Power Budget per Reading across Competing Sensing Principles
Sensing power budgets depend on physical excitation energy, analog settling delays, and converter sampling overhead across operating duty cycles.
Shunt Resistor Insertion Loss
Energy Dissipation
Inserting a resistive element into a power path causes a drop in voltage and a loss of power that would otherwise reach the load. Shunt resistor insertion loss is the ratio of the power consumed by the measuring resistor to the total power delivered to the circuit. This value represents an inherent inefficiency in any current measurement system that relies on Ohm’s law.
Thermal Coefficient
As the current increases, the resistor generates heat which can change its nominal value. High shunt resistor insertion loss leads to self heating, requiring larger physical components or active cooling. This temperature rise can also affect nearby precision components on the circuit board.
Measurement Tradeoff
Low resistance values minimize the impact on the load but produce smaller signals that are harder for amplifiers to read. Increasing the shunt resistor insertion loss improves the signal to noise ratio by providing a larger voltage drop. Designers must find a balance between the accuracy of the reading and the thermal limits of the system.
In battery powered devices, even a small loss can reduce the operational life of the product.
Load Regulation
The presence of the resistor can alter the behavior of a voltage regulator. High shunt resistor insertion loss might cause the output voltage at the load to drop below the required specification.