b-2'7 
2 (B3a) 
r= 
lone PAle ie 
oO 
where f_ is the thermistor resistance at absolute temperature 
I the midpoint of the desired temperature range, and 
ee (B4) 
If we use the value from table B1 where Ee NALS = ASV o WOT alt 
aR 
this temperature aT = 117.6 ohms per °C. Then from eq. (B3a) 
r = 2151 ohms. 
DISCUSSION 
In order to compare the degree of linearity obtained by using 
the two different values of series resistor, ” , calculated above, a 
voltage output, @,, was computed for both cases over the tem- 
perature range. For these computations the simplified circuit, 
figure B4, was used since in the derivation of eq. (B15) the value 
of the linearizing resistor is seen to be independent of 7, and 
FH, (see fig. B3). Using the values of thermistor resistance in 
table B1 and a value of linearizing series resistor, 7 , an excita- 
tion potential, 7 , was calculated by placing the condition that the 
current through the thermistor never exceed a given level (50 x 
10 °’ amperes). Having then fixed the circuit parameters (fig. 
BA) the output, e _, was calculated for each value of thermistor 
resistance (1 degree centigrade intervals). These computed 
values of € asa function of temperature were then compared to 
a standard e which was a linear function of temperature in order 
to associate a quantitative measure of linearity with a given series 
resistor. The standard of linearity was chosen to be a straight 
line between the computed voltage outputs at 9 and 17°C. The 
reason for this choice will be discussed presently. The deviation 
of the computed output from this standard linear output was con- 
verted to a temperature deviation by referring to the slope of the 
49 
