Yokogawa 202 Field Mounting Rate Totalizer Manuel d'utilisateur télécharger pdf (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

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 33 34

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Yokogawa 202 Field Mounting Rate Totalizer Manuel d'utilisateur Page 19