I installed two panels in the Bus. They have a number of different setups. Basically, the external sensors are the same. You stick on on the outside of the tank (after trimming them to length) and pick the panel (or panels) that you want. I use a 712TT panel upstairs and a 711 in the basement. You can add as many panels as you want. I used the basic 711 panel in the basement because it gives me readouts on my 3 tanks as well as battery voltage. That way I can tell what I have while I am refilling or dumping. If I ever need to do a short gray dump I can dump some water out while still retaining enough to flush the sewer hose after the black tank dump the next day or so. If I need to do laundry (yeah right, like I'm the guy who does laundry
) I can make some room in the gray without totally dumping it. You can lock the display to read as you fill or dump so you don't have to run inside and check.
For the main inside panel I use the 712-TT or 712-LT. I began with the 712-TT, which gives fresh water, gray water, black water, LP tank, and battery levels. It also features a full time display of the interior temperature. When you push the button, it displays the outside temperature (they include a remote sender for that as well). I have an outside temperature display on the dash so I mounted the remote sender into the basement water service compartment. That way I can view the basement temperature in the water service area, which is nice for winter camping.
Later on I noticed that they also offered a 712-LT. This looked like a 712-TT except they added two small rocker switches, one for the water pump and one for the LP hot water heater. I relocated the water pump switch to be used as the 120 volt (through a relay) hot water heater switch. Now I don't have to go into the compartment over the entrance door to get at the water heater switches. However, the 712-LT was originally developed for OEM use in Airstreams so it does not have the outside temperature feature and the inside temp only display when you push the button.
I'd pick the 712-TT as a prime panel and you can always add the 711 in the basement if you want it. They are all SeeLevel II series panels, it's only the feature levels that vary. The newer 713 series is a buttonless system that always reads but I'm thinking that could pull battery amps when boondocking. By the way, they can use the existing sender wires so you don't have to pull all new wires to the tanks.
The company has been around a while, making tank monitoring systems for serious industrial applications and petroleum distribution indistry applications and it is all quality trouble free stuff. When you call them you get an intelligent person on the other end who will provide good answers to any questions you may have.