The stable operation of a thermal management system relies on the precise control of coolant levels. As a core sensing component, the coolant level sensor collects real-time signals regarding the liquid level in the reservoir and transmits them to the control unit.
Among them, the coolant level sensor plays an irreplaceable role in industrial manufacturing. The coolant level sensor can control the coolant level, thereby increasing the service life of industrial equipment.
This article will introduce the relevant knowledge of the coolant level sensor.
What is the Industrial Coolant?
Coolant is a liquid used to control and regulate the temperature of machinery, equipment or engines.
Features:
High specific heat capacity: The Coolant has a high specific heat capacity and can absorb and release a large amount of heat.
Corrosion resistance: The coolant needs to have good corrosion resistance. Prevent corrosion of metal parts inside machinery and equipment.
Antifreeze resistance: The coolant needs to have a certain degree of antifreeze. Ensure that it does not freeze in low-temperature environments.
Uses:
Automobile cooling system: Coolant is used in the cooling system of automobile engines. Control the temperature of the engine and prevent overheating.
Industrial equipment: Coolant is widely used in the cooling and heat exchange process of industrial equipment. Maintain the normal operating temperature of the equipment.
Electronics: Coolant is used in high-power components or heat sinks in electronic devices. Prevent overheating damage.
Measuring the level of coolant is a complicated matter. There are many ways to measure coolant. The most commonly used is a coolant level sensor.
Measurement Challenges
1. Temperature throws off level measurement accuracy. When industrial equipment runs hot or cold, the coolant expands and contracts, and bubbles can form too — so the liquid level reading you get at one temperature might be way off from what you see at another.
2. Circulating flow keeps the surface moving. The coolant is always moving through the cooling system, and the fluid hitting the pipework doesn’t let the surface settle down — so getting a precise level reading is tough when the surface won’t stay still.
3. The coolant and the tank itself can easily cause obstruction and interference. Prolonged use of the coolant leads to cloudiness and scaling, whilst oil and impurities adhering to the inner walls of the storage tank obscure the observation scales.
4. Sealed, pressurised tanks cannot be observed directly. Most industrial cooling systems are pressurised and sealed, meaning the lid cannot be opened for measurement; detection can only be carried out indirectly using external sensors.
What is a Coolant Level Sensor?
The level of coolant can be measured with a variety of instruments. This article will introduce 7 sensors that can measure the level of coolant.
Capacitive Level Sensor
Working principle of the capacitive level sensor:
The process fluid has a dielectric constant that is significantly different from air. They measure the change in capacitance between two plates produced by the change in level. There are two versions. One is suitable for fluids with high dielectric constants. The other is suitable for fluids with low dielectric constants.
Capacitive level sensors are suitable for a variety of solids, liquids and mixed materials. They also have contact and non-contact configurations. It means that some of them can be connected outside the container.
Advantages: solid-state, can be non-invasive, compact, and accurate
Disadvantages: may require calibration, can only be used in certain liquids
Applications: tank level monitoring in the chemical, food, water treatment, power and brewing industries
Ultrasonic Level Sensor
Working Principle of Ultrasonic Level Sensor:
The level is measured by calculating the duration and intensity of high-frequency sound waves reflected from the surface of the liquid back to the sensor. The time required is relative to the distance between the sensor and the liquid.
The length of time required for the sensor to react is affected by various elements in the atmosphere above the medium, such as turbulence, foam, temperature, etc. Therefore, the mounting position is critical in these devices.
Advantages: No moving parts. Compact. High accuracy. Unaffected by the characteristics of the medium
Disadvantages: Expensive. Intrusive. Performance may be affected by various elements in the environment
Applications: Non-contact applications with high viscosity and solid particles. For systems requiring remote monitoring
Radar Level Sensor
Radar level sensors and ultrasonic level sensors work on similar principles.
