Instrument calibration is a big deal in a number of situations. Companies that sell product by weight are (or should be) adamant about keeping their scales calibrated. If they read light, they’re giving unintended discounts. If they’re reading heavy, they’re gouging their customers, and their local Weights & Measures folks take a dim view of that.
A much more serious situation, involving errant instrument readings, took place on a U.S. Navy submarine, USS Greenling (SSN-614) in the spring of 1973. They were conducting tests on a firing a new torpedo that was specifically designed for greater depths. While operating at what they THOUGHT was the ship’s “test depth” – the point at which the designers say the hull can be expected to maintain reliable integrity – the Captain, who was in the Torpedo Room, noticed a pressure gauge on a torpedo tube showed a higher-than-expected reading. They quickly realized the depth gauge in the Control Room was not operating properly, and they were, in fact, alarmingly close to “crush depth” – which is exactly as bad as it sounds. That’s a story every submariner hears early in their career, and it’s the reason that instrument calibration (for ALL systems…not just the depth gauges) is taken QUITE seriously.
In certain industrial and commercial ventures, instrument calibration is critical in that same vein: atmospheric monitoring equipment needs to be accurate or people can be poisoned by toxic gases, or suffocated from lack of oxygen, for example. Other processes aren’t life-threatening, but can have major impacts on production and quality. One of these (and the main subject of this blog) is the ability to measure static charge.
EXAIR’s Model 7905 Digital Static Meter is a handheld instrument that quickly & accurately indicates the static charge that resides on an object’s or material’s surface. If it’s in proper calibration, it can be used to gauge the effectiveness and efficiency of static eliminators, by measuring the static charge before, and after, exposure to the static eliminator product. It can also help to identify the source of static charge by showing specifically where the highest charge resides on an object or piece of material.
To do so accurately, though, it has to be maintained in good working order. To ensure this, EXAIR Corporation offers calibration service, available at three levels, depending on your specific needs.
- Level 1 Calibration is performed in accordance with Mil Std 45662A, and is traceable to NIST (National Institute of Standards and Technology) standards. It doesn’t include before/after test data, but does ensure the Static Meter is in good working order and reads accurately. For most typical industrial applications, this is all that’s required.
- Level 2 Calibration complies with Mil Std 45662A, and is traceable to NIST standards as well. It DOES include before/after test results and lists the laboratory standards used (along with NIST test numbers), which may be called for in compliance with your company’s quality programs.
- Level 3 Calibration also complies with Mil Std 45662A and is traceable to NIST standards. This level of calibration, however, is performed by an independent laboratory that is accredited for ISO 17025 compliance. The calibration certificate issued satisfies requirements of:
- Mil Std 45662A
- ANSI/NCSL Z540-1
- ISO/IEC Guide 25
- ISO/IEC 17025
If you don’t recognize any of those requirements, Level 1 Calibration is likely all you need to ensure your Static Meter is functioning properly. A prime example of the need for Level 3 Calibration might be a pharmaceutical goods manufacturer who uses Static Eliminators to ensure cleanliness/sanitation in a packaging evolution, and uses the Static Meter to periodically document the dissipation of the static charge on the packaging material. The before/after results, along with compliance to certain standards, could trigger a safety recall on a potentially unsafe product that presented a very real public health risk.
Russ Bowman, CCASS