Hello, I’m Dave Deiwert with Tracer Gas Technologies. Today I’m going to talk about using Auto Zero on your leak detector. For this demonstration, I’m using the Edwards ELD 500 Dry Leak Detector.
So, I have a calibrated leak on this leak detector, and currently, it’s reading at 1.3×10-7 When I recommend that people know how to use Auto Zero on the leak detector and when to use it, one of the first pushbacks I get from people is, “No, I don’t want to use that because if I lose sensitivity, I’ll miss leaks on my product.”
I believe that this comes from older technology. Early in my career, when you would use Auto Zero on an older leak detector that had analog electronics, you’d probably have a knob you would adjust to lower the displayed leak rate down to zero and then you’d start leak testing.
Well, if your background signal improved—it dropped—during the course of your leak testing on those older leak detectors, if you had an analog meter movement, you’d actually see the leak rate maybe drop below zero and might even be bouncing on the left side of the display of that leak rate meter.
If a person’s leak testing in that situation and they don’t notice that’s happening, absolutely, you could miss leaks in your products and leaky parts get to your customer, and that’s bad. And I think that experiences like that, or even if you’re spraying helium on a vacuum system and you’ve been spraying and spraying looking for a leak, “I know I’ve got a leak but I’m not finding it,” and you come back and find your leak detector is—the leak rate’s dropped down below zero. Now you’re frustrated; “I spent all that time looking for a leak and my leak detector’s misadjusted.”
So I can see where people using leak detectors on the older technology would decide, “Okay, we’re not using Auto Zero. That way we can’t miss leaks.” So how do the newer leak detectors work today?
A newer, modern leak detector that you would use—when you use Auto Zero, if the background improves during the process or the day, then the leak detector is smart. The software in the leak detector can say, “Hey, I can’t have less than zero leakage,” so it will give itself very fast Auto Zero pulses to keep itself at least at zero so you will always see a positive transition leak rate, or delta increase. You will not miss leaks because the background has improved.
And I can demonstrate that. Here I have this calibrated leak that’s reading 1.3×10-7. Let’s pretend this calibrated leak is actually a background signal, that’s the helium in the air or in the process, and let’s say that I’m going to use Auto Zero.
And I drop down from 1.3×10-7. Okay, let’s simulate—if I close this valve, it’s going to simulate the leak rate getting better, I’m sorry, the background improving. And so the leak detector’s—let’s close it off—the leak detector behind the scenes in the software sees the leak rate background is trying to drop, drop, drop, and it’s auto-zeroing, auto-zeroing, auto-zeroing.
So when I reopen this leak, I’m back to 1.3×10-7. So the leak detector will not miss a delta increase in leak rate from the current background signal. For more questions and discussion on this topic and others related to leak detection, reach out to Tracer Gas Technologies.
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