A radar level sensor is an application of microwave (radar) positioning technology in level measurement instrumentation. It transmits energy waves through a device that can transmit energy waves (usually pulse signals). The energy waves are reflected when they encounter obstacles. And a receiving device receives the reflected signal. The level change can be determined by measuring the time difference of the energy wave movement process. The microwave signal is processed by an electronic device. And finally converted into an electrical signal related to the level.
Advantages: The measurement results are very accurate. No calibration is required. Multiple output signal options
Disadvantages: Expensive. Affected by the environment. Limited detection range.
Application: Humid, odorous and dusty environments. They are also used in systems with temperature changes
Hydrostatic level sensor (submersible level sensor)
Working principle of the hydrostatic level sensor:
First, its level sensor consists of a pipe and a probe, which is used to measure the pressure of the liquid. Then, the level sensor converts the measured pressure signal into a measurable electrical signal. And inputs the electrical signal into the control system. The control system converts the electrical signal into a liquid level value. Finally, the display instrument displays the liquid level value.
Advantages: It has a simple structure. Simple installation. It can meet most liquid level measurement requirements. The price of the level meter is relatively low.
Disadvantages: Not suitable for occasions containing impurities and high viscosity. Not suitable for slurry and sedimentation media environments.
Application: Suitable for sewage treatment, liquid level measurement of various pools, etc. And water level monitoring in other industries.
Tuning fork level switch
Working principle of the tuning fork level switch:
The tuning fork level switch uses piezoelectric devices to realize the vibration drive and detection of the fork body. Driven by piezoelectric ceramics, the tuning fork fork body vibrates at a certain mechanical resonant frequency.
When it comes into contact with the measured liquid, the resonant frequency of the fork body will be significantly reduced, and a change in vibration frequency will occur. It is directly reflected in the output signal of the piezoelectric detection device. And then the detection circuit judges the change in the vibration frequency and outputs a switch signal.
Advantages: compact and economical
Disadvantages: invasive, limited number of uses. Does not provide continuous process measurement
Applications: Level control of liquids, powders and fine solids in mining, chemical processing and food and beverage industries.
Float level sensor
A float level sensor is also called a float level switch. A float switch is one of the most cost-effective but well-proven technologies in liquid level sensing. The float switch includes a magnet inside a float and a magnetic reed switch contained in a safety housing. The float moves with the change of liquid and will cause the reed switch to open or close, depending on whether it is in air or liquid. Although the design is simple, the technology provides long-term reliability at an attractive price.
Advantages: No power, direct indication, relatively cheap, various outputs
Disadvantages: Intrusive, moving parts, large size, a large amount of liquid must be present before the float contacts.
Application: Tank level applications using water, oil, hydraulic oil and chemicals.
Two-wire VS Three-wire
Two-wire Coolant Level Sensor
1. Features just two cables, with a shared circuit for both power supply and signal transmission, and a standard 4–20 mA current signal output.
2. Simple wiring and low cable costs make it suitable for confined installation spaces within cooling equipment.
3. Powered by the data acquisition circuit, it runs on low power, wiring is simple, and there are fewer things that can go wrong.
4. It holds up well against electromagnetic interference, but voltage drop becomes an issue over longer cable runs, which puts a cap on how far you can transmit.
5. Fault diagnosis is pretty standard — wire breaks and sensor problems show up right away through the current range.
Three-wire coolant level sensor
1. Three separate cables; power and signal run on their own circuits, so you can get multiple output types — 4–20 mA, 0–5 V, 0–10 V.
2. Line voltage drop doesn’t affect it; the signal stays stable and doesn’t drift even over long distances.
3. Has its own built-in power supply circuit, so sensitivity and measurement accuracy are both better.
4. Needs three cables, which means more material, more wiring work, and a more complicated setup overall.
5. Since power and signal lines are separate, you can troubleshoot by section, and the system works with a broad range of external monitoring gear.
Key differences between the two
Wiring: Two-wire shares one circuit; three-wire keeps power and signal apart.
