Emerson Process Management 2400S manual Performing zero calibration, For DeviceNet Device Profile

Measurement Performance

Example	The flowmeter is installed and proved for the first time. The flowmeter
	mass measurement is 250.27 lb; the reference device measurement is
	250 lb. A mass flow meter factor is determined as follows:
	250
	MassFlowMeterFactor = 1 ⋅ ----------------- = 0.9989
	250.27
	The first mass flow meter factor is 0.9989.
	One year later, the flowmeter is proved again. The flowmeter mass
	measurement is 250.07 lb; the reference device measurement is
	250.25 lb. A new mass flow meter factor is determined as follows:
	MassFlowMeterFactor = 0.9989 ⋅ 250.25----------------- = 0.9996
	250.07
	The new mass flow meter factor is 0.9996.

10.5Performing zero calibration

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 7.5 for information on viewing transmitter status and alarms.

If the zero procedure fails, two recovery functions are provided:

•Restore prior zero, available only from the Calibration dialog box in ProLink II (see

Figure B-1), and only if 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.

•Restore factory zero, available via:

-The display – see Figure B-7

-ProLink II – see Figure B-1

-A DeviceNet tool – use the Diagnostics Object (0x66), Instance 1, Service 0x52. For more information, see the manual entitled Micro Motion Model 2400S Transmitters

for DeviceNet: Device Profile.

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 11.8).

Compensation

Measurement Performance

Troubleshooting

Defaults

Configuration and Use Manual 99