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How air pressure sensors work

Understanding how a pressure sensor works can benefit people interested in creating things. A pressure sensor is an electronic device designed to detect and react to pressure levels. The pressure measurement system comprises the sensor itself plus some other electronic component.

Air pressure sensors are one of the most widely used sensors for measuring and detecting pressure. These devices have become so common that many of us don’t even think about the technological wonders around us. This article will try to understand the basics of pressure sensors better. It will also discuss some interesting applications of pressure sensors in life.

What is air pressure?

Air pressure is a physical force that determines how much effort or pressure you need to push something. We can measure the air pressure in different pascals, atmospheres, kPa, and PSI. Air pressure acts on us as the human body comprises water molecules and gases. So everything in our universe has its levels of air pressure. The normal atmospheric pressure at sea level is around 14.7 psi, or 101.3 kPa (1 kilogram per square centimeter). Once you go higher up in the mountains, air pressure decreases. Huge buildings need special supports to keep them standing upright. You can find a table of atmospheric pressure at various altitudes in this article

Body reactions to air pressure

Different parts of the body respond differently to air pressure. Air pressure affects the respiratory system by either inhaling or exhaling. At sea level (14.7 psi), breathing may be uncomfortable. But, the amount of discomfort varies from person to person. The blood vessels constrict in response to low air pressure, as measured by a blood pressure cuff around the arm. If we raise the pressure quickly (meaning it’s above 14.7 psi immediately), blood will flow back into your arms and legs. If it stays low for a long time, it will flow out through your arms and legs instead.

What are pressure sensors?

air pressure sensors PCB BOARD

A pressure sensor is a device used for detecting and measuring pressure levels. We attach the sensor to an object or container that we are examining. The air pressure applied to the sensors causes them to move, thus creating an electronic output. We often use pressure sensors in industrial processes—for example, oil and gas extraction or in a chemical reaction. A change in pressure may affect the formation of products.

There are two types of pressure sensors: mechanical and electronic. The mechanical type is a metal diaphragm that connects to a spring. When we apply air pressure to the pressure sensor, the spring will close or open depending on whether the pressure increases or decreases. It creates an electrical signal for recording purposes. In contrast, an electronic pressure sensor uses a different material in its construction, such as silicon. RayMing PCB & Assembly it by etching and doping at room temperature. It requires no heating or cooling cycles during production.

Mechanical Operating Principles of pressure sensors

Mechanical pressure sensors consist of a metal diaphragm, diaphragm support, and pressure-transmitting materials. Some examples include rubber and plastic. The diaphragm connects to a central shaft in the most basic form. An electromagnet can rot the shaft that creates an electrical signal. It creates it through different coil connected to its top and bottom ends. The amount of rotation depends on the amount of air pressure applied, and we can use it to measure it. Some pressure sensors use a rubber diaphragm attached to a central shaft. When the sensor detects a change in air pressure, the shaft will vibrate or bend. It creates an electrical signal. Because this type is not very linear and accurate at measuring low pressures, we use them only for high ranges (more than 400 kPa).

Electrical Operating Principles of pressure sensors

Electronic pressure sensors are electronic sensors that we can make cheaply and in large quantities. The basic operating principle is similar to the one used by a mechanical pressure sensor. We apply air pressure to the sensor. Then it produces an electrical signal representing the pressure. However, in contrast to the mechanical type, electronic sensors require no rotating shaft. Instead, a piezoelectric element generates an electrical charge when applied air pressure. The amount of charge produced is directly related to the air pressure applied. Electronic pressure sensors can be very accurate at lower pressures. But they are more expensive and less sensitive at higher pressures (more than 400 kPa).

Electronic Pressure Sensor Circuit

Let’s look at an example circuit for a pressure sensor that can measure up to 5 kPa. The output is in volts. We then convert it to read in kPa using the following formula:

Vout = -log(1+Vin/kPa)

The output voltage Vout is around 1 volt when not applying pressure to the sensor. So, the air surrounding it has zero pressure. As we apply pressure to the sensor, Vout increases, and a multimeter can measure the voltage. The graph in Figure 2 shows how Vout changes with air pressure when we attach the sensor to a container.

Air Pressure sensors

Air pressure sensors help monitor the pressure in a system or provide feedback to an air compressor or other air source. We can use it for many applications. For instance, monitoring the pressure in different reservoirs and the air pressure in a building. We also use it in testing whether it produces a product under specified conditions.

Depending on the type used, a pressure sensor can measure pressures from 0.1 kPa to 20 MPa (one million kPa). The sensor can be a single device or contain multiple sensors, such as a differential pressure gauge.

Since air pressure relates to the amount of molecules in the air, it has different effects on different substances. For example, high air pressure may not affect metals and liquids. But it can damage the skins of plants and animals if we expose them for a long time. It is essential always to monitor the air pressure in an environment, even if the pressure seems normal. Sudden changes in air pressure that occur rapidly can cause serious damage.

Air pressure sensors commonly use air pressure to regulate airflow in a building. Air circulation is essential for maintaining a comfortable temperature. Still, too much or too little circulation can cause excessive moisture or dryness problems. It results in sicknesses and eventually the person’s death inside the building.

