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5. Use the process time at 20°C as the reference time and estimate
the Ct factors for 5°, 30°, 40° and 50°C: divide the reference time
130 minutes in Fig. 3) by the time required for the
respective runs. For this example, shown in Figure 3, the Ct
factors are:
• for 5°C; 30 min/60 min = 0.5
• for 20°C; 30 min/30 min = 1.0
• for 30°C; 30 min/23 min = 1.3
• for 40°C; 30 min/15 min = 2.0
• for 50°C; 30 min/11min = 2.6
The Ct factor for 20°C is always 1.0.
6. Plot the Ct factors against their respective temperatures to obtain
the Ct curve for your method (as shown in Fig. 1).
An alternative method for estimating Ct factors is to optimize the
development method at 50°C, or some other temperature (without
using temperature compensation). Then calculate the time that would
be required for each method step at 20°C, using the general rule that
the process rate will double for every 20°C rise in temperature.
Program these values into the method, but leave the temperatures the
same (those obtained when optimizing the method).
Program the Ct curve and run the method to test the curve. The curve
can then be adjusted and tried again until you are satisfied it fits the
method.
Programming the method
Program your development method using the procedure given at the
beginning of this chapter, but program the process time as the time
required for the step if it were processed at 20°C. Instructions for
programming the Ct curve are given below.
Program the Ct Curve as follows:
1. Press ”step forward” until the Ct curve instruction appears on
the display, for example:
DEV 7 Ct(5,30,40,50)°C = (1.0.1.0,1.0.1.0)
2. To program the Ct factor for 5°C, you must first erase the
default value, 1.0. Press ”CE”.
DEV 7 Ct(5,30,40,50)°C = (0.0,1.0,1.0,1.0)
Then enter the Ct factor, for example, enter 0.5:
DEV 7 Ct(5,30,40,50)°C = (0.5,1.0,1.0,1.0)
3. Press ” ” to move the cursor to the next position; press ”CE”,
and enter the Ct factor for 30°C, for example, 1.3:
DEV 7 Ct(5,30,40,50)°C = (0.5,1.3,1.0,1.0)
4. Press ” ”, ”CE”, and enter the Ct factor for 40°C, for example,
2.0:
DEV 7 Ct(5,30,40,50)°C = (0.5,1-3,2.0,1.0)
5. Operation
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