Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges or vacuum gauges. A manometer is a good example, as it uses the surface area and weight of a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge.
A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: −15 psig or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very accurate readings, especially at very low pressures, a gauge that uses total vacuum as the zero point may be used, giving pressure readings in an absolute scale.
Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system (telemetry).
Note: I am self-studying Material and Energy balance courses and I haven't done fluid mechanics yet.
Case 1) Consider the manometer in the figure below. Levels on both sides of the manometer which are open to the atmosphere are equal.
If we analyse the forces acting on the left side of the...
I was watching a YT video getting prepared for class this coming semester, and in the video, this diagram of a manometer was drawn (see image at end of message). The professor stated that the pressure in the tank (Pt) is = to the pressure at point A. Following this, he said that technically...
Consider a manometer as shown above with different widths W and w.
If we take a mass (red) that is frictionless and does not allow water to leak of mass M, then I would like to calculate the height of water H in the narrow tube of width w. I arrive at a non sensical answer of H = 0 in one...
Some notation:
- the difference between the heights of mercury, which is effectively the height of the mercury in the open end of the tube is ##h_{diff}##
- the volume of gas inside the sealed off end is ##V_{inside}##
- the volume of gas when let outside, "normal volume", is ##V_{outside}##
-...
Having some trouble in answering this question
What I have done so far is calculate the initial pressure difference, then used that to find the new pressure difference when pipe's A pressure increases by 34.4 kPa
Not too sure of where to carry on from here? All I know is that if pipe A is...
Not sure how to start off this question
I'm confused how to begin if I do not the exact pressure on either pipe A or pipe B
Only thing that I can deduce from this is that if pipe A exerts a smaller pressure than before then the mercury column on the left side would rise i.e. the new...
Hey everyone!
Here is the problem I have been tackling but did not end up with the correct answer
The extra red arrows I have labelled in myself and called these distances h1,h2 and h3. I assumed the pressure to be the same at levels A & B, hence i have established expressions for both of...
Having some trouble in answering part b) of this question
I managed to find the right answers for part a) if that is maybe needed in part b) which I got 26.7 kPa, 18.8 kPa, 38.6 kPa and 13.9 kPa for levels A, B, C and air pressure respectively
Not too sure what part b) is technically asking...
(a) Situation (2) is my answer (which cannot be in static equilibrium). The pressures in the lower dashed line (##P_2##) has to be the same on either side (for equilibrium). That means the pressure due to the red liquid is equal to the pressure due to the same length of air column (length)...
Hello!
I have a volume of 50 liters which I pressurize with air so that I read 1 bar on the manometer.
But there is a leakage in the volume so after 30 sec the manometer shows 0,5 bar.
What is then the air flow ( liter / min) of the leakage?
Let's suppose that a water filled u-tube is open to the atmosphere at one end and at the other end it is capped and evacuated. Suppose also that the diameter of the capped evacuated end is drastically larger than the open end. (Ignore effects of boiling or vapor pressure). Would the much larger...
A well-type mercury manometer has a well of 0.02m^2 area and a tube of 40mm^2 area. The liquid has a density of 13,534 kg/m^3.Given that the tube is open to the atmosphere and the well is connected to the inert gas manometer was to measure:
Calculate the pressure of the inert gas in kN/m^2 if...
if we use a water manometer we get the pressure of the gas in manometer by using this forumla :
Pgas = Patmosphere ± ρgh
and if we use the a mercury manometer we use this formula instead :
Pgas = Patmosphere ± h
and here's my question :
why cannot we use the first formula in both of them ...
Homework Statement
Find the flow rate of water. The fluid in the manometer is mercury. ##d_{1},d_{2}## are the diameters in the figure
Homework Equations
Bernoulli, continuity equations
The Attempt at a Solution
We know that
##p_{1}=p_{1Top}+\rho_{water}gh_{2}##...
Hi guys,
I have two questions as follows, ofcourse they may seem too basic, I have read through certain texts (engineering) but I still haven't been able to actually physically understand, so asked here
1) Whats thermodynamic pressure w.r.t physical point of view? - for a gas from...
I need to test this gauge. It reads -0.25 to 0 to +0.25 inches of water. I am using it in the 0.02 to 0.03 negative and positive ranges. What of known value can I use to deflect this gauge maybe .1 or .05 in either or both
directions to test the gauges accuracy?
it gives the option of selecting...
