A Piston DP (Differential Pressure) gauge with a magnetic coupling operates by measuring the pressure difference between two points in a system using a driver piston magnet and Driven rotary magnet. The two pressures (high and low) act on the piston assembly which moves piston proportionally against a spring. This linear movement of piston is transferred magnetically to a rotary magnet, separated from the media, which moves the gauge pointer to show the differential pressure reading. The magnetic coupling provides an isolated, reliable, and accurate measurement without direct fluid contact with the indicating mechanism.

The mechanism avoids direct mechanical linkage with the pointer, reducing wear and risk of leaks, and enabling longevity and precise readings in industrial process control, HVAC, and filtration monitoring applications.

These gauges are typically used in applications with high static or differential pressures and where media isolation is important, such as measuring pressure drops across filters, strainers, or separators. The magnetic piston assembly is durable and resistant to high pressures, often made of Aluminium, stainless steel, brass, Monel and ceramic magnets with robust seals like Buna-N, Viton, EPDM. The gauge can come in various sizes and accuracies, often around ±2% of span, and can be designed for harsh environments with weatherproof cases and with different protection ratings.