Anomaly fluid detection

1. A flowmeter comprising:

a process sensor assembly providing a sensor signal;

a filter stage comprising a low pass filter and a high pass filter and providing a filtered signal from the sensor signal;

a processor:

determining that the filtered signal is indicative of a low flow condition for a first fluid;

altering at least one parameter of the low pass filter and at least one parameter of the high pass filter in response to the low flow condition such that the filter stage provides a new filtered signal;

determining that the new filtered signal is not indicative of a low flow condition for a second fluid; and

generating an alarm in response to the new filtered signal not being indicative of a low flow condition for the second fluid.

2. The flowmeter of claim 1 wherein the flowmeter comprises a vortex flowmeter.

3. The flowmeter of claim 1 wherein altering at least one parameter of the low pass filter comprises altering the at least one parameter of the low pass filter from a value associated with a liquid flow to a value associated with a gas flow.

4. The flowmeter of claim 3 wherein altering at least one parameter of the high pass filter comprises altering the at least one parameter of the high pass filter from a value associated with a liquid flow to a value associated with a gas flow.

5. The flowmeter of claim 1 wherein altering at least one parameter of the low pass filter comprises altering the at least one parameter of the low pass filter from a value associated with a gas flow to a value associated with a liquid flow.

6. The flowmeter of claim 5 wherein altering at least one parameter of the high pass filter comprises altering the at least one parameter of the high pass filter from a value associated with a gas flow to a value associated with a liquid flow.

7. The flowmeter of claim 1 wherein before generating the alarm, the processor waits for a prescribed time and determines that a second new filter signal is also not indicative of a low flow condition for the second fluid.

8. The flowmeter of claim 1 wherein the processor further determines that a low flow condition exists after generating the alarm and ceases generation of the alarm.

9. The flowmeter of claim 1 wherein after ceasing generation of the alarm, the processor resets the at least one parameter value of the low pass filter and the at least one parameter value of the high pass filter.

10. The flowmeter of claim 1 wherein the processor further alters a low flow cut off threshold after altering the at least one parameter of the low pass filter.

11. A method comprising:

determining that there is a low flow condition in a conduit based on a first set of filter parameters;

determining that there is not a low flow condition in the conduit based on a second set of filter parameters; and

generating an alarm in response to the determination that there is a low flow condition based on the first set of filter parameters but there is not a low flow condition based on the second set of filter parameters.

12. The method of claim 11 wherein the alarm indicates a presence of gas in the conduit and the conduit is designated to contain a liquid.

13. The method of claim 11 wherein the alarm indicates a presence of liquid in the conduit and the conduit is designated to contain gas.

14. The method of claim 11 wherein determining that there is a low flow condition based on a first set of filter parameters and determining that there is not a low flow condition based on a second set of filter parameters comprises:

applying a first portion of a sensor signal to a filter stage configured based on the first set of filter parameters to produce a first filtered signal; and

applying a second portion of the sensor signal to the filter stage configured based on the second set of filter parameters to produce a second filtered signal.

15. The method of claim 11 wherein determining that there is a low flow condition based on a first set of filter parameters and determining that there is not a low flow condition based on a second set of filter parameters comprises:

applying a sensor signal to a first filter stage configured based on the first set of filter parameters to produce a first filtered signal; and

applying the sensor signal to a second filter stage configured based on the second set of filter parameters to produce a second filtered signal.

16. The method of claim 11 further comprising after generating the alarm, determining that there is a low flow condition based on the second set of filter parameters and removing the alarm.

17. A process control transmitter comprising:

a sensor assembly generates a sensor signal based on a condition of a fluid in a process environment;

a filter stage receives the sensor signal and applies a low pass filter and a high pass filter to the sensor signal to produce a filtered signal;

a diagnostic component receives the filtered signal and based on a change in the filtered signal:

alters the low pass filter and the high pass filter so that the filter stage produces a new filtered signal; and

sets an alarm state when the new filtered signal indicates the presence of an unwanted fluid in the process environment.

18. The process control transmitter of claim 17 wherein the process environment comprises a conduit.

19. The process control transmitter of claim 18 wherein the change in the filtered signal indicates a low flow condition in the conduit and the diagnostic component sets the alarm state when the new filtered signal indicates the low flow condition is not present.

20. The process control transmitter of claim 19 wherein the filtered signal indicates a low flow condition based on the magnitude of the filtered signal.

21. The process control transmitter of claim 20 wherein the filtered signal indicates a low flow condition based on the frequency of the filtered signal.

22. The process control transmitter of claim 18 wherein the diagnostic component alters the low pass filter and the high pass filter from filter parameters used for a liquid to filter parameters used for a gas.