Answer: a [Reason:] The diagnostically useful frequency range is usually accepted as 0.05 to 150 Hz. Although the electric field generated by the heart can be best characterized by vector quantities, it is generally convenient to directly measure only scalar quantities, i.e. a voltage difference of mV order between the given points of the body.

Answer: c [Reason:] A notch filter is employed to suppress the hum noise generated by the power supply in the ECG circuit. CMRR of the order of 100–120 dB with 5 kW unbalance in the leads is a desirable feature of ECG machines. The instability of the baseline, originating from the changes of the contact impedance, demands the application of the automatic baseline stabilizing circuit.

Answer: c [Reason:] The branch of medicine that deals with the provision and use of artificial devices such as splints and braces is orthotics. A modality-specific appliance that aids the performance of a function or movement by augmenting or assisting the residual capabilities of that function or movement. An orthopaedic brace is an orthosis.

Answer: a [Reason:] Its is true. The sensitivity of an electrocardiograph is typically set at 10 mm/mV. For routine work, the paper recording speed is 25 mm/s. Amplitude measurements are made vertically in millivolts. Time measurements and heart rate measurements are made horizontally on the electrocardiogram.

Answer: c [Reason:] The volume of blood within the dialyzer is known as priming volume. It is desirable that this should be minimal. Priming volume of present day dialyzers range from 75 to 200 ml, depending on the membrane area geometry and operating conditions.

Answer: b [Reason:] The ideal membrane should possess high permeability to water, organic metabolites and ions, and the capability of retaining plasma proteins. The membrane should be of sufficient wet strength to resist tearing or bursting and non-toxic to blood and all body cells.

Answer: a [Reason:] Cupraphan is the commonly used membrane for haemodialysis. It is a membrane consisting of natural cellulose and is considered puncture-proof, and of high tenacity and elasticity. During haemodialysis, different substances of varying molecular weight are to be removed.

Answer: d [Reason:] Instrumentational amplifiers have very high CMRR. The instrumentation amplifier offers the following advantages for its applications in the biomedical field. Some of the are like extremely high input impedance, low bias and offset currents, high slew rate.

Answer: c [Reason:] To achieve optimum performance and to enable the relationship of change in resistance with volume of the cell to hold good, it is recommended that the ratio of the aperture length to the diameter of the aperture should be 0.75:1, i.e. for an orifice of 100 m diameter the length should be 75 m. The instrument based on the Coulter principle works most satisfactorily when the average diameter of the particles ranges between 2 to 40% of the diameter of the measuring hole.

Answer: a [Reason:] It is true. Blood is a poor conductor of electricity. This principal is used in Coulter counters to count the number of RBCs in the blood.

Answer: a [Reason:] The junction at higher temperature in thermocouple is termed as measuring junction.the junction at lower temperature in the thermocouple is called the reference temperature. The cold junction is usually kept at 0*C.

Answer: a [Reason:] In floating electrode the metal electrode does not make direct contact with the skin. The electrode consists of a light weighted metalled screen or plate held away from the subject by a flat washer which is connected to the skin. Floating electrodes can be recharged, i.e. the jelly in the electrodes can be replenished if desired.

Answer: b [Reason:] Photovoltaic cells are very robust in construction, need no external electrical supply and produce a photocurrent sometimes stronger than other photosensitive elements. Typical photocurrents produced by these cells are as high as 120 mA/lumen. At constant temperature, the current set up in the cell usually shows a linear relationship with the incident light intensity.

Answer: d [Reason:] Low pass filter amplifies signals below a certain frequency. Band pass filter amplifies frequencies with in a certain band. Band stop filter amplifies all the frequencies except those in a certain band. High pass filter amplifies signal above a certain frequency.

Answer: a [Reason:] Band pass filter amplifies frequencies with in a certain band. Band stop filter amplifies all the frequencies except those in a certain band. High pass filter amplifies signal above a certain frequency. Low pass filter amplifies signals below a certain frequency.

Answer: a [Reason:] Pulse oximetry is a technology used to measure the oxygen level in your blood and your heart rate. A finger pulse oximeter is equipped with technology to rapidly detect changes in your blood oxygen level.

Answer: b [Reason:] Pulse oximetry is based on the concept that arterial oxygen saturation determinations can be made using two wavelengths, provided the measurements are made on the pulsatile part of the waveform.

Answer: c [Reason:] The two wavelengths assume that only two absorbers are present; namely oxyhaemoglobin (HbO2) and reduced haemoglobin (Hb).Light passing through the ear or finger will be absorbed by skin pigments, tissue, cartilage, bone, arterial blood, venous blood.

Answer: d [Reason:] Most of the absorbances are fixed and do not change with time. Even blood in the capillaries and veins under steady state metabolic circumstances is constant in composition and flow, at least over short periods of time.Only the blood flow in the arteries and arterioles is pulsatile.

