How Variable Resistors Find Use in Aircraft Systems

Variable resistors are essential components in many electronic circuits, providing the ability to adjust and control resistance. Serving a simplistic and straightforward role, these devices are commonly found in diverse applications and industries. In this blog, we will specifically focus on the role of variable resistors in aviation operations, highlighting key types and their function in supporting diverse aircraft systems.

Put simply, a variable resistor is a device that deters the flow of current while providing a means to adjust the degree of resistance. Generally, resistance is manually adjusted through the use of a sliding contact or rotating knob. In other cases, the device may be designed to carry out adjustments in response to environmental conditions. In aviation, the ability to fine-tune electrical resistance within a circuit is vital for the reliable operation of critical equipment ranging from avionics to cabin systems.

Among the most commonly used forms of variable resistors in aircraft are potentiometers, rheostats, and thermistors, each serving distinct functions. A potentiometer is simply a three-terminal resistor that functions as an adjustable voltage divider, where control over currents is executed by varying the position of a sliding contact to change resistance. Potentiometers are often used in aircraft for adjusting instrument calibration, controlling audio levels in communication systems, and fine-tuning the operation of numerous forms of avionics equipment. Their ability to provide reliable and repeatable adjustments makes them highly valuable in the complex and demanding environment of modern aircraft where settings must be constantly changed to meet quickly shifting needs.

Rheostats, while similar to potentiometers, only feature two terminals and a sliding contact for adjustment. They are also built to handle high current levels, where current is changed with a wiper instead of voltage. With such features, rheostats are regularly integrated within equipment where significant electrical loads need to be adjusted, such as in lighting systems and heater controls for aircraft. By adjusting the resistance in these circuits, these resistors can vary current flow to manage the brightness of lights or the intensity of heating elements. The ability to manage power distribution with rheostats is crucial for maintaining the optimal performance of these aircraft systems and others, especially during critical phases of flight.

Thermistors are another type of variable resistor that finds common use in aviation, though they operate differently from potentiometers and rheostats. A thermistor is a heat-sensitive resistor whose resistance changes significantly with variations in temperature. There are two main types of thermistors: Negative Temperature Coefficient (NTC) thermistors, where resistance decreases as temperature increases, and Positive Temperature Coefficient (PTC) thermistors, where resistance increases as temperature rises. In aviation, thermistors are widely used in temperature sensing and control applications, such as monitoring engine and battery temperatures, as well as managing environmental controls in a cabin. The accurate response of these devices to temperature changes makes them essential for ensuring the safe operation of aircraft systems under varying environmental conditions.

The use of reliable variable resistors in aircraft systems offers several advantages, such as their ability to fine tune electrical circuits to keep certain systems within very tight tolerances. Another benefit of using variable resistors in aircraft is their role in power management, where devices like rheostats help manage and optimize electrical power distribution for cost savings and performance. Beyond such benefits, having reliable variable resistors can keep aircraft airworthy and dependable throughout flight with functional electrical equipment.

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