14.3 Zero the meter
Display Menu > Service Tools > Verification & Calibration > Meter Zero > Zero Calibration
ProLink III Device Tools > Calibration > Smart Zero Verification and Calibration > Calibrate Zero
Field Communicator Service Tools > Maintenance > Calibration > Zero Calibration > Perform Auto Zero
Zeroing the meter establishes a baseline for process measurement by analyzing the sensor's output when
there is no flow through the sensor tubes.
Important
In most cases, the factory zero is more accurate than the field zero. Do not zero the meter unless one of the
following is true:
• 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.
Important
Do not verify the zero or zero the meter if a high-severity alert is active. Correct the problem, then verify the
zero or zero the meter. You may verify the zero or zero the meter if a low-severity alert is active.
Procedure
1. Prepare the meter:
a) Allow the meter 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 meter.
2. Modify Zero Time, if desired.
Zero Time controls the amount of time the transmitter takes to determine its zero-flow reference
point. The default Zero Time is 20 seconds. For most applications, the default Zero Time is
appropriate.
3. Start the zero procedure and wait until it completes.
When the calibration is complete:
• If the zero procedure was successful, a Calibration Success message and a new zero value are
displayed.
Configuration and Use Manual Measurement support
MMI-20025166 March 2019
Configuration and Use Manual 207
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