Considerations for Current Sensing
Generally speaking, current sensing involves the generation of a voltage signal that represents the current flowing at a particular position in an electrical circuit. A current sensing resistor needs to be considered as a current-to-voltage converter that, in order to be useful, must be chosen based on the following set of attributes: low value, low inductance, tight tolerance on initial value, high peak power rating, and high temperature rating.
The following details should help you understand some of the considerations that go into the selection and application processes of current sensing devices:
Value
The first factor in determining a sensor’s value is usually the voltage threshold of its circuitry. For more complex applications, where signal amplification is a factor, the choice would be made on ensuring minimal voltage drop across the entire device.
Temperature coefficient of resistance
TCR is a necessary consideration whenever accuracy is a primary concern. Normally specified in unit parts per million per degree centigrade, TCR can be translated into accuracy by using a specific formula.
Power rating
When it comes to choosing the proper technology for a current sensor, power rating is a huge determining factor. An important point for this particular consideration is a deep understanding of the nature of the current waveform on which the sensor will be used. The device may be intended to detect DC current, but may also need to handle, or perhaps even calculate, transient peak currents that result from output capacitor charging, load transients, inrush current surges, etc.