Applications of air pressure sensors

Air pressure sensors help extensively in the medical field because of high or low air pressure on organisms. For example, they monitor blood pressure in human patients. They also keep track of the amount of oxygen and carbon dioxide absorbed and emitted into an organism. We also use air pressure sensors to check whether a patient is still breathing. If there is no response from the patient, you can revive them and take further measures.

1. Automotive application

Air pressure sensors help detect whether you have closed a vehicle’s doors. It can also tell if the cabin’s airbags are working. Hydraulic brakes are a crucial component in passenger safety. They help slow the car down when needed, and they are also responsible for slowing the car down to a stop. If a sensor detects that there is either too much or not enough pressure in the brake lines, it can cause an immediate response from the car. Some responses include reducing power or activating an alarm. Air pressure sensors help in every component of a vehicle’s engine because air is crucial for providing fuel and oxygen to ignite it. If the manifold air pressure sensor detects changes in air pressure, it alerts a driver about potential problems.

A tire air pressure sensor is another example of an application that utilizes air pressure sensors. The sensors inside the tire can detect whether the tire is in good condition. If the sensors detect changes in pressure, they will signal an indicator. On most occasions, the alert is on the vehicle’s dashboard. When a sensor detects high air pressure in a tire, the system will activate a warning light or sound and reduce power until you resolve the problem.

2. Industrial applications

Air pressure sensors are essential extensively in industrial settings. They monitor excessive air pressure or lack of air pressure. For example, a pressurized pipeline can generate a significant amount of force. A force strong enough to cause damage to the pipe and surrounding walls if it ruptures. We install air pressure sensors on pipelines. They help detect leaks or build-ups in pressure and immediately shut off the supply source before it becomes dangerous. Many industries need air pressure sensors. They help in monitoring and controlling the pressure in their factories. Examples include food manufacturing plants, chemical factories, and mines.

Air pressure sensors are suitable for controlling the amount of air supplied. For example, a gas-pressurized fire extinguisher contains compressed gas in the container.

Arduino air pressure sensor The Arduino Uno platform (and other Arduino boards) comes with an analog to digital converter. The sensor circuit connected to the A0 pin measures the pressure in a container by reading voltage changes in the range of 0V to 1.5V.

We can build similar circuits by adding a protection diode between the analog input and ground or shield power supply.

3. Life-saving medical applications

Air pressure sensors monitor blood pressure, essential in monitoring a patient’s health. If a person’s blood pressure drops too low, it can be dangerous for them. Hypotension can lead to problems with heart rhythm, and low blood pressure is also associated with an increased risk of stroke. Air pressure sensors detect changes in air pressure surrounding an organism. It alerts doctors if they change by more than 1 kPa (a kPa is a unit of measurement that equals 1 bar or approximately 14 psi).

4. Weather applications

Air pressure sensors are essential in detecting atmospheric pressure. The pressure changes with the weather so that air pressure sensors can predict the weather. A severe storm is likely to follow if the air pressure drops suddenly and significantly. Monitoring atmospheric pressure can also give information about different weather conditions. They include dust storms, snowstorms, rainstorms, and hurricanes. These are weather conditions that can pose a danger or disrupt everyday life.

Barometric Air pressure sensor Barometric air pressure sensors have been active for many years. You will find them in a small building or room isolated from the outside. Inside the sealed building is an air pump. It pumps in the air from outside until the pressure in the room equals that of the surrounding atmosphere. The sensor measures changes in pressure as it compares them to what it was set to when you first turn it on.

Air Pressure Sensor Arduino Barometric pressure sensors are available on Arduino boards.

Measurement options

Most air pressure sensors operate by measuring the air pressure difference between two output ports. The air pressure sensors are usually equipped with a barometer to measure atmospheric pressure.

We can calibrate air pressure sensors to work with different PVs. The sensor’s type and size depending on whether it is for a general purpose or a specific application where we need a precise output.

Depending on your system’s needs, you may want to purchase a combination of a gauge and a transmitter. That way, you’ll have the choice of a digital display or an analog dial. You can connect the sensor via Bluetooth or by setting it up manually.

A precision pressure sensor measures pressure variations with very low distortion or noise. The output voltage is proportional to the atmospheric and measured air pressure difference.

1. Absolute air pressure sensor:

We use a gauge to measure the pressure of an absolute value such as the bar. To do so, we need to connect the gauge in the middle of a pipeline with an air pressure sensor at one end and a reference gas at the other end. By comparing the air pressure with the atmospheric pressure, you can determine how much pressure is present in your pipeline.

2. Gauge air pressure sensor:

We use a gauge as a transmission device and thus need a pressure sensor connected to the pipeline. Usually, two sensors should measure two different pressures.

3. Differential air pressure sensor:

A gauge measures pressure variations with a very low transmission level. We sense pressure variations directly by the gauge. We use its output to determine the actual air and atmospheric pressure difference. Then, it supplies this output voltage difference to a sensor connected to the pipeline.

