Which instrument uses resistance change in the oil-temperature bulb to display temperature?

Which instrument uses resistance change in the oil-temperature bulb to display temperature?

• A. Bourdon tube-based gauge
• B. Mechanical dial thermometer
• C. Ratiometer-type oil temperature gauge
• D. Capacitance-type temperature sensor

Answer: (C)

Temperature indicators that rely on an electrical resistance element in the sensing bulb are designed to translate resistance changes into a readable temperature value. In a ratiometer-type oil temperature gauge, the oil-temperature bulb acts as a resistor whose value changes with temperature. This bulb forms part of a bridge circuit; as oil temperature rises or falls, the bulb’s resistance shifts, unbalancing the bridge and moving the indicator needle to show the corresponding oil temperature. The other instruments use different physical principles—pressure for the Bourdon-style gauge, expansion of a liquid or metal for the mechanical dial thermometer, or capacitance changes for the capacitance sensor—so they don’t base the display on resistance changes in the oil-temperature bulb.

Temperature indicators that rely on an electrical resistance element in the sensing bulb are designed to translate resistance changes into a readable temperature value. In a ratiometer-type oil temperature gauge, the oil-temperature bulb acts as a resistor whose value changes with temperature. This bulb forms part of a bridge circuit; as oil temperature rises or falls, the bulb’s resistance shifts, unbalancing the bridge and moving the indicator needle to show the corresponding oil temperature. The other instruments use different physical principles—pressure for the Bourdon-style gauge, expansion of a liquid or metal for the mechanical dial thermometer, or capacitance changes for the capacitance sensor—so they don’t base the display on resistance changes in the oil-temperature bulb.