Real-time control techniques for measuring parameters in crude oil storage tanks are described. The techniques enable the height of the oil/water layer in the storage tanks to be measured. By using this measuring technique for the oil-water interface, with the height of the interface in the tanks, coupled with the measurements of the water/oil content ratio, the density and flow rate of crude oil and the net oil quantity can be calculated. Therefore, automatic online computation of crude oil reserves and gross output quantity of net oil can be accurately predicted. The proposed method solves a difficult oil field problem that enables control of oil and gas production volumes to be maintained, particularly in low temperature environments where conventional instrumentation has proved ineffective. The control techniques enable the oil production process to function safely and reliably.