Gems Sensors - PRODUCT NEWS



Acoustic level sensor never touches liquid.

The ExOsenseT non-intrusive liquid level gauge from Gems Sensors
and Controls measures the level of fluid materials in plastic containers
from outside the vessel, eliminating any chance of contamination.

Designed for in-vitro diagnostics, the ExOsense uses piezo resonant
technology to measure level with very accurate, very repeatable results.

The unit has two parts, a sensor which is stuck to the outside of the
wall of the vessel at the required height, and an electronic module with
mini usb connector. The sensor incorporates proprietary transducer
technology employing piezoelectric material. When piezoelectric material
is excited, it creates an acoustic signal as a function of the natural
resonance of the material. ExOsense sensors generate this acoustic
signal, direct it through the bottle wall and sense the reflected pulse.

The amount of energy that is reflected depends on the relative acoustic
impedance* of the vessel wall and its contents. Air has an acoustic
impedance of 0, compared to 1.8 for the wall of a typical plastic
bottle, so if the vessel is empty at the level of the sensor there will
be a strong reflected signal. Water, for example, has an acoustic
impedance of 1.5, similar to the bottle wall, so there will be little
reflection. This enables the ExOsense to measure fluid levels to an
accuracy of ±1.6mm, with a repeatability of ±1mm.

The sensor has a very small footprint, and can used with almost any size
and shape of vessel, from small bottles to large tanks, and most plastic
materials. Since it never comes into contact with the contents of the
vessel, it eliminates any risk of contamination and the need for
compatibility testing. Application of the sensor is very simple: no
special mounting is required as the units have a built-in peel-and-stick
adhesive pad. A connector plug is available to seal the unit when not
connected to the control module, enabling bottles to be washed with the
sensor in place.

The ExOsense is ideal for applications in clinical chemistry, haematology, immuno-chemistry, histology, medical laser systems, haemodialysis and
cytology. It can be used to monitor reagents, waste, diluent, detergent/wash,
dialysate, coolant, saline, and pure water.

More information on ExOsense can be found on Gems Sensors & Controls
new Medical Solutions website: http://www.

* Acoustic Impedance: a material property defined as the product of
sound velocity and material density. The relative transmission and
reflection at an interface are governed in part by the acoustic impedances
of the materials on each side of the interface. The letter Z is used for
acoustic impedance and is expressed in [kg/s m2] = 1 Rayl:
Water Z = 1.5 MRayls; Air Z = 0 MRayls

For more information, please contact :-

Gems Sensors and Controls
Lennox Road, Basingstoke, Hampshire, RG22 4AW UK
Tel: +44 (0) 1256 320244
Website :

April 2006

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