Gauge Decay vs. Differential Decay Testing: Do You Know the Difference?

The idea for this blog post came to me when a customer asked me to explain the difference between Gauge Decay, also known as Pressure Decay, and Differential Decay Testing. Explaining this without visuals was going to be a challenge. Thinking fast, I came up with the dial gauge analogy. Let’s get started!

Analog Gauge Analogy

If you are checking pressure using an analog gauge and the pressure you are measuring is 60 psi (4 bar). In a typical gauge, the gauge sensor has one port, which is connected to measure the pressure and the backside of the gauge is referenced to atmospheric pressure.

Now imagine you need to monitor this gauge for leaks. You would watch for it to change pressure and if you are lucky, you might be able to detect a 1 psi change out of the 60.

Furthermore, suppose you have a second gauge connected to the part you are checking for leaks with one exception – now you have a differential pressure gauge with a 1.0 psi full scale. In this case, instead of the backside of the gauge being connected to atmospheric pressure, it is connected to a reference volume that is also pressurized at 60 psi. Now when you monitor pressure change, you can easily see a 0.25 psi change in pressure. That’s 4 times more sensitive!

Just as we benefit from seeing smaller pressure changes from the differential gauge, leak testers also benefit from the differential sensor. This allows the test to be shorter in most cases.

Why do we need both types of tests?

Not all applications require the sensitivity that Differential Pressure Decay offers. The differential test method is more expensive and has more sophisticated pneumatic test circuits.

Although Differential Pressure Decay testing has its advantages, so does the Gauge Decay method. Offering both techniques allows Uson to match the customer’s application with the correct testing technique thus providing them with the right tool to get their products tested and shipped.

Uson Can Help

Uson’s team of experts can help you with the most complex application challenges. Contact us today!