Hi folks, there is probably an easy way to do this but I don't know how. I have a 144 volt DC battery pack that I want to add a small resistor as method of measuring the current being drawn.
This current measuring shunts are available online pre-made, I'll be buying one that has a 50millivolt drop across it at 200 amps.
I want to input the value into a microcontroller so I need a gain stage to take the 50mV and add 80x or so, so that I get around 4 volts at 200 amps. This gives me some headroom in case the current goes above this, my microcontroller analog input is 5volts max.
At first I thought this would be trivial with an opamp non inverting amplifier, but the problem is that I seem to need a floating gain stage, if I reference ground I end up dumping the high voltage to ground at some point. Here is an example of my schematic that is obviously incorrect.
Do I perhaps add some 1megaohm resistors to the shunt either side to severely limit any currents from +144volts to ground?
Thanks a lot for your help!
This current measuring shunts are available online pre-made, I'll be buying one that has a 50millivolt drop across it at 200 amps.
I want to input the value into a microcontroller so I need a gain stage to take the 50mV and add 80x or so, so that I get around 4 volts at 200 amps. This gives me some headroom in case the current goes above this, my microcontroller analog input is 5volts max.
At first I thought this would be trivial with an opamp non inverting amplifier, but the problem is that I seem to need a floating gain stage, if I reference ground I end up dumping the high voltage to ground at some point. Here is an example of my schematic that is obviously incorrect.
Do I perhaps add some 1megaohm resistors to the shunt either side to severely limit any currents from +144volts to ground?
Thanks a lot for your help!
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