In the world of leak testing and test and measurement we strive for perfection every day. We want them to be accurate, repeatable and reproducible. Is perfection unrealistic? When you’re leak testing, is near enough good enough?
In test and measurement, we usually accept some degree of variation which we refer to as tolerance, acknowledging that in order to get anything from our processes, we have to accept that there will be a range of measurement deviations that will constitute a “pass” result without compromising the safety or performance of the product. Some products have wider ranges of tolerance than others.
Similarly, we can look at the tolerance from an application point of view. If I bake a cake at home, I will use the dial or the digital readout on the oven. If it’s a few degrees off either way, it’s not critical. You’d think I was being pernickety if you saw me using a highly precise digital thermometer to temperature map the oven. However, if I were using the oven to perform a scientific experiment to support a white paper, it would be expected that I describe the experiment accurately so that my peers could successfully repeat it or rely upon the conclusions. For this, I would certainly use the highly accurate thermometer, or I could say that the oven display was calibrated using that thermometer.
In leak testing, the existence of a leak larger than a certain specified size will certainly affect the product performance. Therefore, it’s important to have confidence in the measuring instrument, the leak tester that provided the result. One way you might try to gain that confidence is by testing the part on another leak tester to see if the results are the same. Great, you say, they both gave the same result so it must be true. Not necessarily. Both instruments might have been incorrectly calibrated. Maybe the device that calibrated them was not correctly calibrated itself. Okay, you ask, then what should I do? My advice is to have your leak tester calibrated by the manufacturer using NIST traceable master gauges.
Leak Tester Calibration Using Traceable Master Instruments
At Uson we have dedicated and well-trained technicians who can correctly calibrate your leak tester. We use traceable master instruments and a range of standard leaks that have been verified with traceable instruments. You can buy your own traceable leak masters or calibrated leaks to use as validation or verification devices to confirm the accuracy of your leak tester. If the leak master result does not match the certificate, then either the leak tester or the leak master requires re-certifying.
For calibration services, you can return the leak tester to us and we will perform the calibration. We can also send a service technician to your site. A site visit means less downtime and is a good choice if several instruments require calibration during the same visit. The service technician can also advise on the instrument settings, run diagnostic checks, and back up the instrument programs and data files for you.
Before beginning measurements - In the event the tester has been sitting idle for an extended period of time or before beginning measurements that require highly accurate data, send your tester for calibration or use a certified leak master to verify that it is performing correctly.
After making measurements - When a leak tester has been used for a long time, sensor condition may change. Although rare, this can be detected by frequently challenging or verifying proper operation.
After an event - If the leak tester was hit by something, dropped or exposed to contamination by dust, water or oil, calibration is advised prior to operation.
When observations appear questionable - When you suspect the data’s accuracy is affected by instrument errors, send the instrument in to be calibrated.
Per requirements - When indicated by the manufacturer or your quality management system. Every leak tester will need to be calibrated periodically to make sure it can function properly and safely. Manufacturers will indicate how often the instrument will need to be calibrated.
For questions regarding calibration or other services you are welcome to contact our service department at 281-671-2006 to contact us.