High-five to high-side current sensing

摘要

For over a century the standard method of measuring amperage has used a current-shunt ammeter in series between the load and power source. The shunt, basically a resistor with very low resistance, bypasses the majority of load current around the measuring instrument. Only a proportional fraction of overall load current actually passes through the meter. The technique was called high-side current sensing. However, high-side shunts require isolation in modern electronic control systems because of their direct connection to the high-side voltage rail. Current transformers perform this service in ac power systems. But the size and cost of isolated high-side dc sensing precluded its use in many applications.