Emerson Process Management MICRO MOTION 2400S - Manual (Page 98)

90 Micro Motion ® Model 2400S Transmitters for DeviceNet ™
Measurement Performance
10.2.1 Meter verification
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.
Meter verification does not affect measurement in any way. Micro Motion recommends performing
meter verification at regular intervals.
10.2.2 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 and measures standard.
You may need to calculate and adjust meter factors periodically to comply with regulations.
10.2.3 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, or no flow
• Density calibration
• Temperature calibration
Density and temperature calibration require two data points (low and high) and an external
measurement for each. Zero calibration requires one data point. Calibration produces a change in the
offset and/or the slope of the line that represents the relationship between the actual process value and
the reported value.
Note: For density or temperature calibration to be useful, the external measurements must be
accurate.
Micro Motion flowmeters with the Model 2400S transmitter are calibrated at the factory, and
normally do not need to be calibrated in the field. Calibrate the flowmeter only if you must do so to
meet regulatory requirements. Contact Micro Motion before calibrating your flowmeter.
Note: Micro Motion recommends using meter validation and meter factors, rather than calibration, to
prove the meter against a regulatory standard or to correct measurement error.