Low Side Current sense to detect 24V pulse 100ms-- Non inverting -- Correct Approach?

[az1muth]

Im attempting to sense when a 100ms Pulse occurs on a 24 volt line. The 24V line has a 24 ohm load resistor to create a 1amp load to match the operating conditions. Low side current sensing seems appropriate as the intent is to just sense the pulse has occurred with an Arduino, then take some action. Using a voltage divider works, but does not properly load the 24V load. It seems like a standard opamp like an LT1097 or CA3240 can be used in non-inverting config. A 30 mohm sense resistor below the 1amp load should sense 30 mV, then the feedback and input resistor can set the gain to bring up to 5Volts for the Arduino to read a high. Is this the right approach?

Attached is a quick schematic showing the approach. Any Guidance or advice is appreciated! Thanks!

 

[az1muth]

After doing some more thinking a voltage komparator is a better fit. All I need is a TTL state so putting the sense up on the high side of the load and routing to In+ and In- across the sense should pull change the state of the komparator output. the LM397 should work fine.

 

[esp1]

hi az,
Your proposed method is often used as a low side current detect circuit.
Ensure that the 0V points for the OPA inputs are tied to the same point as the load resistor.

I use the CA3240 OPA, you may have to trim out any OPA input offset voltages.
Also the CA3240 will not swing to +5V if its powered by a single +5V, you could consider a MCP6002 OPA which is rail to rail on its output.
E