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Water Pressure Sensor

Water pressure sensor are frequently used for inlet and outlet water pipe pressure measurement in clean water systems at public utilities.

Water pressure sensor and Water Pipe Pressure Measurement

Water pressure sensor are frequently used for inlet and outlet water pipe pressure measurement in clean water systems at public utilities. Some water systems are fed by the gravity flow of the water, usually, lift stations pump the water to a higher elevation to provide reliable gravity flow. Water pressure in the pump well, water tower needs to be monitored by water differential pressure sensor to control the predetermined water flow rate at the pump input, which turns off the pump at a minimum flow rate to prevent empty run damage. Also, pump well and water tower that undergoes large release of water require water supplement.  Pressure sensor for water pump offer reliable pressure measurement for the pump and the observer can determine when to adjust additional pressure and flow by the measured values.

A water pressure sensor is generally placed in a position such as:

  • the water input side of the pump.

  • Pump output side

  • Clean end location (pump wet well, elevated pipe...)

An important part of digital differential pressure sensor selection is ensuring that any electronic transducer transmitter used is compatible with potable water. Pressure transducers are responsible for monitoring the pressure, at various locations throughout clean water systems and often interface with pumps to show, when increased pressure or flow rates are necessary.



How to select a water pressure transducer Water pressure transducers can measure pressure in several different ways:

1. Absolute pressure VS gauge pressure vs Differential pressures

Absolute water pressure is measured against vacuum or pressure-free.

Gauge pressure measures water pressure under atmospheric pressure. A vent tube is used to allow air to enter the sensor. The vent line can often be run through the power cable supplying the sensor.

Differential pressures show the difference between inlet and outlet close to the pump, or in two water towers, or two water pipes. You can use differential pressure sensor to measure pressure drops across filters or measure flow rates by measuring the difference in pressure across a restriction.


2. Technology

Water pressure sensors or transducers apply an oil-extended silicon unit, the unit contains a crystal chip made of diffused silicon, which bends as pressure is applied and generates electrical power. There is a diaphragm close to strain Wheatstone Bridge, which changes its resistance on 4 lines when force is in contact. This Wheatstone Bridge is used to modify the output voltage of the sensor. Some water pressure sensors provide zero-based outputs, the zero pressure occurs when no actual flow happens. When water flows through the sensor it will generate voltage signals.


For example, One drawback of zero-based output is the difficulty of identifying problems with the sensor itself. For example, in a water-pumping system, a pump might be configured to activate when the water pressure rises above a certain point, perhaps indicating that a certain depth of water has accumulated. If the water pressure sensor has a 0V signal, that might indicate zero pressure – or the sensor may have failed completely, which would mean that the pump did not activate as water levels rose, perhaps leading to a flood. In contrast, a zero reading from a ‘voltage at zero pressure’ sensor would clearly indicate a fault. Some facilities are required zero signal from customer requirements.


For example, LEFOO LFT221 output might be in the range of 0–4.5V. Others offer voltage at zero pressure, with a range such as 1–5V. But the two ranges can function well on different controllers by different signal protocols. By applying an intermediary after the sensor, the signal can be transmitted to 1-5 V,1-10V, 2-10V, whatever you want.


3. Limitations

Since water pressure sensors may come into contact with different kinds of water, you may want to consider their suitability for different pH levels (acidic or alkaline), salt water, chemicals, or other contaminants.



Specifications to consider when choosing a water pressure sensor include:

Pressure measurement range

Accuracy, usually expressed as +-2% of the whole scale

medium compatibility, such as all corrosive medium compatible with PA66 and ceramic, or other range

moisture resistance

Operating temperature range

Venting

Vibration resistance

For wireless water pressure sensors, additional relevant options are:

Transmitter wiring (cable or flying lead)

Transmitter accuracy

Radiofrequency

Electromagnetic interference (0~10 V is anti-electromagnetic)

Sensors that measure gauge pressure must be vented, so you may need to consider sealing methods for outdoor applications, high-pressure water jets (in a car wash or industrial process, for example), or where the sensor will be exposed to a lot of water vapor. An alternative is to use a sealed gauge or a sensor that measures absolute pressure.

Pumping systems may sometimes be subject to ‘water-hammer, where the opening or closing of valves sends a shock wave through the water, causing a pressure transient or pressure spike that may exceed the measurement range of the sensor. To protect against this, some sensors can be fitted with restrictor plugs to slow down water flow and mitigate the effects of the spike.


Water pressure sensors, or water pressure transducers produced by LEFOO company,  are used in residential, commercial clean water distribution utilities for water elevated piping pressure measurement. The inlet and outlet water Pipe pressure measurement in water treatment facilities and water purify industries is very important, in the wastewater treatment industry, the measurement of water flow is also vital.  Water pressure transducer also applied in irrigation systems. LEFOO produces various pressure sensors and transducers with excellent accuracy and long-term stability. There is some basic information in this content to review before making a decision on the type of pressure sensor is required.