Pressure Measurement Basics

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Questions and Answers

Which type of manometer measures absolute pressure?

  • Inclined manometer
  • Cistern manometer (correct)
  • Industrial U-tube manometer
  • Simple U-tube manometer (correct)

What shape is NOT commonly used for diaphragms in capsule gauges?

  • Cylindrical (correct)
  • Dished
  • Flat
  • Conical (correct)

Which of the following is a type of differential pressure measurement?

  • Metallic capsule
  • Single diaphragm (correct)
  • Slack diaphragm
  • Metallic bellows (correct)

Which type of diaphragm is used in bellows?

<p>Slack (C), Dished (D)</p> Signup and view all the answers

Which type of pressure does a gauge pressure measurement indicate?

<p>Pressure relative to atmospheric pressure (B)</p> Signup and view all the answers

What defines pressure in a physical context?

<p>The normal force per unit area exerted by a fluid on any surface (C)</p> Signup and view all the answers

Which of the following is NOT a type of static pressure?

<p>Dynamic pressure (C)</p> Signup and view all the answers

What is the equation used to calculate pressure?

<p>P = F/A (C)</p> Signup and view all the answers

Which tool is commonly used for measuring static pressure?

<p>Manometer (B)</p> Signup and view all the answers

Which type of pressure is defined as the sum of atmospheric pressure and gauge pressure?

<p>Absolute pressure (C)</p> Signup and view all the answers

What type of manometer is the simplest form of pressure measurement?

<p>Simple U-tube manometer (D)</p> Signup and view all the answers

Which type of pressure can vary over time?

<p>Dynamic pressure (B)</p> Signup and view all the answers

Which of the following is NOT a method of measuring pressure?

<p>Alternative liquid measurement (D)</p> Signup and view all the answers

What does the gauge pressure measure?

<p>Pressure relative to ambient atmospheric pressure (A)</p> Signup and view all the answers

Which one of the following is a type of differential pressure measurement?

<p>Inclined manometer (A)</p> Signup and view all the answers

What type of pressure measurement is primarily associated with the Ring balance manometer?

<p>Static pressure (D)</p> Signup and view all the answers

Which of the following manometers utilizes a two-liquid setup?

<p>Two-liquid U-tube manometer (D)</p> Signup and view all the answers

When a pressure difference is applied across the partition in a Ring balance manometer, what occurs?

<p>A rotating moment is established (B)</p> Signup and view all the answers

Which of the following is NOT a type of pressure measured?

<p>Vacuum pressure (A)</p> Signup and view all the answers

What is the main advantage of using a two-liquid setup in pressure measurement?

<p>It increases accuracy and sensitivity (D)</p> Signup and view all the answers

Which of the following pressure measurement types can provide a direct indication of atmospheric pressure?

<p>Absolute pressure (B)</p> Signup and view all the answers

What is the primary advantage of using a two-liquid U-tube manometer for measuring small pressure differences?

<p>The use of two liquids with different densities enhances sensitivity. (C)</p> Signup and view all the answers

In which application is a two-liquid U-tube manometer NOT commonly used?

<p>Measuring atmospheric pressure at sea level. (A)</p> Signup and view all the answers

When measuring differential pressure, which device setup is typically employed?

<p>Single diaphragm manometer (C)</p> Signup and view all the answers

What does the term 'gauge pressure' refer to?

<p>Pressure relative to atmospheric pressure (A)</p> Signup and view all the answers

Which type of pressure measurement is specifically highlighted for its sensitivity to low-density gases?

<p>Differential pressure measurement. (B)</p> Signup and view all the answers

What is one common application of a two-liquid U-tube manometer in industrial processes?

<p>Precise pressure control in chemical and pharmaceutical processes. (C)</p> Signup and view all the answers

Which manometer is particularly suitable for measuring small pressure changes?

<p>Two-liquid U-tube manometer (A)</p> Signup and view all the answers

In a typical manometric setup, what is the primary function of the diaphragm?

<p>To serve as a pressure sensing element (B)</p> Signup and view all the answers

Why are two-liquid U-tube manometers preferred for laboratory experiments involving precise air measurement?

<p>They provide greater precision for low-pressure differences. (C)</p> Signup and view all the answers

How does a two-liquid U-tube manometer compensate for low-pressure fluctuations?

<p>By employing liquids with significantly different densities. (A)</p> Signup and view all the answers

What is the relationship expressed in the formula $p_1 - p_2 = g h (\rho_2 - \rho_1)$?

