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How does a water pressure sensor work

Have you ever wondered how pressure in water impacts our daily lives? We often take water pressure for granted, from kitchen pipes to washing machines. But what is the pressure like in our homes? How does boiling water – which happens at sea level – feel under normal conditions? We’ll explore how a water pressure sensor works to answer these questions and more.

Understanding the working of water pressure sensors is essential in any industry dealing with water. It does not matter if it is at home or a commercial establishment. The water pressure sensor gives you the humidity, temperature, and pressure of the water in your home.

Essentially, a water pressure sensor provides information about water pressure and temperature. To get this information, you need to connect a water pressure sensor with a socket in your outdoor device. You can use this information in your home, washing machines, and heating systems. If you want to know the pressure of hot or cold water at home, you should use a water pressure sensor.

What is a water pressure sensor

Water pressure is the force applied to water. The pressure of water is of two types: static and dynamic pressure.

Static

Static pressure is the difference between atmospheric and water pressure at a given location. It can also be between the air in a room and the supply pressure for drinking taps.

We can measure static water pressure by applying a gauge to a tap or valve or via a manometer on an external tank. However, these methods are cumbersome. Consequently, scientists have developed simpler forms of measuring this pressure. This is where water pressure sensors come in. These devices have a device that measures water pressure quickly and accurately.

Dynamic

The other type of water pressure is “dynamic pressure.” It arises from the movement of the fluid in question, such as a wave on the sea surface or water moving through a pipe. This movement can create friction and turbulence in the fluid. In addition, it results in heat generation and loss. Therefore, it is essential to accurately measure the actual water pressure in a pipe or a tank.

The most commonly used water pressure sensor is the diaphragm-type pressure sensor operated by a pad and spring system. There are different types of water pressure sensors available for you. They include piezoelectric, mounted on a laboratory’s turbine shaft, and barometric. However, these are not as popular as the diaphragm type.

We operate the diaphragm-type pressure sensor using a pad and spring system. It has two pads, one on the diaphragm and the other for mounting. These pads connect to a pressure chamber to measure the pressure using an electronic circuit.

The diaphragm also has a small gap to reduce the area of contact with water. Because of this, the pressure on the diaphragm will be less when compared with the static water pressure. The outside diameter of the diaphragm is almost in direct proportion to the diaphragm’s thickness. Therefore, a thicker diaphragm is preferable as it gives an accurate result.

How does water pressure sensor work?

The water pressure sensor works by measuring the force (pressure) on a diaphragm located underneath the water surface. First, a pressure sensor measures the pressure by converting it into an electrical signal. Then it records this voltage for later analysis. We do this by placing the diaphragm underwater. Next, we measure how it deforms under static or dynamic pressure force.

It directs the force (pressure) parallel to its surface when the diaphragm rest. We distribute the two poles of a simple voltage divider over its surface to measure the water pressure. The lower pole will be underwater and connected to the upper one by a wire. If static pressure exists, then this voltage will be constant. There is no dynamic pressure in an ideal situation as such force would not affect the diaphragm.

When we apply water pressure to the diaphragm, it will alter surface tension, resulting in a change in the force acting on it. The lower pole of the voltage divider will magnify this effect and change its value from 1volt to 2 volts and so on. We convert the signal into an electrical signal using a circuit and record it for later analysis by a long-term memory unit.

Measurement options

The water pressure sensor can measure the state of liquid water. It can measure the pressure exerted by liquid water in a closed area or atmospheric pressure in an open area. The water pressure sensor has different measuring modes of operation:

Absolute:

We measure the water pressure against zero. It is similar to an analog pressure gauge. We measure the pressure against a reference value (zero). The water pressure sensor is not affected by a pressure change in the liquid water circuit.

We need to install the diaphragm above the liquid or atmospheric environment to its surface above zero. It helps measure absolute water pressure. We need to install a diaphragm on top of a liquid-tight container to measure absolute pressure. For instance, a laboratory water container. In this case, the diaphragm will be in direct contact with water.

