Soil Density Measurement and Radiometric Sensors

RhoC 5 | Soil Bulk Density Measurement System

RhoC 5 | Soil Bulk Density Measurement System

The BNC Medusa Radiometrics RhoC-5 soil density meter measures soil bulk density and soil moisture directly in the field, providing a fast and reliable indicator of soil health for agriculture, geotechnical analysis, and construction projects. Using gamma backscatter from a low-activity source, the RhoC-5 determines field bulk density without the need for soil pits or laboratory testing. A 30 mm borehole allows measurements up to 80 cm deep, delivering real-time density data so users can quickly evaluate soil conditions across both vertical and horizontal layers. The rugged and portable system is controlled via WiFi using an Android smartphone app, enabling live monitoring, local data storage, and easy export to a PC or cloud platform. The probe integrates **three sensors—a soil moisture sensor, density sensor, and radar-based depth sensor—**to measure moisture over a 50 mm layer, determine bulk density within a similar depth interval, and precisely report the measurement depth, allowing field workers to quickly assess soil compaction, moisture distribution, and overall soil quality with minimal disturbance.

Features

No need for a soil pit or any laboratory work to determine soil bulk density
The sensor provides the measured densities during measurement in the field

Applications

Measure soil bulk density in the field (agricultural or construction applications)
Measures backscatter of gamma radiation emitted from a (low-activity) source – can be used without legislation

Working Principle of the Density Sensor

The figure above demonstrates schematically how the density measurement works. The small red disk contains a radioactive 22Na source with a low activity below the exemption value. This source will radiate gamma-rays into the soil. This soil will interact with these gamma-rays. One of the interactions that can occur is known as Compton scattering, where the direction and energy of the gamma-ray is altered. The dark grey cylinder in the figure is a scintillation crystal that can detect gamma-rays when they interact with the crystal. Between the crystal and the source, a piece of tungsten is positioned. Tungsten has a very high density, which prevents most radiation from the source from reaching the crystal directly. As a result, most radiation registered by the scintillation crystal has been scattered in the soil surrounding the RhoC 5. With increasing soil density, more radiation will be scattered, and more gamma-rays will be registered. The RhoC 5 has been calibrated to determine the soil density based on the number of gamma-rays detected per second.

The App Interface

Start-Up Screen

The app searches for the hardware when opened. Exporting data is possible even when the app is not connected to the hardware via the Export button on the lower right corner of the start-up screen.

Project Screen

The project screen is accessible via the Project button on the upper left hand corner of the main screen. Measurements are stored via the location tabs on the project screen. Easily delete via the trash icon or add a new project via the New button.

Measurement Screen

This screen is where all measurements are located and readings are filed under each respecitive measurement. The screen above shows “Location 1” and its list of respective readings. Press New to add a new reading, and the name will auto-populate to the current depth. The field bulk density for the reading will be shown continuously during the measurement. An icon with a drop is visible when the soil moisture content has been determined. A progress bar gives an estimate of how long it will take to reach the requested density accuracy. When this accuracy has been reached, a notification sound can be heard. The measurement will continue until the Stop button has been pressed.

Settings Screen

The user can change the behavior of the app through the settings screen.

Desired accuracy: this helps determine when a measurement is completed
Stop automatically: when this is on, the measurement will automatically stop when the desired accuracy is reached
Play sound when done: this will sound a notification once the desired accuracy has been reached

Export Screen

Use the export tab to export data from the phone to the cloud or another device in CSV format. Exporting does not erase data from the phone.

The measurements dropdown list allows you to select a single measurement. It is also possible to select all measurements
When completed only is checked, readings and measurements that have not been completed are excluded from the export
A list separator can be selected to manipulate the content of the created CSV file

Info Screen

This page shows information about the app and the hardware, such as the version number, the serial number, and the calibration date.

CSV Export

The table below shows a description of the headers in the CSV file.

Weight

3.97 lbs

Length

51.85 in

GPS
Accuracy

~0.01g/cm3

Data
Format
Streaming
Sensors
Internal Storage

JSON, NMEA, CSV
RS-232, ethernet and Wi-Fi and Bluetooth
Soil density, GPS, moisture
16 GB

Mechanical
Dimension
Weight
Operating Temperature
IP rating

Diameter: 1.18 in; Length: 51.85 in
3.97 lbs
-20 to +85 °C
IP68

Electrical
Input voltage
Battery

5V
Internal

Connectivity
Wi-Fi
Ethernet
Port

2.4 and 5 GHz
100 Mbps
RS-232

RhoC 5 Datasheet

Downloadable resources such as datasheets, firmware, software, drivers and products manuals. Alternatively, you can browse resources directly by visiting our downloads page.

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