VibrationEngineer

I'm a PLC newbie. I have an eddy current device that measures the "runout" of a shaft. It has an output of 0 to -24Vdc. I will set it at a nominal -8 to -9 Vdc. As I measure the shaft runout, the voltage output from the eddy current device will vary by no more than 200 mV. I need a PLC (and small HMI panel) to read this single analog input. It will capture the minimum voltage, the maximum voltage, subtract the two to give a Total Incidated Runout (TIR) of the shaft. Want to spend less than $1000. The problem I am having is finding an AI that won't get fried when it sees the -24Vdc during the setup of my shaft runout test. Thanks, VE