Industrial Measurements Archives - Electrical and Electronics Blog https://howelectrical.com/category/industrial-measurements/ Power System, Power electronics, Switch Gear & Protection, Electric Traction, Electrical Machine, Control System, Electrical Instruments & Measurement. Mon, 03 Feb 2025 19:35:58 +0000 en-US hourly 1 https://wordpress.org/?v=6.7.2 https://howelectrical.com/wp-content/uploads/2022/10/cropped-cropped-how-electrical-logo-32x32.png Industrial Measurements Archives - Electrical and Electronics Blog https://howelectrical.com/category/industrial-measurements/ 32 32 What is pH Meter? Definition, Construction, Working, Types, Advantages, Disadvantages & Applications https://howelectrical.com/ph-meter/ https://howelectrical.com/ph-meter/#respond Wed, 15 Jan 2025 18:09:23 +0000 https://howelectrical.com/?p=4049 A pH meter is an electronic instrument used to measure the acidity or alkalinity of a solution, expressed as pH. The pH scale ranges from 0 to 14, where a pH of 7 indicates neutrality, values below 7 indicate acidity, and values above 7 indicate alkalinity. A pH meter provides precise pH readings, which are […]

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A pH meter is an electronic instrument used to measure the acidity or alkalinity of a solution, expressed as pH. The pH scale ranges from 0 to 14, where a pH of 7 indicates neutrality, values below 7 indicate acidity, and values above 7 indicate alkalinity. A pH meter provides precise pH readings, which are essential in various scientific, industrial, and environmental applications.

Construction of a pH Meter

pH Meter

A pH meter typically consists of the following components:

  1. pH-Sensitive Electrode: The main sensor of the pH meter, usually made of glass, which responds to hydrogen ion activity. It has a pH-sensitive glass membrane at its tip that interacts with the solution being tested.
  2. Reference Electrode: Contains a stable electrolyte solution (commonly potassium chloride) and serves as a reference point for the pH measurement. Includes a porous plug for ionic exchange with the test solution.
  3. Silver Chloride Coated Silver Wires: Present inside both the pH-sensitive and reference electrodes for electrical connectivity.
  4. Temperature Sensor: Measures the temperature of the solution since pH measurements are temperature-dependent.
  5. Signal Conditioning and Output: Converts the small voltage generated by the electrodes into a readable pH value. The output is displayed on a digital or analog screen.
  6. Electrolyte Solution: Maintains the ionic balance inside the electrodes to facilitate accurate readings.

Working Principle of a pH Meter

The working of a pH meter is based on the Nernst equation, which relates the electric potential generated by the pH-sensitive electrode to the hydrogen ion concentration in the solution.

  1. Electrode Interaction: The pH-sensitive electrode interacts with hydrogen ions in the test solution. The reference electrode provides a stable voltage as a comparison point.
  2. Voltage Generation: The difference in hydrogen ion concentration between the inner solution of the electrode and the external solution generates a small voltage.
  3. Temperature Compensation: The temperature sensor adjusts the pH reading to account for the effect of temperature on the ion activity.
  4. Signal Processing: The generated voltage is processed by the signal conditioning unit, which converts it into a pH value displayed on the meter.

Types of pH Meters

 

Type Description
Benchtop pH Meters Used in laboratories for precise measurements with advanced features like data logging.
Portable pH Meters Lightweight and battery-powered, ideal for fieldwork and on-site testing.
Pen-Type pH Meters Compact and easy to use, suitable for quick tests in less demanding applications.
Industrial pH Meters Designed for continuous monitoring in industrial processes, often integrated with automation systems.
Specialized pH Meters Tailored for specific applications, such as food, pharmaceuticals, or soil testing.

Advantages of pH Meters

  1. High Precision: Offers accurate measurements with minimal errors.
  2. User-Friendly: Easy to operate with digital displays and automatic calibration features.
  3. Versatility: Applicable across various fields, including environmental science, biology, and industry.
  4. Portability: Portable models allow for on-site testing.
  5. Wide Range of Measurements: Suitable for acidic, neutral, and basic solutions.

