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Configuration and Use Manual 91
Measurement Performance
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10.2.4 Comparison and recommendations
When choosing among meter verification, meter validation, and calibration, consider the following
factors:
• Process interruption
- Meter verification requires approximately four minutes to perform. During these four
minutes, flow can continue (provided sufficient stability is maintained); however, current
process data will not be reported.
- Meter validation for density does not interrupt the process. However, meter validation for
mass flow or volume flow requires process down-time for the length of the test.
- Calibration requires process down-time. In addition, density and temperature calibration
require replacing the process fluid with low-density and high density fluids, or
low-temperature and high-temperature fluids. Zero calibration requires stopping flow
through the sensor.
• External measurement requirements
- Meter verification does not require external measurements.
- Zero calibration does not require external measurements.
- Density calibration, temperature calibration, and meter validation require external
measurements. For good results, the external measurement must be highly accurate.
• Measurement adjustment
- Meter verification is an indicator of sensor condition, but does not change flowmeter
internal measurement in any way.
- Meter validation does not change flowmeter internal measurement in any way. If you
decide to adjust a meter factor as a result of a meter validation procedure, only the reported
measurement is changed – the base measurement is not changed. You can always reverse
the change by returning the meter factor to its previous value.
- Calibration changes the transmitter’s interpretation of process data, and accordingly
changes the base measurement. If you perform a zero calibration, you can return to the
previous zero or the factory zero. However, if you perform a density calibration or a
temperature calibration, you cannot return to the previous calibration factors unless you
have manually recorded them.
Micro Motion recommends that you purchase the meter verification option and perform meter
verification frequently.
10.3 Performing meter verification
The meter verification procedure can be performed on any process fluid. It is not necessary to match
factory conditions. Meter verification is not affected by any parameters configured for flow, density,
or temperature.
During the test, process conditions must be stable. To maximize stability:
• Maintain a constant temperature and pressure.
• Avoid changes to fluid composition (e.g., two-phase flow, settling, etc.).
• Maintain a constant flow. For higher test certainty, stop flow.
If stability varies outside test limits, the meter verification procedure will be aborted. Verify the
stability of the process and retry the test.