Having trouble with a non-invasive hall sensor - what am I doing wrong?

Good day all,

I picked up a pair of these sensors some time ago to measure the current draw of my solar setup.

It’s a 0-100Amp DC Hall effect sensor which should output 4-20mA on the output line.

I’ve connected

  • 0V to GND
  • 5v to 5v
  • A 50 ohm pull up between 5V and output
  • Output to A0 on the Arduino
  • The positive “load” cable through the sensor

When I take a reading from A0 using “AnalogReadSerial” I constantly see 984~ there abouts. It doesn’t matter which way around the Hall sensor goes the reading doesn’t change.

To make sure I’m drawing load correctly, I also have an invasive current & voltage sensor (the kind used for hobby remote control cars). I’ve tried varying the load I pull from 1Amp up to 20Amp but no dice.

Does anyone have any hints to get this working?

A 50 ohm pull up between 5V and output

This is wrong and could conceivably have damaged the sensor.

Connect a 250 Ohm resistor from output to ground and measure the voltage across it. The voltage should range from 1 V to 5 V for full scale 4-20 mA output swing, if the device is capable of driving a 250 ohm resistor. Use a smaller resistor if not and calibrate.

Yes, you use a pull-down with a current source output. What you might have done was drive the Arduino pin above 5V and possibly damage it - fortunately this sensor has a +5V supply rather than the standard industrial +24V supply so nothing bad should have happened.

Perhaps judicious testing with a multimeter before connecting to the Arduino analog input would have been sensible - check everything before you break anything! You can also add a 10k resistor in series with an analog input to protect it from abuse in a fairly general and robust manner.

I've given it a try with a 250ohm pull down between output and gnd. I couldn't see any voltage on the multimeter, and the arduino is now registering 0 volts.

Do you think I'ved nuked the sensor?

On a similar note why did he include this schematic on the listing? Seems odd http://i.ebayimg.com/00/s/NTM3WDkzNQ==/z/CDsAAOxy4dNSyN-S/$_57.JPG

The seller doesn't understand how 4-20 mA loops work.