Disadvantages of pH Meters

  1. Calibration Requirement: Requires frequent calibration for accurate results.
  2. Fragility: The glass electrode is delicate and prone to breakage.
  3. Dependency on Temperature: Measurements can be affected by temperature changes if not compensated.
  4. Maintenance: Electrodes need to be cleaned and stored properly to prevent contamination or damage.
  5. Cost: High-quality pH meters can be expensive.

Applications of pH Meters

  1. Environmental Monitoring: Testing the pH of water bodies to monitor pollution levels and aquatic health.
  2. Agriculture: Soil pH testing to optimize crop growth and fertilizer application.
  3. Food and Beverage Industry: Ensuring product quality by monitoring the pH of ingredients and final products.
  4. Pharmaceuticals: Measuring the pH of solutions in drug formulations and quality control.
  5. Chemical Industry: Monitoring reactions and ensuring the safety of chemical processes.
  6. Wastewater Treatment: Controlling pH during the treatment process to comply with environmental regulations.
  7. Biotechnology and Research: Maintaining appropriate pH levels in biological experiments and cell culture media.
  8. Aquariums and Aquaculture: Ensuring suitable pH levels for aquatic organisms.

Conclusion

A pH meter is an indispensable tool in scientific and industrial applications for accurately determining the acidity or alkalinity of solutions. Despite its limitations, advancements in technology have made pH meters more robust, user-friendly, and versatile. Proper maintenance and calibration ensure their reliable performance across a wide range of applications.

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What is Turbine Flow Meter? Working Principle, Diagram, Construction, Advantages & Applications https://howelectrical.com/turbine-flow-meter/ https://howelectrical.com/turbine-flow-meter/#respond Wed, 01 Jan 2025 12:47:32 +0000 https://howelectrical.com/?p=3620 A turbine flow meter is a device used to measure the flow rate of a fluid (liquid or gas) by converting the kinetic energy of the fluid into rotational motion of a turbine. The flow rate is proportional to the rotational speed of the turbine. Figure 1: Turbine Flow Meter. Working Principle of Turbine Flow […]

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A turbine flow meter is a device used to measure the flow rate of a fluid (liquid or gas) by converting the kinetic energy of the fluid into rotational motion of a turbine. The flow rate is proportional to the rotational speed of the turbine.

Figure 1: Turbine Flow Meter.

Working Principle of Turbine Flow Meter

The turbine flow meter is based on Faraday’s Law of Electromagnetic Induction. As the liquid flows through the pipe, it rotates the rotor. The rotor’s blades are equipped with permanent magnets, which create a magnetic field.

When fluid flows through the pipe, the rotor starts to rotate due to the kinetic energy of the flowing liquid. The speed of rotation of the rotor is proportional to the flow rate of the liquid.

As the rotor rotates, the magnetic poles (N and S) of the magnets pass near the coil. This induces voltage pulses in the coil.

The frequency of the voltage pulses corresponds to the rotational speed of the rotor. By counting these pulses, the flow rate of the liquid can be determined.

Construction of Turbine Flow Meter

Pipe (1): Through which the liquid or gas flows.

Rotor (Turbine) (2): Inside the pipe, a rotor or turbine with small permanent magnets is mounted on a shaft. The rotor blades are angled to make the turbine rotates as fluid flows through it.

Shaft (3): The rotor is connected to a shaft that holds it in place and allows free rotation.

Coil (4): A magnetic pickup coil is placed outside the pipe. It senses the magnetic field changes caused by the rotating rotor.

Working of Turbine Flow Meter

At the centre of pipe line a shaft is supported in the bearing. Turbine blades NS, NS, NS pairs are fitted on the shaft. Rate of rotation of rotor is proportional to the rate of flow of liquid through the pipe. At the surface of the pipe a coil having no. of turns is fitted firmly. Now rotor blades rotate as fluid flow is impinged on them. Rotor blades are alternately N-pole, S-pole and hence a magnetic field is around the poles.

