Mettler Toledo M300 FLOW Especificaciones descargar pdf (Pagina 54)

Transmitter M300 FLOW 54

Printed in Switzerland 52 121 319

10.4.2 PID Control Tuning

Tuning of the Gain and Tr for complex or critical applications can be difﬁcult. Many textbooks

are available for this purpose. For tuning of simple, non-critical applications, the following

procedure may be used. The tuning sequence consists of setting initial Gain and Tr values, then

adjusting them by trial and error. There is no one set of initial values for Gain, Tr, and Td that will

work for all ﬂow control systems. However, Gain of 0.5, Tr of 20 minutes, and Td of 0 is often

used to begin the trial and error tuning sequence. It is recommended that Td always be set at 0

for ﬂow control.

Place the output to Manual per section 10.2. Use the  or  keys and set the ﬂow rate to the

desired setting. Place the output to Auto. To assure bumpless transfer from Manual to Auto,

be certain Tr is NOT at 0. Monitor the ﬂow rate, preferably on a trending recorder. If the ﬂow rate

periodically cycles up and down, decrease the Gain value. If the ﬂow rate is steady, increase the

Gain in small steps (about 20% of setting) until the ﬂow rate begins to cycle. Note the frequency

of the cyclic response by watching two or more cycles. Decrease the Gain until cycling stops.

10.4.2.1 Tr Tuning

Decrease the Tr in small steps (about 20% of setting) until the ﬂow rate begins to cycle at a

frequency that is less than that noted in Section 10.3.1. Increase the Tr until the cycling stops.

A ﬁnal value of Tr of 20 minutes may be considered to be little Reset action. A value of Tr of

1 minute may be considered to be signiﬁcant Reset action.

This completes the tuning process.

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Mettler Toledo M300 FLOW Especificaciones Pagina 54