Mettler Toledo M300 ISM Spezifikationen PDF herunterladen (Seite 74)

Transmitter M300 74

Printed in Switzerland 52 121 389

Default control settings provide linear control, which is appropriate for conductivity, dissolved

oxygen and ozone. Therefore, when configuring PID for these parameters (or simple pH control)

ignore settings of deadband and corner points in the Tuning Parameter section below. The non-

linear control settings are used for more difficult pH/ORP control situations.

If desired, identify the non-linearity of the pH/ORP process. Improved control can be obtained

if the non-linearity is accommodated with an opposing non-linearity in the controller. A titration

curve (graph of pH or ORP vs. reagent volume) made on a process sample provides the

best information. There is often a very high process gain or sensitivity near the setpoint and de-

creasing gain further away from the setpoint. To counteract this, the instrument allows for adjust-

able non-linear control with settings of a deadband around the setpoint, corner points further out

and proportional limits at the ends of control as shown in the figure below. Determine the appro-

priate settings for each of these control parameters based on the shape of the pH process titra-

tion curve.

Controller with Corner Points

–120%

–100%

–80%

–60%

–40%

–20%

20%

40%

60%

80%

100%

120%

0 2 4 6 8 10 12 14

Process Variable

Deadband - value

Proportional limit –100% value

Proportional limit +100% value

Error (%)

Direct corner point (value, %)

Set point value

Deadband + value

Reverse corner point (value, %)

10.1 EnterPIDSetup

(PATH: Menu/PID Setup)

While in Measurement mode press the b key. Press the m or . key to navigate to the PID Set-

up – Menu and press [ENTER].

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Mettler Toledo M300 ISM Spezifikationen Seite 74