Air pressure sensor technology

Building air pressure sensors start with a sensor that operates using a piezoelectric material. The piezoelectric materials change size when they are under tension or compression. You can then detect the change in length by applying an alternating voltage across the material.

The air pressure sensor has one output called the output port and two ports that we use as inputs to connect to:

a). Two pressure sensors that measure the differential pressure

b). A reference gas in parallel with the sensor’s output port

The gauge can determine the pressure of the gas. If the pressure increases to more than 1 bar, the reference gas pushes the diaphragm into a fixed volume.

Instrument pressure sensors have analog outputs and do not need any additional electronics. Since there are no moving parts and no auxiliary equipment, these sensors are easy to operate and require little maintenance. This makes them ideal for use in harsh environments where other sensors fail. They are also very reliable in low-level applications such as vacuum systems. Sensor technology is still improving and monitoring more precisely. But they are still the most cost-effective solution.

Resistive air pressure transducer or strain gauge

Many air pressure sensors use a strain gauge made from resistors, usually platinum. When the resistance changes when we stretch or shrink the material, an analog-to-digital converter can detect it.

Precision pressure sensors use a mechanism that can vary the reference gas volume. We connect the gauge to a much smaller gas source such as neon, krypton, or xenon. The reference gas is a very precise volume, working like an absolute pressure sensor.

Capacitive air pressure transducer

We capacitively couple the capacitor that we use to the indicator wire. You should separate the capacitor and the indicator wire a few millimeters. Only hold current as long as there is a voltage change, similar to how a TBI works but with an added decoupling capacitor.

All sensors that use capacitive coupling require a low-voltage power supply. It uses an electronic circuit rather than an electromechanical system.

Acoustic air pressure transducer

This system is similar to capacitive coupling, but it uses an interdigital transducer instead of a capacitor. When we compress the diaphragm, it vibrates, and this causes acoustic waves in the surrounding air. We detect these by a microphone that converts the waves into an analog-to-digital signal.

A pressure sensor that uses acoustic coupling can use in any environment where we can use a microphone.

Inductive air pressure transducer

The inductive air pressure sensor has an aluminum diaphragm at its core. We mount it to a shaft that holds the transducer. Also, we mount the shaft in a magnetically shielded cylindrical chamber. When the diaphragm gets pressurized, it moves closer to the shield. It changes the coil’s inductance, and we can determine this by measuring the voltage across the coil.

Factors to consider when choosing an air pressure sensor

You will not find precisely similar applications. But, an air pressure sensor will generally help in either application (industrial or environmental).

There are several questions to consider before choosing a particular air pressure sensor. They include:

Pressure range

The most important thing to consider is the application’s pressure range you need. Air pressure sensors measure absolute pressure (bar, MPa, or psi) or gauge pressure (kPa, bar, and psi).

Accuracy

The air pressure sensor accuracy depends on its technology, and it may range from a few percent to 2 decimal places.

Precision

The precision of an air pressure sensor also depends on its technology. The higher the precision, the more accurate the measurement.

Noise

Noise is a physical phenomenon. The energy moves through a material when something changes in that material’s properties without a trigger by a signal. It can cause problems in air pressure sensors. It usually manifests itself as inaccurate readings and a longer measurement time (usually 10% to 20%).

Location flexibility

We can mount some air pressure sensors on a pipe. Others can help in other environments. For instance, oil wells, compressors, refrigeration systems, and even glass manufacturing.

Compatibility

The air pressure sensors compatibility depends on the environment it will work in. For example, some work with a high-pressure piping system, while others work at a lower pressure.

Response time

This refers to the time it takes for an air pressure sensor to respond to a new set of pressure conditions. Typically, this is around 2–5 ms, but environmental factors such as high temperatures can slow it down. It can take up to 50 ms.

Accuracy vs. cost

The accuracy of an air pressure sensor is often dependent on the cost. Higher specifications generally have higher costs. Manufacturers price their products based on what the market can bear.

Lifetime cost

You should also consider the manufacturing cost and production cycle. This will determine the overall life-cycle cost of your air pressure sensor.

Energy efficiency

The energy used by an air pressure sensor is also dependent on its technology, ranging from a few milliwatts to tens of milliwatts.

The advantage of using an air pressure sensor is that it is a simple and accurate way to measure pressure levels in any environment.

Limitation of Air pressure sensors

Air pressure sensors depend on their accuracy, precision, and power to run them. Any air pressure sensor system needs appropriate calibration before using it in any application. This is a way to measure the actual pressure levels of a fluid or gas based on its mass and volume. You must calibrate the air pressure sensor before using it. Any change in its design will affect the accuracy of its measurements. This is an essential feature because it enables the manufacturer to meet its standards. It allows the end-user to get accurate results. You must calibrate the pressure sensor before using it. Otherwise, it may not provide reliable readings.

Conclusion

Air pressure sensors are one of the most reliable sensors used in any environment. They are easy to use, accurate and precise, making them perfect for many applications. The main advantage of using air pressure sensors over any other type of sensor is their simplicity and accuracy. You will find air pressure sensors in almost any environment. They include industrial applications, oil wells, compressors, refrigeration systems.