Know What's in the Tank — Before It Becomes a Problem
Level monitoring is critical wherever liquid storage, overflow risk, or leak detection is part of your building or process system. The right level sensor depends on your tank or enclosure type, the liquid media involved, your need for continuous measurement versus a threshold trigger, and how much maintenance access you have. Here's how the main technologies compare.
Float Level Sensors
Float level sensors are one of the simplest and most inexpensive level sensing solutions available. A float attached to a switch rises and falls with the liquid level — triggering a signal when a set mechanical level is reached. They can also be deployed in arrays to capture multiple level thresholds within the same tank or enclosure.
The main vulnerability is debris. If particulates or contaminants in the liquid get caught in the float mechanism, the sensor can fail to trigger or become disabled entirely. Careful attention to the liquid media — its cleanliness, viscosity, and chemical compatibility with the float materials — is important when specifying this sensor type. Output is a switch or voltage signal that triggers when the set level is reached.
Best for: Clean liquid applications, simple high/low threshold detection, budget-conscious deployments, multi-level arrays
Not recommended for: Debris-laden or contaminated liquids, applications requiring continuous level measurement
Magnetic level sensors also use a float but eliminate the electrical wiring connection to the float itself — reducing the risk of tangling and making the sensor far less susceptible to debris interference. Instead, a magnetic sensor is mounted on the outside of the tank and detects the position of the float magnetically through the tank wall, making it easier to service without draining or opening the tank.
Output is a switch or voltage signal that triggers when the set mechanical level is reached — the same threshold-based approach as a float sensor, but with improved reliability and easier maintenance access.
Best for: Applications where debris or tangling is a concern, tanks where external mounting is preferred, situations requiring easier serviceability
Not recommended for: Continuous level measurement, non-magnetic tank materials that prevent magnetic sensing through the wall
Magnetic Level Sensors
Capacitive level sensors detect the presence of liquid by allowing a small electrical current to flow across two electrodes when a conductive liquid covers them. There are no moving parts — the sensor either conducts or it doesn't, depending on whether the liquid is present at the electrode level.
This makes capacitive sensors ideal for leak detection. A sensor placed at floor level or at the base of equipment will trigger immediately when liquid is present — providing an early warning before a leak becomes a flood. Output is a switch or voltage signal that triggers when the sensor is submerged.
Best for: Leak detection, presence/absence detection, sump and drip tray monitoring, conductive liquid applications
Not recommended for: Non-conductive liquids, continuous level measurement, heavily contaminated liquids that may coat the electrodes
Capacitive Level Sensors
Ultrasonic level sensors are our go-to recommendation for most level monitoring applications — and the reasons are straightforward. The sensor mounts above the liquid surface and periodically emits an ultrasonic pulse downward. When the pulse hits the liquid surface it reflects back, and a Time of Flight (ToF) circuit measures how long the return trip takes. Subtracting that distance from the known depth of the tank gives you a continuous, accurate level reading.
Because the sensor never contacts the liquid, debris is not an issue. Maintenance and calibration are simple. Accuracy is excellent, reliability is high, and the price point is reasonable. Unless your application has specific requirements that point to another technology, the ultrasonic level sensor is the right choice. Output is typically 4-20mA or serial communication, compatible with BluNODE CL and BluCORE.
Best for: Continuous level monitoring, tanks with debris or contaminants, applications requiring non-contact measurement, general-purpose level monitoring
Not recommended for: Very turbulent liquid surfaces that may scatter the ultrasonic pulse, extremely narrow or irregularly shaped enclosures
Ultrasonic Level Sensors