Tamson Instruments bv, van 't Hoffstraat 12, 2665 JL Bleiswijk, Netherlands
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+31(0)10 – 522 43 73 Fax. +31(0)10 – 521 19 41
\\word\manuals\tlv25\\mantlv25.doc Date 09-2010 Rev. 1.31 UK
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•
Adjust value to eliminate offset with and ,
•
Press and at the same time to confirm and show bath temperature reading.
Manual tuning
The parameters for the PID control can also be changed manually.
Again this procedure is only to be
followed when automatic tuning is not functioning.
PID parameters can be accessed by pressing:
•
Key for 3 times, display shows “PID”,
•
Key , display shows PD which is the proportional value,
•
Change PD value with and ,
•
Key , display shows Ti which is the integrator value in seconds,
•
Change Ti value with and ,
•
Key , display shows Td which is derivate value in seconds,
•
Change Td value with and ,
•
Key , display shows Lcb,
•
Do not change “auto” value,
•
Key , display shows Hcb,
•
Press and at the same time to confirm and show bath temperature reading.
The control also allows to set the I and D values to zero. The bath will then function as a proportional system.
The “P” parameter can than be varied to an optimal value by trial and error. A higher P will stabilize the
system when I and D are off. The PID parameters can also be determined with the use of the Ziegler Nichols
method described below.
Manual tuning by Ziegler-Nichols
With the process at its normal running temperature:
1
Set the integral time “Ti” and the derivate Time “Td” to off
2
Check if the Lcb and Hcb are set to auto
3
Ignore the fact that the temperature may not settle precisely at the set point
4
If the temperature is stable, reduce the proportional band Pb so that the temperature just starts to
oscillate. If the temperature is already oscillating, increase the proportional band until it starts
oscillating. Allow enough time between each adjustment for the loop to stabilize. Make a note of the
proportional band value “B” and the period of oscillation “T” Set the Pb, Ti and Td parameter values
according to the calculations given in the table below
Type of control
Proportional band “Pb” Integral time “Ti” Derivative time “Td”
Proportional only 2*B
Off
Off
P + I control
2,2*B
0,8*T
Off
P + I + D control
1,7*B
0,5*T
0,12*T
