Analyzing Industrial Measurement Statements

Let's analyze each statement provided in the question to determine which ones are correct regarding various measurement techniques used in industrial applications and healthcare.

Statement A: Ultrasonic method for liquid level measurement is not preferred in industrial applications.

This statement is incorrect. Ultrasonic level measurement is a very common and widely used method in industrial applications for measuring the level of liquids and even some solids in tanks and vessels. It is preferred in many scenarios because it is non-contact, relatively unaffected by density or conductivity of the medium, and suitable for various types of liquids including corrosive ones. Other methods like hydrostatic, capacitive, or radar are also used, but ultrasonic is definitely a preferred method in many industrial settings.

Statement B: In a pH meter, the glass electrode is the reference electrode.

This statement is incorrect. In a typical pH meter setup using a combination electrode, the glass electrode is the measuring electrode (also called the indicator electrode). This electrode is sensitive to the concentration of hydrogen ions (H⁺) in the solution, which determines the pH. The reference electrode provides a stable, known potential that does not change with the pH of the solution, completing the electrical circuit and allowing the potential difference, which is proportional to pH, to be measured.

Statement C: A chromatograph is used for analyzing the composition of a gas.

This statement is correct. Chromatography is a powerful analytical technique used to separate and analyze components in a mixture. Gas Chromatography (GC) specifically uses a gas as the mobile phase to separate volatile components of a sample, which can be in gaseous or liquid form (that can be vaporized). GC is routinely used to identify and quantify components in gas samples, such as air pollutants, natural gas, or forensic samples.

Statement D: The production of Korotkoff sounds in indirect blood pressure measurement is due to pressure pulses produced due to the difference in systolic and diastolic blood pressure.

This statement is correct. Korotkoff sounds are the sounds heard through a stethoscope when measuring blood pressure indirectly using a sphygmomanometer (cuff). These sounds are created by the turbulent flow of blood in the brachial artery as the pressure in the cuff is gradually released. The first sound (systolic pressure) is heard when the cuff pressure drops below the peak pressure generated by the heart's contraction (systole), allowing a small amount of blood to flow turbulently. The sounds disappear (diastolic pressure) when the cuff pressure drops below the pressure when the heart is relaxed (diastole), allowing blood flow to become smooth and laminar again. The pressure difference between systolic and diastolic is what causes the turbulent flow phases that produce these sounds.

Conclusion

Based on the analysis, statements C and D are correct.

Therefore, the correct option is the one listing C and D only.

Revision Table: Key Measurement Concepts

Additional Information on Measurement Techniques

• Ultrasonic Level Measurement: Works by emitting an ultrasonic pulse from a transducer towards the surface of the material being measured. The pulse reflects off the surface and returns to the transducer. The time it takes for the echo to return is measured and used to calculate the distance to the surface, thus determining the level. It is useful for clear liquids and solids but can be affected by foam, heavy vapor, or turbulent surfaces.
• pH Measurement Principle: The glass electrode develops a potential difference across a special glass membrane that is in contact with the solution, proportional to the concentration of H⁺ ions. The reference electrode maintains a constant potential. The pH meter measures the total potential difference between the two electrodes and converts it to a pH value using the Nernst equation: \(E = E_0 - \frac{RT}{nF} \ln(a_{H^+})\), where \(E\) is the measured potential, \(E_0\) is the standard potential, R is the gas constant, T is the temperature, n is the charge (1 for H⁺), F is the Faraday constant, and \(a_{H^+}\) is the activity of hydrogen ions.
• Chromatography: Various types exist, including Gas Chromatography (GC), Liquid Chromatography (LC), Paper Chromatography, Thin-Layer Chromatography (TLC), etc. They all involve a stationary phase and a mobile phase. Components separate based on their differential interaction (adsorption, partitioning) with these phases. GC is specifically suited for volatile or semi-volatile compounds that can be transported by a carrier gas (the mobile phase) through a stationary phase in a heated column.
• Korotkoff Sounds: There are typically five phases of Korotkoff sounds, though only the first (systolic) and the point of disappearance (diastolic) are commonly used for blood pressure measurement. Phase 1 is the tapping sound first heard. Phases 2, 3, and 4 are murmurs or softer thudding sounds. Phase 5 is the point where the sounds disappear completely.