Answer: d [Reason:] Light passing through the ear or finger will be absorbed by skin pigments, tissue, cartilage, bone, arterial blood, venous blood. The absorbances are additive and obey the Beer-Lambert law. Beer-Lambert is combination of Lambert-Bouguer and Beer’s Law.

Answer: b [Reason:] Components of pulse oximeter Probe.

Answer: b [Reason:] This has two LEDs (light emitting diodes), one that transmits infrared light at a wavelength of approximately 940 nm and the other transmitting light at approximately 660 nm.

Answer: a [Reason:] Oxygen saturation is estimated from the ratio (R) of pulse-added red absorbance at 660 nm to the pulse-added infrared absorbances at 940 nm.

Answer: c [Reason:] An accuracy of 1% or better has been reported for the saturation range of above 80% for most transmission type pulse oximeters. Usually, the accuracy is less at lower saturation because of non-linear effects of absorption.

Answer: d [Reason:] The instrument can be empirically calibrated. Subject variability (skin pigmentation, thickness, tissue, sensor location, etc.) has no significant influence on the measurement.

Answer: c [Reason:] For the measurement of oxygen saturation level of blood in localized areas of oxygen deprived tissues on the limbs, head and torso, a skin reflectance oximeter can be employed.

Answer: b [Reason:] The instrument basically depends on monitoring backscattered light from living tissue in two wavelengths. The backscattered light data is then used for the in vivo determination of the blood’s relative oxygen saturation.

Answer: a [Reason:] Cohen and Wadsworth (1972) bring out the difficulties in the extraction of useful information from backscattered light intensity from human tissue. There are vast variations of tissue construction and optical properties among various subjects and in different locations on the same subject.

Answer: b [Reason:] Cohen and Longini (1971) suggested a theoretical solution to some of these problems. They considered human tissues to be composed of parallel semi-infinite layers of homogeneous materials.

Answer: b [Reason:] However, in comparison to transmission, the reflection pulse oximeter has poorer signal-to noiseratio. Mendelson et al (1988) utilized multiple photodiodes around the light source to enhance signal level.

Answer: a [Reason:] However, in comparison to transmission, the reflection pulse oximeter has poorer signal-to noise ratio. Mendelson et al (1988) utilized multiple photodiodes around the light source to enhance signal level.

Answer: b [Reason:] A pair of red and infrared light emitting diodes are used for the light source, with peak emission wavelengths of 665 nm (red) and 935 nm (infrared). The reflected light from the skin at these two wavelengths is detected by a silicon diode.

Answer: c [Reason:] A pair of red and infrared light emitting diodes are used for the light source, with peak emission wavelengths of 665 nm (red) and 935 nm (infrared). The reflected light from the skin at these two wavelengths is detected by a silicon diode.

Answer: b [Reason:] A pair of red and infrared light emitting diodes is used for the light source, with peak emission wavelengths of 665 nm (red) and 935 nm (infrared). The reflected light from the skin at these two wavelengths is detected by a silicon diode. These detected signals are processed in the form of photo-plethysmographs to determine So².

Answer: a [Reason:] A heater was incorporated in the sensor to warm the tissue so as to increase local blood flow. Excellent correlation in comparison with the transmission oximeter has been shown from the calf and thigh.

Answer: b [Reason:] Electromyograph is an instrument used for recording the electrical activity of the muscles to determine whether the muscle is contracting or not; or for displaying on the CRO and loudspeaker the action potentials spontaneously present in a muscle or those induced by voluntary contractions as a means of detecting the nature and location of motor unit lesions; or for recording the electrical activity evoked in a muscle by the stimulation of its nerve.

Answer: a [Reason:] EMG is usually recorded by using surface electrodes because the surface electrodes may be disposable, adhesive types or the ones which can be used repeatedly.

Answer: d [Reason:] EMG measurements are also important for the myoelectric control of prosthetic devices (artificial limbs). This use involves picking up EMG signals from the muscles at the terminated nerve endings of the remaining limb and using the signals to activate a mechanical arm. This is the most demanding requirement from an EMG since on it depends the working of the prosthetic device.

Answer: a [Reason:] The Cathode Ray oscilloscope displays EMG waveforms. Electromyograph is an instrument used for recording the electrical activity of the muscles to determine whether the muscle is contracting or not; or for displaying on the CRO.

Answer: b [Reason:] The amplitude of the EMG signals depends upon various factors, e.g. the type and placement of electrodes used and the degree of muscular exertions. The needle electrode in contact with a single muscle fibre will pick up spike type voltages whereas a surface electrode picks up many overlapping spikes and therefore produces an average voltage effect.

