Differential Pressure Sensors

Differential pressure sensors (differential pressure transmitters) are instruments that measure the difference in pressure between two points in a system (for example, before and after a filter, pump, or flow restriction device). They convert this pressure difference into an electrical signal (typically 4–20 mA, HART, Profibus, etc.) for process control and automation. The operating principle is often based on the deformation of a diaphragm (piezoresistive, capacitive, or other), which responds to the pressure differential.

A modern example is the OPTIBAR DP 7060 C from KROHNE: a compact differential pressure transmitter with integrated absolute pressure and temperature measurement, piezoresistive sensing cell, fast response time (<125 ms), and modular design for versatile mounting.

Characteristics

• Measurement Range: From a few mbar (e.g., 10–30 mbar) to tens of bar (up to 16–40 bar); turndown ratio up to 100:1.

• Accuracy: ±0.035–0.10% (depending on turndown ratio), including nonlinearity, hysteresis, and repeatability.

• Operating Temperature: Typically -40...+85°C (electronics), up to +105°C (sensing element); temperature influence compensation.

• Maximum Static Pressure: Up to 400 bar, with low influence on measurement (≤0.06%).

• Materials: Diaphragms made of stainless steel (316L), Hastelloy, super duplex; filling fluids — silicone/fluorocarbon oil; seals — PTFE, EPDM, FKM.

• Output Signals: 4–20 mA/HART, Foundation Fieldbus, Profibus PA; options with additional analog output.

• Other Features: Overpressure protection, fast response time, signal damping.

Main Areas of Application

• Flow Measurement — for liquids, gases, steam (using restriction devices such as orifice plates or Venturi tubes).

• Level Control — in closed/pressurized tanks, density, and interface detection.

• Filter and Pump Monitoring — detecting contamination, overload protection (e.g., pressure drop across filters).

• Industries:

• Chemical and petrochemical;

• Power generation (including steam systems);

• Water supply and wastewater treatment;

• Ventilation, HVAC (air flow control, filter contamination);

• General industrial processes (machine building, food industry).