Current Sensing Mike Ambrisco
Background All current sensing devices require being in series with the circuit. The easiest way to find current is by adding a.1 Ω resistor or smaller into the circuit and measuring the voltage across, and divide it by the resistance.
Types of Sensors Shunt Resistor ◦ Added known resistance into the circuit in series. Uses a small,.1 Ω or smaller resistor to minimize total voltage drop. Measure the Voltage drop across the resistor. Using ohms law [V=I*R] you can rearrange the formula to find I [I=V/R] V= Voltage, I=Current, R=Resistance. Op Amps ◦ Uses the Shunt Resistor ◦ Outputs a voltage Can be calculated to show calculated current as output voltage. Micro Processing ◦ Uses the Shunt Resistor and Op Amps ◦ Uses the most power ◦ Can display output on LCD display ◦ Easily customizable and easily modified
Cost A Shunt resistor is very inexpensive. ◦ 5 to 20 cents. A Op Amp is also inexpensive. ◦ Up to $1. A Micro Controller with LCD display. ◦ $20 to $100.
Basic Shunt Resistor Setup V1 – V2 Shunt = Current V1 V2
Simple Op Amp Sensors
Micro Processer Setup Micro Controller A2D Converter LCD Display