Measurement Performance
Meter verification either holds the last output value or causes the outputs to go to the configured fault values during the procedure (approximately 4 minutes).
Micro Motion recommends that you perform meter verification on a regular basis.
10.2.2Meter 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.
10.2.3Calibration
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 (see Section 3.5)
•Density calibration
•Temperature calibration
Density and temperature calibration require two data points (low and high) and an external measurement for each. Calibration produces a change in 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.
Flowmeters 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.
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.
82 | Micro Motion® Model 1500 Transmitters with the Filling and Dosing Application |
