Abstract: In a molding machine for producing foundry sand molds the sand is compressed or packed by means of a pressure wave acting on the sand surface produced by explosive combustion of a mixture of fuel and air. The dosing of the fuel to be burned is carried out by a pressure regulated supply pipe, in which a dosing container is filled with fuel, e.g., gas, up to an exactly defined excess pressure. This fuel or gas is thereafter fed to the combustion chamber under relief of the gas pressure in the dosing container down to a lower pressure level.

Abstract: In an exemplary embodiment, several measuring channels include amplifier circuits subject to zero point drift during measuring signal interruptions. For each measuring channel of the radiation receiver, a register comprising a plurality of memory locations for correction values is present, whose input is connected to the measuring channel output following the amplifier circuit and whose output is connected to the measuring channel input in front of the amplifier circuit. Each register supplies to the associated measuring channel input a correction signal having a value in dependence upon the measuring channel output signal during a preceding signal interruption and such as to correct for any zero point drift of the amplifier circuit.