<p>The pressure difference is proportional to the height difference of the liquids. (B)</p> Signup and view all the answers

Which characteristic is critical for accurately measuring pressure in ventilation systems using a two-liquid U-tube manometer?

<p>Sensitivity to small pressure differences. (B)</p> Signup and view all the answers

What is the main advantage of using an inclined tube manometer compared to a simple U-tube manometer?

<p>It provides a longer scale for measuring small differential pressures. (A)</p> Signup and view all the answers

In the formula $p_1 - p_2 = \rho g d \cdot sin \alpha$, what does $d$ represent?

<p>The distance measured along the incline. (D)</p> Signup and view all the answers

When comparing the pressures in an inclined tube manometer, which condition allows the ratio $A_2/A_1$ to be neglected?

<p>When $A_1$ is large compared to $A_2$. (B)</p> Signup and view all the answers

Which of the following types of manometers is NOT mentioned as a type of differential pressure measurement device?

<p>Digital manometer. (D)</p> Signup and view all the answers

What is measured by a differential pressure manometer?

<p>The difference between two pressures. (C)</p> Signup and view all the answers

Which parameter affects the accuracy of a manometer measurement?

<p>The length of the inclined tube. (D)</p> Signup and view all the answers

Which type of pressuring device employs diaphragms in its measurement mechanism?

<p>Diaphragm stack. (A)</p> Signup and view all the answers

When analyzing an inclined tube manometer, which of the following equations correctly relates pressure difference to fluid height?

<p>$p_1 - p_2 = \rho g d \cdot sin \alpha$. (D)</p> Signup and view all the answers

What does the term 'static pressure' generally refer to?

<p>The pressure exerted by a fluid at rest. (C)</p> Signup and view all the answers

What is the primary purpose of using a manometer?

<p>To measure pressure. (D)</p> Signup and view all the answers

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Study Notes

Introduction

  • Inaccurate pressure measurement can lead to disasters

Pressure Definition

  • Pressure is defined as the normal force per unit area exerted by a fluid on a surface
  • P=F/A, where P - Pressure, F - Normal force, A - Area

Types of Pressure

  • Two types of pressures exist: Static and Dynamic
  • Static Pressure: force is constant in time
  • Dynamic Pressure: force is varying in time

Static Pressure Measurement

  • Static pressure measurements include: Absolute, Gauge, and Differential Pressure
  • Pabs = Patm + Pg, where Pabs - Absolute pressure, Patm - Atmospheric pressure, Pg - Gauge pressure

Static Pressure Measurement Methods

  • Manometers are used to measure static pressures
  • Manometers can be classified as the following:
    • Simple U-tube Manometer
    • Industrial U-Tube Manometer
    • Cistern Manometer
    • Two-liquid U-Tube Manometer
    • Inclined Manometer
    • The ring balance
    • Diaphragms and bellows: Single diaphragm, diaphragm stack, metallic capsule, metallic bellows

The Simple U-tube Manometer

  • Consists of a U-shaped glass tube containing liquid
  • Two liquid U-tube manometer: p1 - p2 = g h 𝜌2 - 𝜌1

Applications of Two-liquid U-tube manometer

  • Measurement of Small Pressure Differences in Low-Pressure Systems: used in labs, research settings, air measurement systems to measure small pressure differences
  • Gas and Airflow Measurement in HVAC Systems: used for monitoring airflow in ventilation ducts and filters, provides precision
  • Differential Pressure Measurement for Low-Density Gases: used in fuel cells, controlled gas supply systems to measure differential pressures in gases with low density
  • Industrial Processes Requiring High Sensitivity: used in chemical and pharmaceutical industries where sensitive reactions or materials are used

The Ring Balance Manometer

  • P1 = P2, P1 > P2
  • When there is a pressure difference, a rotating moment is setup

The Inclined Tube Manometer

  • Increase in accuracy due to the increased length of the scale
  • p1 - p2 = 𝜌𝑔 ℎ1 + ℎ
  • ℎ = 𝑑 sin 𝛼
  • ℎ1 = 𝐴2/𝐴1 ⋅𝑑
  • p1 - p2 = 𝜌𝑔𝑑 𝐴2/𝐴1 + sin 𝛼
  • If A1>>A2: p1 - p2 = 𝜌𝑔𝑑 ⋅ sin 𝛼 = 𝜌𝑔ℎ
  • Sensitivity of the inclined tube manometer is given by: 𝑆𝑖𝑛𝑐. = 𝑑/ℎ.

Metallic Capsule

  • Used in capsule gauges
  • Common shapes of diaphragms: Dished, Flat, and c

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