What Is a Digital Pressure Sensor?
A digital pressure sensor is a device that digitally displays the pressure inside a pipe.
This display method has the advantage of reducing the risk of misreading and can be used in dark locations. Digital pressure sensors measure pressure by means of an internal piezoelectric element. Therefore, measurement can be made without directly touching the fluid flowing in the piping.
The sensor used should be changed according to the type of fluid. They are divided into those for liquids, gases, flammable fluids, and so on. In addition, since the sensor is fixed to the piping, attention must be paid to the diameter of the piping.
Uses of Digital Pressure Sensors
While digital pressure sensors are rarely used in the average home, they are used very extensively in industry. In industrial facilities and plants, fluids (e.g., water or oil) are moved through pipes to various devices. A certain force is required to pump the fluid, and this force creates a pressure above atmospheric pressure.
Theoretically, if the same force is applied to the same fluid, the resulting pressure should be the same. However, equipment failure or deteriorating piping can result in pressures that differ from expected pressures.
By detecting and recording these unexpected changes in pressure, digital pressure sensors play an important role in detecting problems at an early stage and contributing to quality control.
Principle of Digital Pressure Sensors
Digital pressure sensors measure pressure when a force is applied to the piezoelectric element contained in the sensor. When pressure is applied, an electric current corresponding to the force is generated, which is processed and displayed as an electrical signal. A typical example of a piezoelectric element is a semiconductor. A semiconductor is a substance that conducts electricity under certain conditions.
Unlike insulators and conductors, the timing of electricity flow can be freely changed by manipulation. The most commonly used material is silicon. A flexible membrane (diaphragm) is attached to a silicon substrate. When pressure is applied, the diaphragm bends, and the silicon substrate bends along with it.
The force causes a piezoelectric effect that changes the state of charge in the substrate, resulting in a voltage. Since the intensity of the current flow changes with the voltage, it is possible to measure how much pressure is applied.
There are also other types that attach a resistive bridge to the diaphragm and measure the amount of strain on the diaphragm as a voltage change. When using the amount of strain, a metal diaphragm is used, and stainless steel is mainly used.
Types of Digital Pressure Sensors
Digital pressure sensors are classified into a wide variety of types according to their application, sensitivity, shape, and scaling range. The major types are listed below.
1. Absolute Pressure Sensor
Absolute pressure sensors can measure pressure with respect to a vacuum. Generally, atmospheric pressure is considered to be one atmosphere, but this type of sensor is based on absolute zero.
This sensor is mainly used for weather forecasting, altimeters, and cleaning equipment.
2. Gauge Pressure Sensor
Gauge pressure sensors can measure pressure with respect to the current atmospheric pressure. In other words, these sensors can read relative pressure changes. These sensors are used for tire pressure measurement in automobiles, air conditioner pressure management, etc.
3. Differential Pressure Sensor
Differential pressure sensors can measure the pressure difference between two pressure sources. These sensors are primarily used to detect clogged filters or to monitor liquid flow.
4. Shield Pressure Sensor
Shielded pressure sensors can set a specific reference pressure and measure the pressure relative to that pressure. They are primarily used for telemetry and data logging.
How to Select a Digital Pressure Sensor
When selecting a digital pressure sensor, many factors should be considered, including the operating environment, fluid of interest, measurement range, and accuracy.
1. Operating Environment
Sensors can be affected by environmental conditions such as high or low temperature, humidity, and vibration. Therefore, it is important to carefully consider the operating environment when selecting a sensor.
2. Target Fluid
The appropriate sensor depends on the type of liquid or gas. Especially when handling corrosive liquids or food, it is necessary to check the resistance of the sensor to the target substance.
3. Measuring Range and Accuracy
The measuring range and accuracy of the sensor are also important selection criteria. It is important to confirm how accurately the sensor can measure within the desired pressure range.
4. Ease of Installation and Operation
Ease of installation and operation of the sensor is also important. The appropriate interface and installation method must be selected in consideration of the location of the sensor and the skill level of the person using the sensor.