Abstract: An automotive engine exhaust emissions analysis system includes a pump for moving emissions through a conduit to a nitric oxide sensor through a relatively low-volume expansion chamber which is bounded in part by an unconstrained elastic membrane exposed to ambient air.

Abstract: An exhaust gas analyzer apparatus having a particle filter between its input and the analyzer. The separator includes a heat exchanger coil coupled to a condenser, an electrostatic separator coupled to the condenser, a source of fluid pressure and a filter medium. A valve is provided between the electrostatic separator and the source of fluid pressure so that the electrostatic separator may be scrubbed periodically. The filter medium is interposed between the valve and the analyzer. A source of power is provided. The electrostatic separator includes an ionizing device for charging the gas exhaust particles and two alternating sets of collector electrode plates having differing electric potential collecting the charged particles to enable generally particle free gas to be discharged to the analyzer. One set of electrode plates are connected to the ionizing device and the other set is grounded. The filter medium serves as a secondary filter so as to assure particle free dry gas is delivered to the analyzer.