Tank Level Monitoring

One possibility is a cellular modem programmed to call one or more cellular phones in case of failure.

We're interested in the tank level so we can schedule deliveries when they fit and are needed, or at least the 4-20 mA signal. Merely having a signal that tells us when the level indicator has failed accomplishes nothing. Did you intend to say something more?

What is the distance from the tank to you .... Prosoft technologies offers high band transmitters that are designed for industrial use - range to 25 Km and one that reaches 45 km. |Other that that is there a phone line you could use or have installed and then you could monitor from all around the world ....

If you have a signal representing level, some very simple electronics and straightforward programming on a small device such as a 'stamp' or an 'arduino' can do it.

level -> signal -> A/D port of the device -> serial (or USB) port of the device -> cellular modem.

Such devices should cost $25-50 and are easily programmed using BASIC or C.

These devices are very robust and self-starting after supply current failures.

We use a combination of a Gasboy System (for fuel management) and a Veeder-Root (for leak detection. Both send information directly to our home office. They have a wide variety of systems and ways of transporting information.

When you say there is "no wireless signal in the area" does that include cell phone coverage. I have a variety of both off-the-shelf and custom solutions using GSM cell phone networks