The machine we started with had no instrumentation.  Our customer requires precise instrumentation to ensure precise sanding. 

We installed a counter with a read-out on the control panel that counts the number of head cycles.  The control panel has the controls for the master power, sanding motor, head direction, and solenoid valves.
For initial strip thickness, we used a digital indicator mounted on the front of the head.  The indicator cost only $69, but it measures to half of a thousandth of an inch.  It is battery powered and has auto-shutoff and turn-on.  It can be zeroed at different heights and we installed a mechanical adjustment to increase flexibility and ease of use.