[potatopotato]

Hi,

I am trying to understand what a manometer does in terms of its function. I do not understand why height difference is from the lower point to the higher point in the following diagram link:

http://www.efunda.com/formulae/fluids/manometer.cfm

Now, according to the website, the calculation of pressure is
delta P = d x g x h
where P = pressure
        d = density of fluid in manometer
        g = gravity (9.8 m/s^2)
        h = difference of height of fluid in manometer

How come difference in height is not the increase of the fluid from initial to final point. Instead, in this diagram the height difference is the higher versus the lower, which means double the increase of height of fluid?

[enahs]

You can not increase one without decreasing the other, though. In order to "force" the other out of the way, work most be done. If you only go by the change in height from the initial position, you will be neglecting the work done on the left half.