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SEN-400 Extrusion Melt Pressure Transducer
Melt Pressure & Temperature Transducer for Extrusion, Blow Molding, Compounding, Film & Sheet
Description

Series 400 transducers are interchangeable with those offered by existing suppliers. Elimination of a liquid metal fill such as mercury assures safe use in applications involving food extrusion, food packaging or extrusion of medical tubing. It also eliminates the expensive costs of toxic waste disposal. Our sensor is highly desirable for chemical applications such as processing photographic film which are extremely sensitive to mercury contamination. Although some transducer manufacturers offer Nak as an alternative to mercury, this highly volatile chemical presents fire dangers in the event of a diaphragm rupture. Nak filled transducers should not be used in any hazardous areas.

Our sensing diaphragm is sapphire which is a single crystal aluminium oxide, the hardest of the oxide crystals and is chemically inert. Sapphire is extremely well suited for diaphragm use. It has a modulus of elasticity 30% greater than stainless steel and is five-times more abrasion resistant than tungsten carbide. The sapphire diaphragm is 5 to 8 times thicker than the 4.5 mil stainless steel diaphragms used in mercury-filled transducers. The sapphires extra thickness and extreme hardness suit Series 400 transducers ideally for highly abrasive extrusion applications in which thinner mercury-filled devices wear out then release mercury into the process. The stiffer diaphragm also provides a response time up to 200 times faster than stand off, filled systems and those employing push rods.

Silicon is one of the most desirable strain gauge materials for critical applications. In silicon-on-sapphire technology the piezoresistive silicon gauges are epitaxially grown onto the sapphire diaphragm forming a homogeneous single crystal, radiation-hardened structure. Unlike other diaphragms, this structure has no hysteresis and provides excellent repeatability and long-term stability. lt can be directly exposed to process media and can withstand operating temperatures up to 700°F. An optional on diaphragm temperature sensor (Silicon RTD is available to sense the temperature of the melt stream at the flush diaphragm.

Other combined pressure and temperature transducers utilize a thermocouple mounted in the stem of the sensor resulting in an inaccurate measurement of the mounting-well temperature. The thermocouple degrades over extended exposure to high temperature. The Silicon RTD on the Series 402 Pressure and Temperature transducer is mounted flush on the sapphire diaphragm directly exposed to the melt stream. The ceramic base further isolates the sensor from the mounting well resulting in an accurate measurement of the melt stream. This arrangement is ideal for ultimate temperature control.

See Specification Data Sheet