Ultrasonic Level Meter: From Technology Selection to Series Production
A battery-powered liquid level meter has to combine dependable measurement with careful energy use. When a tank operates outdoors and can move between locations, changing light, temperature and communication with the customer’s system add further requirements. INVENTRONICS developed an OEM device that brought measurement technology selection, electronics, firmware and production preparation into a single project. The solution entered series production after a dedicated calibration and testing process had been developed.
Project Summary
The device measured liquid levels in tanks, including mobile tanks. It used ultrasonic measurement, an ultra-low-power microcontroller and a COMBO module integrating GNSS positioning with GPRS/GSM communication. Its firmware performed measurements, detected events and periodically exchanged data with the customer’s backend in both directions.
The device achieved a measurement resolution of 1 mm. The work covered both device development and preparation for repeatable manufacturing. Calibration and testing formed part of the path from sensor selection to regular customer deliveries.
| Project fact | Confirmed scope |
|---|---|
| Device role | Autonomous, battery-powered liquid level measurement in tanks, including mobile tanks |
| Measurement technology | Ultrasound with temperature compensation; 1 mm measurement resolution |
| Control and energy | Ultra-low-power microcontroller and firmware handling measurements and event detection |
| Positioning and communication | GNSS and historical GPRS/GSM connectivity with periodic bidirectional communication |
| Production preparation | Dedicated assembly station, calibration and test system; series production and regular deliveries |
Key outcome: the solution connected measurement, positioning and communication with a calibration process prepared for series production.
The Customer’s Challenge
A long-standing INVENTRONICS customer needed an autonomous, battery-powered device. The requirements included at least one year of operation, preferably two, outdoor use and reliable communication with the customer’s own server. Integrated GNSS was needed to locate mobile tanks.
The challenge was to meet these requirements together. An affordable measurement method could struggle in strong light, while a technology less sensitive to its surroundings might not deliver the required accuracy within budget. Measurement, positioning and transmission also drew on a limited energy supply. Selecting a sensor with a promising specification was therefore not enough: the complete architecture had to suit the actual application.
Engineering Decisions
The first step was to compare three measurement approaches against the tanks and customer requirements. Translucent, infrared-transmitting tanks were an important consideration: their material properties affected the operating conditions of an optical sensor.
| Technology | Observation in This Project | Design Consequence |
|---|---|---|
| Infrared optical ToF sensors | The tested sensors lost range and accuracy at approximately 70,000 lux, particularly with infrared-transmitting tanks. | The evaluated solutions were not selected for this application. |
| FMCW microwave radar | Less sensitive to lighting and temperature changes; the evaluated options within the acceptable price range did not deliver the required accuracy. | The cost and measurement requirements were not met together. |
| Ultrasound | A suitable balance of accuracy, cost and outdoor operation. | Selected with production calibration and temperature compensation included in the design. |
Ultrasound offered the best fit among the evaluated solutions. That choice brought an additional task: making calibration and temperature compensation part of both the product and its manufacturing process.
As a general principle, ultrasonic ranging determines distance from the time taken for an echo to return. The speed of sound changes with temperature, so timing alone is insufficient to keep readings consistent as temperature varies. This device incorporated temperature compensation and production calibration of the ultrasonic measurement path. These were deliberate consequences of the technology choice, not additions left until the end of development.
Energy use was the second key area. An ultra-low-power microcontroller was selected, and its power-management modes were used to reduce current consumption. In a battery-powered device generally, both the consumption of each operating state and its duration matter to the energy budget. Measurement, positioning and communication patterns therefore matter as much to battery life as selecting low-power components.
An integrated COMBO module handled positioning and transmission. GNSS located the tank, while GPRS/GSM provided communication with the customer’s server. This historical implementation used 2G; connectivity selection for a new project requires a check of service availability and compatibility with the intended markets.
Architecture from Measurement to Backend
| Layer | Function in the Device |
|---|---|
| Measurement path | Ultrasonic measurement with temperature compensation |
| Low-power control | MCU managing measurements, event detection and energy use |
| Positioning and connectivity | GNSS for location and GPRS/GSM for data transmission |
| Customer system | Periodic bidirectional communication with the customer-owned backend |
The dedicated calibration and test station closed the loop between architecture and production: the measurement path could be calibrated, compensation parameters incorporated and device operation verified before delivery.
INVENTRONICS’ Responsibilities
INVENTRONICS assessed measurement technologies, developed the electronics and firmware, and prepared the solution for series production. Device software covered measurement, event detection and periodic bidirectional communication with the customer’s backend.
The work also included an assembly station and a calibration and test system. This connected measurement requirements to the manufacturing process. For the OEM, the objective was not simply a working device, but an established way to reproduce its measurement performance across subsequent units.
Calibration, Testing and Production
Choosing ultrasound meant making calibration part of production rather than limiting it to development work. INVENTRONICS created a dedicated assembly station, a specialised calibration and test system, and a procedure for calibrating the measurement path. Temperature-compensation parameters were included in the process.
In general engineering terms, calibration and compensation perform different, complementary roles: calibration relates device readings to reference conditions, while compensation accounts for the effect of changing temperature on measurement. Connecting both to manufacturing is particularly important when moving from an individual device to successive units in a production run.
The product entered series production, and INVENTRONICS made regular deliveries to the customer. Moving from technology selection to an established assembly and calibration process was an important project outcome.
Results and Their Meaning
The device combined 1 mm measurement resolution, mobile-tank positioning and backend communication for remote monitoring. Liquid level and location data could therefore serve a shared purpose: remotely observing a mobile asset.
Up to two years of battery life was achieved under the project’s field operating conditions; runtime depends on measurement, positioning and communication patterns. The measurement choice and temperature compensation addressed outdoor requirements, while the calibration process supported repeatable manufacturing.
Value for an OEM
This project illustrates why measurement-device development and production preparation belong together. Selecting ultrasound addressed a particular application problem while introducing calibration requirements. Accounting for both sides of that decision enabled the transition from a technical solution to a product supplied in series.
For another OEM project, the starting points should be tank material and geometry, environmental conditions, required accuracy, measurement and communication patterns, and the intended market. Agreeing on these criteria before component selection helps connect user requirements with technical decisions and production preparation.
Planning a battery-powered measurement device? Contact INVENTRONICS with details of the tank and intended use. Explore our product development services, from electronics and firmware to production preparation.
Frequently Asked Questions
Resolution describes the granularity of a reading, here in 1 mm steps. Accuracy is a separate parameter describing how closely a result agrees with a reference value. A resolution of 1 mm does not mean a measurement error of ±1 mm.
The energy used by each function and how often it runs. A battery-powered design needs to consider measurement, positioning and transmission together with the time spent in the microcontroller’s low-power states.
It offered a suitable balance of measurement performance, cost and outdoor operation. The tested optical ToF sensors lost range and accuracy in strong light, while the evaluated FMCW radar options within budget did not meet the accuracy requirement.
The COMBO module integrated GNSS with GPRS/GSM. Firmware provided periodic, bidirectional communication with the customer’s backend. This was a historical solution using 2G.
No. An assembly station, calibration and test system, and calibration procedure were prepared. The device entered series production and was regularly delivered to the customer.