I am considering the economic viability of a project that must accurately (within a tolerance of, say, 0.5ml) dispense volumes of water from a tank at a constant volumetric flow rate of around 50ml/s. Within the tank, the water may be held at pressures between 1 and 6bar; and at temperatures between 4 and 18°C. The temperature should not be changed by more than 0.5°C during the dispensing. The volume to be dispensed will be controlled electronically (between 10 and 250ml). It is not clear to me what would be the simplest approach, from a pressure regulator in series with a timed valve (which I doubt could achieve the desired accuracy) to some advanced pumping arrangement controlled by electronic flow measurement devices. I imagine it could also be possible to determine the volume of water dispensed via changes in volume remaining in the tank; e.g. the tank could be weighed or include a floating ball measure. Aside from the criteria detailed above, other considerations include: minimising cost (obviously); ease of regular cleaning (the water is for human consumption); and minimising the physical size of the device. I would be extremely grateful for your suggestions.