When the rotor rotates the magnetic field produced by them also rotates. It is a rotating magnetic field. This flux is cut by the number of turns of the coil fitted on the surface of pipe. As per Faraday’s law therefore EMF i.e. voltage is produced in the coil. Value of this voltage depends on the rotational speed of rotor and rotation is due to the flow of liquid.

Voltage ∝ fluid flow rate

The scale is calibrated such that this voltage indicates the fluid flow rate.

Advantages of Turbine Flow Meter

  1. Better accuracy.
  2. Allows low pressure drop.
  3. It provides excellent repeatability and rangeability.
  4. Low maintenance.
  5. Easy installation.
  6. It gives good temperature and pressure ratings.
  7. Accuracy range is from ± 0.25% to ± 0.50%.
  8. Repeatability ranging is from ±0.25% to ± 0.02%.
  9. Available in sizes from 6.25 mm to 60 mm.
  10. Liquid flow rate from 0.1 to 50,000 gallons/minute.

Disadvantages of Turbine Flow Meter

  1. Very costly.
  2. Creates problems for non-lubricating fluids.

Applications of Turbine Flow Meter

  1. For measurements of liquid, gas.
  2. Measuring low flow rates.
  3. In military operations.
  4. Useful in blending system for petroleum industries.
  5. Useful in airborne applications for energy fuel and cryogenic (liquid, Oxygen and Nitrogen) flow measurement.

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What is Venturimeter? Working Principle, Construction, Formula, Diagram and Applications https://howelectrical.com/venturimeter/ https://howelectrical.com/venturimeter/#respond Tue, 31 Dec 2024 11:40:40 +0000 https://howelectrical.com/?p=3595 Figure 1: Venturimeter. A venturimeter is a device used to measure the flow rate of a fluid (liquid or gas) through a pipe. It is based on the principle of Bernoulli’s equation, which relates the pressure, velocity, and elevation of a fluid in steady flow. Working Principle of Venturimeter The venturimeter operates on the principle […]

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Venturimeter

Figure 1: Venturimeter.

A venturimeter is a device used to measure the flow rate of a fluid (liquid or gas) through a pipe. It is based on the principle of Bernoulli’s equation, which relates the pressure, velocity, and elevation of a fluid in steady flow.

Working Principle of Venturimeter

The venturimeter operates on the principle of the Venturi effect, which states that when a fluid flows through a constricted section of a pipe, its velocity increases while the pressure decreases. By measuring the pressure difference between the wider section and the constricted throat, the flow rate can be determined.

Main Parts of Venturimeter

  1. U-tube manometer
  2. High pressure tap
  3. Low pressure tap
  4. Diameter at inlet section (D)
  5. Diameter at throat section (d)
  6. α1 inclined angle (19 to 23°)
  7. α2 inclined angIe (5° to 15°)

Construction of Venturimeter

  1. Inlet Section:
    • A large-diameter section where the fluid enters.
    • It is connected to a high-pressure tap for pressure measurement.
  2. Converging Section:
    • A gradually tapering section reduces the pipe diameter.
    • This accelerates the fluid, increasing its velocity and lowering the pressure.
  3. Throat Section:
    • The narrowest section where the fluid velocity is at its maximum, and the pressure is at its minimum.
    • A low-pressure tap is placed here.
  4. Diverging Section:
    • A gradually expanding section that slows down the fluid, recovering some of the pressure.
    • Ensures the flow returns to normal conditions downstream.
  5. Pressure Taps:
    • High-pressure and low-pressure taps connected to a U-tube manometer.
    • Measures the pressure difference (Δ between the inlet and throat.

Working of Venturimeter

Fluid enters the venturimeter through the inlet, where the pressure is measured using the high-pressure tap. As the fluid passes through the converging section, its velocity increases, and the pressure decreases due to the reduced cross-sectional area. At the throat, the velocity is at its maximum, and the pressure is at its minimum. The low-pressure tap measures the pressure at this point. The U-tube manometer measures the pressure difference between the inlet and the throat. The height difference (Δ) in the manometer corresponds to the pressure difference. The fluid slows down as it flows through the diverging section, recovering some pressure while avoiding flow separation.

