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A Snellen chart is an eye chart that can be used to measure visual acuity.Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor Franciscus Cornelius Donders.
For a pixel pair (one white and one black pixel) this gives a pixel density of 128 pixels per degree (PPD). 6/6 vision is defined as the ability to resolve two points of light separated by a visual angle of one minute of arc, corresponding to 60 PPD, or about 290–350 pixels per inch for a display on a device held 250 to 300 mm from the eye. [24]
A machinist calculator is a hand-held calculator programmed with built-in formulas making it easy and quick for machinists to establish speeds, feeds and time without guesswork or conversion charts. Formulas may include revolutions per minute (RPM), surface feet per minute (SFM), inches per minute (IPM), feed per tooth (FPT). A cut time (CT ...
This would apply to cutters on a milling machine, drill press and a number of other machine tools. This is not to be used on the lathe for turning operations, as the feed rate on a lathe is given as feed per revolution. = Where: FR = the calculated feed rate in inches per minute or mm per minute.
Typical resolution is 500 mickeys per inch (16 mickeys per mm), but resolutions up to 16,000 mickeys per inch (600 mickeys per mm) are available. Muggeseggele A Muggeseggele is a humorous Alemannic German idiom used in Swabia to designate a nonspecific very small length or amount of something; it refers to a housefly 's scrotum .
The chart was designed by Ian Bailey [5] and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. [1] [3] They described their motivation for designing the LogMAR chart as follows: "We have designed a series of near vision charts in which the typeface, size progression, size range, number of words per row and spacings were chosen in an endeavour to achieve a ...
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In the United States the pace is an uncommon customary unit of length denoting a brisk single step and equal to 2 + 1 ⁄ 2 feet or 30.0 inches or 76.2 centimetres. [ 3 ] [ 4 ] The Ancient Roman pace ( Latin : passus ) was notionally the distance of a full stride from the position of one heel where it raised off of the ground to where it set ...