A very simple non-inverting amplifier like this will allow you to measure the resitance as the voltage developed across a divider circuit.
Then you can make the measurement at a much lower (so safe) current.
I'd suggest an MCP6002 and R2=100k, R1=1k to give a gain of 100; then if Rs = 5k1 you will get a test current of 1mA and a 50E resistance will give 5V to the analog input, while a resistance of 1.5E will give 150mV - a reading of around 30 on the adc.