Gauge:

This technique measures the pressure of a liquid about atmospheric pressure. Therefore, it’s similar to a manometer. The water pressure sensor is sensitive to changes in atmospheric pressure. It can only measure relative pressures. If we submerge the water pressure sensor under the liquid, there will be no contact with the atmosphere and work as a gauge. If we want to use it as a manometer, we need to install a diaphragm in the vessel so that its surface is completely submerged underwater.

Differential:

It’s similar to a barometer. We measure the pressure difference between two points.

Typical measurement techniques are Pressure Pipette or Pressure Manifold). The diaphragm must be fully in a liquid-tight container. If we want to measure the pressure differential, we need to install more than one diaphragm in series. We can use this to measure pressure drops across filters and blowers. The water pressure sensor can also measure this pressure difference.

Water pressure sensor technology

The technology behind water pressure sensors is stable and reliable. They are very accurate in measuring the pressure of a liquid in a closed area (capacitor). This technology can also measure atmospheric pressure. However, this measurement mode is not very popular. It is a transducer that generates electric signals in response to changes in pressure. This resistance to pressure change is usually a gauge or transducer for absolute pressure measurement.

The diaphragm is silicon, and it bends as pressure changes.

There are two pads on it:

1. One for the pressure sensor

2. Another for vibration resistance and protection.

This diaphragm technology is suitable for a wide range of applications. They include pressure control valves, water flow control, circulation pumps, and air ejectors. In addition, it provides zero-based outputs in a very small package.

The diaphragm sensor construction consists of anodized aluminum. It uses an electric circuit management system to monitor its pressure output. We connect the mounting metal to the top of the diaphragm with a spring clamp and bottom nut mechanism. The mounting bars are also adjustable. It allows for repositioning at different points on the diaphragm.

Water pressure sensor installation

Water pressure sensors are essential for rapid and accurate installation. Usually, you don’t even need a professional like Rayming PCB & Assembly to install them. The process is very simple, and it doesn’t require any special skills or equipment. Some water pressure sensor types require additional piping. Others may not require drilling or cutting the pipe wall.

Water pressure sensor installation considerations

When installing a water pressure sensor, we should observe some essential points:

1. We should measure a static liquid environment. Do it in a closed area where the dynamic water velocity flow will not affect the diaphragm. If this is not possible, we can install an additional flow meter on-site to measure the flow.

2. It is essential to know the static water pressure (atmospheric pressure). It’s important because we use it as a reference point.

3. We should avoid excessive noise on the output signal at the sensor output connector. We can have noise from phone lines or flashlights on other sensors.

4. Avoid any contact or short circuit that would result in an incorrect measurement of water pressure.

5. We need to avoid wearing the diaphragm (between the sensor and the container).

6. Ensure that a short circuit or high current flow does not damage the sensor.

7. We should not connect voltage higher than .01 volts (the danger of overvoltage is very high).

8. For a remote water pressure measurement, we can use an electrical detector and communication module (EPROM or ROM). We use them to send an output signal towards the sensor without installing it on site.

Maintenance of the water pressure sensor

Water pressure sensors are not very expensive, and they require low maintenance. Their lifespan ranges between 4 and 10 years (depending on the model). You should replace them if they start to give unreliable results. The most important thing to remember is that you shouldn’t repair the water pressure sensor yourself. The manufacturer will warranty it. Make sure to take its calibration certificate with you if you want to have it serviced by a professional.

Water pressure sensor calibration

Water pressure sensors have a unique and easy-to-use calibration system. It makes it super easy to calibrate them. Water pressure sensors are precision instruments, calibrating them against static pressure. The calibration process is quite simple. It does not need any special instruments or equipment. The calibration can give the correct output of water pressure measurements using a fixed reference value.

We should calibrate the water pressure sensor in the following:

1. We measure the water pressure at the reference point on the diaphragm. Therefore, we should measure several times (at different times).

2. We perform the calibration procedure by placing a calibrated reference pressure in contact with the sensor for a few seconds. The result will be an output signal. It indicates the difference between two points on the diaphragm.

3. We perform a mathematical calculation to compare it with a known value and print it on our computer or printer. In this way, we have measured the measured water pressure. We can determine water pressure in the sensor’s container through a simple equation.

