Willem Einthoven

Willem Einthoven built the string galvanometer in the early 1900s, a fine silver-coated quartz thread in a magnetic field sensitive enough to record the heart's tiny electrical signals. His machine weighed about 270 kilograms and needed five people to operate, but it gave medicine the electrocardiogram and the P, Q, R, S and T labels still used. He received the Nobel prize in 1924.