Flow rate measurement:
An orifice meter is primarily used to measure the flow rate in a pipe. It works on the principle of restricting the flow of a fluid through a specifically shaped orifice plate installed in the pipe. The pressure difference created by the orifice plate is directly proportional to the flow rate of the fluid, allowing for accurate measurement.

Working principle:
When fluid flows through the orifice plate, a pressure drop occurs due to the restriction. This pressure drop is measured using pressure taps located upstream and downstream of the orifice plate. By applying the Bernoulli's equation, the flow rate can be calculated based on the pressure difference.

Calibration:
Orifice meters need to be calibrated for accurate measurement. Factors such as fluid properties, orifice plate size, and pressure differentials are taken into account during calibration to ensure precise flow rate readings.

Advantages:
- Orifice meters are simple in design and relatively inexpensive compared to other flow measurement devices.
- They can be used for a wide range of fluid types and flow rates.
- Orifice meters are easy to install and maintain, making them a popular choice for industrial applications.

Limitations:
- Orifice meters can cause energy loss due to the pressure drop across the orifice plate.
- They are sensitive to changes in fluid properties and temperature, which can affect the accuracy of the measurement.
In conclusion, an orifice meter is a reliable and cost-effective solution for measuring flow rates in pipes, making it a widely used instrument in various industries.