Another advantage of the LEM device is that you can use an over-ranged unit to measure lower currents. Say you have a 200A range unit and you only want to measure up to 100A then you simply thread the current carrying wire two times through the core since it is the number of turns within the core that determines the measured range. I have successfully threaded a thin wire around 40 times through a core to calibrate a 100A circuit using a simply 0-3amp power supply.