How Does An Ultrasonic Level Sensor Work?

An ultrasonic level sensor, or an ultrasonic transducer, is a device that uses sound waves to measure the level of liquids or solids in a variety of applications. It works by emitting high-frequency sound pulses across a space and then measuring the time it takes for those pulses to return as they echo off any nearby objects. The time elapsed between the initial signal and the return echo can then be used to calculate the distance between the sensor and an object.

In general, APG ultrasonic level sensors are based on three main product series–IRU, MNU, and LPU. Each of these products has its own unique capabilities in order to measure levels.

IRU Products

IRUs are single-point sensors designed to measure the level of liquids, solids, and slurry in tanks or reservoirs. Their intelligent technology provides reliable measurements when there are changes in environmental conditions.

(Note: All the IRU sensors use the same programming software).

IRU-9400 (Range: 6 in. to 35 ft.)

Versatile Range

The IRU-9400 ultrasonic sensor can detect targets within a frequency range that spans from 6 inches to 35 feet. With this capability, you can measure a broader range without the need for complicated mounting arrangements.

Sensitive Transducer

This sensor utilizes an exceptionally sensitive static transducer to detect challenging targets. It excels at detecting non-reflective and/or soft surfaces. However, please note that it is not suitable for harsh environments and is best used indoors, away from dust.

IRU-6429 (Range: 1 ft. to 30 ft.)

For Data Logging

For comprehensive level measurement, we understand that real-time monitoring may not always suffice. That's why we’ve developed a level sensor with an excitation feature specifically designed for data logging purposes.

Flexible Output

The IRU-6429 provides the convenience of selectable output options. During set-up, users can easily program either an output of 0-2.5 V or 0-5 V as per their requirements.

IRU-5000 (Range: 4 in. to 79 in.)

Short Range Specialists

The measurement of blanking distance is crucial in non-contact level measurement. Thanks to the advanced IRU-5000 ultrasonic sensors, the blanking distance has been reduced significantly to just 4 inches.

Output Options

The IRU-5000 series ultrasonic sensors provide a 4-20mA output, NPN trip points, and a programmable voltage output of 0-2.5 V or 0-5 V.

IRU-3430 (Range: 1.25 ft. to 50 ft.) 

Class 1, Div. 2

Our valued customers handle dangerous substances on a daily basis, and our reliable level sensors have been ensuring their safety for an extensive period. The IRU-3430 continues this legacy with a CSA Class 1, Div. 2 certification.

Impressively Programmable

Our IRU-3430 ultrasonic level sensor comes equipped with its own programming software, allowing you to customize its performance according to your requirements.

IRU-2420 (Range: 1ft. to 25 ft.)

Hazardous Location Certified

The IRU-2420 ultrasonic sensors are designed to be used in hazardous locations that fall under the CSA Class 1, Div. 2 classification.

Flexible Programming

These ultrasonic level sensors were specifically engineered with versatility as a top priority. They boast our convenient IRU programming software, which enables effortless programming across diverse application environments.

IRU-2000 (Range: 1ft. to 25 ft.)

Programming Options

The IRU-2000 ultrasonic sensors are specifically engineered to cater to a wide range of applications, offering extensive programming options to meet diverse requirements.

Surface Mount

These ultrasonic sensors are specifically designed for outdoor applications, making them suitable for use in environments outside of tanks. Instead of using a threaded fitting, these sensors can be easily attached to a flat surface using bolts. The IRU-2000 transducers are commonly utilized for tasks such as absence/presence detection, object profiling, and various other applications.

MNU Products (Modbus Network Ultrasonic)

MNUs are multi-point networkable ultrasonic sensors that can be used for liquid or solid-level measurement applications. The ultrasonic transducer can be connected to any Modbus controller, allowing the user to access and control multiple points in a single system. This offers improved accuracy and features such as waveform analysis, temperature compensation, and fault detection.

MNU IS (Ranges up to 25 ft.)


Obtain a real-time level measurement in just 250 milliseconds.


The setup process for MNU's ultrasonic sensor is straightforward, from easy-to-follow daisy chain wiring to convenient remote configuration via the Internet.

MNU (Ranges up to 40 ft.)

Our Modbus RTU protocol line offers a comprehensive range of features. It is fully compatible with APG’s Tank Cloud and seamlessly integrates with our Modbus Network Display (MND).


The MNU ultrasonic level sensor is designed not only for Tank Cloud remote-level monitoring applications but also for any situation that demands a Modbus ultrasonic sensor.

LPU Products (Loop Powered Ultrasonic)

LPUs are line-scanning sonar that can measure the level of liquids or solids in tanks or reservoirs with long depth ranges. It works by two transducers (an emitter and a receiver) scanning along a one-dimensional plane, creating an accurate, 3D image of the area. This helps identify any obstructions or changes in environmental conditions that may interfere with the measurement.

LPU-2428 (Range 1 to 25 ft.)

The LPU-2428 ultrasonic transmitter is an intelligent and customizable device. It accurately calculates distance, level, flow, and volume in both linear and nonlinear tanks.


The LPU-2127 is specifically crafted with a user-friendly setup in mind. Wiring can be completed swiftly, and programming is conveniently performed using the integrated keypad.

Ultrasonic level sensors are a reliable and accurate way to measure the level of liquids or solids in a variety of applications. Not only do they provide precise readings but they can also detect water levels without touching the surface, making them well-suited for difficult measuring environments. With advancements in technology, they are becoming more user-friendly and cost-effective, making them a popular choice for many industry applications.

At Automation Products Group (APG), we offer a wide range of ultrasonic-level sensors to meet the needs of different applications. From our IRU, MNU, and LPU products, you can be sure to find one that will best suit your requirements.

Want to learn more about how an ultrasonic level sensor works? Get in touch with one of our experts today! We are here to help you find the right solution for your application.

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