Yokogawa 414 Batch Controller User Manual
Page 22
3.3.3 Filtering
Frequency fluctuations caused by pulsating flow through a flowmeter, often
makes the Rate impossible to read with any precision. The Batch Controller 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, A, is the filter constant which is
programmed during the Calibration routine. The times for the display value to
reach 90% and 99% of full swing are given in seconds, for different values of A.
20 Operation
Filtered Response
Time
Unfiltered Response
Rate