Obscure Electrical Components You've Probably Never Heard Of

Introduction

As an electrical engineer, I often come across obscure and little-known electrical components that most people have never heard of before. In this article, I will discuss some of the more unusual and specialized electrical components that even experienced engineers may not be familiar with. Understanding the function and application of these lesser-known devices can greatly expand an engineer's knowledge and capabilities when designing electronic systems and circuits.

Flux Gate Magnetometers

A flux gate magnetometer is a sensor that is used to measure magnetic field strength. The operation of a flux gate magnetometer relies on a ferromagnetic core that is cyclically driven to saturation by an alternating electrical current. Any external magnetic field that interacts with this alternating field in the core induces a voltage in a sensing coil. By analyzing this induced voltage, the flux gate magnetometer can precisely measure the external magnetic field strength.

Flux gate magnetometers are extremely sensitive devices capable of measuring magnetic fields in the picotesla range. Their key advantages are high sensitivity, small size, and low power consumption. Applications for flux gate magnetometers include spacecraft systems, measuring geomagnetic fields, unexploded ordnance detection, and materials testing.

Magnetic Amplifiers

A magnetic amplifier is a specialized transformer that uses magnetic saturation of its core to regulate current flow. It operates similarly to a transistor, controlling the output current flowing through its secondary coil by varying the direct current flowing in its control windings. This control action occurs without any moving parts.

Magnetic amplifiers were commonly used as control elements in early electronics systems before the invention of semiconductor-based amplifiers. They have some advantages over tube amplifiers, such as reliability, robustness, and the ability to directly control strong currents and high voltages. Modern applications of magnetic amplifiers include arc welding control, battery charging, and audio amplification.

Saturable Reactor

A saturable reactor is a magnetic device that uses a coil wound on a ferromagnetic core. A direct current in the control winding drives the core in and out of magnetic saturation. This saturation affects the impedance that the main coil windings encounter. Therefore, a saturable reactor can function like a variable inductor or a magnetic amplifier for controlling alternating currents.

Saturable reactors are employed for managing voltage, current, and power in electric utility transmission networks. They can regulate transmission line voltage, limit short circuit currents, and damp system oscillations. Saturable reactors offer benefits over transistor and vacuum tube controllers due to their simplicity and ability to directly influence high power flows.

Selenium Rectifiers

Selenium rectifiers are metal rectifiers that use selenium as their semiconductor material rather than common materials like silicon or germanium. Selenium has some advantages for power rectification, such as low mass, high dielectric strength, and resistance to radiation damage.

Prior to silicon rectifiers, selenium rectifiers were frequently used in early AC/DC power supplies to convert alternating current to direct current. They were instrumental in the early development of television technology. Modern applications of selenium rectifiers are limited due to their relatively high power losses and slow switching speeds. But they still may be used in high voltage DC power supplies and extreme environment applications.

Unijunction Transistors (UJT)

An unusual type of bipolar junction transistor is the unijunction transistor, or UJT. Unlike regular BJTs, the UJT contains only one p-n junction between its emitter and base regions. It relies on a heavily doped n-type bar of semiconductor for its operation.

The unique characteristics of UJTs make them well-suited for relaxation oscillator circuits and pulse generators. They can provide a low-cost asynchronous triggering element with only a few external components needed. UJTs were historically used in various timing and firing circuits, but other semiconductor devices have mostly replaced them in commercial applications. They are still occasionally found in hobbyist projects and basic electronic training.

Gas-Filled Tubes

Gas-filled tubes encompass a diverse array of vacuum tubes filled with ionizable gas. This category includes thyratrons, trigger tubes, vapor rectifiers, voltage regulator tubes, and early light sources like neon lamps. The gas filling provides specialized operating properties and capabilities compared to high-vacuum tubes.

For example, thyratrons can switch high voltages and currents very quickly in radar modulators and pulsed power applications. Voltage regulator tubes maintain a steady voltage across power transmission lines. While gas tubes have been superseded in most roles by solid-state electronics, they still find uses in some niche applications. The large plasma displays commonly used for public signage are evolved gas-filled tubes.

Magnetic Drum Memory

Magnetic drum memory was an early form of computer memory that stored data on the magnetized surface of a rotating metal cylinder. The drum's surface was divided into discrete tracks, with each track holding a collection of magnetic domains that encoded ones and zeros. Read/write heads interfaced the drum storage with the computer processing circuits. Drums were capable of holding sizable amounts of data for their time while providing relatively fast random access speeds.

Magnetic drums served as main working memory for computers during the 1950s and into the 1960s. Their capacity and speed substantially improved on earlier technologies like delay line memory and Williams tubes. Magnetic drum memory was instrumental in early digital computing development, but was eventually fully replaced by magnetic core memory and other technologies. Drums persisted as storage peripherals into the 1970s before also being superseded by magnetic disks and tapes.

Conclusion

Even for electrical engineers, some of these components like flux gate magnetometers and saturable reactors are quite specialized and unknown to most. But investigating the unique properties and functions of devices like these can expand an engineer's expertise and lead to new ideas or applications. In a field as broad as electrical engineering, there are always new lesser-known components and technologies still being developed. Staying curious and delving into these unexplored areas is key for continued learning.