Apparatus and method for measuring a fluid vapour in a pumping chamber

A fluid testing apparatus comprising:

• a pumping chamber;
• a fluid inlet via which the fluid is drawn into the pumping chamber;
• a fluid outlet via which the fluid is expelled from the pumping chamber;
• a first one-way valve allowing flow of fluid into the pumping chamber from the fluid inlet while preventing flow of fluid out of the pumping chamber back to the fluid inlet;
• a second one-way valve allowing flow of fluid out of the pumping chamber to the fluid outlet while preventing flow of fluid back into the pumping chamber from the fluid outlet;
• an electrical coil;
• a piston in the form of a diaphragm which is displaceable under action of the electrical coil against resilience of the diaphragm, which resilience then returns the diaphragm to an undisplaced condition;
• and
• an electronic controller which controls operation of the apparatus;
• wherein displacement of the piston in one direction draws fluid in the pumping chamber and displacement of the piston in the opposite direction expels fluid from the pumping chamber;
• and
• wherein return of the piston by the resilience of the diaphragm occasions a voltage in the coil which is output by the testing apparatus as a measurement signal;
• and
• wherein the controller uses the measurement signal to determine an indication of an amount of fluid vapour present in the pumping chamber.

A method of testing a fluid comprising:

• drawing the fluid into a pumping chamber;
• subsequently expelling the fluid from the pumping chamber;
• drawing the fluid into the pumping chamber and expelling the fluid from the pumping chamber by displacement of a sprung piston;
• displacing the piston by forcing the piston against the spring force and then using the spring force to return the piston;
• using the displacement of the piston under the sprung force to generate an electrical measurement signal;
• and
• using the measurement signal to determine an indication of an amount of fluid vapour present in the pumping chamber.