current sensing with 1ohm 5watt resistor

hi guys,

can you give me some helpful links for current sensing(already googled, just hoping to find some more useful links that google failed to give)?

This is again is used for my robot arm project. I want to protect my driver and the arm as well from over current. I'm using now a 1ohm 5watt resistor (the white, rectangular stone-like type), it is very shitty though. With a DVM, it shows like 400milli ohms.. I'm considering buying precision power resistors now.

The obvious happens, current flows to the resistor and it gets converted to voltage. since I'm controlling a DC motor, there will be transients/spikes. This voltage will be fed to a Schmitt trigger that will work as the generator of the enable signal for the whole driver circuit.

What I want is to make the schmitt "blind" to those transients (positive and negative). For the negative spikes, I think clipping it should work fine. Another thing is the motor start-up current or direction change current (motor going clockwise then suddenly change its direction to CCW). I think its significantly high, but I'm currently studying the oscilloscope on how to get/measure that waveform.

Any tips? I hope don't it doesn't involve any timers.. I just need filters and opamps for this, I think.

Thanks!

in fact many DVM or DMMs cant measure 1 ohm or less properly. we need not, i suppose, suspect the resistor.
the best method is to pass 0.1 amp current through it and measure the voltage across it, to get 100mV.
it would be a proper test.
It might necessitate making a 0.1 amp constant current source. we can use 7805 in this constant current circuit application.