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Electromagnetic oscillograph
Encyclopedia
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Oscillograph
An oscillograph is an instrument for measuring alternating or varying electric current in terms of current and voltage. There are two instruments that are in common use today:*Electromagnetic oscillograph*Cathode-ray oscilloscope...
which measures variations of electric current by having it go through a magnetic coil. Variations in current induce momentum in the coil, which can be directly measured.
The electromagnetic oscillograph was invented by William Duddell
William Duddell
William Du Bois Duddell was a British electro-physicist and electrical engineer. He was privately educated in the UK and France and rose quickly through the prestigious City & Guilds Schools via scholarships...
.
Some models utilise a mirror which reflects a beam of light, allowing measurement of minute movements of the coil. Other were fitted with a hand, possibly fitted with a pen to record values.