Primary Standard Gas Flow Calibration—The Only Guarantee of Accuracy

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Courtesy of Sierra Instruments, Inc.

At Sierra, we have a saying: “An instrument’s accuracy is only as good as its calibration.”

The accuracy of your mass flow controller (MFC) is essential in assuring the efficiency, performance, and quality of your flow meter. In many cases, if your instrumentation is not calibrated, then a decline in performance is possible due to sensor drift from the factory calibration. Various things cause drift: dirt buildup, aging of the electronics, physical changes in the sensor, etc.

To make sure your MFC is reading at the accuracy you specified at purchase, many users recalibrate or validate flow meter or MFC annually. In some industries, assuring your flow meter’s accuracy is required by either corporate policy or government regulations like EPA, FDA, MACT mandates. There are many ways to calibrate MFCs to assure accuracy including transfer standards, but the best way is a primary standard calibration.

Primary Standard = Precision Calibration

Only primary standard gas flow calibration systems deliver world-class levels of accuracy and traceability.

Here is what to look for in mass flow meter primary standard calibration:

  1. Primary standards are characterized by the basic quantities of time and distance, while transfer or secondary standards, such as laminar flow elements, are calibrated against another device, generally another flow meter. Primary standards can also be verified by every national laboratory.
  2. The calibration standard should be NIST traceable standard accuracy, better than 1% of full scale.
  3. The most accurate primary standards adhere to the NIST “rule of four.” This means the gas flow primary standards are required to be four times more accurate than the device under test. This “rule of four” needs to be a requirement for any factory calibration or calibration house.
  4. Flow meter calibration is both a science and an art–look for expertise in flow meter manufacturing or flow meter calibration. In reality, the manufacturing factory not a third party calibration house, will give the very best flow meter calibration due to the flow calibration core competency and working knowledge of the meter.
  5. Facilities should be ISO 9001 certified and/or ISA 17025 & NAVLAP compliant.

Sierra is one of few manufacturers today that performs a detailed 10-point calibration across the entire mass flow range. We strictly adhere to using primary standards and the NIST “rule of four.” Sierra’s SmartTrak mass flow controller is a prime example of this. SmartTrak’s NIST-traceable standard accuracy is better than 1% of full scale. We offer even better accuracy–as good as half a percent of full scale upon request.

Learn more about utilizing Sierra’s SmartTrak mass flow controller for your next project. Over 100,000 installed SmartTrak mass flow controllers can’t be wrong. And SmartTrak’s unmatched accuracy and performance is guaranteed with a lifetime warranty.

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