NASA NTRS · 19780000065
Controlled freezing of biological samples
Abstract
Apparatus consists of thermocouple connected to semiconductor reference junction. Junction is connected to amplifier that boosts signal by 1,000. High-level signal is displayed on recorder and fed into second amplifier where it is compared with signal from potentiometer of programmed dc reference in bag-temperature programer. Difference in signals indicates output voltage. Remaining circuitry provides zero-phase, time-proportion control of heaters such that heater power is directly proportional to error signal.
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Cygnarowicz, T. A., Williams, T. E.. 1978-06-01. Controlled freezing of biological samples. https://ntrs.nasa.gov/citations/19780000065
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