The Differences Between Water Level Sensor & Level Gauge

1. Introduction to Water Level Measurement

The measurement of water level by a water level sensor is essential for its various applications. Whether it is flood monitoring, where level measurement can be used to estimate the severity and provide early warnings of flooding, wetland studies where water depth is crucial in analyzing the characteristics of the ecosystem, or global sea level measurements for a good understanding of tide predictions and hygrography. Water level measurement is critical in every aspect where water is involved.

In many industrial plants, several water level sensors are incorporated and compared with the normal value to ensure smooth operation. Desalination plants use water level sensors to maintain a constant supply of pure water for the area.

By the end of this article, you will have a clear understanding of how water level sensors work, their various types, applications, and the key differences between water level gauges and sensors.

2. Water Level Sensor

A water level sensor is an instrument that measures the water level of liquids, fluids, and fluidized solids in tanks and systems. Water level sensors can be primarily classified into two categories: contact-type and non-contact-type. Contact type measures the water level by sensing water through conductive probes in contact with the water. The non-contact water level sensors consist of ultrasonic, infrared, and radar level sensors, which do not require contact with water. Water level sensors, whether contact or non-contact types, are designed to provide continuous measurement within a specified range.

2.1. How Water Level Sensors Work?

2.1.1. Submersible Liquid Level Transmitters

This type of water level sensor measures hydrostatic pressure through the diaphragm on the probe. The probe is usually placed on the bottom of the tank whose level is to be measured. The diaphragm is made of ceramic material.

2.1.2. Radar Level Transmitters

Also called optical sensors, this type involves the transmission of electromagnetic waves into the water and the calculation of the time it takes for the waves to reach the water surface and reflect, which is used to measure the distance and hence the level. These are best applicable in a versatile environment that experiences temperature and phase changes.

2.1.3. Ultrasonic Liquid Level Transmitters

Ultrasonic level sensors send an ultrasonic sound pulse and measure the time it takes for the sound to travel from the sensor to the water surface and return to the receiver. Ultrasonic level transmitters are generally more cost-effective than radar level transmitters. Still, they are only suitable for clean and non-extreme conditions, as ultrasonic waves are affected by the properties of the medium through which they travel.

2.1.4. Capacitance Sensing

It consists of two electrodes. One is placed on one side of the water level, and the other electrode is either the tank's lower surface in a metallic tank or any other electrode on the bottom of a non-metallic tank. The higher the water level, the greater the capacitance between the electrodes. The level value is calibrated based on the difference in capacitance value.

2.1.5. Liquid Float Switch

It is a switch that opens or closes according to the set water level. At that level, it triggers the signal, which either displays an alarm or actuates any device or system according to the set conditions. The levels at which the switch is closed and sends signals are predetermined by instrumentation personnel.

2.2. Advantages of Water Level Sensors

Water level sensors have several advantages over a level gauge, which are described below.

• Accuracy: Liquid level sensors provide accurate measurements of water levels compared to manual gauges or the naked eye. Even in many small-scale systems, level sensors are being implemented due to their accuracy.

• Wide Supply Voltage Range: Many sensors, such as radar types, support a broad range of supply voltages (e.g., 12V DC, 24V DC, 220V AC), enhancing their versatility. Submersible sensors often operate within a 10- 30V range.

• Low Maintenance and Running Costs: Water level sensors have very low maintenance costs and a low running cost, resulting in a longer lifespan that contributes to cost savings. No extra fluid is used, unlike some gauges, which reduces waste.

• Non-Conductivity Based: These Sensors are not conductivity-based. The disadvantage of conductivity-based methods is that they require a conductive liquid to measure the level. Moreover, the probability of having an electrical shock is also increased, which is not the case with water level sensors.

• Low Power Consumption: The power consumption of the sensors is significantly lower than that of many electrical components. They have minimal power usage. For example, the ultrasonic water level sensor's highest power consumption level is around 3V.

• Durability: Water level sensors are highly durable and rarely require maintenance or replacement, thereby increasing their lifespan and minimizing both maintenance costs and time. Durable and easy maintenance.

2.3. Applications of Water Level Sensors

A large number of sensors are being used worldwide, with a vast array of applications. Some of them are described below.

2.3.1. Storage Tank

Water level sensors indicate the capacity of storage tanks, allowing for the immediate detection of any changes in level and the identification of leaks, which leads to a sustained water inventory.

2.3.2. Environmental Monitoring:

Measuring water reservoir levels in oceans and rivers is crucial for both hydrological research and environmental safety. Moreover, changes in water levels also help in predicting floods or water shortages, leading to timely risk prevention and mitigation.

2.3.3. Wastewater Treatment and Irrigation:

Water level measurement in wastewater treatment plants enables operators to detect abnormalities, such as leaks, blockages, or excessive water usage, providing a clear picture of the treatment process's effectiveness. In an irrigation system, water level sensors give an estimate of the system's capacity for the area, which is necessary for sustained irrigation.

