You turn off the sensor and inverter, and you get weird numbers. That is to be expected when the pin is essentially open. Your inverter is off but the pin is looking for any possible electrical activity. This is usually noise or outside EMF, and the only way to stop it, would be to let the arduino know the inverter is off. Now you wont be able to actually pause the readings unless you change your program to have a timer or look for the inverter to be off. However you can avoid numbers like 3 or 9 etc. with a pull down resistor. This pull down resistor will make the output read "R0" until the inverter tells it otherwise.
For the timer, if you want to use it. You can look at the incoming data from the inverter and if the data does NOT change after a certain time has passed, you can set the output to 0. This timer can also, (if coded correctly) can "pause" your readings and output nothing at all, or display your readings when a signal is found.