Second Wet Well Level trasmitter addition (Siemens

[Cyanogen281]

I am designing a 4 pump system and need to add a second wet well level. I am using the Maple system graphic interface for the HMI and need to be able to toggle back and forth between the two level transmitters. The PLC (Siemens S7-300) should have a primary wet well level that it reads from but if for any reason that level transmitter were to be malfunctioning it would automatically switch the the auxiliary wet well level transmitter. Could anyone provide any assistance or advice on how this logic would look? i.e. fail over logic?

[Moggie]

What type of sensor are you using? If "digital" just program the input for the neaw sensor where ever the existing sensor input is programmed. If mA signal compare the signals for change in a given time. If no change sensor mybe faulty. If below 4mA then sensor or wiring is faulty.