Working Principle Of A Flowmeter
A flowmeter is an instrument used for measuring the flow rate of fluid in a pipe. Flow measurement is important in a number of the laboratory as well as industrial applications.
The selection of a particular flow measuring equipment depends primarily on the metered fluid and the demands of the associated plant. For example, an aircraft fuel meter requires to be compact and must not be affected by the changes in orientation but has to handle only a clean and non-corrosive fluid.
On the other hand, many industrial flowmeters have to do with fluids that may be corrosive in nature or may contain foreign matters but the equipment may be relatively large and of fixed type.
Additionally, other factors that govern the choice of a particular flow metering device are the various performance parameters like range, accuracy, repeatability, linearity, dynamic response, type of output like analog/digital, etc.
Furthermore, another requirement may be to indicate or record the rate of flow, total flow, or may be both of these quantities. But low measuring devices generally fall into one of two categories, namely primary devices or quantity meters and secondary devices known as rate meters.
The distinction between the two is based on the character of the sensing element that interacts with the fluid flow. The output of the sensing element is then suitably modified so as to indicate or record the measured values.
Quantity measurement, by mass or volume, is usually accomplished by counting successive isolated portions, whereas rate measurements are inferred from the effects of flow rates on pressure, force, heat transfer, flow area, etc. It is quite often possible to obtain the rate of flow from a quantity meters are generally used for the calibration of rate meters.
Quantity or total flow measurements signifies the amount of fluid that flows past a given point indefinite period of time.
The average flow rate is then obtained by dividing the total volume/mass of flow passing through the metering device by the total time taken in the flow measurement process. A typical method used for obtaining an integrated or totalizing quantity of flow is the volumetric tank.
In this volumetric tank method, the flow rate of non-volatile liquids like water is measured by directly measuring the volume or weight of the fluid.
The time required to collect a particular amount of fluid is determined accurately and the average flow rate is thus calculated with improved accuracy may be obtained by using a longer and more precise time measurement as well as a more precise volume/weight measurement.
This quantity measurement technique is frequently used as a calibration technique for water and other flow meters.
Flowmeters are installed on the flow line in a pipe such that the pressure from the pipe forces the indicator to show the volume of fluid passing through the pipe at any given time. Some are in the form of a transparent glass tube while others could be in the form of dial indicators.
How To Make A Simple Flowmeter
To make a simple flowmeter, locate the busiest area in the pipeline especially the elbow joints, for the dial indicator type, make two small holes, one for the fluid inlet while one is for a fluid outlet. Fix the flowmeter’s ports to their various holes.
