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Model railway scales and gauges are standardized in NEM 010, [1] which covers several gauges for each scale. Narrow gauges are indicated by an additional letter added after the base scale as follows: no letter = standard gauge (1,250–1,700 mm or 49.2–66.9 in) m = metre gauge (850–1,250 mm or 33.5–49.2 in)
A special form of the Pirani gauge is the pulsed Pirani vacuum gauge where the sensor wire is not operated at a constant temperature, but is cyclically heated up to a certain temperature threshold by an increasing voltage ramp. When the threshold is reached, the heating voltage is switched off and the sensor cools down again.
The word "gauge" or "vacuum" may be added to such a measurement to distinguish between a pressure above or below the atmospheric pressure. Both mm of mercury and inches of water are common pressure heads, which can be converted to S.I. units of pressure using unit conversion and the above formulas.
Metrology is a wide reaching field, but can be summarized through three basic activities: the definition of internationally accepted units of measurement, the realisation of these units of measurement in practice, and the application of chains of traceability (linking measurements to reference standards).
They measure voltage by means of "voltage balancing", in which the input voltage is compared with an internal reference voltage source using an electronic circuit with a very high input impedance (of the order of 10 14 Ω). A similar circuit modified to act as a current-to-voltage converter enables the instrument to measure currents as small as ...
Planck length; typical scale of hypothetical loop quantum gravity or size of a hypothetical string and of branes; according to string theory, lengths smaller than this do not make any physical sense. [1] Quantum foam is thought to exist at this scale. 10 −24: 1 yoctometer 142 ym Effective cross section radius of 1 MeV neutrinos [2] 10 −21
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So for a vernier with a constant of 0.1, each mark on the vernier is spaced 9/10 of those on the main scale. If you put the two scales together with zero points aligned, the first mark on the vernier scale is 1/10 short of the first main scale mark, the second is 2/10 short, and so on up to the ninth mark, which is misaligned by 9/10.