Liquid flow route

Flow comes from pipe of diameter ‘D’ and introduces inside, then passed through throat of less diameter ‘d’ then comes in the diverging section of inclination of angle α2.

Location of pressure taps from where the manometer tube is introduced – One tap at inlet section and second at middle of throat section. This arrangement provided to measure the pressure difference (P1 – P2) by manometer u-tube.

Derivation of Flow Rate for a Venturimeter

The derivation involves applying Bernoulli’s equation and the continuity equation.

From Bernoulli’s Equation

\[P_1 + \frac{1}{2} \rho v_1^2 = P_2 + \frac{1}{2} \rho v_2^2\]

Rearranging to find the pressure difference:

\[P_1 – P_2 = \frac{1}{2} \rho \left( v_2^2 – v_1^2 \right)\]

The continuity equation is:

\[A_1 v_1 = A_2 v_2\]

From this, the velocity at the inlet (\(v_1\)) is expressed as:

\[v_1 = \frac{A_2}{A_1} v_2\]

Substituting \(v_1 = \frac{A_2}{A_1} v_2\) into the Bernoulli’s equation for pressure difference

\[P_1 – P_2 = \frac{1}{2} \rho \left( v_2^2 – \left( \frac{A_2}{A_1} v_2 \right)^2 \right)\]

Also

\[P_1 – P_2 = \frac{1}{2} \rho v_2^2 \left( 1 – \left( \frac{A_2}{A_1} \right)^2 \right)\]

The pressure difference (\(\Delta P\)) is

\[\Delta P = P_1 – P_2 = \frac{1}{2} \rho v_2^2 \left( 1 – \left( \frac{A_2}{A_1} \right)^2 \right)\]

Rearranging for \(v_2\)

\[v_2 = \sqrt{\frac{2 \Delta P}{\rho \left( 1 – \left( \frac{A_2}{A_1} \right)^2 \right)}}\]

The volumetric flow rate (\(Q\)) is

\[Q = A_2 v_2\]

Substitute \(v_2\)

\[Q = A_2 \sqrt{\frac{2 \Delta P}{\rho \left( 1 – \left( \frac{A_2}{A_1} \right)^2 \right)}}\]

The final flow rate equation is

\[Q = A_2 \sqrt{\frac{2 \Delta P}{\rho \left( 1 – \left( \frac{A_2}{A_1} \right)^2 \right)}}\]

where,

: Cross-sectional areas of the inlet and throat.

Δ: Pressure difference.

: Fluid density.

Advantages of Venturimeter

  1. Accurate measurement of flow rate.
  2. Low energy loss compared to orifice meters.
  3. Suitable for large-diameter pipes.
  4. Good characteristics.
  5. Suitable for flow of suspended fluids.
  6. More accurate.
  7. Low permanent loss.
  8. Suitable for high flow rate.
  9. No tear or wear as surface is smooth.

Disadvantages of Venturimeter

  1. Large size so occupies more space.
  2. Higher cost.
  3. Not easy for inspection.
  4. It cannot be used for small pipe diameters.

Applications of Venturimeter

  1. Used in water supply systems, oil pipelines, and chemical industries.
  2. For measurements, liquids, slurries, dirty fluids etc.

Features of Venturimeter

  1. The main venturi tube is of cast iron or steel.
  2. Flow coefficients = 0.984.
  3. Accuracy much more ± 0.25 to ± 3%.
  4. Sizes 100 mm to 813 mm.

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What is Orifice Meter? Working Principle, Construction and Diagram https://howelectrical.com/orifice-meter/ https://howelectrical.com/orifice-meter/#respond Sun, 29 Dec 2024 09:40:52 +0000 https://howelectrical.com/?p=3579 Figure 1: Orifice Meter. An orifice meter is a device used to measure the flow rate of a fluid (liquid or gas) through a pipeline. Orifice meter is a thin plate with a central narrow aperture which is introduced in a pipeline. Thus, when a fluid stream passes through the narrow constriction of the orifice, […]

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Orifice Meter

Figure 1: Orifice Meter.

