A hot topic in the industry right now is in-situ calibration and the benefit of onsite calibration for thermal mass flow meters.  While thermal flow meters have been touted as accurate instruments to measure gas flow, the instrument’s need for annual calibration is a significant inconvenience and expense, and often dissuades companies from choosing this gas measurement instrument.

What is calibration?

From a simplistic perspective, calibration is the process where a meter is checked for correctness. For a thermal mass flowmeter the unit is checked or compared to a measurement taken at a specific rate or data point, then it is compared to a known standard.

Like any measurement device, the gas mass flow meter needs to be calibrated from time to time to assure the meter is accurate. Without using a calibrated instrument, there’s no confidence in the data being collected. Why spend your company’s funds on a meter to measure gas flow if you’re not willing to assure the information is good? While this is a rhetorical question, I assure you that I have heard many people claim to waive a calibration because of the expense and inconvenience associated with it.

Why is calibration such a problem for thermal mass flow measurement? Imagine buying a meter with the intention of measuring gas at a remote location. There’s the expense of hiring the contractor or employee to mobile to the worksite where the inline unit is installed. Then a year later, hiring another employee or contractor to return to the location, remove the meter and ship it back to the manufacturer (or some third party lab). Then of course, the expense of hiring someone a couple months later to reinstall the now calibrated unit. Calibration in this manner is a labor intensive and costly.

What does in-situ calibration mean? 

The Latin term, in-situ which is used in many contexts can be translated to mean “in position.” In-situ calibration implies that a unit can be calibrated in position or on site which would remove the hassle, and expense of returning the meter to the factory or lab for an annual calibration.

Sage Metering has led the way for onsite calibration of flow meters and offers a real solution to the problem. With Sage’s new technology and In-Situ Calibration Check it is possible to verify onsite that the instrument is calibrated and therefore accurate.  Among the benefits of the In-Situ Calibration Check are saving time and money.  Additionally, by being able to perform frequent calibration checks, your company complies with the EPA GHG Reporting Rule and calibration requirements.

While Sage has pioneered this movement, there are a few thermal flow meter manufacturers now offering an in-situ calibration meter also. In the next couple of articles I will discuss Sage Metering’s approach along with other companies’ in-situ calibration efforts.