Configuration and Use Manual 39
Flowmeter Startup
Required Configuration Optional ConfigurationUsing the TransmitterFlowmeter Startup
5.5 Zeroing the flowmeter
Zeroing the flowmeter establishes the flowmeter’s point of reference when there is no flow. The meter
was zeroed at the factory, and should not require a field zero. However, you may wish to perform a
field zero to meet local requirements or to confirm the factory zero.
When you zero the flowmeter, you may need to adjust the zero time parameter. Zero time is the
amount of time the transmitter takes to determine its zero-flow reference point. The default zero time
is 20 seconds.
•A long zero time may produce a more accurate zero reference but is more likely to result in a
zero failure. This is due to the increased possibility of noisy flow, which causes incorrect
calibration.
•A short zero time is less likely to result in a zero failure but may produce a less accurate zero
reference.
For most applications, the default zero time is appropriate.
Note: In some menus, a convergence limit parameter is displayed. Micro Motion recommends that you
use the default value for convergence limit.
Note: Do not zero the flowmeter if a high severity alarm is active. Correct the problem, then zero the
flowmeter. You may zero the flowmeter if a low severity alarm is active. See Section 7.5 for
information on viewing transmitter status and alarms.
If the zero procedure fails, see Section 12.6 for troubleshooting information. Additionally, if you have
the enhanced core processor:
• You can restore the factory zero. This procedure returns the zero value to the value obtained at
the factory. The factory zero can be restored with ProLink II or the display (if the transmitter
has a display).
• If you are using ProLink II to zero the flowmeter, you can also restore the prior zero
immediately after zeroing (e.g., an “undo” function), as long as you have not closed the
Calibration window or disconnected from the transmitter. Once you have closed the
Calibration window or disconnected from the transmitter, you can no longer restore the prior
zero.
5.5.1 Preparing for zero
To prepare for the zero procedure:
1. Apply power to the flowmeter. Allow the flowmeter to warm up for approximately 20 minutes.
2. Run the process fluid through the sensor until the sensor temperature reaches the normal
process operating temperature.
3. Close the shutoff valve downstream from the sensor.
4. Ensure that the sensor is completely filled with fluid.
5. Ensure that the process flow has completely stopped.
If fluid is flowing through the sensor, the sensor zero calibration may be
inaccurate, resulting in inaccurate process measurement.
To improve the sensor zero calibration and measurement accuracy, ensure that
process flow through the sensor has completely stopped.
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