An orifice meter is a device used to measure the flow rate of a fluid (liquid or gas) through a pipeline. Orifice meter is a thin plate with a central narrow aperture which is introduced in a pipeline. Thus, when a fluid stream passes through the narrow constriction of the orifice, the velocity (i.e., kinetic energy) of the fluid at the orifice plate increases in comparison with its velocity at the entry of the pipe. Thus, the corresponding pressure energy decreases. The reduction in pressure can be measured by the manometer.

Working Principle of Orifice Meter

According to the Bernoulli’s theorem, the increase in the velocity head with the decrease in pressure head can be correlated between the two points i.e., where the manometer is arranged in a pipeline. The velocity of the fluid at the point (before entering the orifice) can be neglected due to the smaller diameter of the orifice than pipe diameter. In such a case, the velocity of the fluid is directly read from the manometer. The velocity of the fluid at the orifice can be calculated from the following formula.

\[{{u}_{0}}=\sqrt{2{{g}_{c}}\Delta H}……(1)\]

Where,

u0 = Fluid velocity at the point of orifice

C0 = Constant of orifice meter

ΔH = Difference in pressure head, m.

This is the simplest and widely used pressure differential flow meter. It consists of a thin plate with a central narrow aperture, which is smaller in diameter than the pipeline in which it is introduced. To measure the pressure difference, the manometer is connected to the pipe. The orifice meter can be placed in the side or bottom of the pipeline.

Working of Orifice Meter

When the fluid is introduced in the pipe, it passes through the narrow constriction of the orifice meter. Two points A and B are chosen in the orifice meter to demonstrate the velocity of the fluid flowing through the orifice. The fluid leaves the constriction of the orifice meter at point B with a velocity higher than the velocity at point A. Thus, the corresponding pressure head at point B is less than the pressure head at point A. The pressure difference (ΔH) is read from the manometer which is arranged at the points A and B.

The Bernoulli’s equation is applied for the two points A and B in the orifice meter as follows,

\[\sqrt{u_{0}^{2}-u_{A}^{2}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H}\]

Where,

u0 = Fluid velocity at the point of orifice meter, m/s

uA = Fluid velocity at the point A, m/s

C0 = Constant

ΔH = Pressure difference, m.

When the diameter of the orifice is very less compared to the diameter of the pipe, then velocity of the fluid at point A (uA) is less compared to the velocity of the fluid at the constriction (u0). Hence, uA is ignored.

Thus, equation (1) becomes

\[\sqrt{u_{0}^{2}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H}\]

\[{{u}_{0}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H}……(2)\]

The value of ‘ΔH’ is read from the manometer and substituted in equation (2) to calculate the velocity of the fluid flowing through the orifice meter, provided that the cross section of the pipe is known. The volume of the fluid flowing per hour is calculated.

In the above stated experimental conditions, the Bernoulli’s theorem is applied as follows.

\[{{X}_{A}}+\frac{u_{A}^{2}}{2{{g}_{c}}}+\frac{{{P}_{A}}}{g{{\rho }_{A}}}-F+W={{X}_{B}}+\frac{u_{B}^{2}}{2{{g}_{c}}}+\frac{{{P}_{B}}}{g{{\rho }_{B}}}……(3)\]

In the above equation, the following assumptions can be made to the orifice meter.

  1. XA = XB because the heights of the points A and B are same and hence the terms get cancelled.
  2. F = 0, friction losses are not appreciable and considered negligible.
  3. ρA = ρB = ρ, because the fluid flowing through the orifice is the same.
  4. W = 0, no work is done by the liquid.