4. The pressure drop of the sensor depends on several factors. They include wall thickness, the specific gravity of the liquid, and the rated pressure. We should not pay much attention to this factor, as we can use an adjustable diaphragm to compensate for it. The pressure drop will typically be less than 0.1 bar (at full scale).

Different output signals of the water pressure sensor

Water pressure sensors can measure a wide range of water pressures. It depends on the model of the sensor. Most water pressure sensors have a voltage-output signal. But some models have current output. Therefore, depending on its application, we can use any model of a water pressure sensor. It gives us an adequate level of accuracy in measuring our needs.

We use the voltage output signal of the water pressure sensor in a wide range of applications. It has a wide dynamic range, and it’s precise enough for direct calibration against static pressure. We can place the output signal in a very small housing. So, you don’t have to take it out from the water pressure system and install it on your instrument. We can display the sensor’s output signal on our PC or PLC for remote control or monitoring.

The current-output signal we can use in systems where the measurement speed is more important than precision. For example, the pressure drop at the sensor is higher. But it has a very fast response to pressure changes as a flow sensor (i.e., mass flow meter).

This type of output signal is helpful in applications that need frequent measurements, for instance, filter systems and boiler flow monitoring.

Arduino water pressure sensor

We can use an Arduino board for the water pressure sensor measurement. Arduino is an open-source platform that enables users to build interactive devices and software.

The water pressure sensor can measure changes in the flow through a filter or in a pump circuit. This is possible using a capacitive displacement sensor.

The analog voltage signal from the water pressure sensor will go to one of the digital input pins of the Arduino board. It can then process it and feed our software or application.

The PCB circuit design of the Arduino water pressure sensor is very simple. A relay or optoisolator can interface the sensor with the processor. The circuit consists of a water pressure sensor, an Arduino board, a relay, and an optoisolator.

The optoisolator interfaces the sensor with the Arduino board to isolate both voltages. In addition, we connect the water pressure sensor with a 10 KΩ resistor and a voltage divider circuit. Finally, it allows for using some other Arduino pins as input.

We can easily attach the water pressure sensor to the PCB using screw terminals. The Arduino board has an ATmega32U4 processor, which can handle up to 5 V and 16 MHz frequencies.

Mercruiser water pressure sensor

It can monitor the engine or transmission’s leaky or overheated cooling system. The sensor generates an alarm when it detects water leaks. It gives you a chance to fix the problem before it causes any damage to the engine.

We can place the Mercruiser pressure sensor in the cooling system to track water leakage. It has a temperature range of 0 °C to 140 °C and a pressure range of 0 bar (0 PSI) to 15 bar (210 PSI). Its measurements are accurate and reliable.

The sensor uses a bimetallic strip for temperature measurement. A molybdenum disulfide covers the bi-metallic strip. It is in the sensor housing that changes electric resistance at different temperatures.

The bi-metallic strip will change electric resistance as the temperature varies. The sensor can monitor the temperature of the coolant, engine oil, or transmission fluid level.

The sensor is accurate and reliable. It will help you in many applications where you need to know the temperature of your cooling system. The sensor will send the temperature information to your PC for real-time monitoring.

You can use this sensor in applications where you need to immerse it in water or oil. However, in some cases, this may cause more damage than good.

Factors to consider when selecting a good sensor

The correction factor of the sensor should be as close as possible to the rated value. That will minimize errors to allow you to compare results directly.

The pressure drop of the sensor in applications also depends on several factors. They include:

1. Type of measurement (absolute vs. gauge)

When selecting a suitable pressure gauge, we should be careful about its accuracy. We can choose a pressure gauge with 1% or more accuracy.

Our application does not need absolute pressure readings but measures fluid flow rate. Therefore, we should use a measuring sensor connected to our flow meter or other flow measuring device. However, we can still calibrate the pressure gauge or sensor to measure our flow rate, whether gauge or absolute.

