Read the passage and answer the following questions : Engineering measurement techniques have made substantial contributions in the accurate determinations of various physiological parameters, that give useful information to clinicians to detect the mal-functioning of the system being measured and also aid in proper diagnosis and patient care. Some of the biomedical instruments may be designed and developed for a particular specialised requirement but a majority of them are adaptations of widely used physical measuring devices. For monitoring the temperature of biomedical subjects, a thermister device is generally used along with a suitable bridge circuit in which the terminal device may be a voltmeter, calibrated in terms of degrees Celsius or Fahrenheit.
For the quantitative measurement of acidity or alkalinity, the instrument used is
pH meter
What is being measured. Acidity and alkalinity are expressed on the pH scale, defined from the hydrogen-ion activity:
\(pH=-\log_{10}[H^{+}]\)
with 7 neutral, below 7 acidic and above 7 alkaline. The instrument that measures it quantitatively is, by name, the pH meter.
How it works. A glass electrode whose thin bulb is selectively permeable to hydrogen ions develops a potential difference against a reference electrode (usually calomel or Ag/AgCl). The cell voltage follows the Nernst equation:
\(E=E_0-\dfrac{2.303RT}{F}\,pH \approx E_0-59.16\ \text{mV per pH unit at }25\ ^{\circ}\text{C}\)
Because the glass electrode has an enormous internal resistance — hundreds of megohms — the meter must present an extremely high input impedance, which is why a FET-input electrometer amplifier is used. The instrument also needs temperature compensation, since the Nernst slope is proportional to T.
Why the other options are wrong.
Both hygrometers — the hair type, which uses the change in length of a strand of hair, and the resistive (humistor) type — measure humidity, the moisture content of air. They have nothing to do with ion concentration.
Chromatography is a separation technique: it splits a mixture into its components by their differing affinities for a stationary and a mobile phase. It identifies and quantifies species, but it does not report acidity as a single number.
Why pH matters in the biomedical context of the passage. Blood pH is held within the narrow band 7.35–7.45; a deviation of a few hundredths signals acidosis or alkalosis, so accurate pH measurement is a routine clinical requirement — another physical instrument adapted to physiological use.
Hence, the instrument used is the pH meter.
Similar Questions
Read the following statements regarding errors in measurement :
(a) Gross errors are mostly due to lack of knowledge and care on the part of the experimenter.
(b) Systematic errors are mostly caused by inherent short-comings of the instruments and components used in measurement.
(c) Random errors are due to sources and causes that cannot be specified for their effects with.
(d) Gross and systematic errors are non-correctable.
Which of the above are correct ?
Blood pressure is measured by
Assertion (A) : In a well-type manometer, ratio of cross-sectional areas of well and the tube is not the factor that determines the scale of the manometer.
Reason (R) : Accuracy of a manometer is not affected by the shape or size of the tubes.
Electrocardiogram is a graphical representation of electrical activity of heart muscle myocardium, in the form of
The amplitude of an electrocardiograph signal is usually of the order of
In the bio-electric phenomenon, ERG is used to detect
An ammeter of 1 mA possesses a resistance of 100 ohms. This ammeter is to be converted into 1A ammeter. The value of shunt resistance required will be :
Followings is the sequence of blocks in spectrum Analyser :
A. Detector & video Amplifier
B. Fixed Frequency Active filter
C. Attenuator (Adjustable)
D. Mixer & Tunable Detector
Choose the correct answer from the options given below :
Read the following statements regarding biomedical instrumentations :
(a) Sphygmos is used for blood pressure measurement.
(b) EMG represents a record of the electrical activity of the brain.
(c) ERG represents the record of potential from the retina.
(d) ECG represents the record of electrical activity of brain.
Which of the above statements are correct ?
Optical pyrometers are used to measure :
Important Questions from Miscellaneous
The ration of the number of girls and boys in a school is 8 : 7. If the percentage increase in the number of girls and boys is 10% and 20% respectively, what will be the new ratio?
The cheapest means of transport is:
The property of Catenation is most readily predominant in:
Which newspaper edited by Bal Gangadhar Tilak, was one of the strongest critics of the British rule?
Which of the following is NOT a cause of food and water contamination?
