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• The zero is required by site procedures.
• The stored zero value fails the Zero Verification procedure.
Prerequisites
Before performing a field zero, execute the Zero Verification procedure to see whether or
not a field zero can improve measurement accuracy. See Section 2.6.
Important
Do not verify the zero or zero the flowmeter if a high-severity alarm is active. Correct the problem,
then verify the zero or zero the flowmeter. You may verify the zero or zero the flowmeter if a low-
severity alarm is active.
11.3.1 Zero the flowmeter using the display
Zeroing the flowmeter establishes a baseline for process measurement by analyzing the
sensor's output when there is no flow through the sensor tubes.
Restriction
You cannot change the Zero Time setting from the display. The current setting of Zero Time will be
applied to the zero procedure. The default value is 20 seconds. If you need to change Zero Time, you
must make a connection to the transmitter from a communications tool such as ProLink II.
Prerequisites
Assign the following as display variables:
• Live Zero or Field Verification Zero
•
Drive Gain
•
Temperature
•
Density
See Section 5.1.2 for assistance.
Procedure
1.
Prepare the flowmeter:
a. Allow the flowmeter to warm up for at least 20 minutes after applying power.
b. Run the process fluid through the sensor until the sensor temperature reaches
the normal process operating temperature.
c. Stop flow through the sensor by shutting the downstream valve, and then the
upstream valve if available.
d. Verify that the sensor is blocked in, that flow has stopped, and that the sensor is
completely full of process fluid.
e. Observe the drive gain, temperature, and density readings. If they are stable,
check the Live Zero or Field Verification Zero value. If the average value is close to 0,
you should not need to zero the flowmeter.
Measurement support
Configuration and Use Manual 187