Mechatronic for Health Sciences MEC 141 Lecture 3

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Questions and Answers

What defines a 'medical device' in the context of biomedical instrumentation?

Any tool used by health professionals.

Devices that solely diagnose conditions without treatment.

Instruments intended for use in scientific research.

Instruments designed for specific medical purposes for human beings. (correct)

Which characteristic of a sensor indicates the smallest change it can differentiate?

Resolution (correct)

Sensitivity

Accuracy

Range

What is meant by the term 'measurand' in biomedical instrumentation?

The technology used in medical devices.

The amount of error in sensor output.

The variable or property that the system measures. (correct)

The range of temperatures measurable by a sensor.

Which statement accurately describes the relationship between sensitivity and resolution in digital sensors?

Sensitivity is closely related to resolution. Signup and view all the answers

Which type of biomedical measurand involves analyzing blood samples?

Offline Signup and view all the answers

What is the main distinction between biomedical instrumentation systems and conventional systems?

Biomedical systems interact with living tissue. Signup and view all the answers

How is accuracy defined in the context of sensor measurement?

The difference between the measured and true value. Signup and view all the answers

What is defined as the closeness between the actual measured value and a true value?

Accuracy Signup and view all the answers

What does response time of a sensor describe?

The speed of output change after input alteration Signup and view all the answers

Which of the following is a standard electric signal range used in modern equipment?

4 to 20 mA Signup and view all the answers

Which part is NOT typically included in a hydraulic system?

Siemens controller Signup and view all the answers

What type of sensor does not come in contact with the biological system?

Noninvasive sensors Signup and view all the answers

Which of the following best describes indwelling sensors?

They communicate with the outside while being inside the body. Signup and view all the answers

Which type of sensors can cause tissue damage when installed?

Invasive sensors Signup and view all the answers

What type of sensors are used for measuring physical quantities such as pressure and flow?

Physical sensors Signup and view all the answers

Which signal is commonly associated with pneumatic systems?

3 to 15 psi Signup and view all the answers

What type of sensors are specifically used to measure biochemical materials in the host?

Bio-analytical sensors Signup and view all the answers

Which of the following is NOT a physical variable measured by physical sensors?

Concentration of DNA Signup and view all the answers

Which statement about thermocouples is correct?

They rely on the Seebeck effect. Signup and view all the answers

What aspect of a resistance thermometer changes with temperature?

Resistance of a metal wire Signup and view all the answers

What material is known to provide the largest linear range of operation for resistance thermometers?

Platinum Signup and view all the answers

What are the two principal regions of a bio-analytical sensor?

A sensing reaction component and a detection mechanism Signup and view all the answers

In a resistance thermometer, how is the change in resistance typically measured?

By supplying a constant current and measuring the voltage Signup and view all the answers

Which of the following describes how a voltage is generated in thermocouples?

Due to energy distribution differences at different temperatures Signup and view all the answers

Which component is commonly present in a glucose biosensor for detecting glucose levels?

Glucose oxidase Signup and view all the answers

Which method is employed by thermocouples to generate a voltage difference?

The Seebeck effect Signup and view all the answers

Which type of sensor can be used to measure changes in mass in a bio-analytical sensor?

Mass sensor Signup and view all the answers

What method is used to measure glucose concentration in the blood sample through a glucose oxidase sensor?

Measuring current flow between electrodes Signup and view all the answers

What effect does increasing temperature have on the resistance of a metal wire in a resistance thermometer?

Resistance increases Signup and view all the answers

In which application are biomedical sensors specifically used for continuous patient monitoring?

Monitoring vital signs like blood pressure Signup and view all the answers

What is a primary role of temperature sensors in control systems?

Maintaining suitable environmental conditions Signup and view all the answers

What characterizes the resistance of a thermistor?

It has a negative temperature coefficient of resistance. Signup and view all the answers

What primarily governs the displacement of a mass on a spring due to acceleration?

The force due to acceleration (F = m · a). Signup and view all the answers

Which of the following is NOT a type of chemical sensor mentioned?

Capacitance Signup and view all the answers

What is the primary role of chemical sensors in biomedical applications?

To determine the concentration or chemical activity of substances. Signup and view all the answers

In the context of displacement and force sensors, what is a primary transduction mechanism?

Converting force to displacement. Signup and view all the answers

Which type of biomedical sensor is characterized by colorimetric analysis?

Optical sensor. Signup and view all the answers

Which of the following best describes the mechanism of thermistors?

They function through thermal generation of free electrons. Signup and view all the answers

Which of the following techniques is used in coulometric sensors?

Quantifying electrical charge in a substance. Signup and view all the answers

What type of mechanical sensor involves deformable membranes?

Displacement sensors. Signup and view all the answers

Which reaction is highlighted in the bio-analytical sensors?

Enzyme–substrate reaction. Signup and view all the answers

Study Notes

Mechatronic for Health Sciences [MEC 141] Lecture No. 3

Lecture is on the design of biomedical instrumentation
A "medical device" is any instrument, machine, appliance, implant, software, material or similar item intended for medical use
Medical device purposes include: investigating, replacing, modifying or supporting anatomy/physiology; supporting or sustaining life; or controlling conception/disinfecting medical devices
Generalized medical instrumentation differs from conventional instruments as the signal source is living tissue or energy applied to living tissue.
Design of instrument must match measurement needs (environmental conditions, safety, reliability); and instrument performance (speed, power, resolution, range)
A generalized medical instrumentation system includes an energy source, sensors, transducers, signal conditioning, a control system, alarms, a display, data storage and output.