Homework Statement
In the image, as the first chapter of thermodynamics class, I understand all things in the answer except the highlighted part (lower bottom of the image). It is not directly related to thermodynamics but about the area ratio of the two ends of the tube, but I do not...
Homework Statement
https://imgur.com/a/nxWvK this is the problem
Homework Equations
P=Patm + dgh
The Attempt at a Solution
I really just need to check if i did this right. I converted the densities to kg/m^3 and did p1= ((1121.689)(9.8)(.15) + ((1019.717)(9.8)(.04)) which gives 2048.61 Pa +...
Homework Statement
so I have been working on this problem :
Diameter1 at wide end: 8cm || V1 = 1.56m/s
Diameter2 at narrow end: 3cm || V2 = 11.094m/s
Force exerted on plate = 87N
Find the manometer reading
Picture below:
Homework Equations
P1+(1/2 ρv1^2)=P2+(1/2 ρv2^2)
1 − 2 = (2 −1)ℎThe...
Homework Statement
If you have a manometer with a 70cm tall water column, what is the largest pressure
that can be measured? Assume that the densities of water and mercury are 1000 kg/m3
and 13 600 kg/m3 respectively
Homework Equations
P=pgh+Patm
The Attempt at a Solution
I've attempted this...
I wonder if it is correct to read an open air manometer in the case of viscous fluid in the following (usual) way. Consider the situation showed in the picture where a viscous fluid is flowing, in fact ##z_C <z_A##.
The reading of the manometer would be ##p_a=\rho g z_a##, ##p_b=\rho g z_b##...
Homework Statement
I have attached a picture of the question.
Homework Equations
P = pgh
The Attempt at a Solution
I can calculate pressures in a barometer using the simple rule that at same height the pressure exerted by tubes is same. But the same rule seems not to imply in manometers...
Chasing a ghost perhaps but in the process of pressure testing a simple propane furnace installation I installed a water Column pressure gauge. Over a period of 11 hours the pressure gauge reading will go from 10" WC to 0" WC. In the course of trying to understand this I installed a manometer...
Homework Statement
Homework Equations
P=ρgh
The Attempt at a Solution
I already have the solution.
My question is simple. I can't understand how I define the direction of pressure in each "changing" point. I also have the solution if needed.
In a reservoir of a well type manometer, the sealing liquid is mercury having a weight density of 132.5 KN/m^3. If the area of the well is 0.02m^2 and that of the tube is 40mm^2. Calculate the height of the measuring column if the applied differential pressure is 70KN/m^2.
Relevant formulae...
Homework Statement
An inverted U-tube monometer, as shown in Figure attached , has air at the top of the tube.
If the pipes contain oil (s.g. = 0.9), h1= 0.6 m, h2= 1.8 m and h= 0.45 m, determine
the difference in pressure between point B and point A.
Homework EquationsThe Attempt at a Solution...
I am trying to establish a mathematical relationship between heights h1 and h2 (please refer to figure attached) for a manometer whose RHS channel is the shape of a triangle (defined by a base length and the angle theta). I want to be able to calculate the heights h1 and h2 for a given change to...
First of all I'd like to apologise for my question, as it will probably be embarrassingly easy to answer but I don't have any idea.
I've recently been given the role of running a manufacturing centre for F1 in Schools and everything is going well apart from one area.
We have a wind tunnel to...
Homework Statement
A simple mercury manometer connected into a flow line gives readings as shown in the figure. Local gravity is standard and the mercury density is 0.488lb/in^3. Find the pressure at points X and Y when the flow line and left leg contain (a) air whose density is 0.072lb/ft^3...
Homework Statement
A closed-end manometer is used to measure the pressure of a sample of a given gas. The level of mercury (Hg) is 18 mm higher in the part of the tube connected to the sample than in the other part. Determine the gas pressure in kilo-pascals, if the atmospheric pressure is...
In my book it talks about a mercury manometer where one side of the U tube is open to air and the other side is connected to a system where a reaction takes place. It then derives ΔP=ρgΔh by setting the force pushing the mercury up equal to the force pushing the mercury down. The force pushing...
