Abstract: A coating thickness gauge is provided with a facility to store one or more zero offset values and to automatically subtract a chosen zero offset value from a measured coating thickness value. The gauge may be used to conveniently determine the thickness of coatings applied to rough surfaces using the zero offset calibration method where the gauge is provided with a key or keys. In order to prevent accidental adjustment of the calibration or any other important operational parameter of the gauge said key or keys must be depressed and held for a predetermined period of time.

Abstract: A beltpress controller performs on-line measurements of output sludge cake thickness. A controller takes a product of the measured cake thickness with belt speed, moisture content and belt width to determine a rate of dry solid output per unit time. The calculated rate is compared with a desired rate and the sludge flow rate is adjusted by adjusting the speed of a sludge feed pump to obtain the desired dry solid output rate. In systems which mix polymer with the sludge to increase the dewatering efficiency, the sizing of a mixing orifice through which the sludge and polymer is provided is adjusted to maintain a substantially constant mixing energy. This prevents errors in the streaming current detector which measures the amount of excess polymer in the filtrate and the controller adjusts the speed of a polymer dosing pump accordingly.