Why Should My Pressure Gauge Pointer be in the Center of the Scale?

As a leader in pressure and temperature instrumentation, Ashcroft recommends customers apply ASME B40.100 guidance, which suggests choosing a gauge range that keeps normal operating pressure near the middle of the scale. This simple best practice supports accuracy, reliability and overall performance.

When selecting a pressure gauge, most people focus on the range, dial size and case style. But where the pointer is positioned during normal operation is one detail that often gets overlooked and can have a big impact on how well your gauge performs. A pointer that regularly sits at the bottom or top of the dial is a sign that the gauge isn’t matched well to the application.

Read this article to understand why the center of the scale matters, how pointer position affects gauge behavior and how to choose a range that keeps your measurement where it belongs.

Why is a pressure gauge's pointer position important?

Pressure gauges display a full-scale pressure range (0–200 psi, for example) on its dial. The pointer moves across this span as the sensing element (Bourdon tube, diaphragm, or bellows) flexes in response to increasing or decreasing pressure.

While a gauge can measure anywhere within that span, it doesn’t perform equally well across it. The midpoint of the span, near the 12 o’clock position, is where the sensing element moves in its most linear, predictable way. That’s why gauges produce their most accurate, stable readings when the pointer lives near the middle of the scale during normal operation.

When you select a range that puts your everyday pressure in this zone, the gauge responds more smoothly, readings are easier to understand and the internal components are subjected to less stress.

How pointer position affects accuracy and readability

The pointer position influences how well the gauge can translate pressure changes into visible pointer movement. Here’s how:

• At low scale values, the sensing element barely moves. Small pressure changes cause tiny pointer shifts, making it harder to get a precise reading.
• At high scale values, the element is stretched close to its limit. The gauge can still read pressure but can experience more wear over time. 
• At mid-scale, the sensing element moves through its most responsive zone. This is where the pointer can show changes clearly and consistently.

So, the more centered the pointer, the better the measurement. 

Protecting the gauge from stress for better performance

Pointer position also affects how much physical stress the gauge experiences.

When the gauge pointer spends most of its time nearing the upper end of its range, the sensing element is repeatedly pulled close to its elastic limit. Over time, this can cause metal fatigue or permanent set, meaning the gauge may not return to zero the way it should. This could lead to drift, inaccurate readings and reduced service life.

On the low end of the scale, the opposite happens and you could lose resolution and readability. Small changes in process pressure barely move the pointer, making it harder for operators to monitor the system.

The optimal operating zone is the center portion of the scale, where the element flexes comfortably without being overstressed. This is where the gauge will last the longest with reliable accuracy.

How pointer position affects gauge performance

The following quick-reference chart breaks down what happens across each part of the scale. It’s a simple visual summary that reinforces why operating near mid-scale delivers the best combination of readability, accuracy, and gauge life.

Figure 1. Pointer Mid-Scale Reference Chart

Applying ASME’s 25–75% Rule 

Now that you understand why pointer position matters, choosing the right gauge range becomes easier.  The goal is to select a gauge that places your typical operating pressure near the center of the dial so that the gauge stays within its most stable, linear, and low-stress region.

A quick example:

• System pressure: ~100 psi
• Recommended gauge range: 0–200 psi

This puts the pointer right near the midpoint where accuracy, readability and element flex are most favorable.

If the application involves significant pulsation, such as pumps, compressors, or rapid cycling, it may also be important to select a wider range or incorporate a pressure snubber, pulsation dampener, or Ashcroft PLUS!™ Performance to help protect the movement.

Selecting the right gauge for your application

Choosing a gauge with the correct range is just one part of the selection process. To ensure optimal performance, also consider:

• Normal and maximum operating pressure and frequency of cycles
• Process media compatibility (brass, stainless steel, or Monel® wetted parts)
• Environmental conditions (temperature, vibration, or corrosive exposure)
• Dampening or overpressure protection if pulsation or spikes are present

Ashcroft offers a broad selection of Bourdon tube, diaphragm, and bellows gauges—along with dampening accessories and overpressure protection—to help ensure your gauge performs reliably and consistently.

Ready to learn more?

With a clearer understanding of the significance of a pressure gauge's pointer position, you may have more questions. Contact us to speak to a product expert, or check out a few related articles that may interest you. In the meantime, download our guide to learn how to avoid pressure equipment failure to protect your people and your process.