The equation (3) is reduced to,

\[\frac{u_{A}^{2}}{2{{g}_{c}}}+\frac{{{P}_{A}}}{g\rho }=\frac{u_{B}^{2}}{2{{g}_{c}}}+\frac{{{P}_{B}}}{g\rho }\]

\[\frac{u_{B}^{2}}{2{{g}_{c}}}-\frac{u_{A}^{2}}{2{{g}_{c}}}=\frac{{{P}_{A}}}{g\rho }-\frac{{{P}_{B}}}{g\rho }\]

\[\frac{1}{2{{g}_{c}}}(u_{B}^{2}-u_{A}^{2})=\frac{1}{u_{B}^{2}}({{P}_{A}}-{{P}_{B}})\]

\[u_{B}^{2}-u_{A}^{2}=\frac{2{{g}_{c}}}{g\rho }({{P}_{A}}-{{P}_{B}})\]

\[u_{B}^{2}-u_{A}^{2}=\frac{2{{g}_{c}}}{g\rho }.\Delta P\text{          }\left[ {{P}_{A}}-{{P}_{B}}=\Delta P\text{ } \right]\]

\[u_{B}^{2}-u_{A}^{2}=2{{g}_{c}}.\Delta H\text{           }\left[ \frac{\Delta P}{g\rho }=\Delta H\text{ } \right]\]

To nullify the differences between the velocities at orifice and at vena contracta (point B) a constant, C0 is included.

\[\sqrt{u_{B}^{2}-u_{A}^{2}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H\text{ }}\]

The velocity through the orifice is u0.

\[\sqrt{u_{0}^{2}-u_{A}^{2}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H\text{ }}\]

uA, is negligible as the orifice diameter is 1/5 th of the pipe diameter or less.

\[{{u}_{0}}={{C}_{0}}\sqrt{2{{g}_{c}}.\Delta H\text{ }}\]

Advantages of Orifice Meter

  1. It is a simple machine having low cost.
  2. It requires less space.
  3. Easy to install and interchange.
  4. Adjustable orifices are available.

Disadvantages of Orifice Meter

  1. Permanent loss of pressure.
  2. When the ratio of orifice to pipe diameter is above 0.75, the results are not accurate.
  3. If the fluid contains solid particles, it may obstruct the orifice.
  4. The orifice meter is not recommended above 1000 psi at 800ºF.

Applications of Orifice Meter

The velocity of the fluid at the two points (A and B) can be calculated. The volume of the fluid flowing per hour can be determined provided that the velocity of the fluid at point A (uA) and cross-section of the pipe are known. Orifice meters are used in industries like oil and gas, water treatment, power, and HVAC for measuring fluid and gas flow. Applications include natural gas pipelines, boiler feed water, steam, chemical processing, slurry flow, and air systems. They’re cost-effective, reliable, and versatile for diverse industrial and commercial flow measurement needs.

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What is McLeod Gauge? Working Principle, Diagram, Construction & Advantages https://howelectrical.com/mcleod-gauge/ https://howelectrical.com/mcleod-gauge/#respond Wed, 25 Dec 2024 10:27:22 +0000 https://howelectrical.com/?p=3529 The McLeod gauge is used for measuring pressures ranging from 0.01 micron to 1 mm of Hg. Figure 1: McLeod Gauge. Working Principle of McLeod Gauge It operates on the principle of compressing a known volume of low pressure gas to a higher pressure and measuring the resulting change in volume by a mercury manometer. […]

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The McLeod gauge is used for measuring pressures ranging from 0.01 micron to 1 mm of Hg.

McLeod Gauge

Figure 1: McLeod Gauge.

Working Principle of McLeod Gauge

It operates on the principle of compressing a known volume of low pressure gas to a higher pressure and measuring the resulting change in volume by a mercury manometer.

Construction and Working of McLeod Gauge

The construction of McLeod gauge is shown in Fig. 1. McLeod gauge comprises a system of glass tubing made of tough glass and mercury is used to trap the known volume of gas. The gauge is connected to the unknown gas whose pressure is to be measured.  The plunger moves up, lowers the mercury level to the cut off positions, entering the gas at unknown pressure through the tube.

This gas fills the tubes down to the cut off position of mercury level. Here the pressure is equal throughout the tubes.