Answer: c [Reason:] A typical EMG signal ranges from 0.1 to 0.5 mV. They may contain frequency components extending up to 10 kHz.Such high frequency signals cannot be recorded on the conventional pen recorders and therefore, they are usually displayed on the CRT screen.

Answer: c [Reason:] A typical EMG signal ranges from 0.1 to 0.5 mV. They may contain frequency components extending up to 10 kHz.Such high frequency signals cannot be recorded on the conventional pen recorders and therefore, they are usually displayed on the CRT screen.

Answer: c [Reason:] The tape recorder is included in the system to facilitate playback and study of the EMG sound waveforms at a later convenient time. The waveform can also be photographed from the CRT screen by using a synchronized camera.

Answer: b [Reason:] A ground electrode is necessary for providing a common reference for measurement. These electrodes pick up the potentials produced by the contracting muscle fibres. The signal can then be amplified and displayed on the screen of a cathode ray tube. It is also applied to an audio amplifier connected to a loudspeaker.

Answer: d [Reason:] A trained EMG interpreter can diagnose various muscular disorders by listening to the sounds produced when the muscle potentials are fed to the loudspeaker.

Answer: c [Reason:] Johnson et al (1977) designed a miniature amplifier circuit fully encapsulated in epoxy resin with two small silver electrodes of 6 mm diameter, exposed flush with the base of the module. The electrode is attached to the skin using adhesive tape.

Answer: d [Reason:] The common-mode rejection should be greater than 90 dB up to 5 kHz. A calibrating square wave signal of 100 mV (peak-to-peak) at a frequency of 100 Hz is usually available. The main amplifier has controls for gain adjustment from 5 mV/div to 10 mV/div for selecting the sensitivity most appropriate to the incoming signal from the patient.

Answer: a [Reason:] Modern EMG machines are PC based available both in console as well as laptop models as they provide full colour waveform display, automatic cursors for marking and making measurements and a keyboard for access to convenient and important test controls. The system usually incorporates facilities for recording of the EMG and evoked potentials.

Answer: b [Reason:] The instrument is useful for making a study of several aspects of neuromuscular function, neuromuscular condition, extent of nerve lesion, reflex responses, etc.

Answer: d [Reason:] The instrument is useful for making a study of several aspects of neuromuscular function, neuromuscular condition, extent of nerve lesion, reflex responses, etc.

Answer: d [Reason:] Cathode ray oscilloscopes are widely used for the display of waveforms encountered in the medical field. These waveforms can be recorded from the CRO screen by running a photographic film through a recording camera fixed in front of the screen. Recorders are either of the single channel type or of the type which record several channels simultaneously.

Answer: c [Reason:] Thermocouple has the widest range of temperature measurement from -184*C to +2300*C. RTD has a range of -200*C to +850*C. Thermistor has a range of 0*C to 100*C where as conventional mercury thermometers range is -37*C to +356*C.

Answer: b [Reason:] The junction at higher temperature in thermocouple is termed as measuring junction. The junction at lower temperature in the thermocouple is called the reference temperature. The cold junction is usually kept at 0*C.

Answer: a [Reason:] The junction at higher temperature in thermocouple is termed as measuring junction. This arrangement is called thermocouple. The junction at lower temperature in the thermocouple is called the reference temperature.

Answer: c [Reason:] When two wires of different material are joined together at either ends, forming two junctions which are maintained at different temperature, a thermo-motive force is generated causing a current to flow around the circuit. This arrangement is called thermocouple. The junction at lower temperature in the thermocouple is called the reference temperature. The junction at higher temperature in thermocouple is termed as measuring junction.

Answer: a [Reason:] The junction at lower temperature in the thermocouple is called the reference temperature. The cold junction is usually kept at 0*C. The junction at higher temperature in thermocouple is termed as measuring junction.

Answer: b [Reason:] The lower temperature junction in thermocouple is maintained at 273 K (0*C). The junction at lower temperature in the thermocouple is called the reference temperature. The junction at higher temperature in thermocouple is termed as measuring junction.

Answer: c [Reason:] The resistance Rt of a metallic conductor at any temperature t is given by Rt = Ro(1+ɑt). Ro is the resistance at 0*C. ɑ is temperature coefficient of resistivity.

Answer: b [Reason:] It is a passive sensor and requires current excitation to produce an output voltage. RTD has very low temperature coefficient.RTD stands for Resistance Temperature Device. Voltage drop across RTD is much larger than thermocouple output voltage.

Answer: c [Reason:] Thermistors are the oxides of certain metals like manganese, cobalt and nickel which have large negative temperature coefficient, i.e. resistance decreases with increase in temperature. Thermistor is used to measure temperature. It is a temperature transducer. With change in temperature its resistance changes. Thus its working principle is variable resistance.