Abstract: A method for inventory maintenance and leak detection in liquid storage tanks and dispensing lines, that combines tank level measurements, tank product temperature measurements, output flow measurements, liquid product characteristics data, initial product delivery volume data, and redundantly calculates changes in the quantity of liquid product within the tank and compares these calculations to determine abnormalities in the changes in the quantities of product within the tank. Changes in the quantity of product within the tank are verified as either the delivery of additional product into the tank or the dispensing of product from the tank as with a customer sale. Changes that cannot be verified as either delivery into or dispensing from the tank are appropriately characterized as possible leak conditions in the tank or lines.

Abstract: A well polish rod temperature sensing system, for use at a well head, comprising(a) first sensor located in proximity to the polish rod to sense its temperatures T.sub.1,(b) second sensor for sensing temperature T.sub.2 of the environment near the well head,(c) and circuitry operatively connected to the first and second sensor to provide an output signal which is a function of the difference between T.sub.1 and T.sub.2.