An introduction to the OSCILLOSCOPE and its uses Colin G4GBP

My oscilloscope is a Leader 1021

How does it work? The core component of an oscilloscope of this kind is the ‘TUBE’. This is a ‘thermionic’ device and is really a modified ‘thermionic valve’ (valve). The simplest valve is a diode (di=two ode=electrode). A diode has two electrodes – an anode and a cathode.

The diode The heater element glows red (typically 650⁰C) and heats the cathode. The cathode has coating that when heated readily gives off electrons. The anode is positively charged and attracts the electrons. An electric current therefore flows between the cathode and the anode

Triode Triode – three electrodes: As with the diode, the Heater heats the cathode. The electrons flow towards the positive anode but the Negatively charged GRID Controls the number of electrons reaching the anode.

Oscilloscope tube Looks like this:

Oscilloscope tube The heater heats. The cathode emits. The ‘Intensity’ controls The number of electrons that are attracted to the anode. The anode has a hole in it so that a BEAM of electrons can hit the back of the glass tube face. This is coated with a special phosphor layer and lights only where electrons strike it.

Oscilloscope tube The spot of light is moved by applying voltages to the Horizontal and Vertical deflection plates. Positive voltages will attract the beam, negative voltages will repel the beam. Thus The beam is ‘steerable’.

Oscilloscope block diagram