Know and Receive the Gauge · 20 min
Pressure gauge fundamentals and working principle
Before you reach for an adjustment, understand what the pointer is responding to. Read the dial, know what gauge pressure means, then follow the pressure through the Bourdon tube and movement.
Course content
Pressure comes in at the socket. The pointer shows what the movement did with it.
Keep three things in mind before you open the gauge. Then use the simulation below to see the complete motion.
The dial shows pressure relative to atmosphere. At no applied pressure, a healthy correctly-zeroed gauge returns to zero.
Zero to full scale is spread across about 270°. The pointer does not make a full revolution.
Pressure moves the Bourdon tip only a small distance. The movement turns that small travel into pointer rotation.
Background: Bourdon history and gauge makes you may meet
The Bourdon-tube sensing principle is still widely used. The case, movement and adjustment arrangement can differ from one gauge family to another.
Identify the gauge in front of you.
Ashcroft, WIKA, NOSHOK, Winters and Dwyer/Omega are examples. Same range does not mean the same movement, zero arrangement, span device or service tool.
Hold one pressure. Look at the dial. Then open the movement.
The view changes, but the applied pressure and pointer position do not. This is the same gauge with the dial removed.
Hairspring: supports the gear train by maintaining light preload. It reduces backlash; it is not part of the pressure-sensing path.
Explain gauge pressure on the 0–1000 psi training gauge.
Recognise the Bourdon-tube principle introduced by Eugène Bourdon in 1849.
Read the make, range, unit and class on the dial.
Recognise the common 270° dial arc used by this training gauge.
Trace socket → Bourdon tube → free end → two-piece link → sector → pinion/spindle → pointer, and explain the hairspring role.
Scope and safety
This lesson demonstrates operating principles only. Do not apply pressure beyond the gauge or reference-equipment rating.
Movement A is the AccessRA training arrangement validated for this course. Other manufacturers and movement families can use different geometry and adjustment methods.
Eugène Bourdon introduced the Bourdon-tube gauge principle in 1849. You will still meet that principle today in gauges from manufacturers such as Ashcroft, WIKA, NOSHOK, Winters, Dwyer/Omega and others. The name on the dial matters for identification, but do not assume the internal movement or adjustment method is identical from one make or model to another.
This training gauge uses a 270° dial arc. Pressure enters at the socket and acts inside the C-shaped Bourdon tube. The tube tries to straighten slightly, so the free end moves only a small distance. Movement A transfers that travel through the two-piece link to the toothed sector, then into the pinion/spindle and pointer. The hairspring keeps light preload on the geared movement to reduce backlash; it does not sense pressure.
The important point is simple: a large pointer sweep comes from a very small movement inside the gauge. Understand that motion first. Adjustment comes later.
On this 0–1000 psi Bourdon gauge, what does gauge pressure mean?
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Why can the pointer travel through about 270° when the Bourdon tip only moves a small distance?
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What is the hairspring doing in Movement A?
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Learner discussion
Field notes from this lesson
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