Gamry Instruments TDC4, Operator'S Manual, Page: 26 / 32

3 - 11
b) Again using the chart, estimate the S, the slope of the initial linear portion of the temperature
rise. The answer should have units of
°
C/second.
In Figure 3-7 the slope is about 7.7 x 10
-4
°
C/second (1
°
C change in 1300 seconds).
NOTE: Again, the key word is estimate. An exact answer is not expected or required.
c) Calculate the normalized slope, R, from the equation:
R = S / % change in output power, 4% in our example.
Continuing the analysis of the data in Figure 3-7, this becomes:
R = 7.7 x 10
-4
°
C/sec /4% = 1.9 x 10
-4
°
C/sec/% output
d) Calculate the proportional gain K
c
from:
K
c
= 1 / RL
in our example,
K
c
= 1/ (1.9 x 10
-4
) (300) = 17 % Output/
°
C
e) The TDC4's proportional band, PRoP, is calculated from:
PRoP = 100% Output/ K
c
in our example,
PRoP = 100% Output / 17% Output /
°
C = 5.8
°
C
f) In the TDC4, the integral reset rate, RESt, is specified in seconds. It is calculated from the
deadtime in seconds using:
RESt = L / 0.4
using the numbers above,
RESt = 300 / 0.4 = 750 seconds
g) The derivative time, RAtE, is specified in seconds. It is calculated from the deadtime in seconds
using:
RAtE = 0.4 * L
using the numbers above,
RAtE = 0.4 * 300 = 120 seconds