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Clinical Chemistry, Vol 20, 1009-1012, Copyright © 1974 by the American Association for Clinical Chemistry
1 National Institutes of Health, Public Health Service, U. S. Department of Health, Education and Welfare, Bethesda, Md. 20014.
A precision thermistor bridge and thermistor is described for use in a thermal titration calorimeter or a
high-speed stopped- or continuous-flow calorimeter of
the Roughton type. These are compared and evaluated
with regard to several other types of detectors, including
the platinum resistance thermometer, thermocouple,
transistor thermometer, and capacitance thermometers. At this time the best detection for our purpose
seems to be a specially constructed 20-100 k
thermistor used in conjunction with a new ac lock-in amplifier
bridge. The sensitivity of the system is equivalent to a
peak-to-peak noise of 25 x 10-6 °C, with a 100-ms
time constant and 1 µW power dissipation in the thermistor. Long-term drift of the bridge, without an oven, was
1 x 10-6 °C/min.
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