Yokogawa 202 Field Mounting Rate Totalizer - Manual (Page 19)

3.4 FILTERING
Frequency fluctuations caused by pulsating flow through a flowmeter, often
makes the Rate impossible to read with any precision.
The Model 202A has a digital filter which will average out these fluctuations and
enable the Rate to be read to four digit accuracy. The ability to select a suitable
filtering level means that highly accurate and stable readings can be obtained
without excessive lag.
The diagram below shows a pulsating signal input together with the effect of
filtering.
As a guideline to the degree of filtering to be used, the following table shows the
response to a step change in input. The value, CAL 06, is the filter constant
which is programmed during the Programming routine. The times for the
display value to reach 90% and 99% of full swing are given in seconds, for
different values of CAL 06.
Programming 17
Filtered Response
Time
Unfiltered Response
Rate