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1. US20110072912 - Method and apparatus for maintaining flow meter tube amplitude over a variable temperature range

Anmerkung: Text basiert auf automatischer optischer Zeichenerkennung (OCR). Verwenden Sie bitte aus rechtlichen Gründen die PDF-Version.

[ EN ]

Claims

1. A method for operating a flow meter including a driver and pickoff sensors coupled to a flow tube, the driver being adapted to vibrate the flow tube in response to a drive signal, the method comprising steps of:
setting a target pickoff voltage;
measuring a flow meter temperature;
generating a temperature compensated target pickoff voltage; and
controlling the drive signal to maintain the temperature compensated target pickoff voltage.
2. The method of claim 1, further comprising a step of identifying a magnetic material of the pickoff sensors and wherein the step of generating a temperature compensated target pickoff voltage comprises compensating for a change in a magnetic field strength of the pickoff sensors.
3. The method of claim 2, wherein the step of generating a temperature compensated target pickoff voltage comprises adjusting the target pickoff voltage using a coefficient of Br for the magnetic material of the pickoff sensors.
4. The method of claim 3, wherein the step of generating a temperature compensated target pickoff voltage comprises using the following equation:
5. The method of claim 1, further comprising a step of setting a meter design temperature, wherein the temperature compensated target pickoff voltage is substantially equal to the target pickoff voltage when the measured meter temperature is within a threshold limit of the meter design temperature.
6. The method of claim 5, wherein the threshold limit comprises a user settable value.
7. The method of claim 5, wherein the threshold limit comprises a predetermined value based on the pickoff sensors.
8. The method of claim 1, wherein the step of generating a temperature compensated target pickoff voltage comprises retrieving a stored value based on a difference between a meter design temperature and the measured meter temperature.
9. A method for operating a flow meter including a driver and pickoff sensors coupled to a flow tube, the driver being adapted to vibrate the flow tube in response to a drive signal, the method comprising steps of:
setting a target pickoff voltage;
measuring a flow meter temperature;
comparing the measured flow meter temperature to a meter design temperature; and
generating a temperature compensated target pickoff voltage if the measured flow meter temperature varies from the meter design temperature by more than a threshold limit.
10. The method of claim 9, further comprising a step of controlling the drive signal to maintain the temperature compensated target pickoff voltage.
11. The method of claim 9, further comprising a step of identifying a magnetic material of the pickoff sensors and wherein the step of generating a temperature compensated target pickoff voltage comprises compensating for a change in a magnetic field strength of a pickoff sensor magnet.
12. The method of claim 11, wherein the step of generating a temperature compensated target pickoff voltage comprises adjusting the target pickoff voltage using a coefficient of Br for the pickoff sensor magnet.
13. The method of claim 12, wherein the step of generating a temperature compensated target pickoff voltage comprises using the following equation:
14. The method of claim 9, wherein the step of generating a temperature compensated target pickoff voltage comprises retrieving a stored value based on a difference between a meter design temperature and the measured meter temperature.
15. The method of claim 9, wherein the threshold limit comprises a user settable value.
16. The method of claim 9, wherein the threshold limit comprises a predetermined value based on the pickoff sensors.
17. A method for maintaining a flow tube amplitude of a flow meter over a variable temperature range, comprising steps of:
applying a drive signal to a driver coupled to a flow tube, the driver adapted to maintain a target pickoff voltage of a plurality of pickoff sensors coupled to the flow tube;
measuring a flow meter temperature;
generating a temperature compensated target pickoff voltage using a temperature coefficient of Br for a magnetic material of the plurality of pickoff sensors; and
controlling the drive signal to maintain the temperature compensated target pickoff voltage, when the difference between the measured flow meter temperature and a meter design temperature exceeds a threshold limit.
18. The method of claim 17, wherein the step of controlling the drive signal comprises adjusting the drive power.
19. The method of claim 17, wherein the threshold limit comprises a user settable value.
20. The method of claim 17, wherein the threshold limit comprises a predetermined value based on the pickoff sensors.
21. The method of claim 17, wherein the step of generating a temperature compensated target pickoff voltage comprises using the following equation:
22. The method of claim 17, wherein the step of generating a temperature compensated target pickoff voltage comprises retrieving a stored value based on a difference between the meter design temperature and the measured meter temperature.
23. A flow meter ( 100), comprising:
a flow tube ( 101, 102);
a driver (D) coupled to the flow tube ( 101, 102) and adapted to vibrate the flow tube ( 101, 102) in response to a drive signal;
a plurality of pickoff sensors (LPO, RPO) coupled to the flow tube ( 101, 102); and
meter electronics ( 20) configured to:
set a pickoff voltage;
monitor a flow meter temperature;
generate a temperature compensated pickoff voltage; and
control the drive signal to maintain the temperature compensated target pickoff voltage.
24. The flow meter ( 100) of claim 23, wherein the meter electronics ( 20) is further configured to identify a magnetic material of the pickoff sensors (LPO, RPO) and generate the temperature compensated pickoff voltage by compensating for a change in a magnetic field strength of the pickoff sensors (LPO, RPO).
25. The flow meter ( 100) of claim 24, wherein the meter electronics ( 20) is further configured to adjust the target pickoff voltage using a coefficient of Br for the magnetic material of the pickoff sensors (LPO, RPO).
26. The flow meter ( 100) of claim 25, wherein the meter electronics ( 20) is further configured to generate a temperature compensated target pickoff voltage using the following equation:
27. The flow meter ( 100) of claim 23, wherein the meter electronics ( 20) is further configured to set a meter design temperature, wherein the temperature compensated target pickoff voltage is substantially equal to the target pickoff voltage when the measured meter temperature is within a threshold limit of the meter design temperature.
28. The flow meter ( 100) of claim 27, wherein the meter electronics ( 20) is further configured to accept a user settable value for the threshold limit.
29. The flow meter ( 100) of claim 27, wherein the meter electronics ( 20) is further configured to store a predetermined value for the threshold limit based on the pickoff sensors (LPO, RPO).
30. The flow meter ( 100) of claim 23, wherein the meter electronics ( 20) is further configured to retrieve a stored value based on a difference between a meter design temperature and the measured temperature and use the stored value to generate the temperature compensated pickoff voltage.