Ell Ell An ell (from Proto-Germanic *"alinō", cognate with Latin "ulna") is a unit of measurement, originally a cubit, i.e., approximating the length of a man's arm from the elbow ("" literally meant the bend ("bow") of the arm ("ell")) to the tip of the middle finger, or about 18 inches (457 mm); in later usage, any of several longer units. In English-speaking countries, these included (until the 19th century) the Flemish ell ( of a yard), English ell ( yards) and French ell ( yards), some of which are thought to derive from a "double ell". An ell-wand or ellwand
Probe tip small tips in nanoscale due to resolution limitation of the optical microscopy. In electron field emission current measurement method, a high voltage is applied between tip and another electrode followed by measuring field emission current employing Fowler-Nordheim curves formula_6. Large fields-emission current measurements may indicate that the tip is sharp and low field-emission current indicates that the tip is blunt, molten or mechanically damaged. A minimum voltage is essential to facilitate the release of electrons from the surface of tip which in turn indirectly is used to obtain the tip curvature. The downside of this method to the several advantages