Abstract
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 kOHgr 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
degreesC, with a 100-ms time constant and 1 microW power dissipation
in the thermistor. Long-term drift of the bridge, without an oven,
was 1 x 10-6 degreesC/min.
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