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20 Model 2700 Transmitter with PROFIBUS-PA
Calibration
3.2.1 Characterization
Characterizing the flowmeter adjusts the transmitter to compensate for the unique traits of the sensor
it is paired with. Characterization parameters (sometimes called “calibration factors”) describe the
sensor’s sensitivity to flow, density, and temperature.
If the transmitter and the sensor were ordered together as a Coriolis flowmeter, then the flowmeter has
already been characterized. Under some circumstances (typically when pairing a sensor and
transmitter together for the first time), you may need to re-enter characterization data. If you are
unsure about whether you should characterize your flowmeter, contact Micro Motion Customer
Service.
3.2.2 Smart Meter Verification
Smart Meter Verification evaluates the structural integrity of the sensor tubes by comparing current
tube stiffness to the stiffness measured at the factory. Stiffness is defined as the load per unit
deflection, or force divided by displacement. Because a change in structural integrity changes the
sensor’s response to mass and density, this value can be used as an indicator of measurement
performance. Changes in tube stiffness are typically caused by erosion, corrosion, or tube damage.
Smart Meter Verification does not affect measurement in any way. Micro Motion recommends
performing Smart Meter Verification at regular intervals.
3.2.3 Meter validation and meter factors
Meter validation compares a measurement value reported by the transmitter with an external
measurement standard. Meter validation requires one data point.
Note: For meter validation to be useful, the external measurement standard must be more accurate
than the sensor. See the sensor’s product data sheet for its accuracy specification.
If the transmitter’s mass flow, volume flow, or density measurement is significantly different from the
external measurement standard, you may want to adjust the corresponding meter factor. A meter
factor is the value by which the transmitter multiplies the process variable value. The default meter
factors are
1.0, resulting in no difference between the data retrieved from the sensor and the data
reported externally.
Meter factors are typically used for proving the flowmeter against a Weights & Measures standard.
You may need to calculate and adjust meter factors periodically to comply with regulations.
3.2.4 Calibration
The flowmeter measures process variables based on fixed points of reference. Calibration adjusts
those points of reference. Three types of calibration can be performed:
•Zero
• Density calibration
• Temperature calibration
Density and temperature calibration require two data points (low and high) and an external
measurement for each. The density and temperature calibration procedure changes the offset and/or
the slope of the line that represents the relationship between process density and the reported density
value, or the relationship between process temperature and the reported temperature value.
Note: For density or temperature calibration to be useful, the external measurements must be
accurate.