DLO-M1 density sensor for liquids

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The DLO-M1 sensor measures the density of liquids in a microelectromechanical system (MEMS). Within the MEMS, the liquid is directed to an omega-shaped microchannel, known as the omega chip. This tiny silicon tube – it is hardly thicker than a hair – is vibrated for the purposes of the measurement. The density of the medium to be measured can be derived from the natural frequency of this oscillation: The denser the medium, the smaller the oscillation.

Thanks to the measurement in the MEMS, the sensor is only 30 x 80 x 15 mm³ in size and can therefore be accommodated even in tight spaces. The high-precision measurement results are immediately available, enabling continuous measurement during the process. The density of liquids depends on their temperature. To compensate for this effect, an integrated platinum resistor measures the temperature of the liquid.

The measured values are transmitted to the higher-level system via an RS232 interface. The sensor uses an ASCII command protocol in the TrueDyne Sensors standard for this purpose.

Cooperation with Testo

From volume (l) to mass (kg)

If, for example, a fuel is pumped from a truck into a tank system, the volume of the liquid in the tank is measured as standard. However, since the density varies depending on the pressure and temperature, it is not possible to make precise statements about the mass. With the DLO-M1 sensor from TrueDyne, you can record the necessary density data during the process and use it to calculate the mass (V·ρ=m).

1. Fuel is pumped from the truck to the tank system. 2. Standardized volumetric measurement in liters. 3. The DLO-M1 density sensor detects the density directly on the truck in a bypass. Thanks to the compact design of the sensor, it can also be integrated into the process at a later stage. 4. Together with the volumetric measurement, the density can be used to calculate the mass in kilograms of the liquid in the tank, which is then transferred to the customer.

Quality monitoring

The density of a liquid depends on its composition. If different liquids are mixed together, the correct mixing ratio can be checked with density measurements. Take heating oil, for example: According to legal requirements, 7 % biodiesel may be added to heating oil. As biodiesel is tax-free, this process is often carried out at the limit of legality. With the DLO-M1 density sensor from TrueDyne, you can monitor the quality of the heating oil during the process.

1. Tank truck for the supply of heating oil. 2. The sensor measures the density of the heating oil directly at the transfer point. The data collected on site shows whether the correct media are present in the correct ratio. 3. The product is handed over to the customer. Good quality is guaranteed.




Density and quantities derived therefrom (e.g., standard density, concentration, etc.)

Permitted media:

Particel free (<30 μm) hydrocarbons like for eg.

  • petrol E5 / E10 / E85
  • diesel B7 / B10 / XTL
  • Jet-A1 (also F-35 or JP-8)
  • M100 (methanol)
  • isopropanol
  • OME* (synthetic fuel)
  • LPG*

Aqueous media like for eg.

  • AdBlue®*
  • Glycole mixtures*

If necessary, media that deviate
from the listed may be used, after
individual clarification. *Optional

Max. measurement error:

Density: ±0,5 kg/m³
(Option: ±[0.2 or 0.01 x abs (T-25°C)] kg/m³ if the value is >0.2³)
Temperature: ±0,3 °C
(Option ±0.15 or. ±[0.0075 x abs(T-25°C)] °C if the value is >0.15)


Density: ±0,25 kg/m³ (Option ±0,1 kg/m³)
Temperature: ±0,1 °C (Option ±0,05 °C)

DLO-M1 max measurement error

Temperature conditions

Permitted medium temperature:

-20…+ 60 °C

Permitted ambient temperature:

-20…+ 60 °C

Permitted storage temperature:

-20…+ 60 °C

Range of application

Permitted density measurement range:

600…1000 kg / m³ (Option 0…1200 kg / m³)

Permitted viscosity range

0,3…5 mPa s (Option 0,3…50 mPa s)

Permitted process pressure range:

0…20 bar (abs)
Bursting pressure 80 bar (abs)

Permitted particle size:

Max. 30 μm

Permitted flow range:

0…10 l / h (water)


Due to the high operating frequency of the micro channel, vibrations (<20 kHz) do not affect the measuring accuracy.

Inlet and outlet runs:

Inlet and outlet runs do not affect the measuring accuracy.

Ambient conditions
Climate class :

IEC/EN 60068-2-1
IEC/EN 60068-2-2
IEC/EN 60068-2-30

Electromagnetic compatibility:

EMV 2014/30/EU (EN 61326-1)

Vibration and shock resistance:

IEC/EN 60068-2-6
IEC/EN 60068-2-27
IEC/EN 60068-2-64

Degree of protection

IPx4, IPx5, IPx6, IPx7 (IEC 60529)


Stainless steel:

  • 1.4404 (316L)
  • 1.4542 (AISI/SUS 630)

Medium wetted material:

Stainless steel:

  • 1.4542 (AISI/SUS 630)

BOROFLOAT® 33 glass
Epoxy resin

Dimensions / design

Design, dimensions in mm


30 mm x 66 mm x 15 mm (without cable and cable bushing)


<150 g

Dimensions measuring channel:

160 x 200 μm (500 nl)

Fluidic interfaces

Fluidic interfaces:

2 x M5 threaded holes with an angle of 45° to the side and the front surface

Electrical interfaces
Cable type:

Fixed installed cable

Cable length:

3 m

Outer diameter of cable:

2.3 mm

Diameter of cores:

4 x AWG 28

Lead of gage:

Digital communication line and power supply in a common shielded cable


Continuous, without the need for a command from the outside
Hardware Standard RS232 Proprietary ASCII output string


Power supply:

Power connection DC 5 to 12 V (max. 400 mW) via power unit with safety extra low voltage (SELV) or protective extra low voltage (PELV)

Voltage strength

The maximum permissible fault voltage between GND (signal ground) and earth must not exceed 36 Vpeek.

Data rate:

10 Saps
(Option acyclique with 100 ms response time)

Cable occupation:

white: VDD (supply voltage)
brown: GND (signal ground)
green: RX (input)
yellow: TX (output)

Note: The cable assignment corresponds to the view of the sensor (DLO-M1)

Certificates and approvals

CE mark:

The density sensor meets the legal requirements of the EC Directives. TrueDyne Sensors AG confirms that the density sensor has been successfully tested by applying the CE mark.


All installed components meet the requirements of the RoHS directive.


The density sensor meets the legal requirements of the EAC-Declaration. TrueDyne Sensors AG confirms that the density sensor has been successfully tested.

Electromagnetic compatibility:

EMC 2014/30 / EU (EN 61326-1)

Product design

Product Design: DLO-M1 / VLO-M1

  1. Housing
  2. Electronic interface for communication and power ­supply
  3. Drill holes for mechanical mounting (6 x M3 threaded holes)
  4. Fluidic interface (2 x M5 threaded holes)


1080x810px_DGF-M1_mechanische Befestigung_1901_TrueDyne_Dichtesensor

Mechanical mounting: DLO-M1 / VLO-M1


DLO-M1_VLO-M1_fluidischer Anschluss

Fluidic interface: DLO-M1 / VLO-M1