Comp II LED Comp II SCX Black SCX Silver SCX White 60s Muscle MINI Factory Match Liquid Filled Non-Filled Direct Mount Engine Thermometers Accessories All Gauges
1" Dial (K) 1½" Dial (A) 2¼" Dial (B) 3" Dial (E) 3" Asphalt (E) 3" Bottom Mount (J) 3" Asphalt (J) 3" Adjustable (ADJ3) 5" Dial (G) 5" Adjustable (ADJ5) 5" Bottom Mount (GJ) Engine Thermometers Capillary Industrial All Thermometers
Utility, Lower Mount SS/Brass, Lower Mount SS/Brass, Center Back SS/Brass, U-Clamp SS/Brass, Panel Mount All SS, Lower Mount All SS, Panel Mount 4" All SS 4.5" Process Gauges
2" All SS (Q3) 2½" All SS (K) 2½" SS/Brass (J) 4" All SS (G) 4½" Process (MPB/SC) 6" All SS (H) All McDaniel Gauges
General Service Severe Service 63mm Severe Service 100mm Diaphragm Gauges Process Gauges All MARSH Gauges MARSH PDF Catalog
Address, Phone, Fax Request Info
Contact Us About Marshall Search Catalog FAQs Site Index

How Does a Mechanical Gauge Work?

Mechanical gauges utilize an internal bourdon tube. One end of the bourdon tube is connected to a gear and shaft assembly that moves a pointer. When the pressure inside the bourdon tube increases, the bourdon tube uncoils slightly. The amount of uncoiling that occurs is proportional to the pressure inside the bourdon tube. As the tube uncoils, its motion activates the gear and shaft system that turns the pointer on the gauge. While all that you see when you look at the gauge is the pointer moving, you should understand that there is a small, bent tube (the bourdon tube) that's coiling and uncoiling with each change in the pressure inside that tube.

bourdon tube

Mechanical pressure gauges are connected directly to the process fluid being measured (i.e. oil). As the process fluid pressure changes the pressure on the bourdon tube also changes which in turn moves the pointer on the gauge.

Mechanical temperature gauges also utilize a bourdon tube. They have a sealed capillary tube and bulb assembly that is filled with temperature sensitive liquid that produces a proportional vapor pressure on the bourdon tube. As the temperature changes, the pressure inside the bourdon tube changes, which in turn moves the pointer on the gauge.

Back to FAQs

About Us · Search Catalog · FAQs · Contact · Site Map · Home

©2022 Marshall Instruments, Inc.
Design: BWE, Inc.

  Auto Gauges Thermometers McDaniel Marsh