Table of Contents
Advertisement
Flowmeter 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: 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 7.4 for
information on viewing transmitter status and alarms.
If the zero procedure fails, two recovery functions are provided:
•
Restore prior zero
•
Restore factory zero
If desired, you can use one of these functions to return the meter to operation while you are
troubleshooting the cause of the zero failure (see Section 11.6). Both functions are available through
ProLink II. Restoring the factory zero is available through the display. Neither function is available
through the Communicator.
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 during zero calibration, the 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.
30
CAUTION
®
Micro Motion
Model 2400S Transmitters with Analog Outputs
Advertisement
Table of Contents
