IN Engineering

force measurement As we know force is a product of mass and acceleration. so, once we know the acceleration we can calculate the force by knowing the mass  of the body. There is a so many method to measure to force given below. Strain gauge load cell Proving ring Hydraulic load cell Pneumatic load cell Reluctance load cell Inductive load cell Magneto elastic load cell Piezoelectric load cell Fibre optic load cell Resonant wire load cell Strain gauge load cell This is a most common type of load cell. Strain gauge load cell is Electrical type force measurement device. As shown in the figure(b) four strain gauges are mounted on the load sensing number. Strain gauge 1 and 3 are opposite to each other and strain gauges 2 and 4 are opposite to each other. Strain gauge 1 and 3 are at 90° as compared to strain gauge 2 and 4 as shown in the figure. strain gauges 1 and 3 measure the direct stress while strain gauges 2 and 4 measure  transverse stress. This type of mounting of the strain...

What is  acceleration? Change in velocity with time is called acceleration.And  distance travel with respect to time is called velocity. SI unit of acceleration is metre per second square (m/s2). All acceleration measuring instrument or accelerometer convert acceleration to force by allowing it to act on a inertial mass. As shown in the figure the mass is in housing connected with spring which has a constant k and damper or dashpot which has constant D. When the body is move a distance Xi the displacement of the mass the in the direction of the motion is Xm. And the relative displacement of spring and damper in the opposite direction of X0. We can connect a potentiometer at X0 by measuring the change in resistance, we can measure acceleration.

Viscosity viscosity is Resistance to flow. it is often referred to as the thickness of fluid. Standard definition it is the measure of the resistance of a fluid to gradually formation by shear or tensile stress. Types D ynamic viscosity which is a measure of the shear stress per unit area required before a sample begins to deform. This characteristic is typically expressed in millipascal seconds (mPa-s). Kinematic viscosity which refers to the resistive flow of a fluid under the influence of gravity. This property is density-dependent and is measured in square meters per second (m 2 /s). The relation between kinematics viscosity and dynamic viscosity is, Kinetic viscosity=dynamic viscosity/density of the fluid Methods to measure viscosity Flow through a capillary tube Drag experienced by falling ball  through fluid Drag experience by one end of the concentric cylindrical carrying fluid between them when other  cylinder is rotating.

 Conductivity Conductivity is a ability of material (solid,liquid or gas) to pass electricity through it. Conductivity measurement required for, Quality control of drinking or process water Quality control of boiler feed water Estimation of total number of iron in a solution Conductivity of a solution depend upon the following factor. Concentration of the solution Mobility of  iron Valence of ions Temperature of the solution The conductance of the solution can be expressed as the, L=σA/d            L=conductance A=Area of the electrode d=distance between two electrodes σ=conductivity of the solution The ratio d/a is called  cell constant)θ  and conductivity expresses σ=θ L         Unit of conductivity Siemens/centimetre is the unit of the conductivity. Conductivity cells Two pole type Four pole type

Hydrometer Hydrometer is a device which measure the density of a given solution. Hydrometer work based on the Archimedes principle.at that State, mg=Vρg Whare , m=mass of the hydrometer g=acceleration due to gravity V=Volume of displaced liquid ρ=density of the liquid Here m and g is constant ,so as density of the solution change the  volume of displaced liquid is also changed. By measuring displace liquid we can measure the density of the given solution. As shown in the figure the hydrometer is mounted on the tank. also  one thermometer is  immersed in a given liquid because of the density of the liquid also change with the temperature changes. So  we need to compensate this density due to change in temperature. so we measure the temperature by using thermometer in order to eliminate the error .

Density measurement By determining the density, we can determine the composition, concentration and also calorific value (for fuel). What is density Density is mass per unit volume. the SI unit of density is kg per metre cube(kg/m3) . gram per centimetre cube(g/cm3) unit is also used. Specific gravity The  specific gravity  is the ratio between the density of an object, and a reference substance. The specific gravity can tell us, based on its value, if the object will sink or float in our reference substance. Usually our reference substance is  water  which always has a density of 1 gram per milliliter or 1 gram per cubic centimeter .

