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Battery Powered Current Sensor

• To limit the earth's magnetic field influence on the current measurement, consider placing the sensor and conductor in a magnetically shielded enclosure.
• Calibrate the measurement circuit by forcing a known conductor current and measuring the resulting voltage output. If sensor to conductor displacement changes, recalibrate.
• Use the trim pot to null the sensor offset, for a zero volt output with no conductor current.
• This sensor circuit can measure DC and AC currents to the bandwidth of the op-amp. Additional bandwidth limitation can be had by placing capacitance across the 475k-ohm feedback resistor.
• Other power supplies can be used with this circuit if the selected op-amp can operate. Note that the 1N4148 diode can be removed if reverse polarity protection is un-needed.
• Magnetic fields larger than 20 gauss at the sensor may require a set/reset circuit to restore performance.
• Consult with application note AN-209 to further understand the principles of current sensing via magnetic fields emitted from conductors.