I'm looking for ideas/suggestions for a completely non-intrusive detection mechanism for an AC motor. I intend to monitor the duration and timestamp of an AC motor. I believe it is a 1/7 HP permanent split capacitor single phase induction motor. I have no access to any of the input wiring, i.e. no sensing or current probes.
My thought was to use a hall effect sensor to detect alternating magnetic fields generated by the stator coils. I connected a latching hall effect sensor, HAL102 with +- 2.5 mT sensitivity, to an oscilloscope and moved it around a mini AC fan. This generated a 60Hz square wave, which was the exact behavior I was desiring. The problem was when I tried to detect the motor I wasn't able to generate any signals.
A qualifier: I'm by no means an expert w/ AC/DC motors. I'm more experienced in digital circuits and embedded software development. I would appreciate any help or ideas. Things I was wondering; What would be the expected magnetic field strength of stator coils at a known distance, thinking inverse square law? What would be the expected magnetic field pattern, i.e. I'm thinking it would be alternating north/south normal to the motor's housing? Any other alternative ideas for monitoring/identifying energized motor. By the way, I don't have access to the rotor and therefore cannot use any encoders.
Thanks in advance for help.
My thought was to use a hall effect sensor to detect alternating magnetic fields generated by the stator coils. I connected a latching hall effect sensor, HAL102 with +- 2.5 mT sensitivity, to an oscilloscope and moved it around a mini AC fan. This generated a 60Hz square wave, which was the exact behavior I was desiring. The problem was when I tried to detect the motor I wasn't able to generate any signals.
A qualifier: I'm by no means an expert w/ AC/DC motors. I'm more experienced in digital circuits and embedded software development. I would appreciate any help or ideas. Things I was wondering; What would be the expected magnetic field strength of stator coils at a known distance, thinking inverse square law? What would be the expected magnetic field pattern, i.e. I'm thinking it would be alternating north/south normal to the motor's housing? Any other alternative ideas for monitoring/identifying energized motor. By the way, I don't have access to the rotor and therefore cannot use any encoders.
Thanks in advance for help.