I am building a test unit to monitor the current delivered by a wiring loom controlled by a current configured LM317.I am going to use a Lascar SP 400 lcd display for the readout.To get the reading i require the data sheet say's that the Rb shunt resistor should be 1R , i see that the sums are fine.My question is on the +v rail is a resistor (Ra) which states it should be 0R.Do i need to use an 0R resistor, if so why, does this afford some protection in the circuit or can i disregard it and just wire straight in.