Download Rosemount Recommended Calibration Practices for Magnetic

Peter Fritsche
Director Global Quality
Emerson Process Management
Rosemount, Inc.
12001 Technology Drive
Eden Prairie, MN 55344
T 1 (952) 828-3265
[email protected]
March 1, 2010
SUBJECT: Calibration and verification of Electromagnetic Flowmeters
This document defines the official Rosemount “manufacturer recommended practice” to assist
users in their compliance with EPA regulations governing Green House Gas measurement points.
It is suggested that users retain a copy of this document in their compliance files.
All Rosemount Magnetic Flowmeters are calibrated prior to shipping in our NIST traceable flow
facilities to determine every meters calibration constant (sometimes called k-factor). This
establishes how the relationship between the induced voltage on the electrodes and the volume of
fluid passing through the pipe. This establishes the calibration factor and accuracy for the meters
entire operating range.
Our labs are designed to calibrate every meter at three velocities – approximately 1, 3 and 10
feet/second (approx 0.3, 1 and 3 m/s) – to determine the calibration factor, which is then used as
the constant over the entire operating range. It is common for some manufacturers to determine
the calibration constant by flowing meters at two velocities. Emerson calibrates at three velocities
to ensure the meters calibration is linear over the entire flow range.
The theory for magnetic flowmeters is based on faradays law, which states:
E=C*V
(Where C = Calibration constant)
C = k * D * B, resulting in
D
E=k*D*B*V
Where:
E = Induced Voltage on electrodes
k = Unit conversion constant
D = Distance between electrodes
For a given meter, the calibration helps us take into account small manufacturing variations in D
(distance between electrodes) and B (Magnetic field strength delivered by the coils) from meter to
meter. The theory shows that the relationship remains constant independent of velocity.
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In-situ Calibration Verification Options:
Smart Meter Verification
Once in the field, the magnetic flowmeter can be verified using Smart Meter Verification. This
internal diagnostic allows users to reconfirm the Magnetic field through key measurements of the
magnetic coil inductance and resistance as well as the measuring electrode resistance. In
addition, Meter Verification also verifies the calibration of the transmitter. Additional information
on the Rosemount Smart Meter Verification option can be found in the attached Technical Note.
Accuracy of 5% can be obtained by selecting a test criteria of less than 2.0% when configuring the
Smart Meter Verification option.
Traditional Meter Verification
In addition, to the Smart Meter Verification option, the magnetic flowmeter sensor and transmitter
can be verified using the attached Magmeter Verification Document.
For new installations, Emerson recommends purchasing 8712E or 8732E transmitters with the
Smart Meter Verification option (DA2 option code) and performing a baseline signature during
commissioning.
For existing installations, Emerson recommends that users with existing 8732E or 8712E utilize
the Smart Meter Verification approach. This is available as a licensed option from the factory. For
installed transmitters that are not currently licensed, a license code can be purchased by calling
Rosemount Customer Central. For users with transmitters of a previous generation, we
recommend that they upgrade the transmitter to an 8712E or 8732E with Smart Meter Verification.
However, if this is not feasible, the traditional meter verification approach may be utilized.
For continuing verification, either approach can also be conducted by one of Emerson’s
Instrument and Valve Services Certified Field Service Technicians. It is Rosemount’s
recommendation that meters be verified once every three years.
When the test criteria is not met in either of the aforementioned approaches or when application
requirements warrant, the magnetic flowmeter may be returned to a Rosemount flowlab for
verification and/or recalibration through Emerson’s Instrument and Valve Services.
Sincerely,
Peter Fritsche
Director Global Quality
Emerson Process Management – Rosemount Flow
1-952-828-3265
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