Abstract: A proving apparatus and method for large capacity rotary type gas meters having a blower assembly for connection downstream to the test meter, a pulsation dampener for connection upstream to the test meter, and a turbine-type reference meter for connection upstream to the pulsation dampener, whereby an ambient test air stream is drawn successively through the reference meter, the pulsation dampener, the test meter and the blower. This arrangement uniquely isolates the reference meter from the effects of the inherent flow pulsations produced by the rotary test meter so that the tested flow measurement from the reference meter is substantially accurate to, in turn, provide the most accurate calculation of the percentage proof of the test meter. A computer is utilized to control various aspects of the testing procedure and to analyze the test data.