Biomedical Instrumentation Design

Biomedical instrumentation systems contain three fundamental components: a sensor, a signal processor, and a storage device
A biomedical sensor in the context of instrumentation is the interface between the electronic instrument and the biological system
Sensor characteristics include:
- Range (difference between maximum and minimum sensed parameter value) exemplified by a thermocouple's 25-225°C range
- Resolution (smallest change sensor can differentiate, or least count of sensor)
- Sensitivity (ratio of output change to a unit change of input), which is closely related to sensor resolution
- Error (difference between measured result and true value)
- Accuracy (difference between measured and true value, thus showing closeness to true value)
- Response time (time sensor takes to respond completely to input change)

Standard Signal Types

Most modern equipment uses standard signal ranges for consistency and calibration
Electrical signal range: 4 to 20 mA
Pneumatic signal range: 0.2 to 1.0 bar (or 3 to 15 psi)
Standard range ensures equipment is readily calibrated
Minimum signal represented by 4 mA/0.2 bar and maximum by 20 mA/1.0 bar

Hydraulic Signal Transmission System

Hydraulic systems consist of storage tanks, filters, hydraulic pumps, pressure regulators, control valves, hydraulic cylinders, pistons, and leak-proof fluid pipelines
Output shaft with piston transfers motion/force, while other components control the system

Pneumatic Signal Transmission System

Involves an intake compressor, cooler, separator, receiver, actuator, control valve, secondary air treatment, pressure switch, and motor control centre

Comparison of Electrical, Hydraulic & Pneumatic Systems

Presents a comparison table for different systems in terms of energy source, storage, distribution, energy cost, rotary actuators, linear actuators, controllable force, points to note (including danger, leakage, and noise issues)

Classification of Biomedical Sensors

Biomedical sensors are classified by how they are used relative to the biological system
- Noninvasive sensors do not contact the biological system (e.g., skin surface thermometers, biopotential electrodes, strain gauges)
- Indwelling sensors are minimally invasive, placed into natural body cavities (e.g., oral/rectal thermometers, intrauterine/stomach pH sensors)
- Invasive sensors require surgical placement and tissue damage
Sensors are also classified by the quantities they measure
- Physical sensors measure physical quantities like displacement, pressure, flow
- Chemical sensors determine concentrations of chemical substances within the host (often regarding biochemical materials)
- Bio-analytical or biosensors measure internal quantities like enzymes

Physical Sensors

Include temperature, strain, force, pressure, displacement, position, velocity, acceleration, optical radiation, sound, flow rate, viscosity, and electromagnetic fields
Temperature sensors:
- The mercury thermometer produces a non-electronic output. Other examples include thermocouples, thermistors, and resistance thermometers.
Thermocouples use the Seebeck effect to create voltage differences across dissimilar conductor junctions dependent on temperature difference.
Resistance thermometers rely on metal wire resistance increasing with temperature. Scattering events from electrons reduce mobility and increase resistance inversely
Thermistors are resistive semiconductor elements with a negative temperature coefficient, relying on increasing electron numbers due to increasing temperature. Consequently, thermistor resistance decreases with increasing temperature.

Displacement and Force Sensors

Force can be sensed through displacement, like a spring stretching due to mass acceleration.
Force is also associated with membrane displacement from pressure differences

Chemical Sensors

Used in biomedical settings to measure chemical concentrations or activity in biological specimens.

Bio-Analytical Sensors

A special class of sensors that use biological molecules (such as enzyme-substrate or antigen-antibody reactions) to target specific molecules in biological samples
Highly specific for biological molecules and can provide a high degree of sensitivity and selectivity
Basic structure of a bioanalytical sensor includes a recognition component (proteins), physical or chemical transducer (detectors), and a biological sensing area. Sensors could be electrical (electrodes, capacitance measurements) or optical (photodetectors) based.

Example of Bio-Analytical Sensor (Glucose Sensor)

The first part of glucose sensor contains glucose oxidase, which oxidizes glucose into glucuronic acid and hydrogen peroxide.
This process consumes oxygen. Thus, a placed oxygen sensor can measure the amount of glucose oxidized by measuring hydrogen peroxide produced or oxygen consumed,

Applications of Biomedical Sensors

Biomedical research (quality control of products)
Patient care (monitoring blood pressure, oxygen saturation, body temperature, and ECG)
Specimen analysis (home blood glucose analyzers, blood analyzers)

Signal Conditioning

This is a crucial element of biomedical instrument design and processing of a signal generated from the interaction between the biological system and the sensor system
Pre-processing: amplifier gain dependent on next stage needs; usually, converting millivolt sensor output to digital; use of specialized digital circuits/microcomputers for logic and arithmetic
Logic and Arithmetic Control: Performing calculations – including filtering- on raw amplified data from patients to measure parameters
Post-processing: Final processing that matches output/adjusts scale of time, frequency, and level; functions which include averaging repetitive signals, reducing noise and converting signal from time to frequency domain

Many Sensors Have

Primary sensing elements (diaphragms converting pressure to displacement), variable conversion elements (strain gauges converting displacement to electrical signals), and the ability to adjust sensitivity by altering the primary sensing component
Variable conversion elements often need external power.

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Description

This lecture focuses on the design and function of biomedical instrumentation, highlighting the importance of medical devices in healthcare. It includes their purposes, performance requirements, and the components of a generalized medical instrumentation system. Understanding these concepts is essential for students in the field of health sciences and engineering.