and the connecting wires and plug connectors. It works because the electrical resistance of most metals increases as their temperature rises. The sensing element is a winding of nickel-manganese wire or a similar alloy in an insulating material, protected by a closed-end metal tube with a threaded hexagonal-head plug. The indicator contains a resistance-measuring circuit, sometimes a modified Wheatstone bridge, and its dial is calibrated in degrees Fahrenheit or Celsius rather than ohms. These thermometers are used widely for carburetor air, oil, and free air temperature in the –70 °C to 150 °C range, while thermocouples handle high temperatures such as cylinder head temperature and exhaust gas temperature.

STUDY TIP

Split temperature instruments into two mental buckets: resistance bulbs for low and medium ranges, thermocouples for high ranges.

KEY POINTS

  • Resistance thermometers cover –70 °C to 150 °C.
  • Metal resistance rises with temperature, and the dial reads degrees, not ohms.
  • Thermocouples, not resistance bulbs, measure cylinder head and exhaust gas temperature.

SOURCES

  • sources/ama-airframe/ch10.txt "Electrical Resistance Thermometer"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.