Now the plunger is moved down to rise the mercury above the cut-off and traps the gas inside the bulb and measuring capillary.

Further pushing of plunger compresses the gas in the measuring capillary and mercury in the reference capillary reaches to zero reference line.

The pressure in the measuring capillary is higher than the measured pressure in the reference capillary. This difference in pressure causes the difference in mercury level in two tubes.

This difference in height represents the rise in gas pressure and unknown pressure is calculated.

Advantages of McLeod Gauge

  1. It is very simple in use.
  2. Measurement is independent of gas composition and it is related to physical dimensions of gauge.
  3. It is a very accurate pressure measuring device.
  4. It can be used as a standard to calibrate other low pressure gauges.

Disadvantages of McLeod Gauge

  1. If the gas contains the vapour, it may not give correct result.
  2. It is applicable to those systems where mercury is tolerable.
  3. It does not give continuous output.

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What is Ionization Gauge? Working Principle, Diagram, Construction & Advantages https://howelectrical.com/ionization-gauge/ https://howelectrical.com/ionization-gauge/#respond Wed, 25 Dec 2024 10:03:57 +0000 https://howelectrical.com/?p=3508 Figure 1: Ionization Gauge. Working Principle of Ionization Gauge Extremely low pressures can be measured with ionization gauge (10-3 torr and below). Ionization means process of producing free electron and a positively charged ions by knocking off an electron from an atom. A simple arrangement of hot filament ionization gauge is shown in Fig. 1. […]

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Ionization Gauge

Figure 1: Ionization Gauge.

Working Principle of Ionization Gauge

Extremely low pressures can be measured with ionization gauge (10-3 torr and below). Ionization means process of producing free electron and a positively charged ions by knocking off an electron from an atom. A simple arrangement of hot filament ionization gauge is shown in Fig. 1.

Working and Construction of Ionization Gauge

The gauge consists of triode vacuum tube i.e. cathode, grid and anode plate. Cathode serves as a heated filament. Grid is positive changed.  The anode plate is maintained at negative potential with respect to cathode.

Thus the cathode plate is positive ions collector and anode plate is electron collector. This assembly is kept in a vacuum system whose pressure is being measured.

The heated cathode emits the electrons which move past the grid. The positive grid accelerates these electrons where they collide with gas molecules causing its ionization.

The anode is negative so positive ions collect there producing plate current Il the electrons and negative ions are collected by grid, produces grid current I2 in the grid circuit.

This ratio of current Il and I2 gives the vacuum pressure measurement. The vacuum pressure is given by,

\[{{P}_{vaccum}}=\frac{{{I}_{1}}}{{{{I}_{2}}K}}\]

Where k is the proportionality constant known as sensitivity of the gauge.

Advantages of Ionization Gauge

  1. Very low pressure measurement up to 10-11 torr is possible.
  2. It can give continuous pressure reading.
  3. They have good linearity.
  4. Best suited for the wide pressure range from 10-3 torr to 10-9 torr.

Disadvantages of Ionization Gauge

  1. Few gases like oxygen carbon dioxide get decomposed by the hot filament.
  2. Chances of burning the filament if exposed to air.

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What is Rotameter? Working Principle, Diagram, Construction, Advantages & Applications https://howelectrical.com/rotameter/ https://howelectrical.com/rotameter/#respond Tue, 24 Dec 2024 21:06:40 +0000 https://howelectrical.com/?p=3468 In rotameter, the area of flow is measured in such a way that the head differential is constant. Hence rotameter is called variable area meter or area meter. Rotameters are widely used for metering purge flows, pump-seal fluid and coolants and lubricants for operating machinery. Figure 1: Rotameter. Working Principle of Rotameter Rotameter consists of […]

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In rotameter, the area of flow is measured in such a way that the head differential is constant. Hence rotameter is called variable area meter or area meter. Rotameters are widely used for metering purge flows, pump-seal fluid and coolants and lubricants for operating machinery.

Rotameter

Figure 1: Rotameter.

