A Magnehelic gauge is a differential pressure instrument that uses magnetic fluid to display pressure readings on a calibrated scale. This analog gauge contains a colored magnetic float in a liquid-filled tube that moves vertically in response to pressure differences, providing visual indication without requiring electrical power. Magnehelic gauges are highly durable and accurate for HVAC applications.
Technical Details
Magnehelic gauges measure pressure ranges from 0-10 inches of water column (in. w.c.) to 0-100 in. w.c., depending on model. The magnetic float design eliminates friction-based pointer mechanisms, allowing for precise readings with repeatability within 2% of full scale. These instruments require no calibration adjustments and operate reliably in temperature ranges from 40°F to 120°F.
HVAC Applications
Technicians use Magnehelic gauges to monitor filter pressure drop, verify blower operation, measure ductwork pressure, and diagnose system imbalances. These gauges are particularly valuable for commissioning work and ongoing maintenance where consistent, reliable pressure monitoring is essential.
Practical Significance
The Magnehelic’s mechanical operation makes it ideal for field conditions where electronic instruments may fail. Its ability to provide instant visual feedback without batteries or calibration makes it a standard tool in professional HVAC service vehicles.