Cathode ray professional#

To experimenters back then, uses other than light bulbs suggested themselves. In manufacture, it was not difficult to pass metal conductors into the bulb, the molten glass making an airtight seal around them. Back then, glass blowing was already a highly developed art and vacuum pumps were on the scene. It was obvious to Thomas Edison and his many technicians in the mid-19th century that a glass light bulb must have virtually all oxygen removed to keep the current-carrying filament from burning up. A good tube has a leakage current in the range of 50-100 μA after a few minutes warming up.ĬRT technology has its roots in the incandescent light bulb.

This makes the grid negative with respect to the cathode, thus giving rise to the grid-cathode leakage current. Because the control grid sits near the cathode, accelerated electrons can reach it. This creates an electron cloud around the cathode. When the cathode heats up, the heating expels electrons from the cathode surface. Only the CRT filament should be energized. With a microammeter connected to the grid and the cathode pins, this voltage causes a grid-cathode leakage current. You supply the filament with the nominal voltage, and a little cathode-control grid voltage appears. One last test checks out the cathode emission. Burns in the fluorescent surface are permanent and look brown. Assuming the phosphor screen lights up, the screen must not have any spots or failures in the phosphor. You should see a resistance of about 2 to 6 Ω. It must show continuity when tested with an ohmmeter. If they are all white, air is in the tube and it is unusable. They should look silvered, shining or a little darkened. They indicate the state of the tube’s vacuum. Nevertheless, there are a few simple tests that can reveal whether a CRT is at least functional and worth additional effort.įirst, there are one or more circular spots in the tube neck, usually near to the base pins that are created when the CRT is manufactured. Tube-based monitors and TVs can be thoroughly wrung out through the application of test patterns specially constructed for that purpose.īecause CRTs today are mainly for niche needs, tube testers generally can be found used on eBay and perhaps from suppliers of special instruments. This display is from Thomas Electronics, Clyde, N.Y.Ī complete test of a CRT takes a relatively long time and requires a tube tester or a specially built circuit which supplies the many voltages and signals necessary for the CRT.

A modern-day CRT display for a military application. Also, a few perfectionist video gamers still rave about the picture quality of video games displayed on high-end CRTs that are now available on eBay for a song. One consumer application that still requires CRTs is that of monitors for arcade games. General-purpose CRTs are no longer manufactured in the U.S., but factories in China and India still make them - for use in TVs, not computer monitors. For example, some kinds of military needs still require a CRT display. CRTs have largely been replaced by flat-screen technologies but CRTs still serve in niche applications.

Cathode ray professional#

Scholarly yet accessible to those with basic physics knowledge, this book should be of interest to historians of science, professional scientists and engineers, teachers and students of physics, and general readers interested in the development of modern physics.The cathode ray tube (CRT) is what made possible TVs, computer monitors, and oscilloscopes as we know them. The author also focuses on the controversies over N-rays, Becquerel's positive electron, and the famous Ehrenhaft-Millikan dispute over subelectrons.

It explores the events leading to Millikan's unambiguous isolation of the electron and the simultaneous circumstances surrounding the birth of Ernest Rutherford's nuclear atom and the discovery of radioactivity in 1896. It also provides an overview of the history of modern physics up to the advent of the old quantum theory around 1920.Ĭonsolidating scholarly material while incorporating new material discovered by the well-respected author, the book covers the continental and English race for the source of the cathode rays, culminating in Thomson's corpuscle in 1897. The book traces the evolution of the concept of electrical charge, from the earliest glow discharge studies to the final cathode ray and oil drop experiments of J.J. Thomson's Electron presents the compelling story of the discovery of the electron and its role as the first subatomic particle in nature. Flash of the Cathode Rays: A History of J.J. The electron is fundamental to almost all aspects of modern life, controlling the behavior of atoms and how they bind together to form gases, liquids, and solids.