A Temperature Control System for the Canadian Pendulum Apparatus

A temperature control system has been developed for use with the Canadian Pendulum Apparatus for relative gravity measurements. This system, which maintains the pendulums at a constant temperature of 40.000C, consists of three major components: a vacuum enclosure in which to house the pendulums; an electronic thermometer to measure their temperature; and an electronic thermostat to maintain a constant temperature. Extensive testing of the system indicates that the temperature of the pendulums may be measured with an accuracy of ±0.01°C and that the electronic thermostat has a stability of about 0.002°C when the vacuum chamber is kept continuously closed. Under normal operating conditions, when the pendulum case is opened regularly to change pendulums, the observed temperature fluctuations amount to a maximum of ±0.025°C. As small corrections may be, applied to the pendulum periods to compensate for these temperature fluctuations, the error in gravity due to temperature effects never exceeds 1/6 mGal.