Tamson Instruments bv, van 't Hoffstraat 12, 2665 JL Bleiswijk, Netherlands
.
+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
pag. 11 / 26
What is tuning
The temperature control of the bath is based on a digital PID system. Due to the use of different fluids in the
bath with their own heat capacity, the use of external cooling and external connected processes(circulation),
the PID parameters have to be optimized after changes to the system. Tuning of the bath results in:
•
Stable temperature control of the bath,
•
No over- or undershoot of the temperature set point,
•
Quick response to deviations from the set point caused by external disturbances.
Tuning can be done automatically or manually. The Parameters mentioned in Table 1 will influence the
control of the bath.
Parameter
Description
Display
Proportional band
The bandwith in display-units over which the output power is
proportional between minimum and maximum
Pb
Integration time
Determines the time taken by the controller to remove stady state
error signals
Ti
Derivative time
Determines the time taken by the controller to react on error
signals.
Td
Low cutback
The number of degrees below set point at which the controller
will cutback the output power in order to prevent overshoot on
heat up.
Lcb
High cutback
The number of degrees above set point at which the controller
will cutback the output power in order to prevent undershoot on
cool down, important when working below 20
°
C.
Hcb
Relative offset
Offset only shown for PD, or P control (I = off). [degrees]
rES
Table 1 Parameters influencing the temperature control
A TLV25 system filled with methanol combined with a KV40 cryostat will give result following in table 2.
Please note that values to your system can differ extremely due to ambient and system tolerances.
Set point
temperature
°°°°
C
Pb – values
Ti – values[s] Td – values[s]
- 10
1,7
340
55
- 20
1,8
444
74
- 30
1,7
340
55
Table 2 PID values for a TLV25 with KV40
A TLV25 system filled with methanol and KV80 will give following results
Set point
temperature
°°°°
C
Pb – values
Ti – values[s] Td – values[s]
- 10
1,8
520
85
- 20
1,7
501
83
- 30
1,9
573
95
- 40
1,8
500
85
- 50
1,8
478
79
Table 3 PID values for a TLV25 with KV80
