| Pendulum measurements of the acceleration due to gravity, accurate to 0.1 milligal or better, are required to provide national and international gravity control networks as well as long range gravity meter calibration lines. As this extreme accuracy is not consistently obtained with the bronze pendulum apparatus of the Dominion Observatory, this instrument is examined to determine who field measurements, carried out since its reconstruction in 1956, are less accurate than had been expected. The errors in these observations are attributed to inadequate temperature and pressure regulation and variations in pendulum temperature of sufficient magnitude to introduce errors as large as two milligals are recorded.;The design of an all electronic timing system to replace the photographic chronograph is outlined. The precision of this instrument is such that its contribution to the overall experimental error amounts to about 0.01 milligals. The design of a more compact and reliable temperature control circuit is also described. (Abstract shortened by UMI.)... |
