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The first soil resistance measuring instrument was invented in the 1950s by Evershed & Vignoles Meggers who made the first insulation and earth resistance testers. [2] One of the most used analog grounding testers in USSR were М416. [3] From the 21st century several companies produced digital earth resistance meters and testers.
As an example, a meter movement that required 1 mA for full-scale deflection, with an internal resistance of 500 Ω, would, on a 10 V range of the multimeter, have 9,500 Ω of series resistance. [20] For analog current ranges, matched low-resistance shunts are connected in parallel with the meter movement to divert most of the current around ...
For choosing a grounding rod there are several selection criteria such as: corrosion resistance, diameter depending on the fault current, conductivity and others. [30] There are several types derived from copper and steel: copper-bonded, stainless-steel, solid copper, galvanized steel ground.
This is partly because the change in deflection itself is small when the resistance measured is too small in proportion to the intrinsic resistance of the ohmmeter (which can be dealt with through current division), but mostly because the meter's reading is the sum of the resistance of the measuring leads, the contact resistances and the ...
A minimum acceptable resistance value is usually specified (typically in the mega ohm (MΩ) range per circuit tested). Multiple circuits having a common return may be tested simultaneously, provided the minimum allowable resistance value is based on the number of circuits in parallel. Five basic isolation test configurations exist: [3]
Measures Resistance of an Winding of Motor or Generator And Measures Earthing's Resistance Microwave power meter: Measures power at microwave frequencies Multimeter: General purpose instrument measures voltage, current and resistance (and sometimes other quantities as well) Network analyzer: Measures network parameters Ohmmeter
Lux meter for measuring illuminance, i.e. incident luminous flux per unit area; Luminance meter for measuring luminance, i.e. luminous flux per unit area and unit solid angle; Light meter, an instrument used to set photographic exposures. It can be either a lux meter (incident-light meter) or a luminance meter (reflected-light meter), and is ...
Low resistance Ohmmeter (LRO) 1923 Multimeter with Amps, Volts and Ohms (AVO) 1928 Multistation watt-hour meter test board 1942 Resistive load box 1950 Cable fault locator 1951 Protective relay test set 1953 Partial discharge (Corona) detection system 1968 Portable digital multimeter 1979 Digital line earth loop impedance tester 1985
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