Shunt (electrical) called a "crowbar" as it is likened to dropping an actual crowbar across a set of bus bars (exposed electrical conductors). An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case the shunt, a manganin resistor of accurately known resistance, is placed in parallel with the moving coil galvanometer, thus all of the current to be measured will flow through it. In order not to disrupt the circuit, the resistance of the shunt is normally very low. The voltage drop across the shunt is proportional to the current
Coal measures Coal measures The coal measures is a lithostratigraphical term for the coal-bearing part of the Upper Carboniferous System. The Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coal Measures Formation. The group records the deposition of fluvio-deltaic sediments which consists mainly of clastic rocks (claystones, shales, siltstones, sandstones, conglomerates) interstratified with the beds of coal. In most places, the coal measures are underlain by coarser clastic sequences known as Millstone Grit, of Namurian age. The top of the coal measures may be marked by an unconformity, the overlying rocks being