A temperature controller using small bead thermistors as temperature sensing elements has been developed. The controller has an over‐all range of +20 to +300°C, or −60 to +190°C, using 51A2 or 32A12 thermistors, respectively, in an ac bridge. Extension of the operating temperature range to other limits is possible using other sensing elements. Linear proportional action is achieved with power relay output by comparing the amplified and rectified bridge signal with a stable and linear sawtooth wave form. This comparison controls the fractional ``on'' time of the power relay during a periodic ``on‐off'' cycle. The controller offers stable control under all conditions of unbalance, and is stable to 0.1°C or better over an eight‐day period.
REFERENCES
1.
2.
B. E.
Noltingk
and M. A.
Snelling
, J. Sci. Instr.
30
, 349
–351
(1953
);Truman S. Gray and Marvin Van Dilla, “Thermistors, their characteristics, uses, and associated circuits,” Climatic Research Laboratory, Army Service Forces, Quartermaster Corps, Lawrence, Massachusetts, Report 180 (October 20, 1945);
Truman S. Gray and Marvin Van Dilla, “Thermistor electronic thermoregulatory,” Climatic Research Laboratory, Army Service Forces, Quartermaster Corps, Lawrence, Massachusetts, Report 180‐A (October 20, 1945).
For additional references, see Veco Data Book, Victory Engineering Corporation, Union, New Jersey (1953).
3.
A controller which is similar to the present one in several respects has recently come to our attention; see F. A. Ransom, National Bureau of Standards, Report 2083.
4.
Type numbers of units obtained from Victory Engineering Corporation, Union, New Jersey.
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© 1956 American Institute of Physics.
1956
American Institute of Physics
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