A pressure measuring and flow-rate controlling device includes: a flattening plate including a fluid cavity in the flattening plate; a flexible contact membrane provided on said flattening plate; a support member configured to secure the flattening plate against a sample; a pressure adjuster; an inlet tube connected to the pressure adjuster at a first end of the inlet tube, the inlet tube connected to a first end of the fluid cavity at a second end opposite to the first end of the inlet tube; and an outlet tube connected to a second end opposite of the first end of the fluid cavity, where the pressure adjuster is configured to control a flow rate of a fluid passing through the fluid cavity based on cell pressure of the sample.

An exhaust after-treatment system includes an exhaust treatment component, a tank for holding an exhaust treatment fluid, and an exhaust treatment fluid dosing system. The dosing system includes a fluid distributor providing exhaust treatment fluid under pressure to a plurality of dosing modules that dose exhaust treatment fluid into the exhaust stream and a return for returning unused exhaust treatment fluid to the tank. A valve is positioned between the fluid distributor and the return and is configured to allow a flow of exhaust treatment fluid from the return to the fluid distributor before being returned to the tank during a purge operation. A controller is configured to open the valve and allow communication between the return and the fluid distributor during the purge operation such that unused exhaust treatment fluid drains during the purge operation.