Water Level Controller: Working Principle, Types, Applications

Water is one of the most essential needs for life. About 0.3% of the water resources in the world are usable. Water shortages already exist in many regions, with more than one billion people without adequate drinking water. This situation is one of the most important indicators of why we should be very sensitive and conscious of our water resources. As the world population increases need for water also increases. However, as a result of different effects and especially human activities, water resources are decreasing, polluted and still used unconsciously. Therefore, it is necessary to take and implement measures as soon as possible and we have to use water resources carefully. The aim of this article is to review the importance of water lever controllers that are used to control water usage in residential and industrial applications.

What is a Water Level Controller?

The water level controller is an electronic device that detects the level of a liquid in a tank. It is used in a wide range of applications such as water and sewer services for office and apartment buildings and industrial applications for iron and steel, food, chemical, pharmaceutical and semiconductor industries.

Other definitions of the water level controller:

• Floatless relay
• Liquid level relay
• Level control relay
• Liquid level monitoring relay
• Automatic water tank level controller

The main application for water relays is for the sensing and control of the level of conductive liquids. The goals of controlling liquids are:

• Automatically supplying water to elevated tanks on buildings.
• Outputting alarms for water shortage or water rise in elevated tanks.
• Automatically discharging wastewater from tanks to sewage lines.
• Detecting water leakage in facilities, from pipes and on floors.

Level control devices are composed of two components: a level controller and electrodes

Level controllers are the controlling units.

Electrodes are the measuring units.

How Does a Water Level Controller Work?

The working principle of a water level controller is based on measuring the apparent resistance of the liquid between two submerged probes. When this value is below the preset threshold displayed on the front face of the unit, the relay changes state.

To avoid electrolytic phenomena, an AC runs across the probes. A rotary switch on the front face can be used to select the desired function and sensitivity range.

Emptying function

As long as the liquid level has not reached the probe maximum, the output relay opens. Once the maximum level is reached, the contact closes, thus allowing the tank to empty (the valve opens, the pump starts, etc). When the level drops below the min. level, the contact opens to interrupt the emptying process.

Filling function

As long as the liquid level has not reached the probe maximum, the output relay stays closed. Once the maximum level is reached, the contact opens and pumping stops. When the level drops below the min. level, the contact closes again and pumping restarts to make the liquid level rise again.

Suitable liquids:

• City water
• Well water
• Rainwater
• Seawater
• Liquids with low-percentage alcohol
• Wine
• Milk, beer, wine, coffee, fruit juice
• Sewage
• Liquids fertilizer

Unsuitable liquids:

• Demineralized water
• Fuels
• Oil
• Liquids with a high percentage of alcohol
• Liquid gas
• Paraffin
• Ethylene glycol

How do electrodes work?

When the level of liquid inside the tank reaches the electrodes a current can flow. But how can this current flow? Looking briefly at the system we can see it is static. i.e. we see a positive potential on one electrode and a negative potential on the other. We can also say one electrode develops a lack of electrons and one has a surplus. The negatively charged electrons attract the positively charged ions, which are present in all conductive liquids, towards the electrodes. So a current flow through the liquid is created.

Types of Water Level Controller

There are three different types of water level relays:

Minimum level control relay

It gives a contact output when the liquid goes below a certain level. It prevents the engine from running idle.

Maximum level control relay

When the liquid goes above a certain level, it gives a contact output. It controls overflow.

Minimum and maximum level control relay

It is a type of relay that includes both features.

Applications of Water Level Controller

The following are a few examples of water level control applications:

Agriculture

Level control in slurry tanks, water tanks, reservoirs, sewage plants, underground wells, and mixing plants.

Flow detection in pipes, channels, and irrigation systems.

Chemical

Level in chemical tanks.

Indication of liquid build-up due to filter blockages.

Alarm control warning of abnormal or dangerously high or low levels.

Food and beverage

Level detection of liquids such as milk products, beer, wine, soft drinks, and water but also sticky or abrasive products such as chocolate or jam.

Water distribution and treatment

For level and pump control.

Fill level control of purified city water, industrial water or sewage.

The hot water supply is heated by solar energy.

Filling application of tank level.