Sage Metering recommends using the Sage In-Situ Verification method at least annually to comply with EPA 40 CFR 98 Periodic calibration verification, Climate Action Reserve(1) Protocols, and CDM Methodologies(2)  protocols to verify that the Sage meter is still in calibration.

In-Situ Verification Procedure

thermal mass flow meter applications
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The Sage Prime and Paramount meter have continuous diagnostics. The raw calibration milliwatts (mW) displays on the upper left-hand corner of the meter’s display, which permits the user to conduct an “in-situ” calibration verification. At any time, the user may compare this reading at a “no flow” condition to the original “zero flow” value noted on the last few lines of your meter’s Certificate of Conformance or the flow meter’s data tag. This comparison not only checks the sensor performance and the “live zero” calibration point, but it also verifies the sensor is clean. This easy field diagnostic procedure also verifies that the sensor is free from contamination, even without inspection. The procedure essentially provides a means to validate that the meter is operating correctly, verifies there is no shift or drift, and may eliminate the necessity for yearly factory calibrations.

Here are the simple steps:

1. Verify that the meter has no gas flow(3). To do so, close the appropriate valves in the process to create a “no flow” condition to check the “live zero” mW output of the actual gas (Note: check at the same pressure indicated on the Certificate of Conformance). If it is impossible to turn off the process gas and the gas must remain flowing, the optional Sage SVA05 or SVA07 Isolation Valve Assemblies permit the user to check “zero” without shutting the gas supply.

Optional Mounting Hardware for the Insertion Flow Meter

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Please refer to SVA Series Isolation Valve Assembly details in the Sage User Manual.

a)      Loosen lower collar clamp completely(4)

b)      Slightly loosen compression fitting until the probe can lift

c)       Lift the probe until the safety chain is taut

d)      Tighten the compression fitting

e)      Close the valve

f)       Check zero mW as per “2” below

(Optionally, the user may conduct an ambient air check by removing the probe and covering the sensor with a plastic bag, or an empty plastic water bottle, or other means of preventing flow.)

2. Note the raw mW on the top of the meter’s display. After one to three minutes of “no flow” stabilization, check the observed reading against the flow meter’s data tag or last line(s) of the meter’s Certificate of Conformance.

3.  A value within five milliwatts of the original factory value indicates that the meter still has the original calibration data (assuming the same gas at the same pressure).

4. A value greater than five mW but less than or equal to 10 mW also suggests the meter still contains the original calibration data. However, the reading may have been influenced by one or more of the following: gas composition, pressure, dirt, non-zero conditions, or sensor orientation. Any of these factors can affect the mWo. The raw mW is a very sensitive data point, making this an effective means to verify calibration data.

5. Note that if the factors noted (gas composition, pressure, dirt, non-zero conditions, or sensor orientation) were the same as the original calibration conditions, we would expect the mWo to be less than or equal to five mW.

6. In some cases, sensor contamination can cause additional heat transfer during the “no flow” test. In this case, clean the sensor by removing the probe, and clean the sensor with an appropriate non-corrosive solvent to remove buildup. Use a soft brush with caution to gently cleanse the sensing surface to avoid damaging the sensor elements (the RTDs).

How do I clean my thermal mass flow meter sensor?

7. To summarize, if the user can accurately simulate the Sage calibration conditions, the user should be within one mW of the initial calibration data. Given that it is not always possible to duplicate these conditions, a mWo within ten milliwatts is an acceptable value. This method permits the user to verify the calibration while the meter is in the pipe and under application conditions.

8. Note, if desired, the user may conduct a second check while using ambient air. This validation method requires that the user remove the sensor from the pipe and insert it in a vessel like an empty plastic water bottle. The mW value for ambient air is on the meter’s Certificate of Conformance.

9. For CAR(1) compliance (for the protocols listed below), Sage recommends (but does not require) a periodic validation check, at least annually, by following this procedure. Alternately, the user may ship the Sage flow meter back to Sage for a calibration check. When doing so, please obtain a Return Meter Authorization (RMA) from the Service Department before shipping the meter.

    • U.S. Landfill Protocol, Version 4.0, Par. 6.2
    • Mexico Landfill Protocol, Version 1.1, Par. 6.2
    • U.S. Livestock Protocol, Version 3.0, Par. 6.2
    • U.S. Livestock Protocol, Version 4.0, Par. 6.3
    • Mexico Livestock Protocol, Version 2.0, Par. 6.2

The maximum allowable drift per these protocols is 5%.

10.  If the mW reading exceeds ±10 mW of the original factory value, the error across the full calibration range is not field-determinable. However, the flow meter can be returned for an “As-Found” comparison to the original calibration data and recalibration.

Download our In-Situ Calibration Verification flyer.


    • (1) CAR (Climate Action Reserve) is a national offsets program that ensures integrity, transparency, and financial value in the U.S. carbon market. It establishes regulatory-quality standards for developing, quantifying, and verifying greenhouse gas (GHG) emission reduction projects in North America. CAR operates alongside a related program, the California Climate Action Registry (California Registry), created by California in 2001 to address climate change through voluntary calculation and public emissions reporting.
    • (2) CDM Methodologies, ACM 0001, “Methodological tool to determine the mass flow of a greenhouse gas in gaseous stream”  (EB61 Report, Annex 11, Page 1).
    • (3) Sage “zeros” the meter in a horizontal pipe. If the user has a vertical line, the mW will be slightly lower at zero flow (see note 4).
    • (4) Use the 9⁄64 Allen wrench to loosen the collar clamp on the SVA05. Use the 3⁄16 Allen wrench for the SVA07).

Other topics from the Sage Prime Manual you may be interested in are:

My Sage flow meter was damaged in shipment

How to Install and Mount my Sage Prime Thermal Mass Flow Meter?

Inline Flow Meter Installation Considerations

Troubleshooting Sage Prime Mass Flow Meters

Flow Profile and Installation Considerations for Insertion Flow Meters

Sage Mass Flow Meters Warranty

Sage Prime Thermal Mass Flow Meter Features and Benefits

Modbus Protocol and Function Codes

Returning Your Sage Flowmeter via Special Delivery

Sage Metering’s Cancellation and Return Policy

HART Protocol and Access Keys

Correction Factors for Biogas Variation From Original Calibration