3. Level Gauge

A water level gauge is a mechanical or visual device that measures the water level. Water level gauges are primarily of 3 types—namely, a tubular water level gauge, a loathing water level gauge, and a sight glass.

3.1. How Level Gauges Work?

• Tubular Water Level Gauge: A tubular water level gauge is simply a tube connected to both the bottom and top sides of the tank whose level is to be measured. The tube has markings that are calibrated in centimeters (cm) or millimeters (mm).

• Sight Glass: The sight glass is small in size and lacks markings. A sight glass is typically used for level measurement of oil in pump or motor bearings.

• Floating Water Level Gauge: A floating water level gauge is a device that utilizes a float that moves with the water level due to the buoyancy force. These gauges of water level are commonly used when continuous monitoring of the water level or auto-actuation is not needed for the equipment. Moreover, these gauges are also used for the validation of non-contact sensors, should any of them malfunction.

3.2. What to Use: Sensor or Gauge?

Water level Sensors are ideal when:

• A real-time, continuous display on an HMI screen is necessary for effective monitoring.
• Automatic actuation and alarm systems require configuration.
• Highly accurate and precise measurements are required for automated actions.

Water level Gauges are suitable for:

• Manual measurements are limited in their application.
• Process industries extensively use tubular gauges to complement various water level sensors.
• Situations where simplicity, low cost, and no automatic actuations are required.

3.3. How to Use Water Level Sensors and Gauges

In the Submersible Water Level sensor, the water level probes are located at various points in the tank whose level is being monitored, which are crucial for accurate indication. Whenever the water level is filled, the one-by-one submersion of the probes sends an electrical signal to the transmitter, indicating that the level is rising. This system can also be used for open-water sources, such as rivers and lakes. Flood levels are also used similarly to submersible water level sensors.

4. Key Differences and Data Accessibility

The best feature of the water level sensor is its real-time monitoring and data analysis capabilities. In manual gauges, the industry operator must always organize reading sheets to maintain a record of the readings. Today's advanced water level sensors have excellent data transmission and analysis systems, which not only provide real-time updates on the water level but also offer options for auto-action if that particular level is critical. The physical distance or pressure measured by the water level sensor is converted into an electronic signal by the transducer, which is then processed by the Programmable Logic Controller (PLC).

Furthermore, sensors maintain a historical trend of water levels over a specific period. This trend data is invaluable for decision-making, allowing users to analyze patterns of level change. Here is a table differentiating a water level sensor and a level gauge:

5.  Summary

Water level sensors provide accurate, continuous, and real-time data for monitoring and automation in various applications, ranging from industrial plants to environmental studies. They boast low maintenance and high durability. In contrast, level gauges are simpler, mechanical or visual devices primarily used for manual measurements or sensor validation, suitable where no actuations are required. Sensors provide superior data accessibility and trend analysis. Here are their key characteristics:

• Accuracy and Reliability: Due to their working principles, water level sensors consistently provide accurate and reliable measurements. Among them, hydrostatic sensors are often considered the most precise.
• Durability and Longevity: Their robust construction and ease of installation contribute to long-lasting durability.
• Minimal Maintenance: Modern water level sensors have low maintenance requirements, resulting in reduced downtime and increased cost-effectiveness.
• Harsh Environment Suitability: Current water level sensors are designed to withstand challenging conditions, including high temperatures and pressures.

If you're looking for high-end, efficient, accurate, and precise water level sensors, consider the Rika Sensor lineup. They include submersible, radar, ultrasonic, and other types of water level sensors applicable in a wide range of areas, such as wastewater treatment plants, chemical processing, irrigation systems, and more. Visit the Rika water level sensor category to explore their full range.

Frequently Asked Questions (FAQs)

1. Can a water level sensor be used for both high and low water levels?

Yes, continuous level sensors can measure both high and low water levels. Water level sensors come with different detection ranges. The high and low water levels should fall within the detection range specified by the manufacturer of the water level sensors.

2. How accurate are water level sensors?

Water level sensors offer varying accuracy. Submersible sensors can achieve an accuracy of up to 0.1% full scale (FS). Radar sensors can achieve precision with an accuracy of ±3mm. Ultrasonic sensors, such as the RIKA RKL-03, offer a range of 0.5%-1% accuracy with a resolution of ±3mm or 0.1% full scale (FS).

3. Can water level sensors be used in hazardous environments?

Yes, water level sensors with ATEX or IECEx certifications can prevent ignition in dangerous atmospheres. These are typically used in chemical processing facilities where handling of hazardous material is unavoidable.

4. Can water level gauges be automated for remote monitoring?

No, a typical water level gauge cannot be set up for remote monitoring. For remote monitoring, water level sensors with the ability to provide analog or digital output are key. Water level gauges typically involve integrating them with sensor-based systems or using computer vision technology to "read" the gauge visually and transmit that information.

5. What is the lifespan of a water level gauge?

Water level gauges have a lifespan of 5-10 years. They require physical observation to check water levels. Water level sensors, on the other hand, have a lifespan of 4-5 years but offer remote monitoring, continuous measurement, an alarm system, and much more.