The document discusses chemical sensors and carbon monoxide sensors. It describes the construction of carbon monoxide sensors, which consist of three electrodes in an electrolyte: a working electrode made of platinum, a reference electrode, and a counter electrode. The working electrode oxidizes carbon monoxide gas that diffuses through a waterproof membrane. The current produced is proportional to the carbon monoxide concentration. It also discusses actuators and electromechanical actuators (DC motors), describing their basic parts and working principles.

1. B.SC III SEM V
- PROF D.B.BOBADE

2. CHEMICAL SENSOR
• Chemical sensor measures presence and quantity of specific chemicals in
the environment.
• Some sensors detect carbon monoxide, automobile oxygen, carbon and
pH value.
• For example, concentration, composite reaction rate, pH and oxidation.

3. CARBON MONOXIDE SENSOR
• CONSTRUCTION:
• It consists of three electrodes in a liquid electrolyte i.e. non metallic liquid
which conducts electricity.
• These three electrodes are:
1. Working electrode (WE)
2. Reference electrode (RE)
3. Counter electrode (CE)

4. • The most important among these electrodes is working electrode made
up of platinum which is catalytic metal to CO.
• It is kept in waterproof membrane so that CO gas diffuses through the
membrane and electrochemically oxidized as shown in figure.

5. • WORKING:
• The electron generated through electrochemical reaction flows from electrode to
the external circuit and produces o/p signal of the sensor.
• Reference electrode provides stable electrochemical potential in electrolyte.
• Reference electrode is protected from exposure to the CO gas so that
thermodynamic potential is always same and remains constant.
• Also, no current is allowed to flow through the reference electrode.
• The counter electrode is provided to complete the electric circuit of
electrochemical cell.
• Its function is to allow i.e. enter or leave electrons to the electrolyte.
• The current generated from electrode is amplified using operational amplifier
which is proportional to the concentration of CO gas.
• This concentration is sensed by the sensing electrode after chemical reaction in
the electrolyte which produces H+ and H- ions.
• The o/p current measured concentration of CO in the air.

6. ACTUATORS
• An actuator is a type of motor for moving or controlling mechanism or
system.
• It is operated by a source of energy generally in the form of current.
• This current converts energy in motion.
• It is also subdivision of transducer.
• They are devices which transfer i/p signal into motion.
• The examples of actuators are electrical motors, hydraulic piston, relay,
piezoelectric actuators and electroactive polymers.

7. ELECTROMECHANICAL ACTUATORS(DC MOTOR)
• CONSTRUCTION:
• Every DC motor has basic six parts i.e. axle, rotor(armature), stator,
commutator, field magnet and brushes.
• In DC motor, external magnetic field is produced by high strain permanent
magnet.
• Stator is a stationary part of motor.
• It includes motor ceasing as well as two or more permanent magnet pole
pieces.

8. • The rotor rotates with respect to stator.
• The rotor consists of winding which is electrically connected to the commutator.
• The brushes are used to keep contact with commutator and rotor winding such that
when power is applied, polarities of winding get energy and stator magnets are
misaligned and rotor will rotate smoothly.
• CIRCUIT DIAGRAM:

9. • WORKING:
• DC motor is a device which converts electrical power into mechanical power.
• Permanent magnet is used to convert direct current i.e. electrical energy into
mechanical energy through interaction of two magnetic fields.
• One field is produced by permanent magnet assembly and other field is
by electrical current flowing in motor winding.
• These two fields produce a torque which rotates the motor as rotor turns, current
the winding produces a continuous torque.
• The brushes are used to remain stationary the rotor on rotating commutator.
• As electrical energy is passed through brushes, it creates a force which generates
reaction between motor field and armature and hence it creates motion on
armature.