A High Precision Thermostat for the Isotopic Analysis of Water by the Falling Drop Method

Abstract

An a.c. bridge thermostat, using two thermistors mounted in two opposite arms as temperature sensing elements, is described. The unbalanced bridge voltage is rectified, after a previous amplification, by a phase sensitive detector, and it is applied to the input of the final stage which controls the heater. The thermostat can be used to maintain the temperature of a liquid bath with a 0.0005°C precision and can be easily reset to different temperatures in the operational range of the thermistors.

Keywords::

• circuits
• isotope analysis
• temperature
• water
• control system