A system, for use in determining a volume in a reservoir, includes a bulkhead, a plunger assembly, and a base. The plunger assembly is connected to the bulkhead. The plunger assembly includes a first plunger and a second plunger. The first plunger has a corresponding first biasing member. The second plunger has a corresponding second biasing member. The base of the reservoir is connected to the first plunger. Movement of the base causes compression or expansion of the first biasing member, which causes compression or expansion of the second biasing member. The bulkhead, the first plunger, and the base define a first portion of the reservoir. Positions of the first plunger and the base, relative to the bulkhead, are based on the volume in the reservoir.