Hi, Just have a basic question on a closed manometer :
http://postimg.org/image/6tq089eoz/
So I do understand the basic idea behind manometers. I see that in this case the pressure of gas is lower than that of the liquid, which is why the liquid is higher on the left side. Now, what I...
Hello,
In this problem, and with problems dealing with pressures in manometers in general, I'm wondering if to calculate the pressure at any given point, you just look at what is above that point. For example, at Point C, there is 12 feet of mercury and 12.65 feet of oil on top of it, as well...
Hello.
I am not skilled in math or physics. I'm interested in building an inclined manometer accurate only enough to measure water column (w.c.) inches scaled to .5 w.c to about 10 percent accuracy.
A very basic manometer can be built to measure inches of water with a utube of small...
Homework Statement
Two pipes are connected by a manometer shown in the figure.
Homework Equations
FR = \gamma*hc*A
yR = yc + \frac{I_xc}{y_c*A}
The Attempt at a Solution
PB - PA = \gammawater*1.1m - \gammaFluid*0.6m + \gammawater*0.8m = 3.33 kPa
I checked my answer and it...
Homework Statement
a manometer consisting of tube that is 1.25 cm inner diameter . on one side , the manometer leg contains mercury,10cc of an oil(S.G.=1.4)and 3 cc of air as a bubble in oil . the other leg contains only mercury . both legs are open to atmosphere and static . An accident...
Problem:
1. The pressure of a gas cell is measured with a mercurcy manometer. The mercury is 32.6 cm higher in the outside arm than in the arm connected to the gas cell. Calculate the gas pressure.
Relevant equations/given data
2. p(Pressure at depth h) = p(Pressure of atmosphere) +...
Homework Statement
The fluid in a manometer tube is 40% water and 60% alcohol (specific gravity = 0.8). What is the manometer fluid height difference if a 50kPa pressure difference is applied across the two ends of manometer?
Homework Equations
P1-P2=50 kPa
P3-P2=(ρgh)alc
P3-P1=(ρgh)h2o...
Is manometer suppose to work below its natural frequency ?
I saw a textbook problem asking to design a manometer with its natural frequency way way below the pressure's fluctuation frequency, so was confused.
Thanks
How does the diameter change from one manometer say of radius x cm to say 2x or 3x cm change the height difference if the liquid in the manometer is of constant mass, density and gravitational field strength remains the same?
P.S could some working also be shown just to get a mathematical...
Homework Statement
The manometer illustrated in Fig. Q2 contains water and kerosene (specific
gravity of 0.82) as indicated. With both ends of the U-tube open the height
H0 =20 mm.
(i) Determine the height, h , when both ends of the tube are open. [4]
(ii) Determine the new value of...
Homework Statement
In the figure attached the pressure at A and B are the same 100 kPa. If water is introduced at A to increase p_A to 130 kPa find the new positions of the mercury menisci. The connecting tube has a diameter of 10 mm. Assume no change in Liquid density.
Homework...
Homework Statement
Determine the pressure of the water in pipe A shown in the figure (p2.56) if the gage pressure of the air in the tank is 2 psi.
I have attached the imageHomework Equations
The Attempt at a Solution
Figure P2.56
I drew a jumpline at 2ft above point A because everything...
Homework Statement
A venture flow-meter can be designed as
shown in the figure. At position 1 the
velocity is 0.5 m/s, and pressure is 1.3 bar.
The cross section area at 1 is two times the
area at 2. The fluid inside the manometer
has a density ρ, and the fluid column has a
high...
Hello. I'm reading a physics book on my own and am learning about pressure measurements. I have a question with how pressure is measured using a manometer. Here is a link talking about it:
http://www.upscale.utoronto.ca/PVB/Harrison/Manometer/Manometer.html
My question is, why do points...
I have been told to calculate the pressure drop between two points in a pipe carrying water using a U-tube manometer. I understand that the pressure drop (P1 - P2) is given by pgh and that h is the difference in manometer fluid levels and g is gravity, but is p the density of the manometer...
See Attached...
Homework Statement
A manometer is used to measure drop across an orifice plate measuring the flow of brine (salt water, s.g. = 1.260).
A) If the pressure drop is expected to be approx 1000 Pa, suggest an appropriate fluid. Why?
B) If the flow rate is anticipated...