LA 55-P Hall Effect Current Sensor Newbie Problem

[King_Pago]

Anyone,

I recently bought a hall effect current sensor (I'm fairly new to this application) as I'm required to build a smart meter. I'm trying to understand how it works using this simple setup: a variable resistor (rated 5A, 240V) connected to the mains. I've got a cord wound around the sensor (as required - arbitrarily, I've got 4 turns). When I read the voltage across the resistor using an oscilloscope, I get a clean sinusoid (230V, 50Hz). However, the output of the sensor is giving me strange waveforms. Shouldn't it be a sinusoid also? I've been struggling with this for a week now. Please see the rough schematics I made below of the circuits to see my setup, where I read the oscilloscope (pink dot on picture) and the output waveform (blue line on the side). What am I doing wrong? On the last setup, I get only the beginning edges of a sinusoidal output but it becomes zero until the next half-wave of the sinusoid.

Setup 1:



Setup 2:



Setup 3:



Your help will be greatly appreciated.

 

[FvM]

If you review the LA 55 datasheet, you'll realize that only the third circuit can work at all. The burden resistor (Rm in the datasheet) should have a value in the specified range. A larger value is possible if you are not utilizing the full LA 55 range (as in your test, where you are loading the sensor with 4*5 A while the range is 50 A.

The output signal must be aquired across the burden resistor (it can't be clearly seen if you connected the probe ground correctly). If it still doesn't work, the sensor might be defective.