Specifications

Transmitter M300 FLOW 54
© 09 / 08 Mettler-Toledo AG, CH-8606 Greifensee, Switzerland Transmitter M300 FLOW
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.