A dual range dynamic pressure differential generator for use at low pressures using a differential over a variable valve for a first stage pressure differential and the differential over a flow accelerator for a second stage pressure differential. Fluorescent, luminescent or colorimetric signals emitted by substrates or enzyme products in the presence of the bacteria are compared to controls to detect and locate the pathogenic bacteria. The cam member is mounted on the floating shaft. A connector body 26 may be engaged with the anchor 22, and has a through bore 27 to accommodate a threaded rod 44. The first c-plate is disposed between one of the a-plates and LCD panel. In the control of the in-cylinder flow velocity, a gas flow velocity in a cylinder is increased by strengthening a swirl flow.