Different methodologies exist for creating leak detection systems. In this blog post, we will focus on leak detection using a pressure decay method which is ideal for detecting very small leak rates.
The diagram below illustrates a classic leak detection setup using pressure decay.
The test part is pressurized from a pressure source. At the first X under "Balance" in the chart above, the pressure setpoint is reached and balance is maintained until the leak detection test begins at the second X. The regulator and valve isolate the test part from the source once pressurization is complete. The pressure sensor monitors and measures the pressurized test part. If the pressure measurement decreases, then air is leaking out of the test part. Measuring the change in pressure over a period of time allows the user to calculate the leak rate.
The availability of easy-to-use, sensitive pressure sensors at low cost lets designers optimize their leak detection design. The AP3/AG3 Series is an example of a pressure sensor well-suited for leak detection applications. The AP3/AG3 is a calibrated and temperature-compensated pressure sensor with ranges from 0-25 kPa up to 0-1000 kPa. Not only does this sensor have high accuracy of ±1.5% full-scale, the AP3/AG3 has built-in threshold detection (consider how easy it is to set the threshold for the start of the leak test). The AP version has a dual-in-line package while the AG version is surface-mount. With a price of of approximately $7 (depending on the model) at 1,000 pieces, the AP3/AG3 provides has an excellent price-performance ratio.
Applications for leak detection include:
- Medical devices such as drug delivery, catheters, valve, oxygen delivery
- HVAC including refridgerant testing, heat exchangers, tubing, radiators, and more
- Automotive testing such as emission systems, fuels, pumps, and cooling systems
- Various industrial applications