SDM: Slurry Density Meter - Non-nuclear density measurement


Dredging and mining companies are increasingly looking for non-nuclear measuring instruments, because of stricter government regulations, increasing safety related costs and the need to reduce nuclear waste. Rhosonics wants to help these customers to create a safe and pleasant working environment. We do this by offering non-nuclear (ultrasonic) technology for density measurement in slurries.

Our ultrasonic density meter eliminates all costs, health and safety risks related to the radiation source. The device is easy-to-use, has no need for any license and gives reliable density values to monitor and improve the production output. We believe that nuclear density meters are no longer needed.

Our solution

Rhosonics introduces the newest generation non-nuclear density meter, the SDM Slurry Density Meter. This instrument is suitable for real-time density measurement in all kinds of slurries. The product uses sustainable ultrasonic technology and is specifically designed for dredging and mineral processing applications after ten years of experience with the predecessor, the model 9690 density meter. The SDM uses a non-intrusive ultrasonic sensor to measure the real-time density of mineral slurries under high density levels and at very large pipes.

By measuring the acoustic impedance of a slurry, the SDM calculates the density of the slurry in-line during the process. The sensor is made of stainless steel and ceramic material. Because of the new sensor material, the sensor has lots of better properties. By making use of ceramics material, the ultrasonic signal is more brightful and powerful than before. Also, the sensor is more wear resistant than its predecessor, model 9690. By means of wafer cells, spool pieces or a weld-on piece, installation is easy. Click on the links below to find out more about the non-nuclear density meter.

Please feel free to contact Rhosonics to learn more about the Slurry Density Meter (SDM).

Download the SDM Brochure: English - Portuguese - Spanish - French

Download the SDM Case Study: Dredging - Mining - Comparison test - Washing Plant

Features and benefits

  • Non-Nuclear density meter, ultrasonic technology
  • Real-time density measurement
  • Durable probe system
  • Lowest possible maintenance needs
  • High accuracy and reproducibility
  • Suitable for all types of slurries
  • Compact integrated system
  • Process connection via HART and 4-20mA
  • Continuous data & system logging

Performance specifications


Ultrasonic Spectral Power /

Acoustic impedance

Density Range:

700 … 3.000 g/l


0.2 g/l


S.G., Density g/l


Up to 0.005 S.G … +/- 0.5%

Decay time:

1 to 99 s (adjustable)


Monochrome display with RGB backlight, visible through glass cover.


Push-buttons, HART, Computer

Optional: RCU Remote Control Unit

General specifications

Process conditions


1 … 16 bar


0 °C … 110 °C (32 °F … 230 °F)

Wetted materials:

Ceramics and Duplex Stainless steel 1.4462

Electrical specifications

Power supply:

18 … 32 VDC, 8 Watt

Optional: Power supply/converter for 90 … 240 VAC


4 … 20 mA / HART


2-way through HART protocol

Optional: RCU unit as converter to Modbus RTU or Profibus DP

Data logging & fault reporting:

Internal memory,

via USB memory stick

Cable entries:

3X M16X1.5, cable OD Ø 3-10 mm

Ambient conditions

Ambient temperature:

-20 °C … +65 °C (-4 °F … 149 °F)


< 95% at 40 °C (noncondensing)




Resistant to moderate / high vibration of pumps

Dimensions and weights


Approx. 6.4 – 6.8 kg

Housing materials:

Coated stainless steel

Housing dimensions:

218–402* (L) x 208 (W) x 170 mm (H)

* Various depths, depending on probe type

Process connection:

UFTP Spool (sensor depth: 146 mm)

Weldolet (sensor depth: 34 or 52mm)

Wafer (sensor depth: 146 or 200 mm)


DIN/ANSI/JIS (others on request)

Nominal pipe size:

Up to 60”

Digital communication via HART

The SDM is a HART certified device. It can communicate digitally with other HART equipment using the analogue 4-20 mA output.

The HART protocol enables remote access and control e.g:

  • Calibration
  • Variable readout
  • Variable ranging
  • Etc.

For more information on the Rhosonics HART implementation see the Rhosonics Field Device Specification (FDS). Click here to open the FDS document. Also, if you want to learn more about HART technology in general, then please click here.

Two Communication Channels

RCU Remote Control Unit / Communication Protocol Converter

The newest Rhosonics instruments, such as the SDM, are supplied with sensor, display and operation panel integrated in a compact all-in-one system. The user interfaces of these instruments can sometimes be hard to reach, for example because of installation in a difficult position of the process pipe. Yet, in these cases, the Rhosonics RCU Remote Control Unit will be the perfect solution.

This multifunctional device is connected to the instrument by cable and can be used to monitor measurement results and change settings real-time at a safe and convenient location near the process. Another feature of the RCU is the communication protocol converter. For example, one of the RCU models is equipped with a HART/4...20 mA signal to Modbus RTU signal converter which can be very useful in case a Modbus RTU output is required. The HART/4...20 mA signal can also be converted to a digital Profibus DP signal. Click here to learn more about the RCU models.


Rhosonics introduces the Slurry Density Meter WT (SDM WT). This robust ultrasonic measuring instrument shows the density value in wt% solids with an accuracy up to 0.005 wt%. The SDM WT can measure the density of challenging water-based slurries in industries like dredging and mineral processing. For many years, nuclear devices were the only option. Nowadays the non-nuclear SDM WT is used to replace these radiation sources. Rhosonics employs the field proven ultrasonic technology for density measurement. The Rhosonics Slurry Density Meter has its sensor, analyzer, cable and software integrated in just one system. The density meter is compact and lightweight. With the SDM WT, we can offer the second generation non-nuclear density meter to customers who were demanding wt% solids as measurement value.

Click here to learn more about the SDM WT.

Performance specifications:


Ultrasonic Spectral Power /

Acoustic impedance

Density Range:

0...80 wt%


0.02 wt%


Density in wt% solids


Up to 0.005 wt% … +/- 0.1% of reading

Decay time:

1 to 99 s (adjustable)


Monochrome display with RGB backlight, visible through glass cover.


Push-buttons, HART, Computer

Optional: RCU Remote Control Unit

The general specifications of the SDM WT are the same as the SDM (see above).

Download the SDM WT Brochure: English

Contact us for more information »