Biomedical engineering is the application of engineering principles and design concepts to medicine and biology. It involves measuring physiological variables using instruments designed for healthcare purposes like diagnosis and therapy. Key factors in medical instrument design include range, sensitivity, linearity, frequency response, accuracy, signal-to-noise ratio, stability, isolation, and simplicity. The man-instrument system combines a human subject, transducer to convert signals, and components like signal conditioning, display, recording and control devices. The goal is to non-invasively gather patient information to aid in diagnosis, evaluation, monitoring and automated control of medical conditions and treatments.

1. Unit-1
Biomedical Engineering
BY- Sanju Sah
St. Xavier’s college, Maitighar
Department of Microbiology
BIOMEDICAL INSTRUMENTATION

2. WHAT IS BME
• Biomedical Engineering (BME) is the application of
engineering principles and design concepts to medicine
and biology for healthcare purposes.
• Healthcare purpose
• diagnostic
• therapeutic

3. BIOMETRICS
• The Branch of Science that includes the measurement of physiological
variables and parameters is known as biometrics.
• For the design or specification of medical instrumentation few factors
must be considered:
• Range : The Range of an instrument is generally considered
including all level of input amplitude and frequency over which
device is expected to operate.
• Sensitivity: It determines how small a variable parameter that can
reliably be measured and also determines resolution of device.
• Linearity: The degree to which variation in the output of an
instrument follow input variation is referred to as linearity of the
device.

4. • Hysteresis: Characteristic of some instrument where by the given value of the
measured variables result in a different reading when reached in an ascending
direction from that obtained when it is reached in descending direction.
• Frequency response: The frequency response of an instrument is its variation in
sensitivity or the frequency range of the measurement.
• Accuracy: Measure of the systemic error can occur in multiple ways, it is very
important that where needed balancing or zeroing is done prior to each set
measurement.
• Signal to Noise ratio: in hospital environment, power line, frequency noise or
interference is common and usually peaked up. It is important to know how and
control the SNR in actual environment where measurement is done.
• Stability: Stability is the ability of the system to resume a steady state condition
following a disturbance at the input rather than be driven into uncontrolled
oscillation. The overall system must be sufficiently stable over the useful range.
• Isolation: Measurement made on patients which is done by instrument must not
produce direct electric connection between subject and ground. Electric isolation is
provided using magnetic and optical coupling.
• Simplicity: All the systems should be as simple as possible to eliminate errors.

5. MAN INSTRUMENT SYSTEM
• Different types of signals can be obtained from the human body:
• Electrical, mechanical, acoustical, thermal. Chemical etc.
• Difficult to measure these physical parameter
• Instruments are used in medicine so that some physical
quantities can be measured or determined which will be used to
better diagnose or treat patient.
• The system which includes both human organism and the
instrument required for measurement of the human is called
man- Instrument System.

6. OBJECTIVES OF M-I SYSTEM
• Information Gathering: Instrument is used to measure physiological
phenomenon and other variables to aid his/her knowledge. In this setting, the
characteristics of the measurement may not be known in advance.
• Diagnosis : Measurement are used in detection and in attempt to correct or
treat the system being measured.
• Evaluation: Measurement are used to determine the ability of a system to
meet its functional requirements. These could be classified as “proof of
performance” or “quality control” tests.
• Monitoring: Used to monitor process or operation to obtain continuous or
periodic information about the state of the system being measured.
• Control: Instrument is some times used to automatically control the operation
of the system based on changes in one of more of the internal parameters or
in the output of the system.

7. Block Diagram of Man Instrument System

8. COMPONENTS
• The Subject : Every system uses measurand for the measurement and the source of this
measurement in know as subject. Measurand are the physical quantity or condition that
instrument measures.
• Stimulus : Many system are designed to measure the response of the subject on the specific
stimulus. The stimulus may be generated by system itself or by external factors (e.g
medicines)
• The Transducer: A device which converts one form of energy to other form is known as
transducer. Transducer are used in man- instrument system to sense the physiological signals
and convert them into another appropriate signal which a system can sense. E.g. thermister-
converts thermal energy into electrical signal.
• Signal Conditioning Equipments: Signal conditioning equipments/ unit converts the output of the
transducer into electrical quantity suitable for operation of the display or recording systems.
Signal conditioning generally includes functions such as amplification. Filtration, analog to
digital or digital to analog conversion.
• Display Equipments: Display unit provides a visible representation of the physiological signals
which can be interpreted by medical professionals.
• Recording, Data Processing and Transmission Equipments: These are used to store the
recorded data, process it into suitable form for transmission to the integrated parts of the
system or remote location.
• Control Devices : consist of devices to automatic control the system or take control the system
with the users input. Control devices generally consists of feedback loop to control the system.