# Rotameter

Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It consists of a tube and float. The rotameter is standard as a result of its linear scale, relatively long measurement range, and low-pressure drop. It is very simple to install and maintain.  In the construction of the rotameter tube, it is marked in the division, and the reading of the meter is obtained from the scale reading at the reading edge of the float, which is taken at the largest cross-section of the float.

## Working principle of Rotameter

The Rotameter's operation is based on the variable area principle. In this principle, fluid flow raises a float in a tapered tube and increases the area for passage of the fluid. The higher the float is the maximum raised if the flow is greater. So the height of the float is directly proportional to the flow rate. With liquids, the float is raised by a combination of the buoyancy of the liquid and the velocity head of the fluid and in gases, buoyancy is negligible, and the Heat responds to the velocity head alone. The float moves up or down in the tube in proportion to the fluid flow rate and the annular area between the float and the tube wall.

The float reaches a stable position within the tube once the upward force is exerted by the flowing fluid and equals the downward gravitational force exerted by the burden of the float.

A change in flow rate upsets this balance for forces. The float then moves up or down, changing the annular area until it again reaches a position where the forces are in equilibrium.

## How to read a Rotameter

Set up the rotameter on a flat surface. it's necessary for the meter to be level. Connect the gas supply through the tube to the rotameter and switch on the gas. Some rotameters keep company with customary fittings for varied-size tubes. Find the ball floating within the middle of the rotameter column.

## How does a rotameter usually get damaged?

Rotameter Flowmeters area unit devices that may measure the flow rate of liquids and gases. Generally, the rotameter could be a tube made from plastic, glass, or metal combined with afloat, that responds linearly to the flow rate of the fluid therein tube.

1. The float of the rotameter does not rotate in modern designs as it used in the early ones.
2. Float shapes and proportions can be varied for different applications.

### Limitations of Terzaghi Theory

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### Streamer Theory of Breakdown in Gases

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### Price Guard Wire Method

Price Guard Wire Method Some form of  Price Guard Wire Method  is generally used to eliminate the errors caused by leakage currents over insulation. Fig. 3.14 illustrates the operation of This Method. In fig 3.14(a), a high resistance mounted on a piece of insulating material is measured by the ammeter voltmeter method. The micro-ammeter measures the sum of the current through the resistor (IR) and the current through the leakage path around the resistor. The measured value of resistance computed from the readings indicated on the voltmeter and the microammeter, will not be a true value but will be in error.   Figure 3.14 Application of  guard  circuit for measurement of high resistance In fig, 3.14 (b), the  guard  terminal has been added to the resistance terminal block. The  guard  terminal surrounds the resistance terminal entirely and is connected to the battery side of the micro-ammeter. The leakage current IL now