2. Pressure measurement range

The range of the sensor directly affects the amount of pressure that our measurement can handle. We widen our measurement as we increase the range. It makes our instrument more versatile for several applications. Since this is a cost-savings project, we should select a sensor whose range will cover most of our needs. Avoid buying another one shortly after.

3. Accuracy 

The accuracy of a pressure sensor can vary with its type and range. The high-end sensors should have better accuracy than low-end or economy-grade sensors. But in general, the pressurized fluids have higher pressure (up to around 100 psi) than air (about 0 psi). Therefore, a pressure range of 0 to 10 psi is sufficient for most applications.

As we increase the size of our flow meter, we will most likely want to increase our pressure range.

4. Media compatibility

Getting the media compatible with our sensor is one of the essential factors in selecting a good sensor. We can use as many different media types as we want, but some will not work together. Also, we make some sensors for specific materials and not for other materials without adjustments.

Most pressure sensors are suitable for low-pressure, high-temperature media. These are suited more for pressure gauges in industrial applications. Some sensors can work with even very high-pressure media. But you can use those only on rare occasions and under special circumstances.

5. Moisture resistance

Use a sensor in an oil or water-filled system if it is not moisture-resistant. Oils and fluids tend to collect on the surface of the seal, which will make the sensor readings inaccurate. They will also degrade the seal, creating dust inside the system or damaging the sensor.

Some sensors are specially designed for use in water and oil and can handle moisture.

We make sensor wires of Beryllium copper. They prevent short-circuiting when moisture enters a circuit.

6. Operating temperature range

The reason that most sensors operate at high temperatures is to protect the whole system. Therefore, they are usually rated to operate at 120 °C or higher temperatures. But these sensors may not be suitable for all applications. Depending on its type, its operating temperature can vary from -30 °C to 200 °C, depending on its type.

This is one of the most important factors to consider when selecting a sensor.

7. Venting

To vent the sensor requires using a tee, a 90-degree elbow, or another proper fitting. If there are any leaks in the system, this will cause pressure loss in the line and inaccurate measurement. If the sensor measures pressure, it will also measure flow rate, tee the sensor, and install a dummy check valve at the end of the line. Some sensors have a vent hole in their top cap, and we can vent them using a small tubing.

8. Vibration resistance

We install most sensors under the hood, making them susceptible to the engine’s vibration. Several “rubber tires” are available to prevent this. We can also use special brackets and mounting points. This will guarantee high performance in a real-time application.

Dynamometer may include a vibration resistance system. A good example is a shim between the sensor and dynamometer to isolate them from vibration. Dynamometers with good isolation systems are generally more accurate than those without them.

9. Transmitter wiring

We must connect a water pressure sensor to a transmitter for a real-time measurement display. It is good to use wiring that moisture and oil do not affect. If the wire does get contaminated, try to clean it without damaging the insulation. If it is really dirty, use more than one wire. But be careful not to use too many wires, which may cause electrical interference. Connect multiple wires in parallel or in a series branch to get the distance from one of the contacts. Use proper wire size and gauge for the installation. Use EPROM for extra protection. Avoid installing a bare sensor with your transmitter. It helps you avoid the possibility of a direct short-circuit or open circuit.

10. Radio frequency identification (RFID)

We can install many pressure sensors with an RFID reader and transmitter in the vehicle. The receiver then reads sensors without any human intervention. The RFID technology is excellent in construction technology. We use it to automatically count and maintain track of materials that move from one place to another.

We adapt the principle using sensors mounted on pallets or warehouses in industry.

11. Electromagnetic interference

Excessive electromagnetic interference can cause the sensor to malfunction. We shield sensors with a metal wrap or Faraday cage to remove potential electromagnetic interference. A necessary compromise is to use shielded wiring and shielding on the sensor’s case and wires.

There is a very low probability of RFI from the vehicle’s electronic components with a shielded system.

Summary

In conclusion, water pressure sensors are essential to any automated system. They help to monitor the liquid level and pressure in lines and tanks. Furthermore, water pressure sensors are not expensive, and we can install them easily. These sensors are very useful in many industries and applications. So it will continue to operate for many years to come. Knowing how the work and choosing a good one will get good results.