I am trying to measure the output from a Hall effect sensor (LEM-LF 310-S) for a welding application.
The maximum output of the sensor is 0-0.25A when sensing 0-500A. This range I need to convert to 0-1V for my measurement equipment (Oscilloscope for testing, later RedPitaya).
So I am using a Shunt with 100mOhm which should give me an output voltage of U=R*I=0.1Ohm*0.25A =0.025V.
This voltage I wanted to amplify with a non-inverted OpAmp (MCP6292) to get 1V as Output-Voltage -> Amplify with a ratio of 40 (a=32.04dB). According to an online calculator 100Ohm & 3.9kOhm are sufficient for the required amplification. The used OpAmp is a dual OpAmp where I just use one of the two.
The supply Voltage of my Sensor is +-15V DC and the supply voltage of my OP-AMP is +5V DC.
I tried to read 0-1V as output with the following circuit but I am receiving nothing but noise:
What I tried already:
- Measuring the Hall-Sensor output directly with a 4Ohm measuring resistance -> as expected
- Checked wiring with multimeter
- Measured output of DC-DC Converter (15V to 5V) = Supply Voltage for OpAmp -> Output voltage is 5.6V (Should be ok according to OpAmps datasheet?)
- Measured resistance of Resistors and Shunt -> as expected
I also thought about adding a capacitor of 100nF to the OpAmps PowerSupply, but I think this is not the problem here?
Hope someone can help me figure out the problem.