What Is a Pressure Transducer?
Pressure transducers, also known as pressure sensors, are devices that convert pressure into an electrical signal for transmission. Commonly used in pressure control applications, they typically convert signals into 4-20 mA DC or 20-100 kPa pneumatic signals, although the latter is less common now.
These devices can measure pressures in gases, liquids, and vapors and are available in absolute and relative pressure types, each suited to specific applications.
Uses of Pressure Transducers
Pressure transducers are widely used in differential pressure flow measurement, pressure measurement, liquid level measurement, and liquid density measurement.
They are also used in control applications, triggering different operations when certain pressures are reached.
Principle of Pressure Transducers
Pressure transducers function by converting pressure-induced displacement into an electrical signal. This signal, often amplified, is transmitted as a direct current. Diaphragms are commonly used for stability.
Applications include:
1. Flow Measurement
Using an orifice in process piping, they measure differential pressure, proportional to the square of the flow rate, to determine gas flow.
2. Liquid Level Measurement
In liquid-filled containers, pressure at the bottom is proportional to the liquid level and density, enabling level measurement.
Components of Pressure Transducers
Pressure transducers measure the displacement caused by pressure using Bourdon tubes, diaphragms, and bellows. Key components of pressure transducers include:
1. Orifice
Used in flow measurement, an orifice is a type of squeezing mechanism used in Shibori flowmeters. This mechanism creates a pressure difference to measure the flow rate.
2. Bourdon Tube
A helical metal pipe that changes curvature in response to pressure, allowing measurement through pointer displacement.
Types of Pressure Measured by Pressure Transducers
Pressure transducers measure different types of pressure:
1. Absolute Pressure
The total pressure, combining atmospheric pressure and gauge pressure. It is often denoted as “abs” for clarity.
2. Gauge Pressure
Measured relative to atmospheric pressure, with zero as the reference.
3. Differential Pressure
Represents the difference between two pressures, important in industrial measurement and control systems.
Pressure transducers play a crucial role in converting these pressure variations into useful electrical signals for various applications.