Working Principle of Rotameter

Rotameter consists of a vertical, slightly tapered, transparent tube, which consists of a plummet or float. The float is free to rise or fall in a tapered glass tube due to the variation in the flow of fluid.

Construction of Rotameter

The rotameter consists essentially of a tapered metering glass tube. Inside the tube is a float, which is the active element of the meter. The float material has a specific gravity higher than that of the fluid to be metered. The spherical slots cut into a part of the float cause it to rotate slowly about the axis of the tube and keep it centred. The stability of the float is ensured by employing a guide along which the float would slide.

Working of Rotameter

With an increase in the flow rate, the float rises in the tube and there occurs an increase in the annular area between the float and the tube. The float adjusts its position in relation to the discharge through the passes the float rides higher or lower depending on the flow rate.

Advantages of Rotameter

  1. Low cost, direct indicating, minimum piping required.
  2. Pressure loss in rotameter is nearly constant and small.
  3. It can handle any corrosive fluid.
  4. It has quite good accuracy especially at low now rates.
  5. It provides linear scale.
  6. It can be compensated for changes in fluid density and viscosity.
  7. The capacity can be changed with relative ease by changing float, tube.
  8. Condition of flow is readily visible.

Disadvantages of Rotameter

  1. It must be installed in vertical position only.
  2. For high pressure and temperature, it is expensive.
  3. When opaque fluid is used, float may not be visible.
  4. It cannot be used with liquid carrying large percentage of solids in suspension.

Applications of Rotameter

  1. It is used for measurement of flow of liquid and gases.
  2. The rotameters are used in large scale drug industries.
  3. The rotameters are used in fermenters to control the supply of air.

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What is Coriolis Flow Meter? Working Principle, Diagram, Construction & Advantages https://howelectrical.com/coriolis-flow-meter/ https://howelectrical.com/coriolis-flow-meter/#respond Mon, 23 Dec 2024 19:40:55 +0000 https://howelectrical.com/?p=3448 Figure 1: Coriolis Flow Meter. The coriolis flowmeter is primarily used to measure the mass flow rate of liquids, and in some cases gas flow measurements. The construction of coriolis flow meter is shown in Fig. 1.  It consists of either a pair of parallel vibrating tubes or else a single vibrating tube that is formed […]

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Coriolis Flow Meter

Figure 1: Coriolis Flow Meter.

The coriolis flowmeter is primarily used to measure the mass flow rate of liquids, and in some cases gas flow measurements. The construction of coriolis flow meter is shown in Fig. 1.  It consists of either a pair of parallel vibrating tubes or else a single vibrating tube that is formed into a configuration that has two parallel sections.

Working Principle of Coriolis Flow Meter

A coriolis flowmeter requires force acting on a tube carrying a flowing fluid. This force actually deforms tubes through which the fluid flows. The amount of deformation depends directly on the mass flow rate through the tubes.

Construction and Working of Coriolis Flow Meter

Tubes are made of various materials of which stainless steel is the most common. They are available in different shapes such as B-shape, D-shape, U-shape etc. The Fig. 1 shows U-shape tube in more detail. The tubes are anchored at two points. The electromechanical drive unit between the two anchors excites vibrations in each tube at the tube resonant frequency.

In the tube, the fluid moves away from and back towards the axis of oscillation, resulting in a changing angular momentum of the fluid. The tube oscillation results into two opposite forces which twist the tube. First one way then the other with each oscillation cycle. The output from pickup sensors are sine waves showing oscillation frequency. Measuring the magnitude of deformation, the mass now rate can be measured.

Advantages of Coriolis Flow Meter

  1. Its measuring principle is independent of fluids pressure, density and viscosity.
  2. Its measurement is independent on Reynold’s number.
  3. Its measurement also independent on upstream and down stream flow velocities.
  4. The meter has high accuracy and high reliability.

Disadvantages of Coriolis Flow Meter

  1. Pipe line size is limited and available upto pipe size of 150 mm only.
  2. Initial cost is high

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