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What is a force? In science, force is the push or pull on an object with mass that causes it to change velocity (to accelerate). Force is represented as a vector, which means it has both magnitude and direction. According to Newtons 2nd law of motion F = m·a Where F = force, m = mass, and a = acceleration Force measurement The most popular method for measuring force is using a strain gauge. We measure the strain developed due to force using strain gauges; and by multiplying the strain with the effective cross-sectional area and Young’s modulus of the material, we can obtain force.  Load cells and Proving rings are two common methods for force measurement using strain gauges.  We will first discuss the principle of strain gauge and then go for the force measuring techniques. Let us now understand what is the strain? What is the strain? The strain is the amount of deformation of a body due to an applied force. More specifically, strain (e) is defined as the fractional change in ...

Displacement, Position and Proximity Sensors Resistive Element or Potentiometer Capacitive Elements Strain Gauged Element Inductive Proximity Sensors Eddy Current Proximity Sensors Differential Transformers Optical Encoders Hall Effect Sensors Pneumatic Sensors Proximity Switches Rotary Encoders Temperature Sensors Thermistors Thermocouple Bimetallic Strips Resistance Temperature Detectors Thermostat Light Sensors Photo Diode Phototransistor Light Dependent Resistor Velocity and Motion Pyroelectric Sensors Tach generator Encoders (rotary and linear) Fluid Pressure Diaphragm Pressure Gauge Tactile Sensor Piezoelectric Sensors Capsules, Bellows, Pressure Tubes Liquid Flow and Level Turbine Meter Orifice Plate and Venturi Tube Differential Pressure Transmitter (DPT) IR Sensor Infrared Transmitter and Receiver Pair Force Strain Gauge Load Cell Cantilever beam Touch Sensors Resistive Touch Sensor Capacitive Touch Sensors UV Sensors Ultraviolet Light Detector Photo Stability Sensors UV Photo...

  Classification of Sensors The scheme of classifying sensors can range from very simple to very complex. The stimulus that is being sensed is an important factor in this classification. Some of the stimuli are Acoustic: Wave, spectrum, and wave velocity. Electric: Current, charge, potential, electric field, permittivity, and conductivity. Magnetic: Magnetic field, magnetic flux, and permeability. Thermal: Temperature, specific heat and thermal conductivity. Mechanical: Position, acceleration, force, pressure, stress, strain, mass, density, momentum, torque, shape, orientation, roughness, stiffness, compliance, crystallinity, and structural. Optical: Wave, wave velocity, refractive index, reflectivity, absorption, and emissivity. The sensors’ conversion phenomenon is also an important factor in the classification of sensors. Some of the conversion phenomena are  magnetoelectric,  thermoelectric  photoelectric.

The following are certain features that are considered when choosing a sensor. Type of Sensing: The parameter that is being sensed like temperature or pressure. Operating Principle: The principle of operation of the sensor. Power Consumption: The power consumed by the sensor will play an important role in defining the total power of the system. Accuracy: The accuracy of the sensor is a key factor in selecting a sensor. Environmental Conditions: The conditions in which the sensor is being used will be a factor in choosing the quality of a sensor. Cost: Depending on the cost of application, a low-cost sensor or high-cost sensor can be used. Resolution and Range: The smallest value that can be sensed and the limit of measurement are important. Calibration and Repeatability: Change of values with time and ability to repeat measurements under similar conditions. Basic Requirements of a Sensor or Transducer The basic requirements of a sensor are: Range: It indicates the limits of the input i...

Measurement is an important subsystem of a mechatronics system, which is used to collect the information on the system statuses such as temperature, humidity, pressure, or proximity and feed it to the microprocessor(s) for controlling the system. Transducer A transducer is an essential part of any information processing system that operates in more than one physical domain such as optical, electrical, magnetic, thermal, and mechanical domains. A transducer in general is defined as a device that converts one form of energy into another using the transduction process. The transduction process or function represents the characteristics or properties of the device used for energy conversion.  For example, the diaphragm in a microphone converts vibrations generated by sound waves into electrical signals. This property of the diaphragm is represented as a transduction function or process. A  transducer has at least one input and one output. In the measurement system, information p...

When the axes of the first gear (i.e. first driver) and the last gear (i.e. last driven or follower) are co-axial, then the gear train is known as reverted gear train as shown in Fig. 3. Fig. 3. Reverted gear We see that gear 1 (i.e. first driver) drives the gear 2 (i.e. first driven or follower) in the opposite direction.  Since the gears 2 and 3 are mounted on the same shaft, therefore they form a compound gear and the gear 3 will rotate in the same direction as that of gear 2.  The gear 3 (which is now the second driver) drives the gear 4 (i.e. the last driven or follower) in the same direction as that of gear 1.  Thus we see that in a reverted gear train, the motion of the first gear and the last gear is  al ike. Let  T 1  = Number of teeth on gear 1, r 1  = Pitch circle radius of gear 1, and N 1  = Speed of gear 1 in r.p.m. Similarly, T 2 , T 3 , T 4  = Number of teeth on respective gears, r 2 , r 3 , r 4  = Pitch circle radii of re...

When there is more than one gear on a shaft, as shown in Fig.2, it is called a  compound train of gear. We have seen in the previous section that the  idle gears,  in a simple train of gears  do not affect the speed ratio  of the system. But these gears are useful in bridging over the space between the driver and the driven.  But whenever the distance between the driver and the driven or follower  has to be bridged  over by intermediate gears and  at the same time a great ( or much less ) speed ratio is required , then the advantage of intermediate gears is intensified by providing compound gears on intermediate shafts.  In this case,  each intermediate shaft has two gears rigidly fixed  to it so that they may have the same speed. One of these two gears meshes with the driver and the other with the driven or follower attached to the next shaft as shown in Fig. 2. Fig. 2 Compounded gear train In a compound train of gears, as sho...