The present invention provides an apparatus for measuring the pressure drop which occurs between two sides of an orifice plate attached to a filter bag. The apparatus includes a chamber with an orifice plate at one end and a pair of tubular pressure taps located on either side of the orifice plate whereby one tap is located on the upstream side of the orifice plate and the other is located at the downstream side. Both taps have a particular location and configuration to avoid clogging whenever the bags are cleaned. The apparatus is used in a sequentially timed and controlled system for measuring and recording bag performance of many bags in a baghouse. The system is formed by attaching the above apparatus to a plurality of bags in a baghouse and connecting the pressure taps from each apparatus to a sequentially activated and controlled valve system which individually measures the pressure drop at each bag through the use of a single differential pressure-measuring device. The controlled valve system also allows purge gas to pass through the taps while isolating the pressure-measuring device from the taps through which the purged gas is passing. The system also includes a baghouse temperature sensor, a baghouse pressure drop measuring device and a recording device so that individual bag flow and fabric drag can be calculated and recorded.