Blind pressure transmitter technology

ifm's blind pressure transmitters use either ceramic capacitive measuring cells or thin film metal strain gauge measuring cells.  Both technologies have their benefits.

Ceramic capacitive

The most important element of the ceramic capacitive technology is the ceramic (Al₂O₃) measuring cell. After assembly, the ceramic cell element resembles a plate capacitor with a reference electrode and a measuring electrode placed 15 µm apart. The capacitance is inversely proportional to the distance between the electrodes. As pressure is applied, the distance changes by a small value and the capacitance changes proportionately. This signal is then converted into pressure by a microprocessor.

• Robust, direct sensing measurement technology
• Eliminates possibility of contamination from diaphragm fill fluid
• Long-term stability of ceramic cell design does not fatigue like stainless steel
• Internal support construction creates very high pressure ratings
• Ceramic cell is more resistant to abrasion, dents or dings that can create measurement offsets
• Highest overload pressure rating, especially with dynamic pressure peaks

The PX and PA sensors use this type of measuring cell.

Stainless steel strain gauge measuring cell

Strain gauges are attached to the stainless steel measuring cell. Pressure of the medium on the measuring cell causes deflection of the strain gauges, which creates a change in resistance. Tension (positive strain) increases resistance and compression (negative strain) decreases resistance. The change in resistance is proportional to the pressure applied.

• Suitable for liquids and gases up to 600 bar (8700 psi)
• No elastomer seal required
• High burst strength at high ranges
• Fully welded all stainless steel diaphragm

The PT and PU sensors use this type of measuring cell.