Emerson MMI-20019043 Manuel D’Utilisation

3.

If the zero verification procedure fails:

a. Confirm that the sensor is completely blocked in, that flow has stopped, and that

the sensor is completely full of process fluid.

b. Verify that the process fluid is not flashing or condensing, and that it does not

contain particles that can settle out.

c. Repeat the zero verification procedure.
d. If it fails again, zero the flowmeter.
For instructions on zeroing the flowmeter, see 

.

Restore normal flow through the sensor by opening the valves.

2.6.3

Terminology used with zero verification and zero

calibration

Zero

In general, the offset required to synchronize the left pickoff and the right pickoff under
conditions of zero flow. Unit = microseconds.

Factory Zero

The zero value obtained at the factory, under laboratory conditions.

Field Zero

The zero value obtained by performing a zero calibration outside the factory.

Prior Zero

The zero value stored in the transmitter at the time a field zero calibration is begun. May
be the factory zero or a previous field zero.

Manual Zero

The zero value stored in the transmitter, typically obtained from a zero calibration proce-
dure. It may also be configured manually. Also called “mechanical zero” or “stored zero.”

Live Zero

The real-time bidirectional mass flow rate with no flow damping or mass flow cutoff ap-
plied. An adaptive damping value is applied only when the mass flow rate changes dra-
matically over a very short interval. Unit = configured mass flow measurement unit.

Zero Stability

A laboratory-derived value used to calculate the expected accuracy for a sensor. Under
laboratory conditions at zero flow, the average flow rate is expected to fall within the
range defined by the Zero Stability value (0 ± Zero Stability). Each sensor size and model
has a unique Zero Stability value. Statistically, 95% of all data points should fall within the
range defined by the Zero Stability value.

Zero Calibration

The procedure used to determine the zero value.

Zero Time

The time period over which the Zero Calibration procedure is performed. Unit = seconds.

Field Verification Zero

A 3-minute running average of the Live Zero value, calculated by the transmitter. Unit =
configured mass flow measurement unit.

Zero Verification

A procedure used to evaluate the stored zero and determine whether or not a field zero
can improve measurement accuracy.

Quick start

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