 Hair hygrometer In the hair hygrometer, horse hair is used to sense the relative humidity because of horse hair is sensitive to humidity. so as the humidity increase or decrease also the length of the horse hair is increase or decrease. by using this property of  horse hair we can measure the humidity. Construction and working As we can see in above figure, there is a number of horse hair connected as shown in the figure. One end of the  Pointer is connected to pivot and other end of the  pointer  is move on the calibrated scale. this scale is calibrated in terms of relative humidity. now as humidity is increase or decrease the length of the hair hygrometer is also increase and decrease. So the pointer is move accordingly on the calibrated scale due to mechanical connection as show in figure. This pointer indicate the relative humidity.

In this method there are two mercury-in-glass thermometers. one thermometer is always covered with Muslin or wick. And one end of this thermometer is kept in a water containing vessel as shown in the figure.This thermometer is called wet bulb thermometer. other dry bulb thermometer  is kept near the  wet bulb thermometer as shown in the. Continuous evaporation of the water from the surface of wet bulb keep its temperature lower than that of dry bulb.  By using psychrometric table we can know the relative humidity of the atmosphere or any place where our device is placed. Temperature difference indicated by the two thermometer is the related to relative humidity of the ambient atmosphere. Note: The variant of this hygrometer is called sling psychrometer. It has a sling attached to it so that unit can be whirled manually before reading is taken.

Well, humidity and  moisture both are same but  when we measure the water vapour present in the air we used term  humidity.  And when we measure  water vapour present in/on any object  then we used term  moisture. There are so many methods to measure humidity and moisture. (1)wet and dry bulb hygrometer (2) hair hygrometer (3) Dunmore cell (4) pope cell etc.

Definition Oxidation reduction potential ( ORP ) instruments( redox potential instruments) are use  to monitor chemical reactions.  ORP  instruments measure the ability of a solution to act as an oxidizing agent, and to quantify ion activity.  Construction As shown in     figure, there is a two solution  separated by porous membranes. the function of porous membrane is isolate two solution physically but hydrogen ions can pass through this membrane for electrical current transfer. Two electrode are immersed in the solution as shown in the figure one is made of zinc and one is made of copper. One current metre is also connected between these two electrodes. This arrangement is called voltaic cell or galvanic cell. Working in the voltaic cell under consideration, zn dissolves into the solution as zn 2 + ions and liberate two electrons.  Liberated electrons travel along the external circuit to neutralize Cu 2 + ions at the Cu electrode.   Like t...

 The Nyquist Theorem, also known as the sampling theorem, is a principle that engineers follow in the digitization of analog signals. For analog-to-digital conversion (ADC) to result in a faithful reproduction of the signal, slices, called samples, of the analog waveform must be taken frequently. The number of samples per second is called the sampling rate or sampling frequency. Any analog signal consists of components at various frequencies. The simplest case is the sine wave, in which all the signal energy is concentrated at one frequency. In practice, analog signals usually have complex waveforms, with components at many frequencies. The highest frequency component in an analog signal determines the bandwidth of that signal. The higher the frequency, the greater the bandwidth, if all other factors are held constant. Suppose the highest frequency component, in hertz, for a given analog signal is fmax. According to the Nyquist Theorem, the sampling rate must be at least 2fmax, or ...

  What is ADC (Analog To Digital Converter)? ADC  stands for  analog to digital converter . It is an electronic device used for converting an  analog signal  into a  digital signal . Block diagram of  ADC Sample The  sample  block function is to sample the input analog signal at a specific time interval. The samples are taken in  continuous amplitude  & possess real value but they are  discrete  with respect to  time . The sampling frequency plays important role in the conversion. So it is maintained at a specific rate. The sampling rate is set according to the requirement of the system. Hold The second block used in ADC is the ‘ Hold’  block. It has no function. It only  holds  the sample amplitude until the next sample is taken. The hold value  remains  unchanged till the next sample. Quantize This block is used for  quantization . It converts the analog or continuous amplitude into...