Transmission distance: Two-wire gets limited by voltage drop; three-wire handles long runs without trouble.
Performance: Two-wire draws less power; three-wire gives you better detection accuracy and sensitivity.
Installation: Two-wire needs fewer parts and is easier to put in; three-wire costs more for cable and labour.
Maintenance: With two-wire you can’t isolate faults by section; three-wire lets you pinpoint which line is acting up.
Signal: Two-wire only does 4–20 mA; three-wire works with multiple signal types, current and voltage both.
Bad Coolant Level Sensor Symptoms
1. Unable to detect water level: It will output a wrong signal. This will cause the control system not to work properly.
2. Inaccurate detection results: When the coolant level sensor is damaged, it may output wrong detection data.
3. System crash or freeze: If the coolant level sensor is seriously damaged, it may cause the entire control system to crash or freeze.
4. Alarm prompt: In some cases, the control system will be designed with an alarm function. When the coolant level sensor is damaged or abnormal, a corresponding alarm prompt will be issued.
FAQ
Practical Applications of Coolant Level Sensors
1. Industrial precision machining equipment:
Commonly found in the water-cooling systems of laser cutters, CNC machine tools, quenching machines and the like — it keeps an eye on coolant levels as things run.
Without enough coolant, core parts overheat, precision drops off, and cutting heads burn out; the system catches this, sounds an alarm through the machine’s PLC, and shuts things down before any of that happens, so machining accuracy and equipment safety are both covered.
2. Large-scale industrial units:
These go into the cooling circuits of water-cooled generator sets, air compressors and hydraulic units. Since these machines typically run round the clock with no one watching, the sensors track liquid levels continuously to stop high-temperature failures and unexpected shutdowns from coolant loss or leaks — keeping the production line from going down.
3. Industrial Temperature Control and Cooling Systems:
Works alongside industrial chillers and mould cooling units to keep the circulating coolant level steady and under watch.
It picks up on problems like pipe leaks and coolant running low before they turn into bigger issues — cutting down on mould deformation, scrapped production, and the maintenance bills that come with all that. They are suitable for a wide range of temperature control and cooling applications on production lines.
How to Check the Coolant Level?
Operation steps:
1. Turn off the chiller and wait for the equipment to cool down.
2. Open the coolant storage tank or water tank and check the coolant level.
3. If the level is below the standard level, there may be leakage or evaporation, and coolant needs to be added.
Note:
Make sure the equipment is shut down during the inspection to avoid accidental water leakage or electric shock.
When adding coolant, use coolant that meets the requirements and avoid using inappropriate water or chemical solutions.
Why Coolant Level Sensor is Important?
1. Ensure cooling efficiency
With time, the water in the coolant may gradually evaporate or be contaminated, while the refrigerant may lose its heat exchange performance due to leakage or aging. Regularly checking the status of the coolant and refrigerant can ensure that the chiller maintains an efficient cooling effect and prevents excessive temperature from affecting the working efficiency of the equipment.
2. Prevent system failure
Insufficient or contaminated coolant and refrigerant can cause system failure, such as compressor overheating, condenser icing, etc., and even damage core components in severe cases. Therefore, timely inspection and replacement of coolant or refrigerant can help avoid unnecessary maintenance costs and equipment downtime.
3. Extend equipment life
Long-term use of unchecked and replaced coolant or refrigerant may aggravate the wear of internal pipes and components of the equipment and reduce the service life of the equipment. Regular replacement can effectively slow down this wear and extend the service life of the equipment.
Coolant is an indispensable medium in various industrial equipment. It can measure the level of the equipment and extend its service life. Measuring the coolant level is very important. I believe that after reading this article, you will have a deep understanding of how to measure the level of the coolant.
Sino-Inst has been focusing on level measurement for more than 20 years. If you need to measure the level of various media, please get in touch with us in time. We will provide you with free measurement solutions.
