A flowmeter includes a process sensor assembly providing a sensor signal and a filter stage comprising a low pass filter and a high pass filter and providing a filtered signal from the sensor signal. A processor determines that a filtered signal is indicative of a low flow condition for a first fluid, alters 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, determines that the new filtered signal is not indicative of a low flow condition for a second fluid and generates an alarm in response to the new filtered signal not being indicative of a low flow condition for the second fluid.