Very near the cathode is an open wire mesh called the grid (G). The screen glows at the point of impact of the electrons. The beam passes through the cylindrical anode into an essentially field-free region where, some 20 cm away, it strikes a fluorescent screen. Proper design and adjustment of the current flowing through these coils results in a narrow, well-focused beam of electrons. In the region on either side of the anode are coils of wire which surround the electron stream. The anode attracts the electrons which accelerate across the space between the cathode and anode, acquiring a high velocity - about 10 7 cm/s. Some 5 cm from the cathode is a positive anode (A 2) maintained at about +500 V potential. These electrons form a cloud around the cathode much like the cloud of water vapor over a heated pan of water. This surface, called the cathode (K), emits large numbers of electrons when heated. Quite near the filament is a special metal oxide surface which is in turn heated by the filament. At the base (back of the instrument case) of this tube is a small wire filament (F) which is heated to high temperature when an electric current flows through it. The nucleus of the oscilloscope is the Cathode Ray Tube (CRT) - a vacuum tube some 30 cm long which you can see in the center of the instrument. When you have completed this laboratory exercise, you should be able to: (1) describe the basic components of an oscilloscope and explain the function of each (2) use an oscilloscope to measure time intervals and potential differences (3) use an oscilloscope to display periodic voltage waveforms (4) use a dual trace oscilloscope to measure phase differences between two signals. In this lab, we will not only be concerned about the shape of some electrical waveforms, but we will also make measurements with this instrument of the frequency, period, and voltage amplitude of electrical signals of an AC nature. A fundamental element of this lab is becoming familiar with this instrument and how to use it in making measurements in a variety of situations.īecause the CRO is primarily a visual display instrument, able to display the waveform of virtually any kind of electrical signal, it is usually employed in situations where the waveform is of some interest, often with some kind of AC circuit. The CRO is the heart of the auto engine analyzer and the patient monitor in a hospital intensive care ward. The device is readily at hand in every electronics shop, every radio and TV station's engineering department, and every physics, chemistry, and engineering research laboratory. They developed, manufactured and distributed valves, radios, telecommunications, televisions, audio equipment and broadcasting services.The cathode ray oscilloscope (CRO) is one of the most versatile instruments available in a modern laboratory. Throughout the 20th century AWA was Australia’s largest electronic organisation. In 1913, following a patent enforcement lawsuit, they formed a new company, Amalgamated Wireless Australia Ltd, with exclusive rights throughout Australasia to patents ‘present and future’ of both Marconi and Telefunken. This item was made by Amalgamated Wireless Australia, a company which began in 1901 as a wireless agent for Telefunken, a German radio apparatus company. This means that the user can only observe qualitative information about the waveform, unless it is calibrated using an external oscillator. ![]() The controls of this oscilloscope do not have any calibrated scales. Instead, all connections are made through soldered wires, which was typical of its time. This model has been constructed completely from vacuum tube technology and predates the use of printed circuit boards. When the electron beam is repetitively swept from side to side by a sawtooth ‘timebase’ voltage, the dot traces out a graph of the voltage as a function of time. The dot can be moved up or down the screen by applying a voltage to the horizontal plates. The beam is then directed onto the phosphor screen at the end of the tube where a glowing dot is formed. These electrons are accelerated and focused into a narrow beam which passes through two pairs of parallel plates, one horizontal and one vertical. The cathode ray tube contains a cathode which is heated and emits electrons. The oscilloscope has a bandwidth of 30c/s to 12 kc/s. Horizontal and vertical shift controls vary the voltages on the deflection plates to shift the display on the screen. It has two amplifiers, one vertical and one horizontal, and adjustable focus and intensity controls for the electron beam. ![]() It has a very small display screen, a little over 5 cm in diameter. This item is an Australian made cathode ray oscilloscope (CRO), dating from around 1950.
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