Hi,

Does anyone know the industry acceptable limit of amplitude attenuation in pulsating liquid flow measurement? Say for instance, a flowmeter measuring pulsating liquid flow at high frequency, due to the slow response time, the meter bounds to be indicating a smaller amplitude in the flow, but how much of this attenuation will be acceptable in various flowmetering applicaition?

 

Dear Betty,

I don’t know if there is a standard or a acceptable limit of amplitude attenuation related with pulsating signals, but I think the limit is related with your accuracy needs.

I think the Nyquist theorem give an interesting point of view and it may help:

Nyquist's theorem: an analog signal waveform may be uniquely reconstructed, without error, from samples taken at equal time intervals. The sampling rate must be equal to, or greater than, twice the highest frequency component in the analog signal.

The key here is to know measurement device sampling rate and what does it measure in each sample (instantaneous value, average value, RMS value of the interval, etc.). If your signal is not sampled fast enough, aliasing will occur, so you will see a false lower frequency signal with a random amplitude which depends on random features like phase shift between signal.

Hope this help,

Sincerely,

Enrique