[geeks] tank sensor

[Geoffrey S. Mendelson]

How about a Maxim (Dallas Semiconductor) DS18S20?

It's a serial device which when activated reads out the temperature.

Here's an example of a place selling them in small quantites I found
with a web search. No relation, just the first hit.

http://store.fungizmos.com/index.php?main_page=product_info&products_id=182&zenid=0653ab63cd96c3cd9b43c3a3bfc20fe6

They have unique serial numbers so that you can string a bunch of them
on one serial port and read them individually. 

If you put a string of them on a tank, you can read the level and keep
track of it from a PC. I have seen notes about 100 foot cable, so the
PC can be in your house. They use very little power so there is not much
chance of a short circuit igniting the tank. (Use a current limiting resistor).

Geoff.
-- 
Geoffrey S. Mendelson, Jerusalem, Israel gsm at mendelson.com  N3OWJ/4X1GM