Selection of the appropriate diaphragm material for melt pressure transducers and transmitters

The selection of the right membrane material for pressure sensors depends entirely on the circumstances under which the sensor is used. It is important to note whether the sensor comes into contact with the material and what properties this material has.

This can be determined more precisely based on the classifications of the individual polymer components. The classifications are:

  • Thermoplastics
  • Elastomers
  • Thermoplastic elastomers
  • Thermosets

The processing of thermoplastics and elastomers includes extrusion, injection molding and compression molding. Pressure measurement and control is essential in all of these methods.

Following materials and coatings are available for selection of membrane construction:

15-5PH stainless steel with Dymax coating

·Provides durability and abrasion resistance

·Default on most sensor models


Provides corrosion resistance

·Not recommended for prolonged use in high temperatures

Inconel 718

Provides abrasion and corrosion resistance

·Recommended for use in temperatures up to 750°F or higher


·Durable protective surface coating

Abrasion resistance


Best abrasion resistant coating available

·Can only be used on Inconel

Titanium Nitride

·Abrasion and adhesion resistance

·Can be used on most membrane materials

Titanium aluminum nitride

·Improved abrasion and adhesion resistance

Standard for Dynisco Echo sensors (membrane material Inconel)


a) The application uses polypropylene:

The standard membrane for the respective pressure sensor is recommended. The standard Dynisco cone is Dymax coated 15-5PH stainless steel. This withstands abrasive material flow well and is reliable in most extrusion environments.

b) The application uses elastomer (TPE):

This material adheres to the standard membrane. To prevent adhesion while limiting the material's ability to deform the cone, a titanium nitride coating is recommended.

c) The application uses fluoropolymers (PTFE):

PTFE has corrosive properties so a standard diaphragm would not last long due to oxidation. Hastelloy may be suggested here.

  • No fill material
  • RoHS compliant for sustainability programs
  • Robust, thicker Inconel diaphragm is coated with DyMax®
  • Optional Type J or K thermocouple is available to provide a melt temperature signal as well as a 4-20 mA temperature output
  • Equipped with a 1/2-20 UNF for installation in standard transducer mounting holes
    • Also available to install 1/2-20 UNF units into a Button Seal application
  • Diaphragm composition of Inconel 718 coated with the abrasion resistant properties of DyMax®
  • Sealed, welded shell and electrical connection available if washdown capability is needed for food or mechanical applications (not available if thermocouple option TCx is selected)
  • Available with thermocouple temperature output
  • 250-10,000 PSI pressure range capability
  • HART digital communication available
  • Direct measurement tip is a simple and elegant design with a more robust diaphragm
  • Direct measurement of process reduces errors transferred by complicated internal support structures, transmission fill materials, or moving push rods
  • Designed to work with universal pressure indicators
User Manual

  • 4-20mA loop-powered output
  • +/- 0.25% accuracy available
  • Wide selection of pressure ranges available
  • Turndown 6:1 (3:1 Turndown for model SPX 2290)
  • Configurations available for use in hazardous locations
  • Remotely configurable via HARTTM
  • Precise, repeatable pressure measurements
  • Output supplied directly to DSC or PLC
  • Meets CE requirements
  • CE ATEX Intrinsically Safe Approved
  • FM Explosion Proof Approved
  • CSA Explosion Proof Approved
  • SIL 2 Certified (Pressure Output)
  • PL'c' Certified (Relay Output)
  • Additional approvals are available


  • 2 year warranty and 60 years of Dynisco industry experience
  • Accuracy better than ±0.5%
  • TiAlN diaphragm coating is standard
  • mV/V, 0-10VDC, or mA outputs available
  • Integral temperature sensor option
  • Available in configurations that fit most extruder applications
  • 1.5M, 3M, 5M, 7.5M & 10M psi pressure range capability

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