Sample Questions

Question 1: Explain sealed gauge and vented gauge?

Answer: 

• Vented Gauge pressure: A vented gauge pressure transmitter lets in the outside air strain to be exposed to the negative side of the pressure sensing diaphragm in order that it continually measures with regards to the ambient atmospheric pressure. Consequently when the pressure process connection is held open to atmospheric air a vented gauge pressure sensor reads zero pressure
• Sealed Gauge Pressure: A sealed gauge reference is practically the same with the exception of that barometric pressure is sealed on the negative side of the diaphragm. This is normally taken on high pressure applications, for example, estimating water driven pressures where atmospheric pressure changes will affect the precision of the sensor. It is the pressure estimated through a sealed gadget in which the zero point is set. This set point is anything that the pressure within the gadget was prior to sealing, which the maker of the sealed pressure gauge chooses.

Question 2: How do you have any idea when to quantify absolute pressure or when to quantify gauge pressure?

Answer:

This isn’t generally clear however for the most part if you have any desire to quantify or control a pressure that is impacted by changes in barometric pressure, similar to the degree of fluid in an open tank for instance; you would pick Vented gauge pressure as you are keen on the pressure perusing minus the barometric pressure component.

If you have any desire to quantify pressures that are not impacted by changes in barometrical pressure, for example spill testing a totally sealed non-adaptable container, you would utilize an Absolute pressure sensor. Assuming a gauge pressure sensor was utilized rather to quantify the container pressure, and the atmospheric pressure changed, then the sensor’s reading would change, regardless of the way that the pressure in the container continues as before.

Question 3: If the atmospheric pressure is 14 psi and a pressure gauge measures the reading as 39 psi. Calculate the absolute pressure that corresponds to this gauge pressure reading.

Answer:

From above parameters:

Atmospheric pressure P_atm = 14 psi

Gauge pressure, P_g = 39 psi

According to the formula,

Absolute pressure P_abs = P_atm + P_g

P_abs = 14 psi+39 psi

P_abs = 53 psi

Hence Absolute pressure is 53 psi.

Question 4: Calculate the corresponding gauge pressure if an absolute pressure instrument reading is given as 38.8 psi and at atmospheric pressure of 15 psi.

Answer:

From the given readings,

Atmospheric pressure P_atm = 15 psi

Absolute pressure P_abs = 38.8 psi

From the known formula

P_g= p_abs – p_atm

Now the Gauge pressure calculated as

P_gauge = 38.8 psi – 15 psi  = 23.8 psi.

Hence Gauge pressure calculated is 23.8 psi.

Question 5: At a depth of 11 m from the free surface what is the absolute pressure of water if P_atm is 102.213 kN.m²?

Answer:

As we know from Hydrostatic law, at any point in a static liquid, the local specific weight of liquid must be equal to the vertical rate of increase of pressure.

Therefore, P_g = p ×g × h

Where, P_g is gauge pressure, p is density of water, g is acceleration due to gravity (9.8 m/s²), h is the height below the static liquid surface

Absolute pressure P_abs = P_g + P_atm

From given data,

h= 11m,  P_atm = 102.213 kN/m²  ,  p= 1000 kg/m³

P_g = p g h = 1000 × 9.8 ×11 = 107800 N/m²= 107.8kN/m²

Applying the equation

P_abs = 102.213 + 107.8 = 210.013 kN/m²

Hence the absolute pressure calculated is 210.013 kN/m² 

Question 6:  What will be the gauge pressure at a depth of 990 m in the ocean when the given density of seawater is 1.02 x 10³ kg/m³? Consider gravitational acceleration g is 9.8m/s².

Answer:

From the given data we know that,

h = 990 m,  p = 1020 kg/m³, g = 9.8m/s²

At a depth h, Gauge pressure P_g = p g h / 10⁵ atm

Where, p is the density of water, g is acceleration due to gravity, h is the depth of the water

Applying the values,

P_g = 1020 ×9.8 × 990 / 10⁵

Therefore P_g = 98.96 atm

Pressure is the force per unit area applied toward a course perpendicular to the outer layer of an item. Numerically, it is represented with a ‘P’. To keep it precise, it is an amount of force following up on a unit area. The simple equation for pressure is P = F/A where P is Pressure, F is Force, and A is Area.

The SI unit for pressure is measured in Pascals (Pa). Other non-SI units are bar and PSI. There are two types of references to quantify pressure,

• Gauge Pressure
• Absolute Pressure