Sage Metering has led the industry in introducing thermal mass flow meter in-situ calibration. In my earlier article, “Benefit of in-situ calibration for thermal flow meters,” I discussed the obvious advantages of being able to calibrate flow meters onsite. Specifically, an “in position” calibration saves time and money. By having a calibration check in the field, the meter does not have to be removed from service each year and returned to the manufacturer (or lab) for calibration. This post discusses Sage Metering’s approach to onsite calibration verification.

thermal flow meter in-situ calibration
The Sage Zeroing Chamber is used to record the “no flow” or 0 SCFM data point taken during the NIST calibration at Sage.

All Sage Meters have the ability to perform the In-Situ Calibration Check as long as a “no-flow” (0 SCFM) condition can be created. This check is quick and easy and doesn’t require a highly skilled technician to perform it. Additionally, other than an isolation valve assembly for the insertion-style meter to create a “no-flow” condition, this feature’s cost is built into the Sage Metering low price.

The Sage In-Situ calibration is truly a check. It not only verifies that the unit is accurate; it also indicates that the sensor is clean. If, for some reason, the meter does not pass the calibration check the first time, in most cases simply cleaning the sensor and re-testing will verify that the meter is accurate and hasn’t drifted or shifted.

Traditionally, thermal mass flow meters have relied upon the Wheatstone bridge, an electrical circuit used to measure resistance, but it is prone to drifting. One of Sage Metering’s unique elements is the ability to use a digital method of driving the sensors. The proprietary technology provides additional benefits, which include: improved signal stability, enhanced temperature compensation, better sensitivity to detecting flow changes, improved resolution, and the capability of adjusting the meter’s operating range to match the customer’s specific operating conditions.

While the meter is manufactured, the Sage Zeroing Chamber is used to record the “no flow” or 0 SCFM data point while subjecting the unit to the customer’s specified conditions (i.e., the gas or gas mix and pressure). This data point at “no flow” is one of many data points used for the flow meter’s NIST traceable calibration and is used as a convenient standard for the calibration check. This data point is conveniently recorded on the meter’s tag and on the meter’s Certificate of Conformance.

To view how easy and quick the Sage Metering operation is, visit In-Situ calibration as easy as 1-2-3. As other manufacturers bring their in-situ calibration solutions to the market, it becomes clear that Sage is still leading the way. At first glimpse, the advantages of the Sage Metering approach over other thermal manufacturers with in-situ calibration capability are:

  • Sage has no additional cost for this feature, while one company charges a $2,000 premium per meter for their in-situ method.
  • The Sage approach is easy as 1-2-3 and fast, while one company requires multiple data points to verify accuracy.
  • A leading thermal mass meter manufacturer also requires a highly skilled technician to verify the accuracy using a nitrogen tank and a pressure regulator and gauge kit at the meter site.
  • If a Sage Sensor is dirty, the in-situ check will not pass, giving the technician a chance to clean the sensor. If the sensor is damaged, it will not pass either. In contrast, one company’s in-situ check cannot determine if the sensor is contaminated or damaged and will continue to provide inaccurate data.

I’ll discuss one of the largest, if not largest, thermal mass flow meter manufacturers’ approach to onsite verification in my next post.

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