# Homework Help: Designing a manometer

1. Nov 22, 2006

### narbij

Basically our task is to design a inclined manometer. with these parameters : the maximum pressure: 7875pa minimum pressure: -3200. what im struggling on is calculating the angle that the manometer should be inclined at. Another parameter that is given is that the angle must be between 0-45 degrees to the horizontal. We are given also the sensitivity that it should be which is 1.77.

the diameter of the vertical tube is 22mm which is constant. the inclined tube has 3 sperate tubes of a 8mm diameter each, therefore the diameter of the inclined tube can be altered.

i have these formulas:
change in pressure = specific gravity of liquid in manometer times L(the column length) times the sin of the angle.

So far i know from theory, if you apply a certain amount of pressure, the fluid would displace a certain amount. Now in the vertical tube, the displacement change in h and in the inclined tube, it would be change in l. The volume of the amount that has been displaced is constant.. So i have made an equation which states that:

change in h * cross-sectional area in the vertical tube of the displaced h= change in l*cross-sectional area in the inclined tube of the displaced l .

Any help would be much appreciated as im extremely extremely extremely extremely extremely stuck

2. Nov 23, 2006

### Staff: Mentor

Sorry, I'm having trouble picturing what you are asking. Could you please sketch the setup and post it here? Thanks.

3. Nov 25, 2006

### FredGarvin

I agree. You are confusing me with the whole 8mm diameter tube allows for a varying diameter bit. You have constant cross sections. You need to develop the balance of forces between the column of liquid and the pressure force.