Search results
Results from the WOW.Com Content Network
Micrometers use the screw to transform small distances [9] (that are too small to measure directly) into large rotations of the screw that are big enough to read from a scale. The accuracy of a micrometer derives from the accuracy of the thread-forms that are central to the core of its design. In some cases it is a differential screw. The basic ...
A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
In electrical engineering, characteristics like current or voltage can be measured by an ammeter, a voltmeter, a multimeter, etc.The ammeter is used in series with the load, so the same current flows through the load and the ammeter.
Ideal test indicator pushed. Prior to modern geared dial mechanisms, test indicators using a single lever or systems of levers were common. The range and precision of these devices were generally inferior to modern dial type units, with a range of 10/1000 inch to 30/1000 inch, and precision of 1/1000 inch being typical.
Accuracy is also used as a statistical measure of how well a binary classification test correctly identifies or excludes a condition. That is, the accuracy is the proportion of correct predictions (both true positives and true negatives) among the total number of cases examined. [10] As such, it compares estimates of pre- and post-test probability.
All measurements are subject to uncertainty and a measurement result is complete only when it is accompanied by a statement of the associated uncertainty, such as the standard deviation. By international agreement, this uncertainty has a probabilistic basis and reflects incomplete knowledge of the quantity value. It is a non-negative parameter. [1]
The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; [1] SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, [2] is a unit of length in the International System of Units (SI) equalling 1 × 10 −6 metre (SI standard prefix "micro-" = 10 −6); that is, one millionth of a metre (or one thousandth of a ...
For instance, the accuracy of land-survey distance measurements when using a laser rangefinder might be 1 millimeter per kilometer of distance; this could be expressed as "Accuracy = 1 ppm." [a] Parts-per notations are all dimensionless quantities: in mathematical expressions, the units of measurement always cancel.